Strecker Aldehydes Research Articles

Multi-response kinetic modelling of the formation of five Strecker aldehydes during kilning of barley malt

Control of aroma formation during production of barley malt is critical to provide consistent and high-quality products for the brewing industry. Malt quality can be affected by the inherent variability of raw material and processing conditions, leading to inconsistent and/or undesirable profiles. Dried green malts were cured isothermally at 65, 78 and 90 °C for 8.4 h, and characteristic aroma compounds (Strecker aldehydes), precursors and intermediate compounds were analysed over time. By kinetic modelling of Strecker aldehydes, based on fundamental chemical pathways, we showed that degradation of Amadori rearrangement products and short-chain dicarbonyls was more sensitive to temperature change due to their higher activation energies compared to other kinetic steps. This study can help maltsters to manipulate formation of Strecker aldehydes, via raw material screening and process control, and hence optimise the organoleptic quality of malts and their products, such as non-alcoholic beers, where these aldehydes play a key role.

From Conventional to Craft Beer: Perception, Source, and Production of Beer Color-A Systematic Review and Bibliometric Analysis.

Beer is a popular beverage consumed globally, and studies have emphasized the benefits of moderate consumption as well as its sensory effects on consumers. Color is a crucial sensory attribute, being the first aspect a consumer notices when assessing a beer's quality. This review seeks to offer detailed insights into how brewing methods, raw materials, and the chemical diversity of beer influence the production of beer color. The chemical mechanisms responsible for color development and how consumers and color systems perceive the color of beer were assessed. A systematic review following the PRISMA methodology, coupled with a bibliometric analysis, was performed using (Rayyan 2022) and (VOSviewer 1.6.20) software to assess and evaluate the scientific research retrieved from the Web of Science Core Collection. The findings highlight the significant roles of malt types, heat brewing processes, control of chemical parameters, and innovative brewing techniques in conventional beer color production. Novel chromophores like perlolyrine, pyrrolothiazolate, and furpenthiazinate are thought to affect Pilsen-style beers, along with melanoidins, Strecker aldehydes, and 5-hydroxymethylfurfural (HMF) in conventional beers. In craft beers, such as fruit- or herb-based beers, flavonoids like anthocyanins, along with other natural pigments and synthetic colorants, are identified as the primary sources of color. However, studies related to the influence of chromophores like perlolyrine, pyrrolothiazolate, and furpenthiazinate on beer color are scarce, and emerging additives, such as pigments from microorganisms, spices, exotic herbs, and leaves of plants, on craft beer offer insights for future research.

Characterization of cooked cheese flavor: Volatile components.

The aim of this work was to identify volatiles that contribute to the aroma of cooked cheese, including the role of fat content in their development during cooking. Volatiles and odorants in cooked mature Cheddar were identified using a combination of SPME (solid-phase microextraction)/GC-O (gas chromatography-olfactometry) and SPME/GC-MS (gas chromatography-mass spectrometry). A selection of the odorants was quantitated in six cheeses, uncooked and cooked, (mature Cheddar, high-, medium-, and low-fat mild Cheddar, mozzarella, and Parmesan). Many compounds showed significant differences between cooked and uncooked cheese; Strecker aldehydes, pyrazines, and furanones were all significantly higher in cooked cheeses than in uncooked cheese, while ethyl esters (key odorants in uncooked cheese) were not detected in any of the cooked cheese. Principal component analysis demonstrated that fat concentration in mild Cheddar was positively correlated with the formation of potential odorants (the Strecker aldehydes, methanethiol, 2-methylketones, and fatty acids) upon cooking. Potential lipid precursors for these compounds are discussed. PRACTICAL APPLICATION: This research can be used by the dairy industry to develop better cheeses, especially low- and reduced-fat cheeses, for use in cooked applications such as toppings for pizzas and ready meals. Alternatively, this research describes key volatile compounds in cooked cheese that can be used by the flavoring industry to develop authentic cooked cheese flavorings.

