Special Issue "Milk and Dairy Products: Linking the Chemistry, Structure, Processing, and Food Properties"

A special issue of Foods (ISSN 2304-8158). This special issue belongs to the section "Dairy".

Deadline for manuscript submissions: 10 March 2023 | Viewed by 13851

Special Issue Editors

Prof. Dr. Song Miao
E-Mail Website
Guest Editor
Department of Food Chemistry and Technology, Teagasc Food Research Centre, Moorepark, Fermoy, P61 C996 Cork, Ireland
Interests: physio-chemical properties of biomaterials; dehydration and granulation; dairy technology; foods structural and textual designs; powder technology; state transition and phase transition in foods; encapsulation of functional food ingredients; functional delivery; stabilization of probiotic and dairy ingredients; plant-based ingredients
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Peng Zhou
E-Mail Website
Guest Editor
State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China
Interests: structure and functionality of dairy proteins; development and application of new dairy ingredients; functional dairy foods and healthy diet

Special Issue Information

Dear Colleagues,

At present, milk and dairy products represent an important component of the diet of humans of all ages, and understanding the different milk constituents and their contribution to the structure, texture, consumer acceptability, and nutritional value of dairy products during processing is very important. New milk sources are emerging and are foreseen to contribute new qualities to existing products. The structural and sensory properties of the dairy products vary significantly depending on the chemistry of milk from different sources and or animal species (e.g., buffalo, goat, sheep, camel, donkey). In this Special Issue we welcome you to contribute submissions (including original research and current review articles) on the chemistry of milk from different animal species, and its effects on the structural, sensory and nutritional value of processed products and the relation between composition, processing and product functionality, with topics such as:

  • Correlations between chemistry, structure and function, and their relations to milk characteristics;
  • The performance of milk from different animal species/breeds during processing and how it affects the structure and sensory properties of the processed dairy products;
  • Effect of processing technologies (traditional and novel) as strategies for quality maintenance or improvement of the main milk components and dairy products (e.g., physical and chemical properties, nutritional value, sensory characteristics).

Prof. Dr. Song Miao
Prof. Dr. Peng Zhou
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Foods is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

  • milk
  • dairy products
  • bovine and non-bovine milk
  • chemistry
  • structure
  • processing
  • sensory quality
  • nutritional quality

Published Papers (15 papers)

