Formation Of Maillard Reaction Products Research Articles

Impact of a minimally processing route for the production of infant formulas on their sensory properties

Infant formulas (IFs), the sole adequate substitute to human milk, undergo several thermal treatments during production that can damage milk proteins and promote the formation of Maillard reaction products, modifying nutritional and sensory properties. The aim of this study was to determine the impact of a minimally processing route based on membrane filtration associated with different levels of heat treatment, on the odor, taste, texture and color attributes of IFs, then to compare with those of commercial milks. Three experimental IFs (produced with membrane filtration associated with low - T-, medium - T+, or high thermal treatments - T+++) were evaluated. Triangular tests conducted with a panel of 50 adults highlighted clear disparities between all the IFs. The same panel applied the Check-All-That-Apply method to evaluate the IFs: the range of variability between T- and T+++ was similar to that between the 2 commercial IFs, and the sensory characteristics of the experimental IFs were not far from the commercial brands for flavor and texture attributes. Analysis performed on the citation frequencies for each descriptor differentiated T-/T+ from T+++, but all the experimental IFs were described with positive sensory characteristics, unlike one commercial IF. Volatile organic compounds (VOCs) content of IFs with low and high thermal treatments were analyzed. Forty VOCs were identified by gas chromatography-mass spectrometry. T- contained a higher quantity of VOCs than T+++, except for benzaldehyde (Maillard reaction product), and aldehydes (oxidation-related products) were the most represented compounds. In conclusion, the processing was associated with sensory differences among IFs, but no marked difference in flavors was found according to CATA and physicochemical analysis. Additionally, no unpleasant sensory descriptors were noted. This shows that the minimally processed route leads to IFs that could fit well within the market from a sensory point of view.

Encapsulation of probiotic Lacticaseibacillus casei with whey protein isolate/soybean hull polysaccharide enhances cell viability in harsh conditions

Whey protein isolate (WPI)-soybean hull polysaccharide (SHP) Maillard reaction conjugates were used to encapsulate Lacticaseibacillus casei and determine the effect of encapsulation on bacterial viability during freeze drying, simulated pasteurization simulated gastrointestinal digestion and storage. The WPI-SHP conjugates were characterized by degree of conjugation, size-exclusion chromatography, infrared and fluorescence spectroscopy and other analyses. The degree of conjugation, the formation of Maillard reaction products and the content of high molecular weight conjugates increased with reaction time. The emulsification capacity and glass transition temperature (Tg) of the WPI-SHP conjugates peaked after 4 days of reaction, at a Tg of 140.51 ± 2.76 °C, an emulsification activity index of 9.12 m2/g and emulsion stability index of 87.01%. WPI-SHP4d had the best protection effect of probiotics under freeze drying, simulated pasteurization and gastrointestinal digestion. These findings provide valuable insights into the selection of encapsulating agents to improve probiotic viability in functional foods.

Mechanisms of flavonoid inhibition of Maillard reaction product formation in relation to whole grains processing

Whole grains (WG) are beneficial to health but have reduced sensory quality, partly attributable to inhibition of Maillard reaction products (MRP) by WG phenolics. The study investigated how major flavonoid classes in cereals affect Maillard reaction pathways. Flavonoids were reacted with xylose-lysine aqueous system at 160 °C/12 min. Additionally, breads were made with catechin, and wheat and sorghum bran fortification. Low Mw MRP were profiled using UPLC-MS/MS, while melanoidins were characterized using fluorescence spectroscopy and HPSEC-MALS. The flavonoids significantly (p < 0.05) reduced both melanoidin content (by 33–86%) and Mw (3.5–15 kDa vs 20 kDa control), leading to lighter bread crust. Flavonoids inhibited MRP via direct condensation with early-stage amines and carbonyls into stable adducts, and reduction of late-stage polymerization reactions, increasing accumulation of cyclic N-containing intermediates. Inhibitory trend was flavones>flavanones>flavanols. C-Ring π-bond dramatically enhance flavonoid MRP inhibition; thus flavone-rich cereal grains are likely to strongly impact MRP-dependent sensory attributes of WG products.