Unveiling the cocoa-carob flavour gap in dark chocolates via instrumental and descriptive sensory analyses

Roasted carob pulp (Ceratonia siliqua) is a cocoa substitute known for its faint cocoa-like resemblance. However, the cocoa-carob flavour gap remains poorly uncharacterised. This study aimed to elucidate the sensory and molecular aspects of this flavour gap in a 70 % dark chocolate formulation via a two-pronged instrumental-sensorial approach. Descriptive Sensory Analysis (DSA) revealed carob-based chocolate was significantly sweeter, less sour and astringent than conventional dark chocolate due to the high total sugar content (45–50 % DM; HPLC/RID), low titratable acidity and tannin content, respectively. As for aroma, a distinct, albeit weak, cocoa-like aroma was present in carob-based chocolate. HS-SPME-GC-MS/FID revealed this was attributed to branched-chain Strecker aldehyde generation during roasting (2-methylbutanal, 1.17 μg/g; 3-methylbutanal, 2.89 μg/g). Notably, there was a distinct lack of alkylpyrazines. Additionally, a distinct woody, tree bark-like odour was uniquely associated with carob-based chocolates. This was due to furfural generation during roasting (2.33 μg/g). In conclusion, the aroma and taste gap between cocoa and carob was successfully characterised in this study. These findings substantiate the potential of carob application in chocolate manufacturing, thus empowering confectioners to make evidence-based decisions when evaluating cocoa substitutes.

Influence of reducing sugars and protein‐to‐sugar ratios on volatile profile, pH, and browning intensity of Maillard‐reacted nutritional yeast hydrolysate

SummaryThis study investigated the effects of reducing sugars and protein‐to‐sugar ratios on generating volatile compounds from nutritional yeast hydrolysates after Maillard reaction. Nutritional yeast extract (NYE) was cleaved using Flavourzyme® at an enzyme‐to‐substrate ratio of 0.5% w/w, followed by heat treatment with varying concentrations of reducing sugars (i.e., hexoses: glucose and fructose and pentoses: xylose and ribose). The results showed that pentoses generate higher numbers and concentrations of volatiles than hexoses, especially furans, Strecker aldehydes, and sulphur‐containing compounds such as dimethyl disulphide. However, hexoses produced higher concentrations of pyrazines. Strecker aldehydes and pyrazines served as key aroma‐active compounds in meat aroma. Likewise, sulphur‐containing compounds played an important role in meat aroma due to their low detection threshold. The results showed that reducing sugars significantly impacts the volatile profile of NYE, potentially influencing the formation of meaty aroma compounds. These findings demonstrate the potential of MRPs to enhance meaty flavours due to the presence of volatile compounds with characteristics of cooked meat.

Changes in meat quality and volatile flavor compounds profile in beef loin during dry-aging

The objective of this study was to evaluate the effects of dry-aging on beef meat quality changes and flavor compound developments during dry-aging periods. The results showed increased pH and weight loss (P < 0.01), while decreased water content, drip loss, centrifugation loss, and cooking loss (P < 0.01) with dry-aging. The extension of dry-aging significantly improved shear force and myofibrillar protein fragmentation (P < 0.05) of beef loins. However, longer-term dry-aged (28 d) meat exhibited much lower a* values, and higher 2-thiobarbituric reactive substances and carbonyl content (P < 0.01) at the end of dry-aging and even subsequent display. A total of 62 volatile flavor compounds were detected with whole dry-aging periods, and aldehydes were the major potential contributors to cooked beef meat flavor. Principal component analysis indicated the difference in flavor compounds profiles between unaged and dry-aged beef. The content of Strecker aldehydes (2-methyl-butanal and 3-methyl-butanal), some acids, heterocyclic compounds, and ethyl acetate increased with the prolongation of dry-aging time. By combining partial least squares discrimination analysis, 34 compounds with variable importance projection (VIP) > 1 were screened as important aroma compounds changed during the dry-aging processing of beef.