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Research

Article
Lipid Profiles of Human Milk and Infant Formulas: A Comparative Lipidomics Study
Foods 2023, 12(3), 600; https://doi.org/10.3390/foods12030600 - 01 Feb 2023
Viewed by 293
Abstract
Infant formulas (IFs) are prevalent alternatives for human milk (HM), although their comparative lipid profiles have not been fully investigated. We adopted lipidomics to analyze and compare in-depth the lipid patterns of HM and IFs. The results indicated that the distribution of fatty [...] Read more.
Infant formulas (IFs) are prevalent alternatives for human milk (HM), although their comparative lipid profiles have not been fully investigated. We adopted lipidomics to analyze and compare in-depth the lipid patterns of HM and IFs. The results indicated that the distribution of fatty acids (FAs) and the structure of triacylglycerols varied substantially in the analyzed samples. A total number of 425 species were identified during the analysis. HM was abundant in triacylglycerols that contained unsaturated and long-chain FAs (>C13), while triacylglycerols in IFs were mainly comprised of saturated and medium-chain FAs (C8−C13). Higher levels of sphingomyelin were observed in HM. Furthermore, HM and IF1 contained 67 significantly differential lipids (SDLs), and 73 were identified between HM and IF2. These SDLs were closely associated with nine metabolic pathways, of which the most significant was the glycerophospholipid metabolism. The results shed light on the differences between the lipid profiles of human and infant formula milks, and provide support for designing Chinese infant formula. Full article
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Article
Plant Protein versus Dairy Proteins: A pH-Dependency Investigation on Their Structure and Functional Properties
Foods 2023, 12(2), 368; https://doi.org/10.3390/foods12020368 - 12 Jan 2023
Viewed by 614
Abstract
Plant proteins are constantly gaining attention as potential substitutes for dairy proteins, due to their suitable functionality and nutritional value. This study was designed to compare the structural and functional responses of different plant protein isolates (soy, pea, lentil, and chickpea) with two [...] Read more.
Plant proteins are constantly gaining attention as potential substitutes for dairy proteins, due to their suitable functionality and nutritional value. This study was designed to compare the structural and functional responses of different plant protein isolates (soy, pea, lentil, and chickpea) with two commonly used dairy protein (whey protein isolates and sodium caseinate) under different pH treatments (pH 3.0, 5.0, 7.0, and 9.0). The results showed that pH had a different alteration on the structural, surface properties and functional properties of plant and dairy proteins. Plant protein generally possessed a darker color, lower solubility, emulsifying properties, and foaming capacity, whereas their foaming stability and water holding capacity were higher than those of dairy proteins. Soy protein isolates were characterized by its comparable proportion of β-turn and random coils, zeta-potential, emulsifying (30.37 m2/g), and water-holding capacity (9.03 g/g) at alkaline conditions and chickpea protein isolates showed good oil-holding capacity (3.33 g/g at pH 9) among plant proteins. Further analysis confirmed that pH had a greater influence on the structural and functional properties of proteins as compared to protein sources, particularly at acidic conditions. Overall, this study might help processors select the appropriate plant protein as dairy alternatives for their target application in plant-based food products. Full article
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Article
Effect of Different Polymerization Degrees and Fatty Acids of Polyglycerol Esters on the Physical Properties and Whippability of Recombined Dairy Cream
Foods 2023, 12(1), 22; https://doi.org/10.3390/foods12010022 - 21 Dec 2022
Viewed by 536
Abstract
Polyglycerol esters (PGEs) are used as emulsifiers in recombined dairy cream (RDC) to improve product quality. In this study, the effects of four PGEs with different polymerization degrees and esterification on the particle size, viscosity, zeta potential, and microrheology of RDC emulsions were [...] Read more.
