Incorporation of Protein Alternatives in Bakery Products: Biological Value and Techno-Functional Properties

Abstract

Wheat-based bakery products are important sources of energy and micronutrients; however, their protein content is lower than that of animal-based foods, and they generally have a high glycemic index. Therefore, incorporating other ingredients could improve the nutritional properties of this type of product. The partial replacement of wheat flour with flours made from other cereals, legumes, and oilseeds has been evaluated, which complements the amino acid profile, improves the rheological properties of the dough, and increases the content of polyunsaturated fatty acids, fiber, vitamins, and minerals. Similarly, the addition of flour from insects has recently gained relevance due to its high biological value protein content, as well as its low production costs and reduced environmental impact. On the other hand, the use of agro-industrial residues such as cheese whey has stood out for its potential for addition to some bread and pastry products, increasing their nutritional value. Therefore, the incorporation of alternative proteins is becoming a valuable tool for developing these types of products, improving their nutritional properties to prevent or control chronic diseases such as obesity, diabetes, hypertension, etc. However, it is important to analyze the incorporation of these ingredients at each stage of production to achieve adequate rheological properties. Likewise, it is necessary to evaluate consumer acceptance, product safety, and the corresponding regulations. This review will address different options for alternative ingredients that can partially replace wheat-based formulations, as well as how they impact the nutritional value and techno-functional properties of these products.

1. Introduction

Today, consumers are increasingly interested in foods that provide health benefits, including ingredients considered functional or that add value to products [1,2]. Therefore, these foods have become the main focus of the growing food industry and the subject of numerous research studies [3,4]. A particularly important aspect within the field of functional foods is the incorporation of proteins of high biological value due to the numerous health benefits associated with the consumption of these proteins [5,6,7]. Such is their essential role in maintaining muscle mass and bone structure, immune response, recovery from illness, and the production of hormones and enzymes [8,9,10].

They are considered proteins of high biological value because they contain all the essential amino acids (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine), and they provide them in adequate proportions to meet human physiological needs. They also have high bioavailability [11,12]. These proteins come mainly from animal-based foods and are considered to be of high biological value due to their complete amino acid profile [5,6]. In particular, bakery products use wheat as their main ingredient, a cereal rich in carbohydrates that provides essential energy to millions of people every day. However, it has a low amino acid profile as it is limited in lysine, threonine, and tryptophan content [8,13,14].

From this perspective, enriching or fortifying bakery products with alternative ingredients that complement their amino acid profile while reducing their glycemic index can become a strategic approach to developing functional foods that contribute to the prevention and treatment of non-communicable diseases [15,16,17,18,19,20,21,22,23,24,25]. There are multiple options for fortifying bakery products and ensuring that they are enriched with the necessary nutrients. For example, alternative cereals to wheat such as oats, barley, millet, quinoa, or amaranth add protein, but also other functional nutrients such as fiber [26,27,28]. These plant proteins not only offer health benefits, but also have a positive impact on the environment, as plant-based diets are estimated to reduce greenhouse gases by 30–52%, land use by 20–45%, and water use by 14–27%, compared to diets based mainly on the consumption of animal products [29,30].

Likewise, the incorporation of legumes such as chickpeas, lentils, beans, and broad beans helps complement the amino acid profile with lysine and tryptophan [31]. The combination of cereals and legumes has been shown to play an important role in the diet in developing countries, as they complement each other to provide high-value proteins. Legumes are also particularly rich in fiber and vitamins [32,33,34]. These proteins can improve the techno-functional properties and shelf life of baked goods when added to them, due to their water retention capacity and the interaction between the proteins and wheat starch, which helps form a three-dimensional viscoelastic network, giving the dough and the final product better properties [35,36]. Furthermore, the incorporation of oilseeds and seeds such as chia, flaxseed, sesame, pumpkin, and sunflower seeds provides polyunsaturated fatty acids, antioxidants, etc., in addition to protein [37,38,39,40]. They also have structuring, emulsifying, and thickening properties, as well as water retention capacity due to the mucilage in the seeds [41,42,43].

Recently, insect flours have been introduced, offering high protein content with a lower environmental impact, since their production requires less water and land use [44,45]. For example, Xie et al., 2022 [46] evaluated the effects of adding mealworm flour (Tenebrio molitor L.). These authors made soda crackers, partially replacing wheat flour with mealworm flour at different levels: MO: 100% wheat, then successively replacing it with mealworm flour in different treatments: M5: 5%, M10: 10%, M15: 15%, and M20: 20%. They found that higher concentrations of mealworm flour significantly improved the nutritional properties, with M20 reaching up to 16.0% protein and 4.0% fiber. However, the color became increasingly darker and reddish as the substitution increased. Similarly, Ayustaningwarno et al., 2024 [47] explored the use of cricket flour (Acheta domesticus) to improve the sensory and nutritional properties of cookies, increasing iron and protein levels. They used different treatments using a 100% wheat control formula (F0), and then partially replaced the percentage with cricket flour: F1 (5%), F2 (10%), F3 (15%), and F4 (20%). The results showed that protein and fiber increased as the substitution level increased, reaching up to 11.64% and 5.67%, respectively, when 20% of the wheat flour was replaced with cricket flour. Insects are an alternative substitute for animal-based foods due to their nutritional benefits, representing an area of opportunity for developing enriched and sustainable foods [48,49].

There are also other alternative sources of protein that could be implemented, such as cheese whey, which is an important by-product of the dairy industry [50,51]. Previously known as industrial waste, it is now recognized for its high nutrient content, including proteins, vitamins, and minerals, and is used in various food industries, such as beverages, breads, jams, etc. [52,53]. Moura-Alves et al., 2025 [54], developed a functional bread using only rye from the region (Trás-os-Montes, Portugal) to which they added liquid cheese whey as a substitute for water. The authors evaluated three formulations: a traditional control recipe with rye flour, wheat, and water (CTR); another combined with the same rye and wheat base, but with water replaced by cheese whey (RW); and finally, a formulation made entirely of rye with cheese whey (FRW). The RW formulation had the highest protein content (~6.54 g/100 g), while the FRW had the highest fiber content (~6.96 g/100 g). However, the FRW received the highest score in the sensory evaluation because it had a firmer texture and a denser crumb. In particular, the addition of whey to bakery products provides important nutritional and techno-functional properties such as emulsifying and foaming capacity, solubility, and antimicrobial activity, which is why it has been used in baking in either liquid or powder form [55,56,57].

The addition of these protein ingredients to bakery products is emerging as a solid strategy for transforming an everyday food into a functional food capable of addressing nutritional deficiencies and preventing and treating chronic diseases [58]. It is important to take an interdisciplinary approach that combines food technology, nutrition, process engineering, and social sciences. The objective of this study is to analyze the technological trends and challenges of incorporating protein ingredients into bakery products for the development of functional breads that balance sensory acceptance, industrial viability, and a product with better nutritional properties.