Differences in development of volatiles and bitter peptides between pre- and post-hydrolysed lactose-free UHT milk during storage

Lactose-hydrolysed UHT milk (LHM) has a limited shelf life, especially due to early browning and off-flavour development. This study aimed to directly compare the development in colour, volatile and bitter peptide formation in pre- (lactase addition prior to UHT treatment) and post-hydrolysed (lactase addition after UHT treatment) milk using three different lactases and stored at 25 or 35 °C for up to one year. Pre-hydrolysed milk exhibited more pronounced browning than post-hydrolysed milk. Furthermore, level of Maillard related compounds like acetic acid and furfural were higher in pre-hydrolysed milk compared to post-hydrolysed milk, whereas post-hydrolysed milk was higher in Strecker aldehyde related volatile organic compounds (VOCs). After storage, level of bitter peptides was higher in post-hydrolysed milk using more impure lactases. Generally, lower VOC concentrations and bitter peptides were observed for LHM produced by more pure lactases suggesting higher purity lactases can aid in the development of ambient long-life LHM.

Influence of Drying and Storage Conditions on the Volatile Organic Compounds Profile of Spirulina Platensis

Spirulina platensis (SP) has gained popularity over the last few years, owing to its remarkable nutritional properties and high potential across various industrial sectors. In this study, we analyzed the volatile profile of eight SP samples from the same strain subjected to different drying (oven-drying, air-drying, and spray-drying) and storing conditions (“freshly prepared” and after 12 months of storage) using HS-SPME-GC-MS. Principal component analysis (PCA) was used as a multivariate technique to discern similarities and differences among the samples. The main aim was to assess the impact of the drying technique on the aroma profile and storage life of SP samples. Air-drying leads to the less pronounced formation of by-products related to heat treatment, such as Maillard and Strecker degradation compounds, but promotes oxidative and fermentative phenomena, with the formation of organic acids and esters, especially during storage. Thermal treatment, essential for limiting degradation and fermentation during storage and extending shelf life, alters the aroma profile through the formation of volatile compounds, such as Strecker aldehydes and linear aldehydes, from amino acid and lipid degradation. High temperatures in spray-drying favor the formation of pyrazines. The findings underscore the trade-offs inherent in choosing an appropriate drying method, thereby informing decision-making processes in industrial settings aimed at optimizing both product quality and efficiency.

Occurrence and Synthesis Pathways of (Suspected) Genotoxic α,β-Unsaturated Carbonyls in Chocolate and Other Commercial Sweet Snacks.

α,β-Unsaturated carbonyls are highly reactive and described as structural alerts for genotoxicity. Ten of them (either commercially available or synthesized here by combinatorial chemistry) were first investigated throughout the chocolate-making process by solvent-assisted flavor evaporation (SAFE) coupled to GC-MS/SIM. Monitored α,β-unsaturated aldehydes were formed during chocolate production, primarily through aldol condensation of Strecker aldehydes triggered by bean roasting. Notably, levels of 2-phenylbut-2-enal (up to 399 μg·kg-1) and 5-methyl-2-phenylhex-2-enal (up to 216 μg·kg-1) increased up to 40-fold. Dry conching caused evaporation of α,β-unsaturated carbonyls, while wet conching partially restored or increased their levels due to cocoa butter addition. Further analyses showed that α,β-unsaturated aldehydes also occurred in most commercial sweet snacks (up to 16 μg·kg-1), although often at lower concentrations than in roasted cocoa or derived chocolates. In the end, none of the monitored α,β-unsaturated aldehydes did raise a health concern compared to current maximum use levels (2-5 mg·kg-1). On the other hand, much higher levels of genotoxic furan-2(5H)-one were found in crepe and cake samples (up to 4.3 mg·kg-1).