A Gently Processed Skim Milk-Derived Whey Protein Concentrate for Infant Formula: Effects on Gut Development and Immunity in Preterm Pigs.

Processing of whey protein concentrate (WPC) for infant formulas may induce protein modifications with severe consequences for preterm newborn development. The study investigates how conventional WPC and a gently processed skim milk-derived WPC (SPC) affect gut and immune development after birth. Newborn, preterm pigs used as a model of preterm infants were fed formula containing WPC, SPC, extra heat-treated SPC (HT-SPC), or stored HT-SPC (HTS-SPC) for 5 days. SPC contained no protein aggregates and more native lactoferrin, and despite higher Maillard reaction product (MRP) formation, the clinical response and most gut and immune parameters are similar to WPC pigs. SPC feeding negatively impacts intestinal MRP accumulation, mucosa, and bacterial diversity. In contrast, circulating T-cells are decreased and oxidative stress- and inflammation-related genes are upregulated in WPC pigs. Protein aggregation and MRP formation increase in HTS-SPC, leading to reduced antibacterial activity, lactase/maltase ratio, circulating neutrophils, and cytotoxic T-cells besides increased gut MRP accumulation and expression of TNFAIP3. The gently processed SPC has more native protein, but higher MRP levels than WPC, resulting in similar tolerability but subclinical adverse gut effects in preterm pigs. Additional heat treatment and storage further induce MRP formation, gut inflammation, and intestinal mucosal damage.

Exploring correlations between soy sauce components and the formation of thermal contaminants during low-salt solid-state fermentation

Soy sauce is a traditional seasoning in Asia and provides a unique flavor to food. However, some harmful Maillard reaction products (MRPs) were inevitably formed during the manufacturing process. Fermentation is a critical step of soy sauce manufacturing and has a significant impact on MRPs formation. Therefore, this study investigated the formation of some characteristic MRPs (e.g., furan, carboxymethyl lysine (CML), 5-hydroxymethylfurfural (5-HMF), α-dicarbonyl compounds) and their correlation with major quality indicators (e.g., free amino acids, reducing sugar, total acid, ammonia nitrogen, total nitrogen, non-salt soluble solids) in low-salt solid-state fermentation soy sauce (LSFSS). The result showed that the levels of furan, CML, and 5-HMF continue to increase during the fermentation process, reaching a maximum after sterilization. Further testing using Person correlation showed that the formation of furan, CML, and 5-HMF in LSFSS was positively correlated with glucose, fructose, α-dicarbonyl compounds, and most of the amino acids, while it was negatively correlated with sucrose and methionine. Among them, the contribution of lysine, valine, isoleucine, leucine, and arginine to furan formation has rarely been reported. Our results provide a good theoretical basis for the control of MRPs during LSFSS fermentation.

Resolving fluorescence spectra of Maillard reaction products formed on bovine serum albumin using parallel factor analysis

Formation of Maillard reaction products (MRPs) is increasingly studied by the use of fluorescence spectroscopy, and most often, by measuring single excitation/emission pairs or use of unresolved spectra. However, due to the matrix complexity and potential co-formation of fluorescent oxidation products on tryptophan and tyrosine residues, this practice will often introduce errors in both identification and quantification. The present study investigates the combination of fluorescence excitation emission matrix (EEM) spectroscopy and parallel factor analysis (PARAFAC) to resolve the EEMs into its underlying fluorescent signals, allowing for better identification and quantification of MRPs. EEMs were recorded on a sample system of bovine serum albumin incubated at 40 °C for up to one week with either glucose, methylglyoxal or glyoxal added. Ten unique PARAFAC components were resolved, and assignment was attempted based on similarity with fluorescence of pure standards of MRPs and oxidation products and reported data from literature. Of the ten fluorescent PARAFAC components, tyrosine and buried and exposed tryptophan were resolved and identified, as well as the formation of specific MRPs (argpyrimidine and Nα-acetyl-Nδ-(5-methyl-4-imidazolon-2-yl)ornithine) and tryptophan oxidation products (kynurenine and dioxindolylalanine). The formation of the PARAFAC resolved protein modifications were qualitatively validated by liquid chromatography-mass spectrometry.