Polyglycerol esters (PGEs) are used as emulsifiers in recombined dairy cream (RDC) to improve product quality. In this study, the effects of four PGEs with different polymerization degrees and esterification on the particle size, viscosity, zeta potential, and microrheology of RDC emulsions were investigated, and the whipping time, overrun, serum loss, and firmness of the RDC emulsions were recorded. The results show that the addition of the PGEs reduced the particle size (from 2.75 μm to 1.48–1.73 μm) and increased the viscosity (from 41.92 cP to 73.50–100 cP) and stability (from 0.354 to 0.105–0.128), which were related to the change in interfacial properties and the weakening of Brownian motion, but there were differences in the effect on the whipping behavior of the RDCs. Although the addition of 0.9% triglyceride monolaurate gave the emulsion the best stability, the RDC had a longer whipping time (318 s) and a lower overrun (116.6%). Comparatively, the 0.7–0.9% concentrations of PGE55 and tripolycerol monostearate (TMS) provided RDC with good stability and aeration characteristics, allowing inflation within 100 s and expansion rates of up to 218.24% and 186.88%, respectively. In addition, the higher degree of polymerization of polyglyceryl-10 monstearate (PMS) did not work well at any concentration. These results contribute to understanding the mechanism of action of PGEs and improving the quality of RDC. Full article
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Article
Changes in Milk Fat Globules and Membrane Proteins Prepared from pH-Adjusted Bovine Raw Milk
Foods 2022, 11(24), 4107; https://doi.org/10.3390/foods11244107 - 19 Dec 2022
Viewed by 979
Abstract
Milk fat globules (MFGs) have tri-layer biological membrane structures, and their compositions are gaining more interest for their physiological benefits. In this study, the changes in MFGs and milk fat globule membrane (MFGM) proteins after cream separation from different pH bovine raw milk [...] Read more.
Milk fat globules (MFGs) have tri-layer biological membrane structures, and their compositions are gaining more interest for their physiological benefits. In this study, the changes in MFGs and milk fat globule membrane (MFGM) proteins after cream separation from different pH bovine raw milk were investigated. Raw milk samples were adjusted to pH 5.30 and 6.30 using citric acid at 25 °C. The effect of pH and centrifugation on the structure of MFGs was evaluated by means of particle size, zeta potential and confocal laser scanning microscopy (CLSM). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to analyze the proteins in the obtained fractions. It was found that both pH and centrifugation could affect the particle size of all samples. As the volume distribution (Dv; Dv (10), Dv(50)and Dv (90)) decreased, the corresponding specific surface area (SSA) increased, and span and uniformity values showed the same trend. The decrease in the zeta potential of MFG correlated with the Dv(50), which was further confirmed by CLSM observation. More butyrophilin (BTN) and periodic acid Schiff 6/7 (PAS 6/7) were lost in cream samples at pH 5.30. The findings could provide valuable knowledge for the application of MFGs ingredient in the food industry since their structures and compositions could affect their potential functional and physiological properties. Full article
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Article
Impact of Flaxseed Gums on the Colloidal Changes and In Vitro Digestibility of Milk Proteins
Foods 2022, 11(24), 4096; https://doi.org/10.3390/foods11244096 - 18 Dec 2022
Viewed by 629
Abstract
Flaxseed (Linum usitatissimum L.) mucilage is one of the most studied plant seed gums in terms of its techno-functional and health-promoting properties. Nonetheless, the interplay of flaxseed gum (FG) with other food biopolymers, such as milk proteins, under in vitro digestion conditions [...] Read more.
Flaxseed (Linum usitatissimum L.) mucilage is one of the most studied plant seed gums in terms of its techno-functional and health-promoting properties. Nonetheless, the interplay of flaxseed gum (FG) with other food biopolymers, such as milk proteins, under in vitro digestion conditions remains underexplored. The aim of the present work was to investigate the colloidal interplay between flaxseed gum (golden or brown) and milk proteins (sodium caseinate or whey protein isolate) under simulated in vitro digestion conditions and its relationship with the attained in vitro protein digestibility. The presence of flaxseed gum in the milk protein food models and in the oral food boluses obtained was associated with the occurrence of segregative microphase separation. Flaxseed gum exhibited a prominent role in controlling the acid-mediated protein aggregation phenomena, particularly in the sodium caseinate gastric chymes. The addition of FG in the food models was associated with a higher amount of intact total caseins and β-lactoglobulin at the end of the gastric processing step. Monitoring of the intestinal processing step revealed a very advanced cleavage of the whey proteins (>98%) and caseins (>90%). The degree of the milk protein hydrolysis achieved at the end of the intestinal processing was significantly higher in the systems containing flaxseed gum (i.e., 59–62%) than their gum-free protein counterparts (i.e., 46–47%). It was postulated that the electrostatic milk protein complexation capacity and, to a lesser extent, the thickening effect of flaxseed gum influenced the in vitro digestibility of the milk proteins. Full article
