Effect of Roasting and Storage on the Formation of Maillard Reaction and Sugar Degradation Products in Hazelnuts ( Corylus avellana L.)

Novel insight into Amadori compounds: Fate of Amadori compounds in food supply chain

Amadori compounds, pivotal intermediates in the Maillard reaction, act as flavor enhancer, browning precursor, and functional component. Amadori compounds consisting of diverse amino and carbonyl groups might show distinct flavor attributes and functional activities. Food production involves many supply chain stages where thermal treatment might produce Amadori compounds, and processing techniques and circumstances might affect the generation and stability of Amadori compounds. Moreover, gastrointestinal digestion might also influence the stability of Amadori compounds. To date, there is a lack of comprehensive review on the impact of various supply chain stages and digestion on Amadori compounds. This paper reviewed all reported Amadori compounds derived from diverse reducing sugars (glucose, xylose, ribose, maltose) and amino-containing compounds (common and specific amino acids, peptides), and compared differences in synthetic efficiency, flavor property, and functional activity among them; aggregated qualitative techniques; encapsulated quantitative techniques including indirect quantification and direct quantification, and intuitively compared strengths and weaknesses of these techniques; and outlined influence of processing, cooking, storage, and digestion on formation and stability of Amadori compounds. Appropriate processing techniques and conditions favored the generation and stability of Amadori compounds. Baking, frying, and roasting greatly facilitated Amadori compounds accumulation compared to steaming and boiling. Prolonged cooking at relatively low temperature favored Amadori compounds accumulation, whereas high-temperature cooking for a short duration resulted in fewer accumulation. Amadori compounds showed greater digestion resistance and could be absorbed by the intestine. This review offers scientific instruction for producing high-quality products with abundant Amadori compounds, or extracting plentiful Amadori compounds from processed foods as versatile food additives.

Effects of roasting on physicochemical characteristics and flavor substances of germinated brown rice

Roasting can dissolve the nutrients accumulated in germinated brown rice (GBR). This study investigated the effects of roasting on physical properties, nutrients and flavor substances of GBR. Results demonstrated that longer roasting time resulted in more browning and a decrease in the moisture content. The total soluble sugar content increased significantly, while the soluble protein content decreased initially and then slightly increased. Roasting also resulted in a decrease in γ-aminobutyric acid (GABA) content. However, the content of total phenolics increased significantly. Phenolic acids content increased and then decreased with the roasting time. The volatile components of GBR were found to be mainly organic sulfides and furans after roasting, 1-pentene-3-alcohol and 2-butanone (dimer) were the most differentiating components contributing to the distinguish of roasting times. Correlation analysis showed that total soluble sugar and GABA were important flavor precursors. These findings provide a theoretical basis for development of GBR-based products.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-024-01655-4.

Changes in α-Dicarbonyl Compound Contents during Storage of Various Fruits and Juices

α-Dicarbonyl compounds (α-DCs) are commonly present in various foods. We conducted the investigation into concentration changes of α-DCs including 3-deoxyglucosone (3-DG), glyoxal (GO), and methylglyoxal (MGO) in fresh fruits and decapped commercial juices during storage at room temperature and 4 °C, as well as in homemade juices during storage at 4 °C. The studies indicate the presence of α-DCs in all samples. The initial contents of 3-DG in the commercial juices (6.74 to 65.61 μg/mL) are higher than those in the homemade ones (1.97 to 4.65 μg/mL) as well as fruits (1.58 to 3.33 μg/g). The initial concentrations of GO and MGO are normally less than 1 μg/mL in all samples. During storage, the α-DC levels in the fruits exhibit an initial increase followed by a subsequent decrease, whereas, in all juices, they tend to accumulate continuously over time. As expected, 4 °C storage reduces the increase rates of the α-DC concentrations in most samples. From the viewpoint of the α-DC contents, fruits and homemade juices should always be the first choice for daily intake of nutrients and commercial juices ought to be mostly avoided.