The Influence of Cooking Methods and Muscle on Beef Aroma Profile and Consumer Satisfaction: Insights from Volatile Compound Analysis

The objective of this study is to determine the effect of two distinct cooking techniques, namely roasting and stewing, on the formation of volatile compounds in various beef muscles (Semimembranosus, Biceps femoris, and Rectus femoris) and how this relates to consumer acceptance. The research employs the concept of volatile “marker” compounds to discern the influence of cooking techniques on the flavor profile of beef. Eighteen “marker compounds” were selected to represent a number of the mechanisms of formation and quantified in beef subjected to two different cooking methods. While no statistically significant differences were observed in consumer evaluations between the two cooking methods, notable disparities emerged in the consumer assessments of specific muscle cuts. Notably, the Rectus femoris muscle received the highest ratings (p &lt; 0.05) among other evaluated muscles. The utilization of Solid-Phase Microextraction (SPME) and gas chromatography–mass spectrometry (GC-MS) methods for the analysis of volatile “marker compounds” in beef proved effective in highlighting significant differences in flavor compound classes between cooking methods, and these differed between muscles. The main effect was of the cooking method with stewed beef aroma having approximately 39× more dimethyl trisulphide, 9× more dimethyl disulphide, 7× more pentanal, 3× more hexanal, and twice as much benzaldehyde and 2-methylthiophene. Dimethyldisulphide, dimethyltrisulphide, hexanal, and heptanal, therefore, emerged as characteristic volatile compounds associated with the stewing cooking technique, suggesting their potential as markers for lipid and other oxidation reactions. This work indicates that certain lipid oxidation compounds, Strecker aldehydes, and sulfur compounds can be markers for the undesirable and/or desirable flavors of cooked beef, but that this depends on the cooking method chosen. It shows that flavor differences may be understood through the analysis of volatile flavor compounds in association with palatability and other chemical measurements.

Use of Botanical Ingredients: Nice Opportunities to Avoid Premature Oxidation of NABLABs by Increasing Their ORAC Values Strongly Impacted by Dealcoholization or Pasteurization

Even when fresh, non-alcoholic, and low-alcoholic beers (NABLABs) exhibit significant staling defects due to premature oxidation. In this study, the antioxidant power of eleven fresh commercial NABLABs was assessed by means of three different assays: the oxygen radical absorbance capacity (ORAC), the linoleic acid-induced oxidation (TINH), and the indicator time test (ITT). Only the first two assays, both involving radicalar degradations initiated by AAPH, were found to correlate with each other. NABLABs displayed lower ORAC values than conventional beers (on average, 6127 μmol eq. Trolox/L), except for three samples made with special-colored malts or dry-hopped. Dealcoholization was the step with the greatest impact on the ORAC value (up to a 95% loss) and on flavan-3-ols, sotolon, and polyfunctional thiols, while pasteurization strongly affected color, TBA, and Strecker aldehydes. ORAC assays applied to hop, alternative cereals, and various botanical ingredients indicated that mashing with red sorghum, dry hopping/spicing, and wood maturation could bring the antioxidant power of a NABLAB close to those of conventional beers. With an ORAC value not reached by any other tested botanical ingredient (5234 µmol eq. Trolox/g), African Vernonia amygdalina leaves (traditionally used for Rwandan Ikigage beers) emerged here as the best candidate.

Effects of ultrasound pretreatment on flavor characteristics and physicochemical properties of dry-cured ham slices during refrigerated vacuum storage

The application of ultrasound to dry-cured ham may be an option to improve the flavor of meat products storage at vacuum for long periods of time. To investigate the ultrasound-induced influence on flavor characteristics of ham, slices of 9 and 12 months of processing were vacuum packaged and stored at refrigerated temperatures up to 40 d to study the changes of volatile compounds by using solid phase micro-extraction (SPME) and GC-MS and their sensory profile by free choice profile (FCP). Besides, the changes in physicochemical properties (pH, humidity, water activity, color and composition) after ultrasound and storage were determined. Results showed that ultrasound changed the flavor profile of ham slices especially in 12 m hams and after 40 d of storage, with decreased level of linear and Strecker aldehydes and increased level of ketones and alcohols. Sensory results suggested that ultrasound favored the formation of cured and nutty odors with a higher impact in long processing hams (12 m) as observed in the volatile profile as well as increased redness without affecting other physicochemical properties. Therefore, ultrasound is a potential approach to improve the flavor and color characteristics of dry-cured ham slices during vacuum refrigerated storage.

