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Article

Characteristics of Molecular Properties of Carbohydrates and Melanoidins in Instant Coffee and Coffee Substitutes

by
Krzysztof Buksa
* and
Michał Szczypek
Department of Carbohydrate Technology and Cereal Processing, University of Agriculture in Krakow, Balicka 122, 30-149 Krakow, Poland
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(23), 12627; https://doi.org/10.3390/app152312627
Submission received: 20 October 2025 / Revised: 13 November 2025 / Accepted: 25 November 2025 / Published: 28 November 2025
(This article belongs to the Special Issue Food Polysaccharides: Chemistry, Technology and Applications)
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Abstract

The aim of this study was to compare, under standardized conditions, the content and molecular properties of carbohydrates occurring in extracts from roasted coffee beans and in coffee substitutes made from roasted chicory root, barley, wheat, spelt, and rye. The study revealed an over 8% higher carbohydrate content, primarily polysaccharides of a molar mass greater than 1800 g/mol, in instant Arabica coffee extract compared to Robusta coffee. Significant differences were also demonstrated in the carbohydrate composition of Arabica and Robusta coffee extracts, as well as coffees obtained using laboratory and industrial methods. Coffee substitutes generally contained more polysaccharides and two to five times more oligosaccharides of a molar mass ranging from 400 to 1800 g/mol, and consequently, total carbohydrates, compared to coffee extracts. The high oligosaccharide contents (11–25%) of very diverse monosaccharide composition found in instant coffee substitutes indicate the potential prebiotic effects of these products. The highest melanoidin content among instant coffee extracts and coffee substitutes was found in a coffee substitute made from roasted chicory. Furthermore, extract from Arabica coffee contained higher amounts of melanoidins than Robusta coffee.

1. Introduction

Coffee, an infusion made from ground, roasted coffee beans, is considered one of the most widely consumed beverages in the world. Its flavor, aroma, and caffeine content are key reasons for its popularity [1]. Coffee is a complex chemical mixture consisting of over a thousand different chemicals [2].
Coffee has been known in Europe only since the 16th century, when Leonhard Rauwolf described it in his diaries from his travels in the Middle East [3]. Previously, decoctions made from grains or spices were popular in Europe. The production of instant extracts made from grains, a substitute for real coffee, flourished in the mid-20th century. The global geopolitical situation contributed to the significant increase in the production of coffee substitutes. Coffee substitutes owe their popularity to their pleasant taste and good solubility [4].
Currently, real coffee comes in many forms, such as whole-bean roasted coffee, ground roasted coffee, powdered coffee, decaffeinated coffee, instant coffee, agglomerated coffee, and freeze-dried coffee [5,6]. Coffee substitutes come in the form of ground roasted coffee beans or dried instant extracts (agglomerate or freeze-dried) [7].
Polyphenols, terpenes, and caffeine are among well-known substances contained in coffee [8]. Coffee substitutes also contain numerous bioactive substances. It is important to note that coffee substitutes, unlike real coffee, do not contain caffeine or harmful oxalates [9]. A coffee substitute containing chicory adds a great amount of dietary fiber in the form of inulin, which is classified as a prebiotic [10]. Chicory root contains fructooligosaccharides, which selectively stimulate the growth of Bifidobacteria, which can suppress pathogens [11,12,13,14].
Even though carbohydrates constitute the dominant part of real coffee extracts in terms of quantity [15,16,17,18] and coffee substitutes [4], there is a noticeable lack of information in the publications to date on the carbohydrate composition and the size of carbohydrate molecules in extracts constituting coffee substitutes.
Studies conducted so far have shown that Arabica coffee extracts contain more polysaccharides than Robusta coffee [16,19]. The main carbohydrate fractions of true coffees are mannans or galactomannans, arabinogalactans, arabinogalactomannans, cellulose, and pectins [20,21].
It has also been shown that the coffee roasting process affects the depolymerization of polysaccharides and reduces the total carbohydrate content in coffee [20,21,22,23,24,25,26,27].
Maillard reactions occur during coffee roasting. Reducing sugars react with amino acids, leading to chemical transformations. In the final roasting stage, melanoidins are formed from sugars, amino acids, peptides, and phenolic acids [28,29,30,31].
The most popular raw materials for the production of coffee substitutes are chicory root [32] and barley grain [33]. Coffee substitutes, depending on the raw materials used in their production, may contain polyphenols, inulin, soluble fiber, and mineral salts [34,35,36]. It should be noted that coffee substitutes are appreciated by consumer groups who cannot consume caffeine, such as pregnant women or children.
The main carbohydrate found in coffee substitutes made from roasted cereal grains is starch, while inulin is the main polysaccharide found in coffee substitutes made from chicory root [4,37]. Data in the literature indicate that coffee substitutes also contain non-starch polysaccharides, including pectins [33,34,35,37,38,39].
It should be emphasized, however, that data on the content, molecular structure, and molecular weight of carbohydrates in coffee substitutes are fragmentary and incomplete. Due to the authors’ use of different carbohydrate analysis methods, there is also a lack of a proper comparison of the carbohydrate composition of instant coffees and coffee substitutes. The literature lacks information on the content and molecular properties of melanoidins in coffee substitutes.
The goal of this study was to characterize under standardized conditions the molecular properties of carbohydrates and melanoidins in instant products from coffee and coffee substitutes.