THE ANALYSIS OF THE SELECTED BIOACTIVE PARAMETERS OF BLACK GARLIC PREPARED IN THE SHORT FERMENTATION MODE

Background. Garlic (Allium sativum L.) is characterized by many health-promoting properties due to the presence of sulfur compounds, including allillin, S-allyllocysteine and the high content of polyphenolic compounds. In order to eliminate specific organoleptic characteristics – unfavorable from some consumers’ point of view, garlic can be subjected to a special, low-temperature heat treatment, referred to as aging. This process results in the hydrolysis of poly- and oligosaccharides (fructans) with the participation of intracellular enzymes (fermentation) and the formation of Maillard reaction products (condensation of sugars with amines). As a result, the color, consistency, taste and smell of the final product change and the so-called black garlic is obtained. The aim of the study was to compare the antioxidant properties and the level of total polyphenols, saccharide profile, the content of selected B vitamins and released amino acids of two varieties of raw and black garlic. The experiments were carried out with the use of a commercial short-term fermentation unit from TIROSS. The process was carried out at 70 °C for 192 hours. The amo unt of released amino acids was determined by the ninhydrin method, the content of polyphenols was found using the Folin-Ciocâlteu reagent,antioxidant properties were specified using DPPH free radical and the content of vitamin B and saccharide profile by HPLC. Results and conclusions. The results obtained indicate not only an increase in antioxidant activity, the sum of polyphenols and riboflavin, but also a decrease in the level of free amino acids and thiamine in the garlic obtained after the aging process. The project is in line with a global trend related to the nutrition model oriented towards a vegan diet and the search for new, health-promoting ingredients or recipes based on raw materials with already pre-confirmed attributes as ingredients of functional food.

Flavor improving effects of cysteine in xylose–glycine–fish waste protein hydrolysates (FPHs) Maillard reaction system

A promising way to utilize fish by-products is to develop hydrolysis of fish proteins with enzymes. The obtained fish protein hydrolysates (FPHs) are rich in peptides and amino acids, but bitterness and aroma defects impede further utilization of FPHs. The present study adopted Maillard reaction to improve FPHs’ flavor and illustrated the role of cysteine in this system. We investigated the impact of cysteine (0, 0.25%, 0.5%, 0.75%, and 1%) on the browning intensity, free amino acids (FAAs), molecular weight distribution, structure of MRPs, volatile compounds changes and organoleptic characteristics of xylose–glycine–FPHs Maillard reaction systems. Results showed that the addition of cysteine lowered the browning degree of Maillard reaction products (MRPs) by inhibiting the cross-linking of small peptides and reducing the production of melanin. GC–MS and GC–IMS analysis indicated that cysteine inhibited the formation of furans and nitrogen-containing compounds and facilitated the formation of sulfur-containing compounds contributing to the meaty flavor. Sensory analysis revealed that 0.25–0.75% range of cysteine increased the meaty, caramel, umami, mouthfulness and salty notes, and caused a decrease in bitter taste of the MRPs as confirmed by GC–MS. A highly significant correlation between the organoleptic characteristics and physicochemical indicators of MRPs was found by Mantel test. These results elucidated the influence of cysteine on the formation of Maillard reaction products and will help improve the flavor profile of meat flavorings.Graphical

Formation of Maillard reaction products in a model bread system of different gluten-free flours.

