Strecker Aldehydes Research Articles

Determination of 13 Volatile Aldehyde Compounds in Wine by GC-QQQ-MS: p-Benzoquinone to Dissociate Hydrogen Sulfite Addition Products

This study validates a new methodology which allows the direct quantification of 13 volatile aldehyde compounds related to oxidative off-flavours in wine. The compounds investigated were four (E)-2-alkenals ((E)-2-heptenal, (E)-2-hexenal, (E)-2-octenal and (E)-2-nonenal), four Strecker aldehydes (2-methylpropanal, 3-methylbutanal, methional and 2-phenylacetaldehyde) and five general aldehydes (hexanal, furfural, 5-methylfurfural, benzaldehyde and nonanal). This methodology involved the addition of p-benzoquinone to release the aldehydes bound to hydrogen sulfite, collection via solid phase extraction, derivatisation by o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride and quantification by gas chromatography triple-quadrupole mass spectrometer in multiple reaction monitoring mode. Overall, the limit of detection, limit of quantification, accuracy (recovery, 98–103%) and precision (repeatability and reproducibility, RSD ≤ 15%) are sufficient to enable routine measurement of the 13 aldehyde compounds in wine. Sixteen commercial white and red wines of varied varieties and vintages were analysed with this methodology. White wines trended to have higher concentrations of the aldehyde compounds in comparison with the red wines.

Quality-driven design of sponge cake: Insights into reactivity, furan mitigation and consumer liking

This work highlights the importance of considering reactivity into the quality-driven design of heat-treated foods, which should cover the mitigation of process-induced contaminants and the improvement of the sensory properties of the foodstuff. The joint effects of formulation and baking conditions on reactivity and several quality aspects (i.e. volatile generation, physical properties, sensory and consumer tests), followed by product optimization (i.e. consumer liking and furan mitigation) were studied. While key markers are affected by all factors and their interactions, the effect of sugar and whole egg are the clearest. Furan would be predominantly generated from glucose via caramelization and/or Maillard reaction, whereas the formation of Strecker aldehydes and lipid oxidation products would be favoured by precursors in whole egg. Formulations with a low glucose content, baked at low temperatures/short times lead to optimal products. Egg-based ingredient content may be set according to preference or by applying different optimization approaches.

The Impact of Enhancement, Degree of Doneness, and USDA Quality Grade on Beef Flavor Development

The objective of this study was to determine the impact of enhancement, degree of doneness (DOD), and USDA quality grade on beef volatile flavor compounds from cooked strip loin steaks. This study also aimed to evaluate relationships between volatile compounds and consumer sensory responses. Beef strip loins (n = 72; 24/grade) of 3 quality grades (USDA Prime, Low Choice, and Low Select) were enhanced (8% of green weight with brine containing 0.35% salt and 0.4% sodium phosphate) or not enhanced, and cooked to 3 DOD (Rare: 60°C; Medium: 71°C; Very Well Done: 83°C) before volatile analysis. Volatile compounds were evaluated through a split-plot design where enhancement level and quality grade were used as the whole plot factors and DOD served as the subplot factor. Principal component analysis (PCA) was utilized to explore relationships between volatile compounds, consumer response, and treatments. The majority of compounds (n = 32) were impacted (P < 0.05) by the interaction between DOD × enhancement × quality grade. Four compounds- methanethiol, dimethyl-disulfide, methyl-benzene, and acetic acid were affected (P < 0.05) by enhancement × DOD. Two compounds- dimethyl sulfone and d-limonene, were impacted (P < 0.05) by quality grade × enhancement. Phenylacetaldehyde and hexanoic acid, methyl ester was affected (P < 0.05) by the interaction of USDA quality grade × DOD. The DOD main effect was only implicated in Maillard products (P < 0.05), including 2-methylbutanal, a Strecker aldehyde, and 2 pyrazines (methyl-pyrazine and trimethylpyrazine). Nonanal was the only compound impacted (P < 0.05) by a quality grade effect. No enhancement main effects were observed for any compounds (P > 0.05). In agreement, PCA indicated volatile compound production was primarily driven by degree of doneness and quality grade. There was no strong link between enhancement and beef volatile flavor compound development, despite the dramatically improved flavor liking scores from consumers.