2. Materials and Methods

Research material consisted of the following products purchased on the local market:
-
Roasted coffee beans 100% C. Arabica (AB) and 100% C. canephora (Robusta, RB);
-
Lyophilized instant coffee powders of two commercially available brands (L1 and L2);
-
Coffee substitutes (instant) produced from roasted chicory root (C), roasted barley grains (B), roasted spelt wheat grains (S), and a blend of roasted grains of barley and rye, and chicory root (BRC).
To limit the influence of sample variability in the case of roasted coffee beans and samples L1, L2, and coffee substitutes (C, B, S, and BRC), three batches were mixed together before use in research.

2.1. Preparation of Lyophilized Samples of Arabica and Robusta Coffee Beans

Roasted coffee beans (AB and RB samples) were grounded using a knife mill (Bosch, Gerlingen, Germany).
In order to prepare coffee extracts (AR-EX and RO-EX), 4 g of grounded coffee was weighed and brewed in 400 mL of 95 °C water for 4 min. After 4 min, the suspension was filtered through paper filter (Filter Discs, Qual, Grade 3W, 65 g/m2), until 400 mL of brew was obtained. Extracts were placed in vessels and frozen at −18 °C. Frozen samples were lyophilized in a freeze-dryer (Labconco, Kansas City, MO, USA). To calculate the yield of obtained instant coffee, the obtained lyophilized samples were weighed.

2.2. Determination of Dry Basis Content in Instant Coffee and Coffee Substitutes

Dry basis content was determined by the gravimetric method according to ISO-11294-1994 by drying samples at 103 °C for 2 h and weighing [40].

2.3. Determination of the Caffeine Content in the Samples

Caffeine content was determined according to [41] using the chromatographic system (Knauer, Berlin, Germany) equipped with column AQUASIL C18 (250 × 4 mm), at 25 °C, and a UV detector operating at 278 nm. The mobile phase was water–THF (0.1% THF in water, pH 8)–acetonitrile (90:10, v/v), and the flow rate was 0.8 mL/min. The extracts were filtered through a filter paper to remove the particulate matter. Ten milliliters of filtrate, adjusted to pH 8 with 0.1 M NaOH, were subjected to the cleanup procedure using the Supelclean LC-18 SPE cartridges as described by Srdjenovic et al. [41]. Prior to the analysis, the samples after cleanup were filtered through a 0.22 μm nylon filter and injected (10 µL) into the HPLC.
The HPLC system was calibrated using 0.02–0.2 mg/mL caffeine standard solutions. Data were processed in EuroChrom (Knauer, Berlin, Germany) and Clarity (ver. 4.0.1.700, DataApex, Prague, Czech Republic) software.