2. Role of Proteins in Bakery Products

Proteins have essential technological characteristics that influence the dough and the final baked product. A key characteristic is their water retention capacity; when exposed to water, the hydrophilic parts of the polypeptide chains, particularly the ionizable carboxyl and amino groups, hydrate and unfold [59]. This swelling allows the glutenin and gliadin fractions to align and interact, forming a cohesive viscoelastic matrix. This matrix can resist deformation during kneading, traps carbon dioxide in the dough, and expands with oven steam, significantly affecting the final volume and uniformity of the crumb [60].

On the other hand, the elasticity and extensibility of wheat depend mainly on glutenins, which create elasticity through disulfide bonds, while gliadins improve extensibility due to their flexible structures and fewer disulfide bonds [61]. This balance is vital for kneading tolerance, gas retention, and dough stability during fermentation. Too much elasticity can result in dense products, while excessive extensibility can lead to structural failures during baking [62]. Similarly, protein solubility, which is affected by pH, ionic strength, and temperature, influences the availability of polar and nonpolar groups at air–water or oil–water interfaces [63]. Greater solubility improves emulsifying (stabilization of fats in dough) and foaming (incorporation of air into whipped dough) capabilities, which promotes a softer crumb with better texture [64,65].

Water retention occurs during cooling after baking, with proteins acting as water reservoirs, delaying starch retrogradation, which is the main cause of crumb hardening, and prolonging the sensory shelf life of bread [66]. Gelation creates cohesive networks at denaturation temperatures between 60 and 80 °C (Figure 1). These networks connect with gluten and gelatinized starch, improving structural support, clean cutting, and compressive strength in enriched breads or cakes. In gluten-free products, the gelation of plant or animal proteins is crucial to replace the structural function of gluten [67]. Moreover, proteins play a key role in film formation and crust development during baking and surface drying, as they create a semipermeable film that controls moisture migration and improves crispness [68]. This film, rich in reactive amino acids, is essential for the Maillard reaction with reducing sugars, which results in melanoidin compounds that provide a golden color and a desirable aroma. In addition, proteins can produce peptides with antioxidant and immunomodulatory properties during digestion or dough maturation. The selection of protein sources rich in limiting amino acids and the optimization of processing improve the functional value of the final product [69].

3. Techno-Functional Properties of Wheat Proteins

Wheat proteins, composed mainly of glutenins (polymeric) and gliadins (monomeric are the key functional and technological components of bakery product [70]. Upon hydration and mechanical energy input, the hydrophilic domains of these proteins unfold, enabling the formation of a cohesive three-dimensional network stabilized by disulfide, hydrogen, and hydrophobic bonds [71]. This viscoelastic matrix combines the elasticity provided by high molecular weight glutenins with the extensibility attributed to less cross-linked gliadins; the balance between these two characteristics is fundamental in determining kneading tolerance and CO₂ retention capacity during fermentation [72]. In addition, these proteins exhibit emulsifying and foaming properties: their amphipathic regions align at the air–water or oil–water interface, reducing surface tension and stabilizing the fine gas bubbles that contribute to the formation of uniform crumbs with low bulk density (Figure 2). At the same time, their significant hydration capacity inhibits starch retrogradation, delaying hardening and preserving the softness of the bread throughout its shelf life [73].

4. Alternative Protein Sources in Bakery Products

It is important to analyze the nutritional deficiencies of wheat in order to complement it effectively. For this reason, it is essential to evaluate both the protein content and the amino acid profile of the ingredients (

Table 1. Abundant and limiting amino acids in alternative protein sources.

Group	Source	Abundant Amino Acids	Limiting Amino Acids	Reference
Vegetables	Oat	Methionine, cysteine	Lysine	[76,78,79]
	Rye	Methionine	Lysine, Threonine	[76,80]
	Rice	Methionine, cysteine	Lysine	[76,80]
	Quinoa	Lysine, Methionine	None clearly limiting (almost complete profile)	[76,81,82]
	Lupine	Lysine, Arginine	Valine, cysteine, and methionine	[75,76]
Seeds and nuts	Nut	Arginine, Glutamic acid	Lysine, Methionine	[38]
	Chia	Lysine, Arginine	Methionine	[83]
	Pumpkin seeds	Tryptophan, Arginine	Lysine	[43,84]
	Sunflower seeds	Arginine, Glutamic acid	Lysine	[43]
	Sesame seeds	Methionine, Cysteine	Lysine	[43]
Legumes	Bean	Lysine	Methionine	[85]
	Chickpea	Lysine, Tryptophan	Cysteine, methionine, and tryptophan	[86]
	Lentils	Lysine, Tryptophan	Methionine	[87]
	Broad beans	Lysine, Arginine	Methionine and tyrosine	[40]
	Soy	Lysine, Arginine	Cysteine, Methionine (although less limiting than in other legumes)	[75,88]
Sub-products	Liquid cheese whey	Lysine, Leucine, Isoleucine, Valine	No limitations (full profile)	[51,89]
	Cheese whey powder	Lysine, Cysteine, Leucine	No limitations (full profile)	[51,89]
	Cheese whey concentrate (34%)	Lysine, Leucine, Valine	No limitations (full profile)	[51,90]
	Cheese whey concentrate (80%)	Lysine, Leucine, Tryptophan	No limitations (full profile)	[51,90]
	Cheese whey isolate	Lysine, Leucine, Isoleucine	No limitations (full profile)	[51,90]
Insects	Beetles	Lysine, Methionine	Generally balanced, minor limitations in tryptophan	[91,92]
	Caterpillars	Lysine, Threonine	Minor limitations in methionine	[91,93]
	Bees	Lysine, Arginine	Minor limitations in tryptophan	[93]
	Grasshoppers	Lysine, Threonine	Mild limitations in methionine	[91,94]
	Locusts	Lysine, Valine	Methionine	[91]
	Crickets	Lysine, Threonine, Valine	Slightly low in methionine	[91,94]
	Termites	Lysine, Methionine	Almost complete profile, slight deficiencies in tryptophan	[91,94]

). This ensures that, upon addition, they can combine to form a protein of high biological value while simultaneously increasing the total protein content [74,75,76,77].

4.1. Cereals

Wheat is the main cereal used as flour in the production of bakery products. However, there has been growing interest in alternative plant-based flours (

Table 2. Protein ingredients at their substitution level in wheat-based bakery products, as well as their protein content in dry matter.