Impact of different enzymatic hydrolysates of whey protein on the formation of pyrazines in Maillard model systems.

The generation of pyrazines in model systems containing enzymatically hydrolyzed whey protein under dry heating conditions was studied. Pyrazines are important Maillard flavor compounds. Hydrolysates, obtained with different peptidases (pepsine, chymosine, thermolysin and a non-specific peptidase from Aspergillus melleus), contained a varying peptide profile and free amino acid content. The impact of each hydrolysate on the generation of flavor volatiles was measured by HS-SPME-GC/MS. The presence of oligopeptides had an enhancing role on the generation of pyrazines while, in contrast, free amino acids contributed to a lesser extent in pyrazine formation, except in the hydrolysate using the non-specific peptidase because of its high free amino acid content. Typically, 2,5(6)-dimethylpyrazine was the most abundant pyrazine found, although in the chymotripsine hydrolysate also other pyrazines were dominant. The hydrolysate obtained from the non-specific peptidase contained a larger variety of pyrazines, including the typical Strecker aldehydes originating from specific amino acids. This study demonstrates that oligopeptides are important Maillard flavor precursors.

Insight into the evolution of flavor compounds during cooking of common beans utilizing a headspace untargeted fingerprinting approach

Beans age during storage leading to prolonged cooking times. Chemical reactions that occur during cooking lead to volatile production and flavor generation. Whereas few studies profiled the volatile fingerprint of either non-cooked beans or beans cooked for a specific time, this study explored the evolution of volatiles through headspace fingerprinting of beans cooked at 95 °C to different extents. The influence of aging of beans on this evolution was investigated. Cooking time clearly influenced the evolution of volatiles for both fresh (non-aged) and aged beans. Aged beans exhibited more discriminant compounds than fresh beans regardless of texture considerations due to differences in pre-history of the beans. Strecker aldehydes, sulphur compounds and furan compounds were identified as marker compounds and were linked to mainly lipid oxidation and Maillard reactions. In conclusion, both aging prior to cooking and the cooking process itself largely influence the evolution of volatile compounds during cooking.

Characterization of hot pepper spice phytochemicals, taste compounds content and volatile profiles in relation to the drying temperature

The aim of this study was to investigate how the use of increasing hot air drying temperature affects the phytochemical content and the volatile profile of hot pepper spice. A comprehensive characterization of spice from Italian varieties dried at different temperatures (50, 57, and 64°C) was performed, including general quality indexes, phytochemicals, functional properties, and volatile profile. In dried peppers capsaicinoids were completely retained; a remarkable loss of ascorbic acid was observed, while carotenoids amount decreased of about 39%. The retention of tocopherols was higher at 50 and 57°C. The Folin Ciocalteu index showed a steep decrease after drying, but the opposite trend was observed when it was measured using a correction factor to exclude the ascorbate contribution. The volatile profile changed with the increase in drying temperature, due to the production of Strecker aldehydes, methional, and tetramethylpyrazine, and a reduction in esters, terpenoids, and 2-isobutyl-3-methoxypyrazine. Practical applications Among the processing methods used to produce spice, hot air drying is still the most common. Standard industrial drying process is carried out with air temperatures usually above 70°C, but, in order to enhance the product quality, the processing parameters should be carefully chosen. The appropriate use of lower drying temperatures may increase the retention of phytonutrients and the sensory properties, both aspects which meet the consumers’ expectations. The characterization of spice should be both related to the taste components and to the amounts of phytonutrients and vitamins, very high in hot peppers. The comprehensive results of this study suggest that a better preservation of quality characteristics could be achieved using temperatures under 60°C.