2.4. Analysis of Molecular Weight Distribution of Carbohydrates and Melanoidins in Instant Coffee Samples and Coffee Substitutes

To determine the molecular weight distribution of carbohydrates and melanoidins in the samples, 20 mg of sample was dissolved in 6 mL of 100 mM NaNO3 (mobile phase) using a magnetic stirrer for 30 min at 70 °C. Solutions were then carried to Eppendorf vials and centrifuged (21,000× g, 10 min). After centrifugation 100 µL of supernatant was injected into an SEC (Size Exclusion Chromatography) system consisting of OH-pak columns (OH-pak SB-G, SB-804, SB-802.5, and SB-802 in series, Shodex, Tokyo, Japan). The mobile phase flow rate was 0.6 mL/min, and column temperature was 60 °C. After separation, double detection was applied—refractometric detection to measure the content of the carbohydrate fraction and UV/VIS detection at 420 nm to detect melanoidins. Calibration of the SEC system was performed using pullulan standards (Shodex Standard, Macherey–Nagel) with known molecular masses, maltose, and glucose. Molecular mass distributions were used to calculate the apparent molar mass (Mw) using EuroChrom (Knauer, Berlin, Germany) and Clarity (ver. 4.0.1.700, DataApex, Prague, Czech Republic) software.

2.5. Analysis of Monosaccharide Profiles After Acid Hydrolysis of Instant Coffee and Coffee Substitutes Using HPLC/RI Method

The monosaccharide composition of AXs was determined by the HPLC/RI method after acid hydrolysis according to [42]. To analyze the monosaccharide profile, 20 mg of lyophilized sample was hydrolyzed in 2 mL 2M TFA (trifluoroacetic acid). Hydrolysis was carried out at 100 °C on a magnetic stirrer for 3 h. After hydrolysis, the sample was evaporated, re-dissolved in 2 mL of water, and centrifuged (2100× g, 10 min). The supernatant (20 µL) was injected into an HPLC/RI system (Knauer, Germany) equipped with SPG and SP0810 sugar columns (Shodex, Tokyo, Japan) in series and a refractometric (RI) detector. The eluent was bi-distillated water with a flow rate of 0.6 mL/min; the separation was performed at a column temperature of 70 °C. Calibration of the HPLC system was performed using glucose, xylose, galactose, arabinose, mannose, and fructose standard solutions (0–1 mg/mL; R2 > 0.997). Monosaccharide content in coffee and coffee substitutes was calculated using calibration curves for each sugar in EuroChrom (Knauer, Berlin, Germany) and Clarity (ver. 4.0.1.700, DataApex, Prague, Czech Republic) software.

2.6. Statistical Analysis of the Results

All measurements were carried out at least in triplicate. For the statistical analysis of the results, the Statistica 13 (StatSoft, TIBCO Software Inc., Tulsa, OK, USA) software was used. The obtained results were subjected to analysis of variance (ANOVA). The significance of differences between the average values was verified by Tukey’s test at a significance level of 0.05.