Exploring oat lipid profile and changes in volatile profile of oats upon cooking into porridge using a foodomics approach

This study aimed to comprehensively characterize the lipid profile and volatile compounds in oat-based products and investigate how their volatile compositions change upon cooking into porridge. Twelve commercially available oat products with distinct fatty acid compositions were selected. Using a foodomics approach involving gas chromatography-mass spectrometry (GC-MS) fingerprinting and chemometrics, the study classified volatile profiles within oat samples and identified discriminant compounds responsible for differences. The results highlighted variations in volatile components spanning chemical groups (alkanals, alcohols, Strecker aldehydes, esters, and terpenes), reflecting differences in volatile attributes across brands. Similar profiles among products from the same manufacturer indicated links between variety, processing methodologies, and volatile profiles. Comparing dry and porridge samples, except for notable shifts in some cases, consistent volatile profiles and discerning compounds after cooking suggested key elements persist, implying potential parallels in volatile profiles pre- and post-preparation. This study underscores the potential of the foodomics approach for understanding volatile profiles in oat-based products, aiding flavor enhancement and optimizing product quality.

Formation of staling aldehydes in different grain bed layers in an industrial scale maltings

Understanding the contribution of raw materials to the quality of the final product is crucial for the food industry. In the brewing process, malt delivers various compounds that compromise the flavour stability of beer, including staling aldehydes and their precursors. The primary aim of this study was to investigate the evolution of staling aldehydes and their cysteinylated counterparts throughout industrial scale pale malt production. The second objective was to study the extent to which process related gradients (e.g., temperature, moisture) may contribute to the differential formation of free and bound state aldehydes. Samples were collected from two industrial scale, pale lager malt production processes as a function of process time (germination, kilning, and cooling) and the position of the kernals in the grain bed (bottom, middle and top layers) during kilning. The levels of free and cysteinylated aldehydes were determined. The results show that the initial stage of germination is accompanied by enzymatic fatty acid oxidation as reflected by the formation of hexanal and trans-2-nonenal. Drying at elevated temperature (at a critical moisture content of 6-9%) results in the intensified formation of cysteinylated Strecker aldehydes and furfural. Moreover, a rapid increase in the formation of (cysteinylated) Strecker aldehydes furfural and trans-2-nonenal continued through kilning. A clear effect of temperature and moisture gradients was observed on the formation of aldehydes and it is concluded that exposure to heat load plays a critical role in the development of cysteinylated aldehydes during malt production. This publication is dedicated to the memory of Professor Luc De Cooman.

Comparison of Storage-Related Volatile Profiles and Sensory Properties of Cookies Containing Xylitol or Sucrose.

Excessive consumption of simple sugars is responsible for non-communicable diseases such as obesity, cardiovascular diseases, and diabetes. Xylitol has anticarcinogenic, prebiotic-like characteristics and a lower glycaemic index and caloric value than sugars, which makes it a valuable alternative sweetener. The aim of this study was to examine the effects of storage of volatile compounds and sensory profiles of cookies containing xylitol as a sucrose alternative or sucrose by applying solid-phase microextraction gas chromatography/mass spectrometry and quantitative descriptive analysis. The volatile compound profiles of both kinds of cookies were similar, especially regarding markers of Maillard reactions (Strecker aldehydes, pyrazines) and unfavourable compounds (aldehydes, hydrocarbons, and organic acids). Throughout the period of storage lasting 0-9 months, the total content of hydrocarbons was stable and averaged 10.2% in xylitol cookies and 12.8% in sucrose cookies; their storage for 12 months significantly (p < 0.05) increased the contents to 58.2% and 60.35%, respectively. Unlike sucrose, xylitol improved the stability of the pH and water activity of cookies and sensory attributes such as buttery aroma and texture characteristics during 12 months of storage. The results indicated that 9 months of cookie storage was the maximum recommended period. The inclusion of xylitol in cookies might replace sucrose and high-fructose-corn syrup and synthetic additives commonly used in industrial production.