Protein Origin	Ingredient	Level of Substitution (%)	Protein (g/100 g Dry Matter)	Reference
Vegetables	Oat	10–20	10–17	[97,98]
	Rye	<30	9–15	[99,100]
	Rice	<50	6–8	[101]
	Quinoa	10–15	13–15	[102,103]
	Lupine	≤20	35–40	[77]
Seeds and nuts	Nut	5–10	5–15	[104,105]
	Chia	5–15	16–20	[106,107,108]
	Pumpkin seeds	5–10	30–33	[109]
	Sunflower seeds	5–16	20–21	[110]
	Sesame seeds	5–10	17–18	[107,111]
Legumes	Bean	10–30	21–24	[112,113]
	Chickpea	10–30	19–21	[114,115]
	Lentils	≤20	24–26	[116,117]
	Broad beans	10–20	24–26	[118]
	Soy	>20	36–40	[119,120]
Sub-products	Liquid cheese whey	10–15	0.8–1.0	[121,122]
	Cheese whey powder	10–15	11–14	[122,123]
	Cheese whey concentrate (WPC 34%)	10–15	34–36	[124]
	Cheese whey concentrate (WPC 80%)	10–15	77–82	[122,123]
	Cheese whey isolate (WPI)	10–15	85–90	[122]
Insects	Beetles	5–10	40–65	[44,125]
	Caterpillars	5–10	45–60	[126]
	Bees	5–10	50–65	[127,128]
	Grasshoppers	5–20	60–70	[129]
	Locusts	5–20	60–70	[130]
	Crickets	5–30	60–70	[131,132,133]
	Termites	5–10–15	35–65	[126]

), and their use to replace wheat in the baking industry is a current research focus, mainly due to the rise in public demand for gluten-free breads [95]. In addition, in view of dietary trends, proteins free of the allergens present in wheat proteins are being sought to improve the nutritional value of bread [96].

4.1.1. Oat

In this case, oat flour is used in gluten-free formulations, but due to its high protein levels, its application as a partial replacement for wheat flour in bread making has been limited until now. A commercial oat bread made with yeast and containing up to 35% oat flour was acceptable to consumers in terms of taste, crumb softness, and appearance [97,134]. Interest in the use of thermally processed oat products as a functional replacement for wheat flour has grown along with a greater understanding of the flavor and texture profiles that oats can contribute to bakery products [98,135].

Oat flour has a total oil content of up to 7.8%. Ground oats, whether untreated or subjected to mild heat treatment, are rich in various essential nutrients, including a protein content ranging from 12.1% to 17.8%, approximately 4.7 mg of iron, and around 177 mg of zinc, along with β-glucan levels between 2.8% and 10% in the flakes [136,137]. As a result, oat flour has a higher protein content compared to other cereals and has a higher concentration of non-starch polysaccharides. These nutritional levels are significantly higher than the protein content found in refined wheat flour, which consists mainly of a mixture of the monomeric amino acids glutamic acid and proline [138,139,140]. Together, they form a cohesive network of soluble starch and glutenins in saline and alkaline solutions, allowing the formation of viscoelastic doughs suitable for bread production [141]. For example, Ivanišová et al., 2023 [142], used black oat flour (Norik and Hucul varieties) at concentrations of 3, 6, and 9% to replace wheat flour in bread, which had a significantly higher protein content (p < 0.05) with values between in which the formulation with up to 30% substitution had a protein content of 11.94% and a higher crude fiber content of 6.73% compared to the control bread. mineral levels also increased, especially magnesium (~73.00 mg/100 g), iron (~45.00 mg/100 g), and calcium (~40.00 mg/100 g). Likewise, in the sensory evaluation, the enriched formulations obtained a better score than the control formulation.

In this context, the addition of alternative plant-based flours is rapidly becoming an extremely popular and beneficial choice, due to their remarkable nutritional qualities and exceptional versatility as a replacement for half of the total amount of wheat flour traditionally used [106,143].

4.1.2. Rye

Similarly, rye can be an excellent addition to mixtures that replace refined wheat during bread production. Diets containing whole rye, whole rye grains, and bread made with whole rye have beneficial effects on weight loss, improved lipid profile, and reduced blood pressure in overweight and obese individuals with metabolic syndrome [54]. Most of these beneficial effects have been associated primarily with the high fiber content of rye, although other biologically active compounds present in rye may also contribute to these effects [99].

Rye flour has a good content of non-gluten proteins such as secalin. It has gluten and gliadin in proportions opposite to those of wheat, resulting in severe technological restrictions for its use in bread making [100]. Dough made with rye flour has a limited ability to form a viscoelastic dough that can expand and maintain its structure during the bread making and baking process. This creates the need to implement formulation, mixing, kneading, leavening, and baking techniques to develop a method that compensates for these effects that could negatively alter the final product [144].

For this reason, the best method for using rye is to prepare a natural sourdough starter for 20 h, which is then mixed with the main dough. Rye-based products depend more on how arabinoxylans contribute to the viscoelasticity of the dough and structure of the bread [145,146]. However, the flavor of rye flour can remain strong in bread, evoking the rural bakery of yesteryear. Bread made solely from rye has a tradition of intense flavor and color, resulting from a careful Maillard reaction during the prolonged steaming process of the dough [147]. The incorporation of rye flour in bread production offers numerous advantages, both in terms of nutritional and sensory benefits. Beyond its distinctive contributions to flavor and texture, rye’s high fiber content, low glycemic index, and potential biologically active compounds make it a valuable addition to diets focused on weight loss, improving lipid profiles, and lowering blood pressure [148,149]. By understanding and leveraging the natural characteristics of rye, bakers can create innovative bread options that address a wider range of dietary needs [150].

4.1.3. Rice

Rice is a staple food in most parts of the world, but its use in bakery products is relatively uncommon [151]. Rice is usually processed for consumption as boiled or steamed whole grains, or ground into rice flour and then processed into various forms, such as noodles, batter, vermicelli, pancakes, rolls, and cakes [152]. Rice-based bakery products can be combined with other cereal flours in compound flour formulations to produce a wide variety of bakery products [153]. Since rice flour lacks gluten, which gives leavened products a reticular structure, leavened products made from rice flour require viscoelastic properties; white rice does not provide this property [154].

For this reason, rice flour can be used as a substitute for wheat in the production of gluten-free bread. The protein content can be increased through additional extractions and by subjecting it to alkaline and acid treatments [101]. This improves the quality of the protein, making it more suitable for inclusion in wheat flour with the aim of improving the formation and structuring properties of the dough. These functional proteins play a key role in optimizing the characteristics of the final bakery product [155].

To further improve the protein content, ultra-fine rice flour can be produced using ultrasonic bath-assisted wet milling with extended milling times [156]. This process produces rice flour with the highest protein content, reaching 7.4%, along with a high mineral content. This specialized type of rice flour can effectively replace wheat flour and be combined with vegetable proteins to optimize the rheological properties and other desirable attributes of bread [157]. The design of formulations using novel techniques can contribute to achieving the desired parameters, ensuring the consistent production of gluten-free bread with excellent sensory properties and high protein content [158].