3. Results and Discussion

In Table 1, the percentage of dry matter in the instant coffees and their substitutes was shown. The dry matter content in all instant coffee samples and their substitutes was similar. The highest dry matter content was determined in the barley-based coffee substitute (B), while the lowest was determined in the freeze-dried instant coffee (L2). According to data in the available literature, the dry matter content in instant coffees typically ranges from 93.3% to 98.9% [7,43,44]. The differences in dry matter content could have been influenced by the different hygroscopicity of the products.
Caffeine content varies depending on the botanical species of coffee, the growing conditions, the degree of roasting of beans, the degree of extraction, and the production method [45,46]. The caffeine content in the lyophilisates obtained by the laboratory method of C. arabica AB–EX and C. canephora (Robusta) RB–EX (Table 1) was within the upper limits of the ranges of 2–4% and 4–6% indicated in the literature [4,47]. The commercially available freeze-dried coffees tested had significantly lower caffeine content than those obtained through extraction and freeze-drying in the laboratory, which could be due to the use of different raw materials, the degree of bean roasting, the degree of extraction, and the production method. Caffeine was not detected in the coffee substitutes. Coffee substitutes, in agreement with the reported values in the literature, do not contain caffeine, which is considered one of their advantages [36].
Size Exclusion Chromatography (SEC) analysis using dual detection was performed to obtain information on the composition of instant coffees and coffee substitutes. Refractometric detection (RI) was used to characterize the carbohydrate fraction, and UV detection at 420 nm [41,48,49,50,51] was used to characterize melanoidins in the instant products studied. The elution profiles obtained by RI detection, characterizing the carbohydrate fraction of instant coffees and coffee substitutes, are presented in Figure 1.
The carbohydrate elution profiles obtained from SEC analysis showed significant differences, indicating significant variation in the content and molecular mass distribution of carbohydrate fractions present in instant coffees and coffee substitutes. In the elution profiles obtained from 14 to 28 mL, carbohydrates of different molar masses were detected. Data in the literature indicate significant variation in the molar mass of the carbohydrate fraction of coffees [39]. Based on the calibration of the SEC system, the elution profiles were divided into sections characterizing molecules of different molar mass. Polysaccharide molecules with a mass exceeding 1800 g/mol were identified in the 14–25.2 mL range, oligosaccharide molecules of a molar mass of 400–1800 g/mol were identified in the 25.2–26.4 mL range, while sugars with a molar mass less than 400 g/mol (mono- and disaccharides) were detected in the 26.4–28 mL range.
Because the area under the elution profile in these ranges is proportional to the carbohydrate content, the areas were converted to the apparent (related to maltose standard) content of individual carbohydrate fractions, and the apparent total carbohydrate content in both the instant coffees and their substitutes was calculated. The results are presented in Table 2.
Based on the conducted analyses, it was found that the Arabica coffee extract (AB-EX) had a significantly higher polysaccharide content compared to the Robusta coffee extract (RB-EX). The Arabica coffee extract also contained more mono- and disaccharides, but fewer oligosaccharides than the Robusta coffee extract. The Arabica coffee extract contained more total carbohydrates compared to the Robusta coffee extract. Data in the literature indicate a higher total carbohydrate content in Arabica coffee than in Robusta coffee, which confirms the obtained results [52]. The literature lacks information on how the content of individual carbohydrate fractions affects the total sugar content in coffee extracts. This study demonstrated that polysaccharides are primarily responsible for the higher total carbohydrate content in Arabica coffee extracts compared to Robusta coffee extracts.
Commercial coffee extracts contained more total carbohydrates compared to laboratory-produced extracts. This was likely due to the use of a different raw material (likely a blend of Robusta and Arabica coffee) and differences in the technological process [19,22,53]. For economic reasons, commercial coffee extracts could be obtained with higher yields than laboratory extracts and contained more extracted carbohydrates. Data on the technological process of instant coffee production and extraction efficiency are not available, making it impossible to verify this hypothesis.
The tested instant coffee substitutes (C, B, S, and BRC) contained more polysaccharides and oligosaccharides, and, consequently, total carbohydrates compared to instant coffee extracts both commercial (L1 and L2) and produced in laboratory from coffee grains (AB–EX and RB–EX; Table 2). The higher polysaccharide and oligosaccharide content in the coffee substitutes resulted from the presence of starch and fiber (including resistant starch, cellulose, arabinoxylans, and β-glucans) in the cereal raw materials [54], and in the case of C and BRC samples, from the presence of inulin in the chicory root [55].