In this study, we determined the levels of Maillard-type products (furosine, free fluorescent advanced glycation end products, 3-deoxyglucosone, methylglyoxal, and N-ε-carboxymethyllysine) in a model gluten-free bread made of wholegrain white, brown, wild, red, and black rice flour, as well as of yellow and purple corn flour. The total protein, lysine, arginine, and cysteine contents were found to relate directly to the formation of Maillard-type products. The malvidin, ferulic, syringic, sinapic, and p-coumaric acids present in gluten-free breads were effective against the formation of furosine, fluorescent compounds, and dicarbonyls, but were ineffective in mitigating CML. Although the bread formulated with purple corn flour had the lowest levels of furosine and fluorescent compounds, this formulation led to an increase in N-ε-carboxymethyllysine and adversely affected the bread's aroma, on account of the presence of polyphenols responsible for a bitter aroma, which were at their highest concentration (1942.34µg/g) in this bread.

Goat milk powders enriched with grape pomace seed extract: Physical and techno-functional properties

This study aimed to evaluate the physical (particle size and ζ-potential) and techno-functional properties (emulsifying and foaming) of goat milk powders enriched with grape pomace seed extract (TME), as promising food ingredients in the formulation of functional food. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Raman spectroscopies, along with advanced chemometric tools were employed as well as Scanning Electron Microscopy (SEM) for analyzing TME powders. All powders exhibited a unimodal particle size distribution and ζ-potential values more negative than −36 mV. ATR-FTIR and Raman spectroscopies combined with principal component analysis (PCA) demonstrated distinct separation among skimmed goat milk (M), thermally treated skimmed goat milk (TM), and TME powders in different spectral regions (amide I, II, III, and fingerprint region). This separation resulted from the applied thermal treatment, the presence of phenolic compounds and their complexes with goat milk proteins, and the formation of Maillard reaction products. SEM analysis confirmed the different morphology and shapes of M, TM and TME powders. The 0.1% solutions of M, TM and TME exhibited good emulsifying properties (emulsion activity index and emulsion stability index) but showed poor foaming properties, except for the M sample. Solution concentrations higher than 0.1% for all samples (0.5% and 1.0%) displayed poor techno-functional properties. In summary, a schematic representation of the arrangement of casein micelles in 0.1% M, TM and TME samples, on oil/water and air/water surfaces was provided. The production of TME powders represents an innovative strategy for waste recovery in the production of functional food ingredients with good emulsifying properties.

Wheat Roll Enhanced by Buckwheat Hull, a New Functional Food: Focus on the Retention of Bioactive Compounds.

Wheat roll enhanced by buckwheat hull was used as a model for determining the retention of bioactive compounds during technological steps. The research included analysis of the formation of Maillard reaction products (MRPs) and retention of bioactive compounds such as tocopherols, glutathione, or antioxidant capacity. About a 30% decrease in the content of available lysine in the roll was observed compared to the value obtained for fermented dough. Free FIC, FAST index, and browning index were highest for the final products. The increase of analyzed tocopherols (α-, β-,γ-, and δ-T) was noticed during the technological steps, with the highest values found for the roll with 3% of buckwheat hull. A significant reduction in GSH and GSSG content occurred during the baking process. The observed increase in the value of the antioxidant capacity after the baking process may be the result of the formation of new antioxidant compounds.

The impact of dosage sugar-type and aging on Maillard reaction-associated products in traditional method sparkling wines

Liqueur d’expedition (dosage) is a final sugar addition made to sparkling wine which determines the sweetness and balance of the finished product. In the present study, the influence of dosage sugar composition on Maillard reaction-associated products and precursors in traditional method (bottle-fermented) sparkling wines was evaluated over 18-months of storage in climate-controlled cellar conditions (14 °C, 70 % relative humidity). Evaluated dosage sugar-types included glucose, fructose, cane-derived sucrose, beet-derived sucrose, maltose, and Must Concentrate Rectified (MCR) Sucraisin®, which were compared to a zero dosage (no sugar added) control. Maillard reaction-associated products were quantified by headspace solid-phase microextraction coupled to gas-chromatography-mass spectrometry (HS-SPME-GC/MS), and precursors including sugars and amino acids, were measured by enzymatic assay and proton (1H) nuclear magnetic resonance (NMR) spectroscopy, respectively. Partial least squares discriminant analysis (PLS-DA) was used to effectively discriminate between wines based on aging duration but did not adequately separate wines treated with different dosage sugar-types. Decreases in alanine and glycine were observed after 18-months of cellar aging, suggesting that Maillard reaction product formation may be partially related to their depletion. Benzaldehyde and ethyl-3-mercaptopropionate were identified as discriminatory Maillard reaction-associated compounds when comparing 0- and 18-month aged wines, with benzaldehyde increasing and ethyl-3-mercaptopropionate decreasing over the aging period. This research contributes to an increased understanding of Maillard reaction pathways in the unique low-temperature and low pH sparkling wine matrix and establishes the relatively greater effect of aging duration compared to dosage sugar-type on the formation of Maillard reaction-associated products. The combined application of HS-SPME-GC/MS and 1H NMR based metabolomics presents new insights into the chemical composition of sparkling wines during aging.