4.1.4. Quinoa

Additionally, quinoa flour offers a number of health benefits. In particular, its high protein content provides benefits in baking. The unique flavor of quinoa flour can be described as delicate, sweet, herbaceous, toasty, or nutty, with hints of cocoa and coffee. The inclusion of quinoa flour in bread resulted in a distinctive, though not unpleasant, flavor characteristic of quinoa. Its approximate protein content is between 13.57% and 16.5% [102]. For this reason, quinoa flour is a value-added ingredient to mix with wheat flour and maximize protein levels in bread. Quinoa protein is rich in all essential amino acids, making it a complete source of plant-based protein. The high protein or fiber content in the flour contributes to bread made with quinoa flour having a moisture absorption similar to wheat-based bread. This property influences the gelatinization and retrogradation properties of starch [159].

Quinoa protein is composed of 51% albumins and 39% globulins, both of which are hydrophilic proteins. Albumin protein can capture free radicals in the body, which are the result of oxidation reactions [160]. Globulins also have an antioxidant effect, but their main function is to play a key role in the body’s immune response. The free amino acids released from quinoa protein during the baking process contribute to the Maillard reaction, which generates the final color of the bread crust [103].

Quinoa flour is also a good source of vitamins and minerals, such as magnesium, zinc, potassium, and vitamins E and C. It has been classified as a “pseudocereal” because, although it is a grain-like seed, it is not a true cereal [161]. This means that flour obtained from quinoa seeds is naturally gluten-free, so it can be consumed by people with celiac disease. This is highly recommended for people with celiac disease who have various micronutrient deficiencies, as it is not overly processed and naturally contains nutrients such as protein, vitamins, and minerals [162,163].

Quinoa flour can be easily incorporated into many recipes, from gluten-free bakery products to traditional ones, to increase protein content while significantly improving texture and flavor [164]. It has been reported that adding quinoa flour at a concentration of 10% maximizes the protein content of bread that participants were more willing to consume. Furthermore, quinoa flour alone, at this tested percentage, could be a viable flour for increasing protein content and being accepted by consumers [165]. As demonstrated by Coţovanu et al., 2023 [161], who evaluated the baking characteristics of wheat bread supplemented with quinoa flour of various particle sizes (large, medium, and small), assessing the physical, textural, nutritional, and sensory aspects. The results reported by the authors indicate a reduction in the fall index, water absorption, dough stability, and dough extensibility, which resulted in breads with less volume and more compact doughs due to the weakening of the protein–starch–water network. Likewise, all bread samples enriched with quinoa had an improved nutritional profile with an increase in protein of up to 19% more compared to the control. However, the best nutritional level was achieved by the formulation with medium particles, with 13.89% protein and 1.59% fiber.

4.2. Legumes

The increase in world population and prosperity has led to higher protein consumption in the diet. For this reason, incorporating more plant-based proteins into our diet will reduce the use of agricultural resources and greenhouse gas emissions compared to animal proteins [166]. In this case, plant-based proteins such as peas, beans, chickpeas, and lentils can be a solution for increasing protein in bakery products, with their content varying between 17% and 46%, compared to cereals, which provide 8%. Incorporating these legume flours increases the protein, fiber, mineral, and vitamin content [32,167].

Adding legume flours to traditional wheat breads could contribute to developing a product with higher protein content and better quality, thanks to their balanced amino acid profile [168]. However, higher levels of ingredient replacement can reduce the stability and strength of the dough, leading to stiffer breads with lower volume due to reduced gluten and interactions between fiber and water [169]. For this reason, acceptable breads can be made with low levels of replacement, although ingredients that interact to avoid these negative effects can be used, and fermentation could also help mitigate these effects [170].

It is important to establish the formulation, as combining legume flour with cereals affects the properties of the dough, such as volume expansion, growth, and viscoelasticity [171]. Legume flour has recently been used in bakery products such as breads, cakes, and cookies, providing a wide range of nutritional and textural benefits. This depends mainly on the level of flour substitution. Adding 20% to 30% legume flour can increase the protein and dietary fiber content and reduce the glycemic index of bread. However, enriching them changes how they are processed and their properties, and predicting these changes is a challenge when formulating and baking [33,172]. It is important to mention that although legumes are highly nutritious, they generally contain antinutritional compounds. Legumes are rich in phytic acid, an antinutritional factor because it can chelate transition metal ions, which promotes mineral deficiencies. They also contain protease inhibitors, tannins, and oligosaccharides that can cause flatulence Legume flour requires pre-treatment before incorporation into formulations. These processes reduce oligosaccharides, eliminate bitter compounds, decrease antinutritional factors, and improve protein digestibility, ensuring higher nutritional value [173]. The incremental impact of legume-enriched bakery products is being specifically analyzed in relation to the potential generation of new applications for the development of low glycemic index bakery products. With the continuous development of new bread products, the industry and consumers have a greater variety and more specialized natural food options [174].

The introduction of legume flour into wheat flour can pose technological challenges such as a decrease in gluten due to its partial replacement by legume proteins and competition for water retention [175]. It should be noted that legume flour has a higher affinity for water due to the presence of a large number of hydroxyl groups in legume proteins, which improves its ability to retain moisture [176]. This characteristic is essential to ensure adequate hydration and the subsequent formation of cohesive dough matrices, especially in gluten-free formulations [177]. Likewise, the variation in protein and fiber content among different types of legumes can lead to unique emulsifying capabilities, which can improve product development [178]. This is mainly due to the protein fractions found in legumes, which can stabilize oil and water mixtures thanks to their hydrophilic and hydrophobic characteristics [179].

On the other hand, baking processes significantly influence the gelling behavior of legume flours [180]. As the temperature increases from 40 °C to 70 °C, a pronounced increase in the modulus of elasticity (G′) is observed, mainly due to water absorption and starch granule swelling [35,181]. This temperature-induced gelation is essential, as it facilitates the formation of a stable network within the matrix of bakery products. Further heating to around 95 °C causes an additional increase in G′, largely attributed to the denaturation of the globulin proteins present in these legumes. The denaturation process improves hydrophobic interactions, which are essential for the formation of the gel necessary for the textural integrity of food products [182]. The rheological characteristics of legume-based mixtures, supported by water retention capacity values, confirm the potential for improving gel strength, which is essential for innovations in both nutritional and functional food products [183].

Thus, the addition of legume flours has been associated with improved foaming capacity, due to their globular protein and albumin content. For example, soy protein has the highest foaming stability, exceeding 90%, closely followed by proteins from green lentils, peas, and red beans. These findings underscore the importance of selecting appropriate plant protein sources to optimize desirable foaming properties in bakery products [112].