It should be emphasized that coffee substitutes generally contained 2 to 5 times more oligosaccharides than traditional coffee extracts. The highest amounts of oligosaccharides were found in coffee substitutes made from barley (B) and spelt (S). Among the coffee substitutes tested, the high content of polysaccharides and mono-/di-saccharides was found in the roasted chicory sample (C). The monosaccharide content in coffees resulted from the enzymatic and thermal breakdown of sucrose into the aforementioned simple sugars. According to the literature, the sucrose content in Arabica coffee beans ranges from 3.4% to 8.5% [56], while the sucrose content in Robusta coffee beans ranges from 3.3% to 6.1% [56].
In order to investigate what kind of monosaccharides constitute the carbohydrates in the tested instant coffee extracts and coffee substitutes, in the next stage of the work, the content of monosaccharides released after an optimized acid hydrolysis of the extracts was determined, and the results are presented in Table 3.
Laboratory-prepared Arabica and Robusta coffee extracts contained large amounts of galactose and mannose. The Arabica coffee extract contained more mannose and arabinose, but similar amounts of galactose, compared to the Robusta coffee extract. Based on the literature, the identified sugars originated primarily from galactomannans and arabinogalactans, which are the main polysaccharides present in coffee [20,57,58,59]. The higher content of galactomannans in Arabica coffee is confirmed by the literature [17,18,60,61]. Coffee extracts also contained a small amount of glucose and approximately 4% fructose. Low levels of glucose and fructose in coffee have also been reported by other authors [57,62]. It should be emphasized that the characterization conducted in this study concerns the water-extractable carbohydrate fraction (not the whole seed/grain), and the obtained results will vary depending on the raw material and the technological process, particularly the degree of coffee roasting and extraction efficiency. Commercially available instant coffees (L2 and L1), similar to extracts prepared using the laboratory method, contained large amounts of galactose and mannose, as well as significantly smaller amounts of glucose, arabinose, and fructose. The total monosaccharide content determined after acid hydrolysis (Table 3) correlated with the total sugar content determined using the SEC method (Table 2), but the content determined after acid hydrolysis was significantly lower, which can be explained by the partial degradation and loss of sugars during acid hydrolysis. Based on the data in Table 3, it was found that coffee substitutes contained more total sugars after acid hydrolysis, while the Robusta coffee extract contained the least.
Coffee substitutes obtained from cereal grains, i.e., spelt wheat (S) and barley (B), were characterized by a particularly high content of glucose released from starch and other glucans during acid hydrolysis [63]. Cereal-based coffee substitutes also contained small amounts of xylose, galactose, arabinose, mannose, and fructose. These sugars were most likely products of hydrolysis of arabinoxylans, galactomannans, and fructans contained in cereal grains [64,65,66,67,68]. It should be emphasized that the presence of these polysaccharides in coffee substitutes, along with the high content of the oligosaccharide fraction, which may also include the aforementioned non-starch carbohydrates, indicates the potential prebiotic effects of these products. It was shown that raffinose occurring in barley grain can be fermented by Bifidobacteria [69], as well as maltotriose and maltotetraose [70]. Spelt and rye grain contain carbohydrates such as fructan, fructooligosaccharides, and arabinoxylans and are considered sources of highly fermentable but poorly absorbed short-chain carbohydrates and polyols (designated FODMAPs–Fermentable Oligo-, Di- and Mono-saccharides And Polyols) [71].
The coffee substitute made from roasted chicory root (C) contained very high amounts of fructose, with a 7% glucose content, which was a consequence of the high content of inulin and fructooligosaccharides in the raw material [4,55,72]. The chicory coffee substitute also contained a low content of arabinose and trace amounts of galactose, indicating the presence of arabans and arabinogalactans in the extract. The coffee substitute obtained from a mixture of chicory, barley, and rye (BRC) contained mainly polysaccharides composed of glucose (glucans), but also significant amounts of fructose (inulin and fructooligosaccharides) and smaller amounts of arabinose, xylose, galactose, and mannannose (arabinoxylans, galactomannans, and other non-starch polysaccharides). The rich carbohydrate composition of the BRC coffee substitute was a consequence of the use of various raw materials in its production.