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Article
Major Causes of Variation of External Appearance, Chemical Composition, Texture, and Color Traits of 37 Categories of Cheeses
Foods 2022, 11(24), 4041; https://doi.org/10.3390/foods11244041 - 14 Dec 2022
Viewed by 454
Abstract
Cheeses are produced by many different procedures, giving rise to many types differing in ripening time, size, shape, chemical composition, color, texture, and sensory properties. As the first step in a large project, our aim was to characterize and quantify the major sources [...] Read more.
Cheeses are produced by many different procedures, giving rise to many types differing in ripening time, size, shape, chemical composition, color, texture, and sensory properties. As the first step in a large project, our aim was to characterize and quantify the major sources of variation in cheese characteristics by sampling 1050 different cheeses manufactured by over 100 producers and grouped into 37 categories (16 with protected designation of origin, 4 traditional cheese categories, 3 pasta filata cheese categories, 5 flavored cheese categories, 2 goat milk categories, and 7 other categories ranging from very fresh to very hard cheeses). We obtained 17 traits from each cheese (shape, height, diameter, weight, moisture, fat, protein, water soluble nitrogen, ash, pH, 5 color traits, firmness, and adhesiveness). The main groups of cheese categories were characterized and are discussed in terms of the effects of the prevalent area of origin/feeding system, species of lactating females, main cheese-making technologies, and additives used. The results will allow us to proceed with the further steps, which will address the interrelationships among the different traits characterizing cheeses, detailed analyses of the nutrients affecting human health and sensorial fingerprinting. Full article
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Article
Comparative Peptidomics Analysis of Milk Fermented by Lactobacillus helveticus
Foods 2022, 11(23), 3885; https://doi.org/10.3390/foods11233885 - 01 Dec 2022
Viewed by 508
Abstract
Lactobacillus helveticus is one of the commonly used starter cultures for manufacturing various fermented dairy products. However, only a few studies have explored the cleavage region preference of L. helveticus with different cell envelope proteinase (CEP) genes. In the present study, we profiled [...] Read more.
Lactobacillus helveticus is one of the commonly used starter cultures for manufacturing various fermented dairy products. However, only a few studies have explored the cleavage region preference of L. helveticus with different cell envelope proteinase (CEP) genes. In the present study, we profiled the peptide composition of milk samples fermented by three different L. helveticus strains by means of peptidomics to illustrate their different proteolysis patterns. The result revealed that the differences in peptide profiles of milk samples fermented by different L. helveticus strains were mainly a result of variations in the peptide patterns of the casein fractions, which were correlated with CEP genotypes. This was mainly reflected in the extensiveness of the hydrolysis region of αS1-casein and the degree of β-casein hydrolysis. Bioactive peptides were mostly derived from the hydrolysis region common to the three L. helveticus strains, and DQHXN-Q32M42 fermentation resulted in the highest diversity and abundance of bioactive peptides and a significant antihypertensive effect in spontaneous hypertension rats. Full article
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Article
Incorporation of Blue Honeysuckle Juice into Fermented Goat Milk: Physicochemical, Sensory and Antioxidant Characteristics and In Vitro Gastrointestinal Digestion
Foods 2022, 11(19), 3065; https://doi.org/10.3390/foods11193065 - 02 Oct 2022
Viewed by 655
Abstract
The addition of fruit juice may improve the physicochemical and functional characteristics of dairy products. The study evaluated the effect of 1–6% (v/v) blue honeysuckle juice (BHJ) on the physicochemical, sensory and antioxidant characteristics of fermented goat milk (FGM) [...] Read more.