Mechanochemistry of Strecker degradation: Interaction of glyoxal with amino acids

Mechanochemistry is rapidly evolving into a versatile and green method for chemical synthesis. Due to its unique reaction conditions, ball milling of sugars and amino acids mainly leads to the formation of Amadori products with minimum degradation. In this study, we milled glyoxal trimer dihydrate with twenty proteogenic amino acids to demonstrate the formation of Strecker degradation products. HS-GC/MS studies indicated that Strecker degradation proceeded to selectively generate Strecker aldehyde and unsubstituted pyrazine as the major volatiles. Moreover, ESI/qToF/MS studies demonstrated for the first time the formation of the proposed key Strecker degradation intermediates, such as the condensation products and their decarboxylated products, indicating the similarity of the mechanism of Strecker reaction under ball milling to that proposed under hydrothermal reaction conditions. These studies provided supporting evidence that ball milling at ambient temperatures could be used as a novel synthetic approach to prepare precursors of aroma-active volatiles through Strecker degradation.

PSVIII-23 Volatile Flavor Profile of Wet Pet Food Influences Canine and Feline Palatability Performance

Abstract Volatile flavor compounds as they relate to canine and feline palatability of wet pet food has yet to be established in the industry. The objectives of this study were to determine volatile compounds in wet pet food in diets that performed differently in palatability feeding studies. Five pairs of wet pet food diets (n = 3 feline; n = 2 canine) were obtained from separate manufacturing facilities and were selected based on palatability preference (P &amp;lt; 0.05, n = 3) or palatability parity (P &amp;gt; 0.05, n = 2). Volatile compounds were extracted using solid phase microextraction and analyzed via gas chromatography-mass spectrometry. Diets were analyzed in triplicate. Significance was determined at P &amp;lt; 0.05. Alcohols, aldehydes, and hydrocarbons comprised the main groups, and 58 total volatile compounds were identified. 1-octen-3-ol, an artifact of lipid oxidation, was found in all diets and was consistently greater (P &amp;lt; 0.05) in diets that were less preferred in palatability testing. A feline diet less preferred in palatability performance had increased concentrations (P &amp;lt; 0.05) of volatile compounds such as furfuryl alcohol and 2-pentyl furan, derived from both the Maillard reaction and thermal lipid degradation pathways, respectively. Conversely, a canine diet with palatability preference was greater (P &amp;lt; 0.05) in lipid degradation products such as 2-pentyl furan, 1-hexanol, and p-xylene. Overall, one set of diets had an increased (P &amp;lt; 0.05) production of Maillard reaction products including Strecker aldehydes, furans, and pyrazines whereas lipid degradation products were predominant in the second set. In conclusion, these data generally showed a significant difference (P &amp;lt; 0.05) in Maillard reaction and lipid degradation products in each pair of diets. Future studies are warranted to better understand how the volatile compound profile impacts palatability for canines and felines. Taken together, the results of this study suggest that volatile compound profile analysis could be utilized to further elucidate influencers of pet food palatability preferences.

Formation response of kilned specialty malt odorant markers to controlled malting process parameters.

Kilned specialty malts provide relevant colour and flavour characteristics to beer and other beverages. Alongside the thermal load, the availability of Maillard precursors directly affect the malt aroma formation. To investigate the influence of process parameters on the flavour characteristics of kilned specialty malts, a full factorial design of experiments was applied varying malt modification degree, curing temperature and time in three levels (33). Analysis of response surfaces revealed a predominant influence of the modification degree and curing temperature on the formation of Strecker aldehydes and pyrazines. Odorants such as 2-methylpropanal and 2-ethyl3,6-dimethylpyrazine presented higher concentrations varying between 429.45 and 478.22µg∙Kgmalt-1 and 12.49 to 16.75µg∙Kgmalt-1 respectively, at samples produced under 100°C and high modification degree. Sensory analysis revealed strong correlations between the odorant markers and typical malt flavour attributes, endorsing the applicability of such methodology on the development and optimisation of kilned malt specialities.