Understanding chemical pathways of brown centre formation in laboratory induced and conventionally dried nut-in-shell macadamia kernels

World tree nut production has increased rapidly by around 50 % in the past decade; however, nut defects cause losses. For example, we know that brown centres are a major internal discolouration defect in macadamia nuts and are linked to the storage of nut-in-shell under improper conditions at high temperature and humidity. However, key chemical changes in brown centre kernels have not been described. In this study, we compared brown centres and white kernels from: 1) samples that were "induced" in the laboratory by storing at high moisture concentration; and 2) samples that were dried immediately after harvest using industry best practice methods recommended by the Australian Macadamia Society (AMS). We measured the moisture concentration, sugar concentration, fatty acid concentration, peroxide value, nutrient concentration and volatile compounds of induced and AMS samples. Our results showed that storing nut-in-shell macadamia under wet and hot conditions increased brown centres compared with samples immediately dried using the AMS regime, 10.33 % vs 1.44 %, respectively. Induced brown centres had significantly higher moisture concentrations than induced white centres. Volatile compounds including nonanoic acid, octanoic acid and 2,3 butanediol were identified and associated with brown centre formation in macadamia kernels and the initiation of lipid oxidation. Our results suggest sugar hydrolysis and the Maillard reaction are associated with brown centres both in laboratory induced samples and those formed using industry best practice drying methods. Our study suggests improper drying and storage at high temperature and high humidity are likely to result in brown centre formation. We recommend brown centre losses can be reduced by appropriate drying and storage practices.

Influence of heat treatments on the functionality of soy protein hydrolysates in animal cell cultures

Soy protein hydrolysates enhance integral viable cell density (IVCD) and recombinant protein production (Immunoglobulin, IgG) in cell cultures, but their functionality varies from batch-to-batch. This is undesirable since it affects both quantity and characteristics of the recombinant proteins. It is hypothesized that the variability of hydrolysates is due to variations in meal and hydrolysate processing treatments. To study this, hydrolysates were produced from meals heated at 121 °C/0-120 min. The heating decreased free amino acid and reducing monosaccharide contents in meals (0.72-0.27% and 3.3-2.6%) and hydrolysates (14.7-7.1% and 16.9-7.9%). Dry heating introduced large variation in the IVCD ((115-316%), but additional heating in suspension reduced it (131-159%). The decrease in IVCD variation corresponded with decreased variation in carboxymethyl-lysine (CML) and lysinoalanine (LAL) contents. Thus, meal and hydrolysate processing induced substantial variation in hydrolysate functionality. It is therefore critical to establish strict process controls for meal and hydrolysate production to ensure consistency.

Amadori compounds: analysis, composition in food and potential health beneficial functions

Amadori compounds (ACs) are key intermediates of the Maillard reaction, and found in various thermally processed foods. Simultaneous analysis of multiple ACs is challenging due to the complex amino acid and carbohydrate compositions, and the different food matrices. Most studies focus on the effects of ACs on food flavor and related sensory properties, but not their biological functions. However, increasing evidence shows that ACs possess various beneficial effects on human health, thus a comprehensive review on the various biological activities is warranted. In this review, we summarized the composition and content of ACs in different foods, their formation and degradation reactions, and discussed the latest advances in analytical methods of ACs and their biological functions related to human health. Limitations and research gaps were identified and future perspectives on ACs research were proposed. This review points to the needs of systematic and comprehensive in vitro and in vivo studies on human health related biological functions of ACs and their mechanisms of action, particularly the synergistic effects with other food components and drugs, and roles in intestinal health and metabolic syndrome.

Investigation on the contents of heat-induced hazards in commercial nuts

The purpose was to investigate the contents of heat-induced hazards by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in 44 commercial nuts. Results showed that content ranges of Acrylamide (AA), 5-hydroxymethylfurfural (5-HMF), N^ε-carboxymethyl-lysine (CML), N^ε-carboxyethyl-lysine (CEL), 3-Deoxyglucosone (3-DG), Glyoxal (GO), and Methylglyoxal (MGO) were ND-123.57 µg/kg, 0.57-213.42 mg/kg, 3.18-18.67 mg/kg, 3.98-57.85 mg/kg, 1.5-133.86 mg/kg, 0.45-1.59 mg/kg and 0.29-13.84 mg/kg, respectively. Sunflower seeds contained more heat-induced hazards followed by pistachios, cashews, almonds, walnuts and hazelnuts. The content of 5-HMF was positively correlated with the content of 3-DG. CML exhibited positive correlation with content of GO while no correlation between CEL and MGO. Higher levels of 3-DG and 5-HMF were observed in nuts produced with sugar and honey. Deep processing had a stronger promoting effect on CML and CEL formation. These data could provide a crucial guide for consumers to select nut products which might reduce heat-induced hazards intake.