4.3. Oilseeds

Seeds and nuts offer numerous benefits when used in bakery products. They contain high amounts of protein, monounsaturated and polyunsaturated fatty acids, dietary fiber, vitamins, and minerals. In addition to these nutrients, seeds and nuts contain several non-nutritive components such as phytates, phenolic compounds, flavonoids, and saponins, collectively known as bioactive compounds [184].

The consumption of seeds and nuts in the diet can improve gastrointestinal function, relieving indigestion, and benefit heart health by reducing low-density lipoprotein cholesterol levels. The inclusion of seeds and nuts in bakery products improves protein content and gluten levels, contributing to the maintenance of nutritional value and the improvement of textural aspects [104]. The most commonly used in the baking industry are: almonds, which are used raw or toasted, usually whole; walnuts, which are used raw or toasted, chopped or ground; as well as chia seeds, which are mainly used raw, and flax seeds, which can be used raw or with some heat treatment [41]. As described by Marpalle et al., 2014 [185], who developed a functional bread enriched with flaxseed flour, a control bread made with 100% wheat flour was used, which was then gradually replaced with raw and toasted flaxseed flour at 5%, 10%, and 15%. The results showed that the increase in flaxseed flour is directly proportional to the increase in protein and fiber, with the bread with the highest substitution obtaining up to 21.6% protein and 7.20% fiber compared to 10.55% protein and 3.40% fiber in the control. Similarly, higher levels of substitution resulted in darker dough and a denser product. On the other hand, Miranda-Ramos et al., 2020 [186], conducted tests substituting wheat-based bakery products with chia derivatives. Based on a 100% wheat control bread, they replaced 5 and 10% whole chia seeds, 5 and 10% whole chia flour, 5 and 10% semi-defatted chia flour, and 5 and 10% low-fat chia flour to evaluate how this affected the nutritional and functional value of the bread. The results showed that chia-enriched breads had higher protein levels, with bread enriched with 10% defatted chia flour having the highest level at 25.2%. In terms of fiber, bread enriched with 10% whole chia seeds had the highest content at 8.7%. The least commonly used seeds, in order of highest to lowest consumption, are: pumpkin seeds, which can be eaten raw or roasted, with or without their shells, and can be ground; sunflower seeds, which can be eaten raw or roasted, with or without their shells, and can also be ground [187].

On the other hand, walnuts are rich in alpha-linolenic acid, a plant-based omega-3 fatty acid. This particular acid is known to reduce the risk of heart disease, and studies have shown that it also supports cognitive function in people with cognitive impairment. Pecans are also an excellent source of monounsaturated fatty acids and contain phenolic antioxidants. Pecan consumption has shown positive effects in reducing low-density lipoprotein cholesterol levels. In addition, pecans may contribute to the prevention of breast disease, gallstones, and certain types of cancer [39].

By incorporating natural ingredients such as seeds or nuts into these products, bakers can create new options with added functional characteristics. Some seeds, such as chia, flaxseed, and sesame seeds, have exceptional biological value, as they are not only rich in protein but also have high levels of fiber. These seeds have been shown to help lower blood cholesterol levels and promote digestive health [105]. To take advantage of these benefits, significant efforts have been made to incorporate these seeds into various semi-processed and baked goods. This approach not only improves the sensory characteristics of these products but also allows the market to offer a fresh alternative that promotes healthier and more natural food choices [109]. However, incorporating seeds into bakery products poses challenges for the industry. The high levels of polyunsaturated fatty acids present in these seeds can lead to rancidity issues, which are perceived through the smell of the bread [188]. This makes bread particularly susceptible to spoilage when stored at room temperature. By addressing these technical obstacles, the industry can continue to provide a wider range of options that meet growing demand [189]. From a biochemical perspective, proteins derived from oilseeds (mainly albumins and globulins) have amphipathic regions that allow them to function as emulsifying agents by adsorbing at the interface between water and fat. This process effectively reduces interfacial tension and stabilizes dispersed systems [190].

In addition, these proteins exhibit foaming capacity as a result of their migration to the air-water interface, where they can undergo partial denaturation and form cohesive films around gas bubbles [191]. Furthermore, thermal denaturation reveals reactive groups (-SH, -COOH, and -NH₂), which play a fundamental role in the formation of three-dimensional gel networks through mechanisms such as hydrophobic interactions, disulfide bonds, and hydrogen bonds, improving the structure, cohesion, and elasticity of the crumb [192].

On the other hand, soluble fibers and polysaccharides, especially those found in seeds such as chia and flaxseed, show a high affinity for water due to their hydroxyl and carboxyl groups [193]. This affinity contributes to their exceptional water retention capacity and facilitates the formation of gels that stabilize the dough and improve the overall texture of the bread. It is hoped that bakery product formulations will be adaptable to increase protein content, thereby improving their nutritional profile while maintaining acceptable consumer perception [107].

5. Other Protein Sources

5.1. Insects

Population growth, water shortages, pollution, and high livestock costs have driven research into alternative sources of protein such as edible insects. For this reason, a line of research has been initiated with the aim of expanding and exploiting the potential of edible insects in human nutrition through innovative technological applications [125]. Adding insects as a source of protein in bread can increase the value of bakery products, increasing their protein content and transforming them into functional and beneficial foods. The introduction of insects into the culinary world presents an opportunity to explore new flavors, textures, and nutritional benefits, improving the overall dining experience [44]. Insects can be raised in small spaces and at low cost, even using organic waste for feed, which increases sustainability and reduces environmental impact compared to livestock farming. Therefore, these properties could meet the growing demand for protein while minimizing environmental impact, creating new economic opportunities, and supporting local communities [126]. However, it is essential to carefully select substrates, ensuring that they are free of animal remains, animal waste, residual antibiotics, and chemicals to guarantee microbiological safety and compliance with legal regulations, promoting a healthier and more sustainable approach to food production [127,128].

Insects are a rich source of protein, containing between 25% and 75%, and lipids between 10% and 70%, depending on the species. They are also rich in fiber and minerals such as iron, magnesium, and zinc [131]. However, despite all these benefits, there is still a rejection of these types of products in Western markets, as they tend to be considered pests. For this reason, incorporating them in more acceptable forms such as flour, pasta, or extracts could be a way to increase their consumption. Proteins from insects are considered better in terms of nutritional properties than legumes, as they contain all the essential amino acids and also contain more protein [132]. It is important to explore different formulations for incorporating insect flour into the development of bakery products in order to establish the right recipe that is acceptable to consumers while maintaining optimal nutritional quality [194].