The addition of fruit juice may improve the physicochemical and functional characteristics of dairy products. The study evaluated the effect of 1–6% (v/v) blue honeysuckle juice (BHJ) on the physicochemical, sensory and antioxidant characteristics of fermented goat milk (FGM) during 21 days of refrigerated storage and in vitro gastrointestinal digestion. The incorporation of BHJ significantly increased (p < 0.05) the water-holding capacity, viscosity, redness (a*) value, total phenolic content (TPC) and ferric ion-reducing antioxidant power during storage. Additionally, BHJ affected the microstructure and sensory score of the samples. FGM treated with 4% (v/v) BHJ exhibited the highest overall acceptability. The supplementation of BHJ diminished the goaty flavor and promoted in vitro protein digestion. Furthermore, the TPC was enhanced in addition to the antioxidant activity of FGM containing BHJ throughout the in vitro digestion. Therefore, FGM supplemented with BHJ serves as a novel and attractive goat dairy product. Full article
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Article
Changes in Caprine Milk Fat Globule Membrane Proteins after Heat Treatment Using a Label-Free Proteomics Technique
Foods 2022, 11(17), 2705; https://doi.org/10.3390/foods11172705 - 05 Sep 2022
Viewed by 697
Abstract
Milk proteins are prone to changes during the heat treatment process. Here, we aimed to study the changes in caprine milk fat globule membrane (MFGM) proteins with three heat treatment processes—ultra-pasteurization (85 °C, 30 min), ultra-high-temperature instant sterilization (135 °C, 5 s), and [...] Read more.
Milk proteins are prone to changes during the heat treatment process. Here, we aimed to study the changes in caprine milk fat globule membrane (MFGM) proteins with three heat treatment processes—ultra-pasteurization (85 °C, 30 min), ultra-high-temperature instant sterilization (135 °C, 5 s), and spray-drying (inlet, 160 °C and outlet, 80 °C)—using the label-free proteomics technique. A total of 1015, 637, 508, and 738 proteins were identified in the raw milk, ultra-pasteurized milk, ultra-high-temperature instant sterilized milk, and spray-dried reconstituted milk by using label-free proteomics techniques, respectively. Heat treatment resulted in a significant decrease in the relative intensity of MFGM proteins, such as xanthine dehydrogenase/oxidase, butyrophilin subfamily 1 member A, stomatin, and SEA domain-containing protein, which mainly come from the membrane, while the proteins in skimmed milk, such as β-lactoglobulin, casein, and osteopontin, increased in MFGM after heat treatment. Among these different heat treatment groups, the procedure of spray-drying resulted in the least abundance reduction of caprine milk MFGM proteins. Additionally, it showed heating is the key process affecting the stability of caprine MFGM protein rather than the spray-drying process. These findings provide new insights into the effects of heat treatment on caprine MFGM protein composition and potential biological functions. Full article
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Article
Evolution of Volatile Compounds during Ripening and Final Sensory Changes of Traditional Raw Ewe’s Milk Cheese “Torta del Casar” Maturated with Selected Protective Lactic Acid Bacteria
Foods 2022, 11(17), 2658; https://doi.org/10.3390/foods11172658 - 01 Sep 2022
Cited by 1 | Viewed by 590
Abstract
In traditional soft ripened cheeses made with raw milk, the use of protective cultures is infrequent. In the present work, the effect of selected (for their activity against Listeria monocytogenes) protective cultures of Lactocaseibacillus casei 116 and Lactococcus garvieae 151 was evaluated, [...] Read more.
In traditional soft ripened cheeses made with raw milk, the use of protective cultures is infrequent. In the present work, the effect of selected (for their activity against Listeria monocytogenes) protective cultures of Lactocaseibacillus casei 116 and Lactococcus garvieae 151 was evaluated, on the evolution of volatile compounds throughout the ripening and on the final sensory characteristics of traditional soft ripened “Torta del Casar” cheese. For this, both strains were separately inoculated in raw cheeses and ripened for 90 days. The selected LAB strains did not affect physicochemical parameters, including texture and color of the ripened cheeses. However, they could have a positive effect on the aroma, for the generation of methyl branched acids and for the reduction in compounds derived from β-oxidation of fatty acids. Thus, these protective cultures, in addition to contributing to their safety, could improve quality of the ripened cheeses. Full article
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Article
Soybean-Oil-Body-Substituted Low-Fat Ice Cream with Different Homogenization Pressure, Pasteurization Condition, and Process Sequence: Physicochemical Properties, Texture, and Storage Stability
Foods 2022, 11(17), 2560; https://doi.org/10.3390/foods11172560 - 24 Aug 2022