Corylus avellana L. Natural Signature: Chiral Recognition of Selected Informative Components in the Volatilome of High-Quality Hazelnuts

The volatile fraction of plant-based foods provides useful functional information concerning sample-related variables such as plant genotype and phenotype expression, pedoclimatic and harvest conditions, transformation/processing technologies, and can be informative about the sensory quality. In this respect, the enantiomeric recognition of the chiral compounds increases the level of information in profiling studies, being the biosynthesis of native compounds often stereo-guided. Chiral native volatiles mostly show an enantiomeric excess that enables origin authentication or support correlation studies between chemical patterns and sensory profiles. This study focuses, for the first time, on the enantiomeric composition of a large set of chiral compounds within the complex volatilome of Corylus avellana L. belonging to different cultivars (Tonda Gentile Romana, Tonda Gentile Trilobata, Anakliuri) and harvested in different geographical areas (Italian and Georgian). Besides native components profiled in raw kernels, volatiles formed after technological treatment (i.e., roasting) are also considered. Headspace solid-phase microextraction combined with enantioselective gas chromatography-mass spectrometry enables the accurate tracking and annotation of about 150 compounds across many samples. The results show that chiral compounds have diagnostic distribution patterns within hazelnut volatilome with cultivar and harvest region playing the major role. Moreover, being some of these chiral molecules also key-aromas, their distribution has a decisive impact on the sensory properties of the product. In particular, the enantiomeric composition of (E)-5-methyl-2-hepten-4-one (filbertone) resulted to be discriminant for origin authentication. The enantiomeric distribution showed, according to literature, an excess of the (S)-enantiomer in both raw and roasted samples volatilome with larger differences in raw samples. The amount of both (R) and (S)-filbertone increases during roasting; the most marked increase for (R)-enantiomer is observed in Italian samples, thus supporting evidence of better hedonic properties and more pleasant odor and aroma.

Chemical Stability of Proteins in Foods: Oxidation and the Maillard Reaction

Protein is a major nutrient present in foods along with carbohydrates and lipids. Food proteins undergo a wide range of modifications during food production, processing, and storage. In this review, we discuss two major reactions, oxidation and the Maillard reaction, involved in chemical modifications of food proteins. Protein oxidation in foods is initiated by metal-, enzyme-, or light-induced processes. Food protein oxidation results in the loss of thiol groups and the formation of protein carbonyls and specific oxidation products of cysteine, tyrosine, tryptophan, phenylalanine, and methionine residues, such as disulfides, dityrosine, kynurenine, m-tyrosine, and methionine sulfoxide. The Maillard reaction involves the reaction of nucleophilic amino acid residues with reducing sugars, which yields numerous heterogeneous compounds such as α-dicarbonyls, furans, Strecker aldehydes, advanced glycation end-products, and melanoidins. Both protein oxidation and the Maillard reaction result in the loss of essential amino acids but may positively or negatively impact food structure and flavor. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Quantification of advanced glycation end products and amino acid cross-links in foods by high-resolution mass spectrometry: Applicability of acid hydrolysis