Likewise, the most commonly consumed insects worldwide are beetles 31% (Coleoptera), caterpillars 18% (Lepidoptera), bees, wasps, and ants 14% (Hymenoptera), grasshoppers, locusts, and crickets 13% (Orthoptera), cicadas, mealybugs, and bedbugs 10% (Hemiptera), termites 3% (Isoptera), dragonflies 3% (Odonata), flies 2% (Diptera), among others 5%). Entomophagy is commonly practiced in many regions of the world and is influenced by the culture of each region [44,48,49,133]. Insects represent a remarkable opportunity as alternative protein sources in the modern era, extending their use beyond bread to a wide range of food products. Efforts are being made to increase the incorporation of cost-effective insect proteins into food preparation, developing insect-based recipes, cooking techniques, and farms dedicated to insect breeding to ensure consumer access to this protein source in a convenient and palatable manner [195]. On the other hand, the functional properties of insect-derived proteins make them valuable ingredients for various bakery products [196]. Insect flours containing negligible amounts of starch do not effectively reinforce the gluten network in dough; on the contrary, they tend to weaken the overall strength of the dough despite their remarkably high protein content, which is often considered advantageous [197]. However, the high protein content presents a large number of hydroxyl groups, which increases its water retention capacity, benefiting the rheological properties of bakery products [198].

Similarly, the proteins present in insect flours have emulsifying capacity, which is attributed to their hydrophobic domains, which are rich in amino acids such as leucine, isoleucine, or valine, and align with the fat phase, while their hydrophilic regions, which contain residues such as glutamic acid, lysine, and serine, align with the aqueous phase [199]. This unique structure facilitates rapid adsorption at the water–oil interface, leading to a reduction in interfacial tension and stabilization of the fat droplets in suspension [200]. Likewise, insect flours contain proteins with structural attributes that give them foaming capacity by acting as natural surfactants. This characteristic becomes evident when the proteins are adsorbed at the air-water interface, causing a reduction in surface tension and the formation of a viscoelastic film that envelops the gas bubbles [201].

Therefore, during the kneading and rising stages of aerated doughs, the proteins undergo partial denaturation, exposing the hydrophobic groups (–CH₃, –CH₂–) that are normally hidden within the tertiary structure [202]. The partially denatured proteins then migrate to the air-water interface, where they orient themselves amphipathically: the hydrophobic residues align toward the gas phase (air bubble), while the hydrophilic residues (–COOH, –NH₂, –OH) position themselves toward the aqueous phase. The proteins fuse at the interface, forming a cohesive layer through the establishment of hydrogen bonds, hydrophobic interactions, and Van der Waals forces. This process stabilizes the bubbles, thus preventing their collapse or fusion [203].

Insect proteins also have moderate to high gelation capacity, which depends on factors such as processing methods, protein content, degree of denaturation, and environmental conditions, including pH, temperature, and humidity [204]. When subjected to temperatures between 55 and 95 °C, these proteins undergo the breakdown of non-covalent interactions, specifically hydrogen bonds, Van der Waals forces, and hydrophobic interactions, thus revealing the internal functional groups. In particular, sulfhydryl groups (–SH) are capable of forming disulfide bridges (S-S), while hydrophobic regions facilitate protein aggregation through nonpolar interactions [205]. In addition, polar groups such as hydroxyl (–OH), carboxyl (–COOH), and amino (–NH₂) contribute to the establishment of cross-links through hydrogen bonds and electrostatic interactions [206]. These functional groups begin to associate systematically, resulting in the formation of a gelatinous matrix through the interactions mentioned above [207]. Therefore, it is important to highlight the importance of edible insects in the food industry, which represents an exciting frontier with great potential. From addressing global protein deficiency to promoting sustainability and supporting local communities, insects as a source of protein have the potential to revolutionize food production and consumption. Embracing innovation and new technologies can unlock the full potential of edible insects and create a more resilient and nutritious food system for future generations (Figure 3) [129].

5.2. Cheese Whey

The use of resources is a priority today. The circular economy emphasizes the reuse and recycling of waste, which allows it to be used to make value-added products in the food, pharmaceutical, and cosmetics industries. This not only benefits the economy but also biological systems [208]. Cheese whey is a by-product of dairy processing, mainly from cheese pressing. It is obtained when rennet is added to pasteurized milk, causing it to coagulate and form a semi-solid mass rich in casein and fat. After this mass has matured and dried, it becomes cheese [209]. What remains after this mass is removed is whey, a greenish-yellow liquid with a sour but pleasant taste. Previously, it was mainly used in animal nutrition, but recently, applications have been found in dry mixes, bakery products, and in the production of cheese and yogurt [209].

It should be noted that it is one of the largest wastes in the dairy industry, as approximately nine liters of effluent (85–90% of the volume of milk) are produced for every kilogram of cheese, and it retains approximately 55% of its nutrients, including 20% of the total protein. Its main components are water, accounting for 93% of the volume, lactose, accounting for 70–72% of the total solids, whey proteins, accounting for 8–10%, and minerals, accounting for 12–15%. These are mainly calcium, potassium, sodium, and magnesium salts, as well as traces of zinc and copper [210]. However, cheese whey proteins have been extensively studied for their significant ability to increase the protein content of bakery products, while also providing high biological value. These proteins have low moisture levels, which gives them exceptional hygroscopic rigidity. This is one of the reasons why they can be incorporated into foods such as bakery products, as they improve the structure of bread [121].

For this reason, the use of milk proteins in the baking industry has shown improvements in the rheological properties of bread, as whey proteins have the ability to form an intricate three-dimensional network through gluten bonds [211]. This network is primarily responsible for gas retention, thus determining the structure of the dough, volume expansion, and consequently influencing the softness and density of the bread [122]. The unique functional properties of whey proteins, such as their complete amino acid composition, allow for effective technological interventions in the formulation of bakery products, opening up opportunities for the use of dairy by-products. The bioavailability and bioactivity of whey protein-enriched bakery products contribute to the growth of the bakery sector [123,212]. Likewise, these proteins meet the essential amino acid requirements of the human body, as the body cannot produce them, relying on these proteins as a reliable source. Cheese whey has been successfully included in bakery products at levels of up to 4%, representing up to 20% of the total protein content. However, bakery products can only tolerate a maximum protein content of 6%, highlighting the importance of maintaining an optimal ratio [213]. Whey can be easily incorporated into bakery products to improve both their nutritional and functional properties, as it increases the amount of protein and in turn improves crust browning, crumb texture, and flavor. It also affects the rheological properties of the dough as it has properties as a foaming agent, emulsifier, gelling agent, and improves viscosity [124]. As demonstrated by Tsanasidou et al., 2021 [214], who conducted a study to evaluate the partial substitution of wheat-based bread; in which a 100% wheat control without whey was used, then the percentage of water replaced by whey was varied, with W25 replacing 25% of the total water, W50 replacing 50%, and W100 replacing 100% of the water with cheese whey. It was found that the whey-based formulations reduced the development time and stability of the dough in the farinograph, which could be due to their high salt and lactose content. Likewise, as the amount of whey increased, the volume of the bread decreased and the color of the crust became darker, mainly due to the Millard reaction. On the other hand, among the treatments, the one with the highest protein levels was W100 with 12.4% protein; however, W25 (11.4% protein) and W50 (11.9% protein) were well accepted by the evaluators in terms of flavor and texture.