Differential evolution of Strecker and non-Strecker aldehydes during aging of pale and dark beers

To determine characteristics associated with stability, 35 commercial beers were aged naturally. Chemical instability, as determined by increase in aldehyde concentration during aging, was associated with beer color. In particular, darker beers produced disproportionately high levels of Strecker aldehydes. Other attributes of fresh beer showed little or no correlation with stability. The relationship between color and instability was confirmed experimentally by brewing and fermenting worts of different color, which were otherwise identical. Increases were noted also for the non-Strecker aldehydes furfural and hexanal during aging but concentrations were not influenced by beer color. Potential aldehyde precursors: higher alcohols and amino acids, were not higher in the dark worts and the higher aldehyde concentration is therefore not dependent on pre-cursor concentration. Supplementation of the amino acid isoleucine to fresh beer promoted the formation of 2-methylbutanal particularly in dark beers, presumably due to increased Strecker degradation. Conversely, addition of the higher alcohol 2-methylbutanol led to higher concentrations of 2-methylbutanal irrespective of beer color. Increased Strecker degradation reactions may explain, at least in part, the higher level of Strecker aldheydes observed in dark beers after aging.

Volatile flavor compounds vary by beef product type and degree of doneness.

This study aimed to determine how quality grade and degree of doneness (DOD) influence the development of volatile compounds among beef whole muscle and ground patties. Volatile compounds were quantified via head space solid phase microextraction from samples tempered in refrigerated temperatures (3 to 5 °C), room temperature (24 to 26 °C), or cooked on an electric clamshell-style grill to an endpoint temperature of 55, 60, 71, or 77 °C. Collected samples were subsequently determined by gas chromatography mass spectrometry. Prominent compounds known to be the result of the Maillard reaction or lipid degradation were retained for comparison. Four Strecker aldehydes, 4 pyrazines, and one ester had a 3-way interaction between quality grade, DOD, and product type (each P < 0.001). Pyrazine concentrations did not differ (P > 0.05) in ground patties and was comparably greater (P < 0.05) in steaks; in Prime and Low Choice steaks, pyrazine concentration increased (P < 0.05) as DOD increased. A 2-way interaction between quality grade and product type was observed for acetaldehyde, dimethyl disulfide, 1-penten-3-ol, butanoic acid, hexanal, octanal, nonanal, and 2-heptanone. Among which, octanal and nonanal were greater (P < 0.05) in Prime steaks compared with ground patties. Another 2-way interaction, quality grade and DOD, was observed in 2 ketones, an alcohol, 2 esters, and 2 aldehydes. For example, 2,3-butanedione was greater (P < 0.05) in concentration in Prime 4 °C samples compared with Low Choice and Standard. The final 2-way interaction of DOD and product type was observed in 3 ketones, 2 sulfur compounds, 2 esters, 5 aldehydes, 2 carboxylic acids, and a ketone. For example, 2-heptanone was greater (P < 0.05) in concentration in ground patties compared to steaks in all degrees of doneness except 4 °C. Overall, these results indicate that the volatile flavor profile of beef is greatly influenced by product type and DOD. Generally, consumers select beef based on product type and determine their cookery approach. Therefore, consumers may greatly influence final beef flavor profile.

Development and optimization of a HS-SPME-GC-MS methodology to quantify volatile carbonyl compounds in Port wines

A method based on headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-triple quadrupole/mass spectrometry detection (GC-TQ/MS) with a prior derivatization step with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) was developed to quantify carbonyl compounds in different categories of Port wines. Optimal extraction conditions were obtained incubating 2 ml of wine with 2.3 g/l of PFBHA for 10 min and extracted during 20 min at 32 °C. The method was validated for 38 carbonyl compounds (alkanals, alkenals, Strecker aldehydes, dialdehydes, ketones and furan aldehydes) with regard to linearity, repeatability, inter and intra-day precision and accuracy, showing that the method is suitable for the determination of carbonyl compounds in wines. Tawny wines with ‘indication of age’ (10–40 years old) presented the highest levels of some carbonyl compounds, such as propanal, pentanal, hexanal, Strecker aldehydes, diacetyl, methyl glyoxal, 3-pentanone and 2-furfural, whereas Ruby wines were characterized by the highest amounts of some unidentified compounds.