In parallel with the analysis of the molecular weight distribution of carbohydrates (Figure 1), the content and size of melanoidin molecules in instant coffees and coffee substitutes were determined using additional UV detection at a wavelength of 420 nm (Figure 1, right scale).
In all elution profiles of melanoidins contained in instant coffee extracts and coffee substitutes, the presence of two fractions of these compounds was observed. The high-molecular-weight fraction was visible as a distinct peak between elution volume of 14 and 19.2 mL. A low-molecular-weight melanoidin fraction was also observed as a peak between elution volume of 19.2 and 30 mL. Data in the literature indicate the presence of melanoidin fractions of different molar mass in coffee [73,74,75]. Coffee substitutes made from barley (B), spelt (S), and barley, rye, and chicory (BRC) contained a very high molar mass compound appearing as a peak with an elution volume of 14–15.6 mL (Figure 1).
High-MW fractions are most likely to be complexes of melanoidins with polysaccharide, which is indicated by the data from the literature and some shared peaks of melanoidins and carbohydrates.
Carbohydrates, including arabinogalactans, seem to be part of melanoidin complexes present in coffee brew [73,76]. Researchers indicate that future studies are required to better understand the nature of coffee melanodins and the mechanisms of their formation [75]. There are reports of galactomann-like and arabinogalactan-like carbohydrates being present in the melanoidin population of roasted coffee [77]. It was also found that the high-molecular-weight material (HMWM) of an instant barley beverage is mostly composed of carbohydrates (89%), and HMWM from instant coffee contained 59% carbohydrates [39].
Due to the highly complex and heterogeneous nature of the molecules, there are currently no commercially available coffee melanoidin standards. To obtain information on the melanoidin content in the instant coffees and their substitutes, the areas under the peaks in the elution profiles determined using a UV detector at a wavelength of 420 nm were integrated. The peak areas, proportional to the melanoidin content, are presented in Table 4.
During coffee roasting, the chemical composition of the beans changes due to the degradation and transformation of compounds (carbohydrates, proteins, and phenolic compounds) [75,78]. Melanoidin content in coffee is often assumed to be due to unidentified compounds, but these compounds may also include low-molecular-weight Maillard reaction products and other substances. It is not known whether high-molecular-weight fractions of roasted coffee can be divided into polysaccharides, proteins, and melanoidins, as arabinogalactans, galactomannans, and proteins are believed to be integral parts of melanoidin complexes [31]. Melanoidins of very high molar mass in coffees may contain not only amino acid and carbohydrate fractions, but also non-carbohydrate and non-protein chromophoric and phenolic groups, as well as non-covalent complexes composed of low-molecular-weight melanoidins and high-molecular-weight carriers, such as polysaccharides [31].
After roasting, a decrease in the content of carbohydrates, proteins, free amino acids, and chlorogenic acid is observed, while lipids, mineral salts, aliphatic acids, caffeine, and trigonelline retain their relative content. Based on this, it can be concluded that melanoidins are formed from, among other compounds, carbohydrates, proteins, and free amino acids, and also contain chlorogenic acid [28,29,30,75,79].
Significant differences in melanoidin content were observed among the instant coffees tested, likely due to differences in raw materials, varying degrees of coffee bean roasting, and different technological processes. The laboratory-prepared freeze-dried extract of Arabica coffee (AR–EX) had a higher melanoidin content compared to the Robusta coffee extract (RB–EX). L2 and L1 instant coffees contained lower melanoidin levels than Arabica coffee, similar to those observed in Robusta coffee. It is likely that the commercially used extraction process does not lead to increased melanoidin content in the finished product—instant coffee.
The highest melanoidin content among instant coffees and their substitutes was determined in the roasted chicory coffee substitute (C), while the lowest was found in the spelt product (S). Chicory contains more melanoidin-forming components, especially fructose from inulin, than coffee and coffee substitutes based on cereal grains, and therefore the tested coffee substitutes containing these raw materials contained more melanoidins [4,79].
It should be noted that the exact composition and structure of melanoidins are not yet well understood. It is not known whether the high-molecular-weight compounds considered melanoidin fractions are actually melanoidins, or whether they are complexes of low-molecular-weight melanoidins and high-molecular-weight carriers. Further research is needed to understand all the synthesis pathways and the precise course of the melanoidin-forming reactions, as well as to determine their structure.