An analytical method was developed and validated for simultaneous identification and quantification of advanced glycation end products (AGEs), amino acid cross-links, lysine and arginine in foodstuffs based on acid hydrolysis, hydrophilic interaction chromatography and high-resolution mass spectrometry. The method proved to be sensitive, reproducible and accurate for furosine, N-Ɛ-(carboxymethyl)lysine, N-Ɛ-(carboxyethyl)lysine, methylglyoxal and glyoxal-derived hydroimidazolones (MG-H and GO-H isomers, respectively), glyoxal lysine dimer, lysinoalanine, lanthionine, lysine and arginine. LOD and LOQ values in water were found to be 0.9-15.5 ng/mL and 2.8-47 ng/mL, respectively, and increased to 1.4-60 ng/mL and 4.4-182 ng/mL in liquid infant formula. Recovery values ranged from 76 to 118% in four different food matrices. Microwave-assisted hydrolysis for 11 min had similar efficiency as conventional hydrolysis, which requires overnight incubation. Acid stability of each compound was determined during microwave and conventional hydrolysis, and showed that the MG-H1 isomer is partially converted to the MG-H3 isomer during acid hydrolysis.

An overview of conventional and emerging techniques of roasting: Effect on food bioactive signatures

Roasting is a food processingtechnique that employs the principle of heating to cook the product evenly and enhance the digestibility, palatability and sensory aspects of foods with desirable structural modifications of the food matrix. With the burgeoning demand for fortified roasted products along with the concern for food hygiene and the effects of harmful compounds, novel roasting techniques, and equipment to overcome the limitations of conventional operations are indispensable. Roasting techniques employing microwave, infrared hot-air, superheated steam, Revtech roaster, and Forced Convection Continuous Tumble (FCCT) roasting have been figuratively emerging to prominence for effectively roasting different foods without compromising the nutritional quality. The present review critically appraises various conventional and emerging roasting techniques, their advantages and limitations, and their effect on different food matrix components, functional properties, structural attributes, and sensory aspects for a wide range of products. It was seen that thermal processing at high temperatures for increased durations affected both the physicochemical and structural properties of food. Nevertheless, novel techniques caused minimum destructive impacts as compared to the traditional processes. However, further studies applying novel roasting techniques with a wide range of operating conditions on different types of products are crucial to establish the potential of these techniques in obtaining safe, quality foods.

Advances in cultivar choice, hazelnut orchard management, and nut storage to enhance product quality and safety: an overview

European hazelnut (Corylus avellana L.) is a major species of interest for nutritional use within the Betulaceae family and its nuts are widely used throughout the world in the chocolate, confectionery, and bakery industries. Recently its cultivation has been expanded in traditional producer countries and established in new places in the southern hemisphere, including Chile, South Africa, and Australia. Introducing hazelnut in new environments could reduce its productivity, lead the trees to experience eco-physiological disorders, and expose the crop to high pressure from common and new pests and diseases. Thus, new approaches in cultivar choice guidance, in the sustainable orchard management and even in nut storage and kernel quality evaluation are urgently required to improve the hazelnut production and processing chain. The main objective of this study was to systematize the published information regarding recent findings about the cultural operations that directly influence nut and kernel quality, support varietal choice for new plantations, and list the recent advances in nut storage and in quality and safety evaluation. © 2020 Society of Chemical Industry.

Methylglyoxal-hydroimidazolones (MG-Hs) instead of Nɛ-(carboxymethyl)-l-lysine (CML) is the major advanced glycation end-product during drying process in black tea

This study was to examine the formation of advanced glycation end-products (AGEs) in black tea during drying process at 90, 120, and 150 °C for 1 h. Nine AGEs including Nɛ-(carboxyethyl)-l-lysine (CEL), Nɛ-(carboxymethyl)-l-lysine (CML), three isomers of methylglyoxal-hydroimidazolones (MG-Hs), three isomers of glyoxal-hydroimidazolones (GO-Hs), and argpyrimidine were quantified by using HPLC-MS/MS with isotope-labelled internal standard. Results showed that each AGE during the drying process of 150 °C was significantly higher (p < 0.05) than at 90 and 120 °C, and argpyrimidine was only found in the treatment of 150 °C. MG-H1/3 was first quantified as the major AGE during drying at 120-150 °C, the content respectively reached to (39.66 ± 2.61) μg/g and (58.88 ± 1.76) μg/g after 1 h drying, where CML content only had (19.86 ± 1.02) μg/g and (23.71 ± 1.40) μg/g. This study indicated that arginine derived-AGEs are the key components of black tea AGEs.