53 Impact of Packaging Types on Cooked Beef Volatile Flavor Compounds.

The objective of this study was to evaluate the impact of packaging type and muscle on beef volatile flavor compounds produced from grilling. Gluteus medius (GM) and Longissimus lumborum (LL) steaks were fabricated into 2.54 cm steaks and packaged in carbon monoxide modified atmosphere (CO), high oxygen (HIOX), polyvinyl chloride overwrap (OW), rollstock (ROLL), or vacuum (VAC) packaging and held for 7 days in dark storage. Steaks were then placed in retail coffin cases for 48 hours, except for VAC, which were held in darkness. Following the 48 hours, steaks were vacuum packaged and frozen at -20℃ until volatile compound analysis. Steaks were cooked to a medium degree of doneness (71℃) prior to analysis. Compounds evaluated were derived from various flavor development pathways, including Maillard reaction products and lipid derived compounds. Interactions between packaging type and muscle (P < 0.05) were observed for 2,3-pentanedione and 1-pentanol - two lipid derived compounds. Packaging significantly impacted lipid degradation products, as HIOX packaging possessed the greatest amount (P < 0.05) of 1-octen-3-ol, 1-octanol, dodecanal, nonane, pentane, tetradecane, 2-pentylfuran, 2-heptanone, 1-octene, and hexanoic acid, methyl ester when compared to all other packaging schemes. Contrastingly, ROLL packaging exhibited the greatest amount (P < 0.05) of 2-methy1-1-pentene and 2,4-dimethyl-1-heptene. For Maillard reaction products, HIOX possessed a greater amount of phenylacetaldehyde (P < 0.05) than ROLL and VAC treatments, but was similar (P > 0.05) to OW and CO. Dimethyl sulfide was present in the greatest amount (P < 0.05) in ROLL, VAC, and CO than HIOX and OW, which were similar (P > 0.05). When evaluating the impact of muscle on Maillard reaction products, LL steaks produced a greater amount (P < 0.05) of the Strecker aldehydes 3-methylbutanal and 2-methylbutanal than GM steaks. Similarly, LL steaks also produced a greater amount (P < 0.05) of methyl pyrazine, 2,5-dimethylpyrazine, and dimethyl sulfone. Contrastingly, GM steaks produced a greater amount (P < 0.05) of 2,3-butanedione, 3-hydroxy-2-butanone, and dimethyl sulfide than LL steaks when cooked. Within lipid derived compounds, LL steaks possessed a greater amount (P < 0.05) of ethanol and butryrolactone. However, GM steaks exhibited a greater amount (P < 0.05) of 2,3-butanediol and octanoic acid, which are indicators of lipid oxidation. These results suggest steaks in HIOX packaging undergo a greater amount of lipid oxidation in comparison to other packaging types. This could lead to detrimental effects of beef flavor when purchased by consumers.

Formation and Accumulation of Acetaldehyde and Strecker Aldehydes during Red Wine Oxidation.

The main aim of the present work is to study the accumulation of acetaldehyde and Strecker aldehydes (isobutyraldehyde, 2-methylbutanal, isovaleraldehyde, methional, phenylacetaldehyde) during the oxidation of red wines, and to relate the patterns of accumulation to the wine chemical composition. For that, eight different wines, extensively chemically characterized, were subjected at 25°C to three different controlled O2 exposure conditions: low (10 mg L−1) and medium or high (the stoichiometrically required amount to oxidize all wine total SO2 plus 18 or 32 mg L−1, respectively). Levels of volatile aldehydes and carbonyls were then determined and processed by different statistical techniques. Results showed that young wines (<2 years-old bottled wines) hardly accumulate any acetaldehyde regardless of the O2 consumed. In contrast, aged wines (>3 years-old bottled wines) accumulated acetaldehyde while their content in SO2 was not null, and the aged wine containing lowest polyphenols accumulated it throughout the whole process. Models suggest that the ability of a wine to accumulate acetaldehyde is positively related to its content in combined SO2, in epigallocatechin and to the mean degree of polymerization, and negatively to its content in Aldehyde Reactive Polyphenols (ARPs) which, attending to our models, are anthocyanins and small tannins. The accumulation of Strecker aldehydes is directly proportional to the wine content in the amino acid precursor, being the proportionality factor much higher for aged wines, except for phenylacetaldehyde, for which the opposite pattern was observed. Models suggest that non-aromatic Strecker aldehydes share with acetaldehyde a strong affinity toward ARPs and that the specific pattern of phenylacetaldehyde is likely due to a much reduced reactivity toward ARPs, to the possibility that diacetyl induces Strecker degradation of phenyl alanine and to the potential higher reactivity of this amino acid to some quinones derived from catechin. All this makes that this aldehyde accumulates with intensity, particularly in young wines, shortly after wine SO2 is depleted.