Daily assessment of malting-induced changes in the volatile composition of barley (Hordeum vulgare L.), rye (Secale cereale L.), and quinoa (Chenopodium quinoa Willd.).

Barley (Hordeum vulgare L.) is the traditional malting cereal and is primarily used for beverages, whereas rye (Secale cereale L.) is mainly used in baked goods. Conversely, quinoa (Chenopodium quinoa Willd.) is a gluten-free pseudocereal, rich in starch and high-quality proteins, and can be used in a similar manner to cereals. The sharp bitterness of unprocessed rye and the earthy aroma of native quinoa interfere with the acceptance and development of food products. Malting of barley is known to improve its processing properties and enhance its sensory quality. Therefore, the effect of germination and kilning on malt quality (e.g., viscosity) as well as the volatile composition of barley, rye, and quinoa were monitored. Moreover, temporal changes on the volatile patterns of rye and quinoa at the different stages of malting were compared to barley. In total, 34 volatile compounds were quantified in the three (pseudo)cereals; the alcohol group dominated in all unprocessed samples, in particular, compounds contributing grassy notes (e.g., hexan-1-ol). These grassy compounds remained abundant during germination, whereas kilning promoted the formation of Maillard reaction volatiles associated with malty and roasted notes. The volatile profiles of kilned barley and quinoa were characterized by high concentrations of the malty Strecker aldehyde, 3-methylbutanal. In contrast, green, floral notes imparted by phenylacetaldehyde remained dominant in rye malt. Hierarchical cluster analysis of the volatile data discriminated the samples into the different stages of malting, confirmed the similarities in the volatile patterns of barley and rye, and indicated clear differences to the quinoa samples. PRACTICAL APPLICATION: In this study, the effect of germination and kilning on the chemical and volatile composition of barley, rye, and quinoa was examined. Temporal changes on the volatile patterns of rye and quinoa at different stages of malting were compared to barley. Understanding the differences among the (pseudo)cereals as well as the influence of processing on malt quality and aroma development can help find new food applications.

Improvement of Robusta coffee aroma by modulating flavor precursors in the green coffee bean with enzymatically treated spent coffee grounds: A circular approach

Spent coffee grounds (SCG) are by-products obtained from the industrial process of instant coffee production or alternatively after brewing of coffee at the point of consumption. This solid residue represents one of the largest waste materials worldwide, making this fraction a rational target for valorization. The composition of SCG varies significantly depending on the brewing and extraction methods. However, this by-product is mainly composed of cellulose, hemicellulose polysaccharides and lipids. Here, we report on the enzymatic hydrolysis of industrial SCG by the use of a combination of specific carbohydrate active enzymes, enabling sugar extraction yield of 74.3 %. The generated sugar-rich extract, primarily composed of glucose (8.41 ± 1.00 % of total SCG mass) and mannose (2.88 ± 0.25 % of total SCG mass), is separated from hydrolyzed grounds and soaked with green coffee. After drying and roasting, the coffee soaked with SCG enzymatic extract displayed lower earthy, burnt and rubbery notes as well as smoother and more acidic notes in the flavor profile as compared to untreated reference. Aroma profiling performed by SPME-GC–MS corroborated the sensorial effect, with a 2-fold increase in the generation of sugar-derived molecules such as Strecker aldehydes and diketones after soaking and roasting and a 45 % and respectively 37 % reduction in phenolic compounds and pyrazines. This novel technology could represent an innovative in situ valorization stream for the coffee industry, coupled with sensory improvement of the final cup.