4. Conclusions

This study demonstrated for the first time that the higher carbohydrate content in Arabica coffee extracts compared to Robusta coffee is primarily due to polysaccharides of a molar mass greater than 1800 g/mol. Significant differences were also observed in the carbohydrate composition of Arabica and Robusta coffee extracts, as well as instant coffees obtained using laboratory and industrial methods.
No caffeine was detected in the coffee substitutes tested. The coffee substitutes contained more polysaccharides and two to five times more oligosaccharides of a molar mass ranging from 400 to 1800 g/mol, and, consequently, more total carbohydrates, compared to instant coffee extracts. The high oligosaccharide contents of very diverse sugar composition found in the coffee substitutes indicate the potential prebiotic effects of these products.
The elution profiles of melanoidins present in instant coffee extracts and coffee substitutes revealed the presence of high- and low-molecular-weight fractions of these compounds. The highest melanoidin content among coffee extracts and substitutes was determined in the coffee substitute made from roasted chicory. Furthermore, higher amounts of melanoidins were found in the Arabica coffee extract compared to the Robusta coffee extract.

Author Contributions

Conceptualization, K.B.; methodology, K.B.; software, K.B.; validation, K.B.; formal analysis, M.S. and K.B.; investigation, M.S. and K.B.; resources, K.B.; data curation, K.B. and M.S.; writing—original draft preparation, K.B. and M.S.; writing—review and editing, K.B.; visualization, K.B.; supervision, K.B.; project administration, K.B. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Applsci 15 12627 g001aApplsci 15 12627 g001b
Figure 1. Elution profiles obtained by separation on SEC columns of carbohydrates (-●-; RI detection—left scale) and melanoidins (-○-; UV detection at 420 nm—right scale) in instant coffees and coffee substitutes. On the top scale, calibration of the SEC system is shown (M—molar mass).
Figure 1. Elution profiles obtained by separation on SEC columns of carbohydrates (-●-; RI detection—left scale) and melanoidins (-○-; UV detection at 420 nm—right scale) in instant coffees and coffee substitutes. On the top scale, calibration of the SEC system is shown (M—molar mass).
Applsci 15 12627 g001aApplsci 15 12627 g001b
Table 1. Dry mass and caffeine content in coffee and coffee substitutes.
Table 1. Dry mass and caffeine content in coffee and coffee substitutes.
Sample TypeSample CodeDry Mass Content [%]Caffeine Content [%]
CoffeeAB-EX95.3 ± 1.1 b3.9 ± 0.5 d
RB-EX94.7 ± 0.7 b6.6 ± 0.3 e
L195.8 ± 1.6 b3.1 ± 0.4 c
L293.0 ± 0.5 a2.1 ± 0.3 b
Coffee substitutesC96.8 ± 0.7 b0.0 ± 0.1 a
B98.3 ± 0.0 c0.1 ± 0.1 a
S95.3 ± 0.6 b0.0 ± 0.1 a
BRC96.4 ± 0.9 b0.1 ± 0.1 a
Mean values marked with same letters in lowercase do not display statistically significant difference for significance level p < 0.05.
Table 2. Apparent carbohydrate content in coffee and coffee substitutes.
Table 2. Apparent carbohydrate content in coffee and coffee substitutes.
Content of
Polysaccharides
of Mw > 2000 g/mol [%]		Content of Oligosaccharides
of Mw 500–2000 g/mol
[%]		Content of Mono- and Disaccharides Mw < 500 g/mol [%]Content of Total
Carbohydrates
[%]
Coffee