Limitation of Maillard Reactions in Lactose-Reduced UHT Milk via Enzymatic Conversion of Lactose into Galactooligosaccharides during Production

Lactose-hydrolyzed (LH) ultrahigh temperature (UHT) processed milk is more prone to Maillard reactions and formation of advanced glycation end products (AGEs) during processing and storage than conventional (CON) UHT milk because of the presence of free galactose and glucose. Commercially available β-d-galactosidases with transgalactosylating activity can incorporate galactose into galactooligosaccharides (GOSs) and potentially limit Maillard reactions in this lactose-reduced GOS-containing milk. The aim of this study was to examine the extent of Maillard reactions in a lactose-reduced GOS milk compared to LH and CON milk after UHT processing. The GOS milk had significant lower levels of lysine- and arginine-derived AGEs compared to LH milk, while their concentrations were similar to those found in CON milk. The total concentration of measured Arg-derived AGEs was similar to the total concentration of Lys-derived AGEs in the three types of milk, indicating that Arg is an important source of AGEs in milks. Interestingly, the GOS milk generated threefold higher concentrations (up to 330 ± 6 μM) of 3-deoxyglucosone (3-DG, a C6 α-dicarbonyl). These results demonstrate that GOS milk could be a potential alternative for LH milk for lactose-intolerant individuals, although further studies are needed to understand the increased formation of 3-DG in GOS-containing milk.

Lipids Promote Glycated Phospholipid Formation by Inducing Hydroxyl Radicals in a Maillard Reaction Model System

Food-derived glycated phospholipids is potentially hazardous to human health. However, there are few studies on the effects of lipids on the formation of glycated phospholipids. In this work, two model systems were established: (1) a model system including 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (PE), glucose, and Fenton reagent and (2) a model system including PE, glucose, and five kind of vegetable oils. The contents of carboxymethyl-PE, carboxyethyl-PE, Amadori-PE, hydroxyl radical (OH•), glyoxal, and methylglyoxal were determined with high-performance liquid chromatography mass spectrometry. The results of the first model system showed that OH• oxidized glucose to produce glyoxal and methylglyoxal, which then reacted with PE to form carboxymethyl-PE and carboxyethyl-PE. OH• also oxidized Amadori-PE to form carboxymethyl-PE. The results of the second model system showed that vegetable oils with higher number of moles of carbon-carbon unsaturated double bond in vegetable oil per kilogram could produce more OH•, which promote the formation of carboxymethyl-PE and carboxyethyl-PE by oxidizing glucose and oil. We elucidated the effects of oils on the formation of glycated phospholipids in terms of OH• and intermediates. This work will contribute to better understanding the formation mechanism of glycated phospholipids with oil.

Investigations on the Maillard Reaction in Sesame ( Sesamum indicum L.) Seeds Induced by Roasting

This study investigated the formation of Maillard reaction products in sesame seeds under different roasting conditions. Sesame seeds were roasted at 150, 180, 200, and 220 °C for 10 min, and thermal process contaminants including 5-hydroxymethylfurfural, acrylamide, furan, and dicarbonyl compounds (1-deoxyglucosone, 3-deoxyglucosone, methylglyoxal, and diacetyl) together with glycation markers namely N-ε-fructosyllysine, N-ε-carboxymethyllysine, and N-ε-carboxyethyllysine, were monitored. Roasting induced the formation of 5-hydroxymethylfurfural, acrylamide, and dicarbonyl compounds, except furan, significantly ( p < 0.05). 5-Hydroxymethylfurfural and acrylamide content of roasted sesame seeds were found to vary as 3-40 mg/kg and 135-633 μg/kg, respectively. Dicarbonyl compounds were in the following order: methylglyoxal > 3-deoxyglucosone > 1-deoxyglucosone > diacetyl. On the other hand, N-ε-fructosyllysine concentration decreased while the roasting temperature increased; however, N-ε-carboxymethyllysine and N-ε-carboxyethyllysine formation was induced under those conditions. This is the first study reporting the formation of thermal process contaminants and glycation markers in sesame seeds through Maillard reaction during roasting.