Application of tea polyphenols as additives in brown fermented milk: Potential analysis of mitigating Maillard reaction products

Brown fermented milk (BFM) is favored by consumers in the dairy market for its unique burnt flavor and brown color. However, Maillard reaction products (MRP) from high-temperature baking are also noteworthy. In this study, tea polyphenols (TP) were initially developed as potential inhibitors of MRP formation in BFM. The results showed that the flavor profile of BFM did not change after adding 0.08% (wt/wt) of TP, and its inhibition rates on 5-hydroxymethyl-2-furaldehyde (5-HMF), glyoxal (GO), methylglyoxal (MGO), Nε-carboxymethyl lysine (CML), and Nε-carboxyethyl lysine (CEL) were 60.8%, 27.12%, 23.44%, 57.7%, and 31.28%, respectively. After 21 d of storage, the levels of 5-HMF, GO, MGO, CML, and CEL in BFM with TP were 46.3%, 9.7%, 20.6%, 5.2%, and 24.7% lower than the control group, respectively. Moreover, a smaller change occurred in their color and the browning index was lower than that of the control group. The significance of this study was to develop TP as additives to inhibit the production of MRP in brown fermented yogurt without changing color and flavors, thereby making dairy products safer for consumers.

Effect of cereal bran phenolic profile on Maillard reaction products formation during hydrothermal treatment

Maillard reaction products (MRP) contribute to sensory quality of various foods. Whole grains (WG) are rich in phenols which may influence Maillard reaction pathways during thermal processing and impact WG product sensory attributes. This study investigated how WG phenolic profile affects MRP formation. Amylase-hydrolyzed wheat (white and red) and sorghum (white, red, tannin) brans were hydrothermally processed at 150 °C/6 min, and characterized for MRP using colorimetry, fluorescence spectroscopy, HPLC-MS/MS, and HS-SPME/GC–MS. Bran phenolic structure, and to a lesser extent content, had larger influence on MRP formation than protein/amino acid profile. Polymeric tannins (both in situ and when added to wheat brans) strongly inhibited volatile and non-volatile MRP intermediates and melanoidin formation, likely via their carbocation depolymerization intermediates trapping furans. Principle component analysis demonstrated clear segregation of volatiles formation based on bran phenolic profile. Phenolic composition should be considered in WG product formulation and processing to achieve desired MRP formation.

Spray-Drying Impact the Physicochemical Properties and Formation of Maillard Reaction Products Contributing to Antioxidant Activity of Camelina Press Cake Extract.