Viewed by 768
Abstract
The purpose of this research was to explore the impacts of different homogenization pressures, pasteurization conditions, and process sequence on the physical and chemical properties of soybean oil body (SOB)-substituted low-fat ice cream as well as the storage stability of SOB-substituted ice cream [...] Read more.
The purpose of this research was to explore the impacts of different homogenization pressures, pasteurization conditions, and process sequence on the physical and chemical properties of soybean oil body (SOB)-substituted low-fat ice cream as well as the storage stability of SOB-substituted ice cream under these process parameters. With the increase of homogenization pressure (10–30 MPa), the increase of pasteurization temperature (65 °C for 30 min–85 °C for 15 min), and the addition of SOB before homogenization, the overrun and apparent viscosity of ice cream increased significantly, and the particle size, hardness, and melting rate decreased significantly. Thus, frozen dairy products of desired quality and condition could be obtained by optimizing process parameters. In addition, the SOB ice cream showed better storage stability, which was reflected in lower melting rate and hardness and more stable microstructure compared with the full-milk-fat ice cream. This study opened up new ideas for the application of SOB and the development of nutritious and healthy ice cream. Meanwhile, this research supplied a conceptual basis for the processing and quality optimization of SOB ice cream. Full article
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Communication
Effects of Drying Methods on Serum Protein Powder Properties
Foods 2022, 11(14), 1996; https://doi.org/10.3390/foods11141996 - 06 Jul 2022
Viewed by 726
Abstract
This study investigated the effects of atmospheric spray drying (ASD), low-pressure spray drying (LPSD) and freeze drying (FD) on the properties of serum protein powder, including the basic characteristics of the powder, bioactive proteins and changes in protein profile, using a proteomics approach. [...] Read more.
This study investigated the effects of atmospheric spray drying (ASD), low-pressure spray drying (LPSD) and freeze drying (FD) on the properties of serum protein powder, including the basic characteristics of the powder, bioactive proteins and changes in protein profile, using a proteomics approach. The total solid and water activity of the powder obtained by FD was significantly higher than that obtained by ASD and LPSD. There was no significant difference in the content of fat, lactose or solubility between the three kinds of powders. The concentration and activity of the proteins/enzymes in the serum protein powder made from LPSD were not altered after drying, similar to FD, although both parameters decreased after ASD. The microstructure of the powder observed by scanning electron microscopy indicated that the powder manufactured by ASD and LPSD was spherical in structure, while that manufactured by FD was flake-like. In total, there were 245 proteins identified in the serum protein concentrate and powder from the three drying methods. These findings indicate that LPSD is an effective and cost-saving method for producing serum whey protein powder. Full article
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Article
The Effect of Heat Treatment on Cow’s Milk Protein Profiles
Foods 2022, 11(7), 1023; https://doi.org/10.3390/foods11071023 - 31 Mar 2022
Cited by 2 | Viewed by 1460
Abstract
Milk is a food of high nutritional value processed by heat treatment. Heat treatment of milk is a technological process designed to inhibit the growth of microorganisms and extend the shelf life of products. The heating process directly affects the molecular structure of [...] Read more.
Milk is a food of high nutritional value processed by heat treatment. Heat treatment of milk is a technological process designed to inhibit the growth of microorganisms and extend the shelf life of products. The heating process directly affects the molecular structure of whey proteins by the process of denaturation. It leads to the formation of a whey protein–casein polymer complex. Based on these facts, milk heat-treatment conditions should be controlled during milk processing. This work focuses on describing the whey protein denaturation process and formation of the complex of whey protein with casein. The effect of heat treatment on individual milk protein fractions alpha-casein (α-cas), beta-casein (β-cas), kappa-casein (κ-cas), beta-lactoglobulin (β-lg) and alpha-lactalbumin (α-la) was studied by SDS-PAGE. Formation of the whey protein–casein polymer complex increased significantly (p < 0.05) on increasing the temperature and duration of the heat treatment. Full article