5.3. Single-Cell Protein

Single-cell protein, derived from microbial biomass such as algae, fungi, bacteria, or yeast, has become a viable and sustainable alternative to address the growing global protein deficit [215]. The fermentation process required to produce it requires minimal space and water resources, can use waste substrates, and produces significantly lower carbon emissions compared to conventional animal protein sources. This form of protein has a protein content of between 45% and 70% and includes a full range of amino acid profiles, B vitamins, and essential trace elements [216]. When incorporated into cereal-based matrices, it effectively mitigates lysine and tryptophan deficiencies present in gluten, increases protein density by approximately 15%, and provides bioactive compounds with antioxidant and hypocholesterolemic properties [217]. For example, Mahmoud et al., 2024 [218] evaluated the incorporation of microalgae into a bakery product, in which wheat flour was replaced with 4% flour containing biomass from Chlorella vulgaris, Phaeodactylum tricornutum, and/or Tetraselmis chuii, A 100% wheat control bread was also evaluated. The aim was to assess the impact on the rheological behavior of the dough, its nutritional value, and its bioactive profile. Consequently, C. vulgaris weakened the dough matrix, resulting in a more compact and firm dough. On the other hand, T. chuii and P. tricornutum had no noticeable effect on the volume of the bread. Likewise, all species showed a dark green hue in the bread and increased its nutritional value in terms of protein by 12.18% for C. vulgaris, 11.08% for T. chuii, and 11.31% for P. tricornutum. Similarly, Hernández-López et al., 2023 [219] evaluated the effects of spirulina (Arthrospira sp.) in a bakery product made from four different types of flour: Manitoba (00/251), Ground-force whole wheat flour (whole/126), standard bakery flour (0/W105), and organic bakery flour (2/W66). The biomass partially replaced the wheat at two levels, 1.5% and 2.5%, for all wheat varieties. The results showed that antioxidant capacity increased as the addition of microalgae increased; however, this affected the volume of the bread and gave it a greenish hue. Likewise, in the sensory evaluation, the formulations with 2.5% were well accepted by consumers. On the other hand, formulations with spirulina showed an increase in their nutritional values, particularly the one made with Manitoba at 2.5% with up to 13.2% protein. Single-cell proteins are obtained from microbial cells, usually in dry or purified form, and are characterized by their high protein content and broad amino acid profile. For production, it is important to select strains that grow rapidly, accumulate high levels of protein, and are non-pathogenic [220]. Production also requires adequate substrate preparation, controlled bioreactor conditions, efficient protein separation from the medium, and post-harvest treatments such as enzyme reduction, thermal inactivation, and drying (Figure 4) [221].

Some types of GRAS (Generally Recognized As Safe) microorganisms used are: yeasts with a dry protein content of 40–55% (Saccharomyces cerevisiae, Candida utilis, Kluyveromyces marxianus), filamentous fungi with 43–48% (Fusarium venenatum, Rhizopus oligosporus), microalgae with 60–70% (Arthrospira/Spirulina, Chlorella, Scenedesmus), and bacteria with 50–80% protein (Cupriavidus necator, Methylococcus capsulatus) [222,223] (

Table 3. Microorganisms used to produce single-cell protein and add it to food products.

Microorganism	Protein (%)	Substrate	Production Conditions	Food Applications	Reference
Algae
Arthrospira platensis (“Spirulina”)	55–70	Autotrophic media (water, CO2, mineral nutrients)	Phototrophy in open ponds or photobioreactors; alkaline medium (pH ≈ 9–11) with NaHCO3/CO2; 25–35 °C; continuous, aerobic	Fortification of bread, pasta, cookies, yogurt, and other fermented dairy products	[223]
Arthrospira (Spirulina) platensis	63	Synthetic saline medium	30–35 °C, 16 h of light, continuous cultivation	Food supplements, functional beverages, nutraceuticals	[228]
Gracilaria domingensis	10.5–18.6	Natural coastal cultivation	Seasonal harvesting, without induced cultivation	Direct consumption in salads, dried seaweed, agar	[229]
Palmaria palmata	~35	Marine harvesting	Open sea farming, cold-temperate	Salads, soups, fermented products	[230]
Ulva faciata	Up to 35	Diluted effluent from the sodium carbonate industry	In situ cultivation on contaminated coastline	Direct consumption, effluent purification	[231]
Chlorella sp.	~47.1	Wastewater from the food industry	25–30 °C, pH 6.8–7.2, controlled lighting	Protein flours, powdered supplements, green drinks	[232]
Chlorella salina	22–48	Biodiesel production effluent	Cultivation in photobioreactors	Dietary supplements, food fortification	[233]
Yeasts
Saccharomyces cerevisiae AXAZ-1	~30	Waste mixture: beer bagasse, molasses, whey, potato peelings, and orange peelings	Solid state fermentation; 30 °C; adjusted humidity; pH 4.5–5.0; 5–7 days	Enrichment of animal feed, enrichment of bakery products	[234]
Candida utilis	46.1	Potato starch pulp + wastewater	Submerged aerobic fermentation; 30 °C; 300 rpm; aeration 0.1 vvm; 6 days; pH 7.0	Experimental animal feed (tested on mice), Use for fermented beverages	[235]
Candida utilis ATCC 9950	40.6	Potato wastewater (deproteinized) + glycerol (5%)	Submerged culture at 28 °C; 200 rpm; 72 h; pH 5.0	Feed yeast (food use authorized by GRAS)	[236]
Kluyveromyces marxianus CHY1612	~38	Cheese whey + urea	Continuous aerobic fermentation; 40 °C; pH 3.5; HRT 24 h	Animal feed, plant-based yogurts, probiotic drinks, gluten-free breads	[237]
Bacteria
Methylococcus capsulatus	60–70	Methane or methanol as a carbon source	Submerged and aerobic fermentation in loop bioreactors; methane or biogas as sole carbon/energy source; 35–45 °C; moderately neutral; 48-h batches produce ~10 g biomass L−1	Bacterial flour for aquaculture feed, evaluated in products for human consumption due to its high protein content	[238]
Bacillus subtilis	49.1	Soybean hull	Solid fermentation, 40 °C, 3 days	Potential in the formulation of fermented foods and nutritional enhancers	[239]
Bacillus subtilis	45.40	Hydrolyzed ram’s horn	Liquid culture, 30 °C, pH 7.0, 24 h	Feed, not directly applicable to humans; used in SCP studies	[240]
Bacillus licheniformis CGMCC 1.813	38.21	Residue and water from potato starch processing	32.8 °C, pH 6.67, 1.78% inoculum, 2 days	Use in animal feed; GRAS potential	[241]
Fungi
Fusarium venenatum QuornTMA3/5	44	Glucose derived from starch (syrup), mineral salts, ammonia	Continuous air lift fermenter, glucose as substrate, ~30 °C, pH ≈ 6, highly aerobic; biomass harvested continuously	Meat analog products	[216]
A. niger “strain 2”	6 → 18	Green banana flour	SSF in reactor 15 kg; humidity 42%; incubation 38 °C→30 °C (hot air 60 °C); air 0.8–2.4 m3 h−1; 43 h fermentation (total 60–68 h)	Protein-rich banana flour for animal feed (livestock, shrimp)	[242]
A. niger (wild citrus strain)	25.6	Decolorized lemon pulp (≈14% solids)	“Slurry state” (semi-liquid medium); 30 °C; agitation 220 rpm; pH adjusted to 4.0; 5 days	Protein ingredient and source of pectinase for the citrus industry itself	[243]
A. niger H3 (UV/EMS mutant) + Bacillus licheniformis (two-step fermentation)	46.1	Potato starch pulp and wastewater (15:4 w/w mixture)	Step 1: Solid pre-hydrolysis 4 days (A. niger, 28 °C) → Step 2: Submerged fermentation 6 days; 30 °C; 300 rpm; pH 7.0; 0.1 vvm air	Flour for animal feed (palatability validated in mice)	[244,245]