Spray-drying is one of the most popular techniques in the food industry for converting liquid material from a fluid state into a form of dried particles to produce encapsulated or instant products. Instant products are considered as convenient foods; moreover, the goal of encapsulation is to close the bioactive compounds in a shell, preventing them from being affected by environmental factors. The purpose of this study was to examine the influence of spray-drying conditions, in particular three inlet temperatures, on the physicochemical and antioxidant properties of powders obtained from Camelina Press Cake Extract (CPE). The CPE was spray-dried at 140 °C, 160 °C and 180 °C. The solubility, Carr and Hausner Indexes, tapped densities and water activity of the powders were analyzed. The structural changes were also detected using FTIR spectroscopy. Additionally, the characteristics of the initial and reconstituted samples and their rheological properties were evaluated. The antioxidant potential, total polyphenols and flavonoids content, free amino acids, and the Maillard reaction products contents in the spray-dried powders were also evaluated. The results indicate a cascade of changes between the initial and reconstituted samples, and important changes in the bioactive potential of samples. The inlet temperature significantly influenced the solubility, flowability and particle sizes of the powders, as well as Maillard products formation. The results of the rheological measurements illustrate the changes after the reconstitution of extracts. This study indicates the optimal parameters of CPE spray-drying, those that yield favorable physicochemical and functional values, which may open up a promising path for CPE valorization, indicating its potential and the possibilities of its use.

Changes in structure, functional properties and volatile compounds of Cinnamomum camphora seed kernel protein by Maillard reaction

In this study, Cinnamomum camphora seed kernel protein isolate (CPI)−dextran (DX) model system was used to investigate the impacts of reaction temperatures (70−100 °C) and times (1−4 h) on the structure, functional properties and volatile compounds of Maillard reaction products (MRPs). The formation of MRPs was confirmed by SDS-PAGE, ultraviolet absorption and degree of glycation. Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy showed that the secondary structure of MRPs tended to be more regular than native CPI. Moreover, MRPs had a lower free sulfhydryl group content and higher surface hydrophobicity than native CPI. Fluorescence spectra revealed that the tryptophan residues of CPI were transferred to a more hydrophobic microenvironment. The solubility and emulsifying stability of CPI were decreased, while the foaming activity, foaming stability, emulsion stability and apparent viscosity of CPI were significantly improved (p < 0.05) after Maillard reaction. Furthermore, MRPs exhibited significantly improved (p < 0.05) thermal stability and ABTS+• radical scavenging activity than native CPI, while the DPPH+ radical scavenging activity and ferric reducing power were decreased. In addition, volatile compounds, including aldehydes, ketones, benzenes and esters, were identified in MRPs. These results provide a theoretical guidance for future studies on CPI-DX conjugates.

Protective influence of heat treatment on the light-induced riboflavin (vitamin B2) degradation in dairy products

Milk is the most important source of riboflavin (Vitamin B2) in many nations. Riboflavin absorbs light in the ultraviolet region and generates singlet oxygen in milk leading to the oxidation of nutrient components and affects the sensory quality of dairy products. The purpose of this work was to elucidate the effect of heat-treatment on the light-induced riboflavin degradation in the model solution of milk bases and milk samples. Although the photo-degradation of riboflavin in all samples was decreased with the increasing of illumination time, the reductions of riboflavin light oxidation were found in all milk model samples and heated milks in according to the formation of Maillard reaction products during heating. The amount of riboflavin remained in control sample (1.5 mg/l riboflavin) was 1.67 % after 2.5 hour illumination. But, it was 34 % and 60 % in the heated lactose and casein solution and milk at 120oC, 45 min, respectively. The increasing of heating time leaded to the increasing of protective ability of milk and model samples against riboflavin photo-degradation. The study clarified that heat treatment of whey proteins, casein and milk might induce the formation of Maillard reaction products that enhanced the protective ability against photo-degradation of riboflavin.

Formation of Maillard Reaction Products in Aged Sorghum Vinegar during Ageing and Protective Effects of Pure Vinegar Melanoidin Against CCl4-Induced Rat Hepatic Damage.