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Article
Microstructural, Physicochemical, Microbiological, and Organoleptic Characteristics of Sugar- and Fat-Free Ice Cream from Buffalo Milk
Foods 2022, 11(3), 490; https://doi.org/10.3390/foods11030490 - 08 Feb 2022
Cited by 2 | Viewed by 1835
Abstract
Ice cream is a popular dessert product across the world. Structure, body, taste, and odor properties are created by adding non-milk ingredients and milk ingredients. The main aim of the study is to decrease the caloric value of ice cream by using sugar [...] Read more.
Ice cream is a popular dessert product across the world. Structure, body, taste, and odor properties are created by adding non-milk ingredients and milk ingredients. The main aim of the study is to decrease the caloric value of ice cream by using sugar and fat replacements. Ice cream treatments were investigated based on microstructural, chemical, physical, microbiological, sensory, and calorific values. Four different ice creams were used (control ice cream (SC1), ice cream with stevia (SC2), ice cream with sucralose (SC3), and ice cream with sorbitol (SC4)). The chemical properties in all treatments of ice cream were significantly recorded (p < 0.05). The highest sucrose and fat levels were detected in the SC1 treatment compared with the other treatments (p < 0.05). The lowest fat and sugar amounts were observed in the SC2, SC3, and SC4 treatments (p < 0.05). The highest viscosity, overrun, and hardness values (p < 0.05) were detected in the control ice cream. Total aerobic mesophilic bacterial counts were not significantly recorded between different ice cream treatments (p < 0.05). The sensory scores were not significantly affected by sweeteners and bulk agents in the different treatments. The highest calorific value was calculated in the SC1 samples (p < 0.05). On the other hand, the lowest calorific value was calculated in SC2, followed by the SC3 and SC4 treatments. In scanning electron microscopy (SEM), the gel exhibited a homogeneous structure with a fine network within the SC2, SC3, and SC4 treatments, as it contained a cohesive structure with small-sized pores. Full article
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Article
The Effect of High Protein Powder Structure on Hydration, Glass Transition, Water Sorption, and Thermomechanical Properties
Foods 2022, 11(3), 292; https://doi.org/10.3390/foods11030292 - 21 Jan 2022
Viewed by 1803
Abstract
Poor solubility of high protein milk powders can be an issue during the production of nutritional formulations, as well as for end-users. One possible way to improve powder solubility is through the creation of vacuoles and pores in the particle structure using high [...] Read more.
Poor solubility of high protein milk powders can be an issue during the production of nutritional formulations, as well as for end-users. One possible way to improve powder solubility is through the creation of vacuoles and pores in the particle structure using high pressure gas injection during spray drying. The aim of this study was to determine whether changes in particle morphology effect physical properties, such as hydration, water sorption, structural strength, glass transition temperature, and α-relaxation temperatures. Four milk protein concentrate powders (MPC, 80%, w/w, protein) were produced, i.e., regular (R) and agglomerated (A) without nitrogen injection and regular (RN) and agglomerated (AN) with nitrogen injection. Electron microscopy confirmed that nitrogen injection increased powder particles’ sphericity and created fractured structures with pores in both regular and agglomerated systems. Environmental scanning electron microscopy (ESEM) showed that nitrogen injection enhanced the moisture uptake and solubility properties of RN and AN as compared with non-nitrogen-injected powders (R and A). In particular, at the final swelling at over 100% relative humidity (RH), R, A, AN, and RN powders showed an increase in particle size of 25, 20, 40, and 97% respectively. The injection of nitrogen gas (NI) did not influence calorimetric glass transition temperature (Tg), which could be expected as there was no change to the powder composition, however, the agglomeration of powders did effect Tg. Interestingly, the creation of porous powder particles by NI did alter the α-relaxation temperatures (up to ~16 °C difference between R and AN powders at 44% RH) and the structural strength (up to ~11 °C difference between R and AN powders at 44% RH). The results of this study provide an in-depth understanding of the changes in the morphology and physical-mechanical properties of nitrogen gas-injected MPC powders. Full article
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