). Similarly, there is research in which microalgae have been used to enrich wheat-based breads with a substitution of between 1–6% spirulina; however, microalgae impart a green color, which affects consumer acceptance [224]. Microalgae or textured yeast have also been added to extruded snacks and energy bars. They have even been added to dairy products with the addition of casein from the single-cell protein Candida utilis [225]. These proteins serve to partially reinforce the protein network and improve water retention capacity [226]. However, excessive amounts can lead to a reduction in gluten concentration, which could cause a decrease in bread volume of up to 22% or an increase in crumb firmness. Nevertheless, these negative effects can be mitigated by making appropriate adjustments to hydration levels and kneading time [227].

6. Challenges in the Use of Alternative Protein Ingredients

Wheat-based formulations are widely studied and standardized and are considered the benchmark for textural and sensory properties in bakery products. For this reason, when developing products with alternative flours, the goal is to make them as similar as possible to traditional wheat bread [96,246]. Consequently, it is important to focus research on each stage of production—mixing, kneading, proofing, and baking—to determine the optimal point for obtaining the best rheological and flavor properties in the dough and the final product [247]. The partial replacement of wheat flour is mainly justified by sustainability and health considerations; however, this transition faces multiple technological, sensory, cultural, and regulatory obstacles [248,249]. It is widely reported that when bread is made with other types of flour, it exhibits increased darkening, increased crumb hardness, volume loss, crumb deterioration due to an imbalance in the protein–starch–water network, and changes in starch retrogradation [250,251]. According to reports, tests with breads partially substituted with alternative flours such as other types of cereals, legumes, and oilseeds show acceptable rheological properties in a low substitution range of ≈5–20%, while higher substitutions tend to significantly modify rheological and sensory properties [252,253]. Despite research focusing on substituting or replacing wheat consumption in bakery products, this has been limited to pilot tests due to low consumer acceptance, with a large percentage unaware of the nutritional benefits of this change [254,255].

Another obstacle to consider is obtaining approval for consumption. However, it is not only a matter of allowing the use of emerging ingredients such as insect-derived flours and single-cell protein, but it is also important to analyze possible contaminants, allergens, toxins, additives, and physicochemical parameters in greater depth [256,257]. In the European Union (EU), Regulation 1169/2011 (consumer information) [258] imposes strict rules on the clear presentation of information, especially novel ingredients, as well as a declaration of allergens (such as lupin, nuts, sesame, etc.) (Malila et al., 2024 [259]). Similarly, Regulation (EU) 2015/2283 (Novel Foods) [260] requires specific authorizations for innovative flours, making it necessary to test each ingredient to rule out any risk to consumers (Grundy et al., 2024 [261]). On the other hand, the Codex Alimentarius Commission, Standard for Wheat Flour (CXS 152-1985), 1985, revised 2016–2021 [262], requests information on contaminants, residues, and additives that apply to supply and control when formulating mixtures in this type of composite product (Wang & Jian et al., 2022 [96]; Boukid & Gagaoua et al., 2020 [263]). In addition, the FDA (Food and Drug Administration)—(21 CFR Part 136: “Bakery Products Standards of Identity)” [264] defines the standards of identity for breads, rolls, and similar products in the US, so when unconventional flours are substituted or added, it must be evaluated whether the product complies with the standard and whether it is necessary to change the name or designation. Likewise, the FDA—“Food Labeling Guide” (2025) (Program, 2025) [265] indicates the current requirements for nutritional labeling, allergen ingredient declarations, and formulation. Similarly, the FAO (Food and Agriculture Organization)/WHO (World Health Organization) Codex—“CXS 192-1995: General Standard for Food Additives (GSFA)” [262] establishes the list of additives and conditions for use by category, which is essential for adjusting formulations in bakery products with non-conventional flours.

7. Final Remarks

The integration of alternative proteins into wheat-based matrices serves as an effective strategy to enhance the protein content and adjust the glycemic index of baked goods by partially substituting rapidly digestible carbohydrates. The alternatives with substantial technological validation comprise non-wheat cereals, legumes, whey protein (both isolates and concentrates), single-cell proteins derived from microorganisms, and insect proteins. The combination of these proteins with soluble fibers (such as β-glucans and arabinoxylans) and starches exhibiting reduced enzymatic susceptibility encourages a more moderated glycemic response while maintaining adequate energy intake.

From a technological standpoint, the primary challenge lies in achieving an equilibrium between rheological characteristics and gas retention subsequent to the partial substitution of wheat. To ensure industrial viability, it is imperative to carry out tests involving gradual substitutions, while validating each formulation through standardized protocols encompassing composition, alveography or rheometry, specific volume, gelatinization properties, texture, shelf life, and sensory acceptance. In conclusion, the successful development of functional breads necessitates a formulation design grounded in evidence-based principles, optimization of processing techniques, and comprehensive sensory evaluation to accomplish the performance triangle of enhanced nutrition, sensory acceptance, and sustainable scalability within the industry.