AB-EX39.7 ± 0.8 b2.0 ± 0.9 a5.6 ± 0.4 ab47.3 a
RB-EX31.3 ± 0.7 a3.2 ± 0.2 ab7.8 ± 0.3 b42.3 a
L142.9 ± 1.5 bc3.9 ± 0.3 ab9.6 ± 2.9 b56.3 b
L247.3 ± 1.0 cd4.7 ± 0.1 b6.7 ± 0.7 ab58.6 b
Coffee substitutes
C58.0 ± 1.1 e11.4 ± 0.3 c17.6 ± 1.9 c87.0 d
B59.2 ± 2.3 e25.3 ± 0.5 d6.0 ± 0.3 ab90.6 d
S47.4 ± 1.1 cd25.5 ± 0.2 d2.3 ± 0.2 a75.2 c
BRC52.1 ± 0.3 d10.8 ± 0.9 c6.2 ± 0.5 ab69.0 c
Mean values marked with the same letters in lowercase do not display a statistically significant difference for the significance level of p < 0.05.
Table 3. Monosaccharide content (d.b.) after acid hydrolysis in the tested instant coffee and coffee substitute samples.
Table 3. Monosaccharide content (d.b.) after acid hydrolysis in the tested instant coffee and coffee substitute samples.
Glc
[%]		Xyl
[%]		Gal
[%]		Ara
[%]		Man
[%]		Fru
[%]		Total Sugar [%]
Coffee
AB-EX 2.8 ± 0.1 a 0.4 ± 0.3 a 14.3 ± 0.2 b 1.6 ± 0.3 c 17.9 ± 1.1 cd 4.8 ± 0.1 d 41.8 ± 1.0 b
RB-EX 0.8 ± 0.1 a 0.3 ± 0.1 a 14.3 ± 0.5 b 0.9 ± 0.4 ab 14.4 ± 0.4 b 3.6 ± 0.1 cd 34.3 ± 0.6 a
L12.7 ± 0.1 a0.1 ± 0.1 a20.7 ± 0.5 c0.6 ± 0.1 ab18.5 ± 0.5 d1.8 ± 0.1 b44.5 ± 0.7 c
L21.6 ± 0.2 a0.3 ± 0.3 a24.2 ± 0.4 d2.7 ± 0.2 c16.1 ± 0.2 bc2.3 ± 0.2 bc47.2 ± 0.0 d
Coffee substitutes
C 7.2 ± 0.1 b 0.4 ± 0.3 a 0.3 ± 0.2 a 0.8 ± 0.4 ab 0.0 ± 0.1 a 48.5 ± 0.5 f 57.3 ± 0.2 e
B61.9 ± 1.3 d0.9 ± 0.1 ab0.5 ± 0.1 a0.8 ± 0.1 ab0.4 ± 0.2 a0.5 ± 0.1 a65.0 ± 0.7 f
S 63.5 ± 1.3 d 1.4 ± 0.3 b 1.0 ± 0.1 a 0.3 ± 0.1 a 0.3 ± 0.2 a 0.4 ± 0.2 a 67.1 ± 0.9 f
BRC 47.1 ± 1.0 c 1.4 ± 0.1 b 0.5 ± 0.2 a 0.6 ± 0.3 ab 0.2 ± 0.1 a 8.4 ± 0.6 e 58.2 ± 0.7 e
Mean values marked with the same letters in lowercase do not display a statistically significant difference for the significance level of p < 0.05.
Table 4. Peak area of melanoidins (detected at 420 nm).
Table 4. Peak area of melanoidins (detected at 420 nm).
Sample CodePeak Area of Melanoidins Detected at UV420nm
[mV × min]
Coffee
AB-EX83.3 ± 0.5 e
RB-EX53.3 ± 0.8 b
L164.3 ± 1.1 c
L252.7 ± 0.9 b
Coffee substitutes
C98.1 ± 1.2 f
B63.8 ± 1.1 c
S24.7 ± 1.4 a
BRC71.7 ± 0.8 d
Mean values marked with the same letters in lowercase do not display a statistically significant difference for the significance level of p < 0.05.
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Buksa, K.; Szczypek, M. Characteristics of Molecular Properties of Carbohydrates and Melanoidins in Instant Coffee and Coffee Substitutes. Appl. Sci. 2025, 15, 12627. https://doi.org/10.3390/app152312627

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Buksa K, Szczypek M. Characteristics of Molecular Properties of Carbohydrates and Melanoidins in Instant Coffee and Coffee Substitutes. Applied Sciences. 2025; 15(23):12627. https://doi.org/10.3390/app152312627

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Buksa, Krzysztof, and Michał Szczypek. 2025. "Characteristics of Molecular Properties of Carbohydrates and Melanoidins in Instant Coffee and Coffee Substitutes" Applied Sciences 15, no. 23: 12627. https://doi.org/10.3390/app152312627

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Buksa, K., & Szczypek, M. (2025). Characteristics of Molecular Properties of Carbohydrates and Melanoidins in Instant Coffee and Coffee Substitutes. Applied Sciences, 15(23), 12627. https://doi.org/10.3390/app152312627

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