The processing method generally affects the toxicity and biological activity of aged sorghum vinegar. This study investigates the changes in the intermediate Maillard reaction products of sorghum vinegar during ageing and the in vivo hepatoprotective effects of pure melanoidin obtained from it. High-performance liquid chromatography (HPLC) and fluorescence spectrophotometry were utilized to quantify intermediate Maillard reaction products. The CCl4-induced liver damage in rats was used to evaluate the protective role of pure melanoidin in rat liver. Compared with the initial concentration, the 18-month ageing process caused a 1.2- to 3.3-fold increase in the concentrations of intermediate Maillard reaction products, i.e. 5-hydroxymethylfurfural (HMF), 5-methylfurfural (MF), methyglyoxal (MGO), glyoxal (GO) and advanced glycation end products (AGEs). The concentrations of HMF in the aged sorghum vinegar were 6.1-fold higher than the 450 μM limit standard for honey, implying the need for shortening the ageing of the vinegar in practice for safety concerns. Pure melanoidin (Mr>3.5 kDa) demonstrated significant protective effects against CCl4-induced rat liver damage, as evidenced by normalized serum biochemical parameters (transaminases and total bilirubin), suppressing hepatic lipid peroxidation and reactive oxygen species, as well as increasing glutathione amount and restoring antioxidant enzyme activities. Histopathological analysis revealed that melanoidin in vinegar reduced cell infiltration and vacuolar hepatocyte necrosis in rat liver. The findings demonstrated that a shortened ageing process should be considered in practice to ensure the safety of aged sorghum vinegar. Vinegar melanoidin is a potential alternative for the prevention of hepatic oxidative damage. This study demonstrates that the manufacturing process had a profound influence on the generation of vinegar intermediate Maillard reaction products. In particular, it revealed the in vivo hepatoprotective effect of pure melanoidin from aged sorghum vinegar, and provides insight into the in vivo biological activity of melanoidin.

Comprehensive two-dimensional gas chromatography-time of flight mass spectrometry as a tool for tracking roasting-induced changes in the volatilome of cold-pressed rapeseed oil

The aim of this study was to track changes in the volatilome of cold-pressed oil and press cakes obtained from roasted seeds and to combine it with the profile of non-volatile metabolites in a single study, in order to understand pathways of volatile organic compound (VOC) formation caused by thermal processing. Comprehensive two-dimensional gas chromatography-time of flight mass spectrometry was used for the analysis of VOCs in cold-pressed oils and corresponding press cakes obtained after roasting of seeds at 140 and 180 °C prior to pressing. Contents of primary metabolites (amino acids, saccharides, fatty acids) as well as selected secondary metabolites (glucosinolates, polyphenols) were determined, as many of them serve as precursors to volatile compounds formed especially in thermal reactions. After roasting, the formation of Maillard reaction products increased, which corresponded to the reduction of free amino acids and monosaccharides. Moreover, levels of the products of thermal oxidation of fatty acids, such as aldehydes and ketones, increased with the increasing temperature of roasting, although no significant changes were noted for fatty acids. Among sulphur-containing compounds, contents of the products and intermediates of methionine Strecker degradation increased significantly with the increasing temperature of roasting. Degradation of glucosinolates to nitriles occurred after thermal treatment. The results of this study confirmed that seed roasting before cold pressing has a significant effect on the volatiles, but also indicated roasting-induced changes in non-volatile metabolites of oil and press cake. Such an approach helps to understand metabolic changes occurring during rapeseed processing in cold-pressed oil production.Graphical

Effects of traditional and advanced drying techniques on the physicochemical properties of Lycium barbarum L. polysaccharides and the formation of Maillard reaction products in its dried berries

This study explored the effect of three different industrial drying methods on the physicochemical, nutritional, and safety profile of goji berries. The hot-air (HD) and microwave drying (MD) methods yielded berries with relatively high polysaccharide content, while vacuum freeze-drying (FD) yielded dried berries with better sensory qualities but relatively less polysaccharide content. The polysaccharides obtained from the HD and MD berries had lower molecular weight, high antioxidant activity and high degrees of Maillard reaction. Further investigations revealed that all three methods, in particular HD and MD, generated high levels of intermediate Maillard reaction products (55.8–86.3 mg/kg) and advanced glycation end-products (fluorescent intensity of 26784–51712), based on significant reduction of reducing sugar and amino acids in the HD and MD berries (p < 0.05). These findings highlight the need to scrutinize the effectiveness of traditional and emerging drying technologies used to produce safe fruits.