Viscozyme L pretreatment on palm kernels improved the aroma of palm kernel oil after kernel roasting

With an interest to enhance the aroma of palm kernel oil (PKO), Viscozyme L, an enzyme complex containing a wide range of carbohydrases, was applied to alter the carbohydrates in palm kernels (PK) to modulate the formation of volatiles upon kernel roasting. After Viscozyme treatment, the content of simple sugars and free amino acids in PK increased by 4.4-fold and 4.5-fold, respectively. After kernel roasting and oil extraction, significantly more 2,5-dimethylfuran, 2-[(methylthio)methyl]-furan, 1-(2-furanyl)-ethanone, 1-(2-furyl)-2-propanone, 5-methyl-2-furancarboxaldehyde and 2-acetyl-5-methylfuran but less 2-furanmethanol and 2-furanmethanol acetate were found in treated PKO; the correlation between their formation and simple sugar profile was estimated by using partial least square regression (PLS1). Obvious differences in pyrroles and Strecker aldehydes were also found between the control and treated PKOs. Principal component analysis (PCA) clearly discriminated the treated PKOs from that of control PKOs on the basis of all volatile compounds. Such changes in volatiles translated into distinct sensory attributes, whereby treated PKO was more caramelic and burnt after aqueous extraction and more nutty, roasty, caramelic and smoky after solvent extraction.

Identifying the Influence of Post-Mortem Aging Length and Method on Flavor and Tenderness of Beef Strip Loins

ObjectivesAging of beef is one widely-accepted method to enhance palatability characteristics. There has not been a study published aimed specifically at identifying the effect of aging on flavor compound development. Therefore, the objective of this study was to identify compositional changes in flavor and tenderness of beef aged at different lengths and using different methods.Materials and MethodsPairs of strip loins (n = 38) were collected from commodity USDA Choice beef carcasses and fabricated into a total of 8 sections per carcass. Sections were randomly assigned to 1 of 8 aging treatments: 1) 3 d wet-aged; 2) 14 d wet-aged; 3) 28 d wet-aged; 4) 35 d wet-aged; 5) 49 d wet-aged; 6) 63 d wet-aged, 7) 21 d dry-aged; 8) 14 d wet-aged followed by 21 d dry-aged. Upon completion of treatment, sections were fabricated into 3 steaks, each of which was allocated for sensory, shear force, or chemical analysis. Sensory attributes, including beef lexicon flavor notes and tenderness, were quantified by a trained panel using a 15-point scale. Slice shear force (SSF) and Warner-Bratzler (WBSF) shear force was determined for each sample. Uncooked samples were analyzed for volatile organic compounds known to contribute to beef flavor as well as fatty acids. Treatment comparisons made within the same carcass were tested for significance using SAS PROC GLIMMIX (SAS Inst. Inc., Cary, NC) with ɑ < 0.05.ResultsWet-aging longer than 35 d resulted in decreased (P < 0.01) ratings for beef flavor ID, browned, and roasted flavors and increased (P < 0.01) ratings for sour, oxidized, nutty, musty/earthy, and liver-like. However, beef wet-aged up to 28 d showed no change (P ≥ 0.05) in flavor notes. Dry-aging resulted in the greatest ratings for beef flavor ID, browned, and roasted. Additionally, the additive effect of using both wet- and dry-age methods resulted in intensification of the musty/earthy and nutty flavor notes typically associated with dry-aged beef, as well as sour notes. The SSF and WBSF generally decreased as aging time increased. Yet, no significant differences (P ≥ 0.05) in SSF values were found past 35 d of wet-aging, and no significant differences (P ≥ 0.05) in WBSF values were found past 28 d of wet-aging. Volatile flavor compound analysis showed n-aldehydes nonanal, octanal, and hexanal increase up to 35 d of wet-aging and decrease at subsequent aging lengths. Additionally, Strecker aldehydes phenylacetaldehyde, 2-methylbutanal, and 3-methylbutanal all increased after 35 d of wet-aging. Finally, ethanol production increased substantially after 35 d of wet-aging, while acetaldehyde production decreased at the same aging length.ConclusionThese findings show aging as an effective method of improving palatability attributes in beef. Yet, utilizing extreme aging parameters changes the flavor profile of beef, as notes of sour, oxidized, nutty, musty/earthy, and liver-like develop, without a meaningful improvement in tenderness. This change in flavor profile may, in part, be due to volatile changes late in the wet-aging period, where the oxidative breakdown of lipids, generation of aldehydes, and the dehydrogenation of acetaldehyde to ethanol occur. Additionally, dry-aging in combination with wet-aging creates a unique flavor profile. Ultimately, these results provide a baseline for establishments to select an aging protocol best suited for their need in promoting a high-quality eating experience.

Green Tea Polyphenols Decrease Strecker Aldehydes and Bind to Proteins in Lactose-Hydrolyzed UHT Milk.

The effect of epigallocatechin gallate enriched green tea extract (GTE) on flavor, Maillard reactions and protein modifications in lactose-hydrolyzed (LH) ultrahigh temperature (UHT) processed milk was examined during storage at 40 °C for up to 42 days. Addition of GTE inhibited the formation of Strecker aldehydes by up to 95% compared to control milk, and the effect was similar when GTE was added either before or after UHT treatment. Release of free amino acids, caused by proteolysis, during storage was also decreased in GTE-added milk either before or after UHT treatment compared to control milk. Binding of polyphenols to milk proteins was observed in both fresh and stored milk samples. The inhibition of Strecker aldehyde formation by GTE may be explained by two different mechanisms; inhibition of proteolysis during storage by GTE or binding of amino acids and proteins to the GTE polyphenols.

Unraveling the inhibitory effect of dihydromyricetin on heterocyclic aromatic amines formation.

Heterocyclic aromatic amines (HAAs) are mutagens and rodent carcinogens. Flavonoids have attracted considerable attention for development into effective inhibitors against the formation of genotoxic HAAs in thermally processed foods. The inhibitory effect of dihydromyricetin (DMY) on the formation of key HAAs, including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]-quinoxaline (MeIQx), and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), was significant. In chemical models, DMY (0.05 mmol, 0.1 mmol, and 0.2 mmol) significantly decreased the amount of PhIP formed (43.0%, 54.7%, and 75.7% respectively). A significant inhibitory effect on the formation of MeIQx and 4,8-DiMeIQx was also observed. Moreover, DMY (0.05%, 0.1%, and 0.2%) reduced the generation of PhIP (by 48.0%, 59.0%, and 80.1% respectively) and that of MeIQx (by 45.8%, 62.0%, and 76.7% respectively) in fried beef patties. The results indicate that DMY could be converted into myricetin during thermal processing, and both DMY and myricetin could trap phenylacetaldehyde, a major Strecker aldehyde of phenylalanine, in a similar manner to thus inhibit the generation of PhIP. This study provides valuable information for the development of effective strategies to minimize HAA content in thermally processed foods and also sheds light on the mechanism that accounts for the inhibitory effect. © 2017 Society of Chemical Industry.

Temperature effect on formation of advanced glycation end products in infant formula milk powder

For a standard infant formula milk powder, browning reactions were shown to become limiting for shelf-life for storage at higher temperature rather than lipid oxidation. Advanced glycation end (AGE) products were found in the temperature range 65–115 °C to have an energy of activation for their formation of 28 kJ mol−1 following crystallisation of the powder using an indirect ELISA method for determination of AGE. This energy of activation was larger than the energies of activation of 6.5 and 5.7 kJ mol−1, as found for formation of the Strecker aldehydes 2- and 3-methyl butanal, respectively. Formation of AGE occurred in the browning reaction sequence later than Strecker degradation. At 25 °C less than 0.1 ng mg−1 AGE was formed in storage for 2 months. Toxicity could only be detected for storage for longer than 1 month at 65 °C, where AGE formation is approximately 2 ng mg−1.

Prediction of key aroma development in coffees roasted to different degrees by colorimetric sensor array

We developed a colorimetric sensor array (CSA) that is sensitive to highly contributory volatile compounds of coffee aroma for discrimination of coffee samples roasted to different roast degrees. Strecker aldehydes and α-diketones were significantly higher for the medium roast than the other roast degrees. The development of several sulfur compounds was pronounced in the medium-dark and dark roasts, except for dimethyl sulfide, which was only detected in the light roast. The CSA method coupled with principal component analysis or hierarchical cluster analysis successfully distinguished the roasted coffee samples according to roast degree. Partial least squares regression results showed that the CSA responses were well-correlated with the concentrations of volatile compounds in the coefficient of determination (rp2) range of 0.686–0.955. These results demonstrate that the CSA rapidly responded to coffee aroma compounds and was capable of predicting coffee aroma development.

High temperature storage of infant formula milk powder for prediction of storage stability at ambient conditions

Hexanal formation and pentanal formation were found to be early signs of quality deterioration of both a high lipid infant formula milk powder and a high protein infant formula milk powder with similar lactose and water content; these aldehydes were sensitive predictors for shelf-life at ambient conditions using short term storage at temperatures up to 55 °C. Higher temperature loads such as 70 °C were found to induce rapid lactose crystallisation entailing a rising water activity, higher levels of free radicals, rapid browning and formation of Strecker aldehydes from protein degradation, of which all were found to be unsuitable for shelf-life prediction. Advanced glycation end products were not detected during storage at 25 °C for up to 18 weeks and the rate of oxygen consumption for the reconstituted milk drink was not affected by storage of the infant formulas at 25 °C; neither can be recommended for shelf-life prediction.

Consumer sensory evaluation and chemical composition of beef gluteus medius and triceps brachii steaks from cattle finished on forage or concentrate diets.

The objective of this study was to assess the impact of cattle finishing diet and muscle type on meat quality. Consumer sensory response, proximate composition, Warner-Bratzler shear force (WBSF), fatty acid composition, and volatile compounds were assessed from the gluteus medius (GM) and triceps brachii (TB) muscles of cattle ( = 6 per diet) which were grain-finished (USUGrain) on conventional feedlot or 2 forage diets, a perennial legume, birdsfoot trefoil-finished (USUBFT; ), and grass-finished (USUGrass; ). Diet had an interacting effect with muscle for all sensory attributes ( ≤ 0.002), except aroma and flavor ( ≥ 0.078). In forage-finished beef, tenderness, fattiness, overall liking, and WBSF tenderness of GM was greater ( < 0.05) than TB, whereas for USUGrain, the tenderness, fattiness, overall liking, and WBSF tenderness of both muscles were similar ( > 0.05) but the juiciness of TB was more liked than USUGrain GM ( < 0.05). The juiciness of forage-finished beef did not differ ( > 0.05) between GM and TB. Lower ( < 0.05) intramuscular fat (IMF) percent was determined for USUGrass beef in comparison with USUGrain beef. The IMF percent of USUBFT beef was similar ( > 0.05) to both USUGrass and USUGrain beef. However, IMF percent was not impacted by muscle type ( = 0.092). The ratio of -6:-3 fatty acids was affected by muscle dependent on diet ( = 0.016). The ratio of -6:-3 fatty acids was affected by the interaction of muscle × diet ( = 0.016). Between forage diets (USUGrass and USUBFT), -6:-3 ratios were similar ( > 0.05) between GM and TB, whereas within USUGrain, the GM was greater ( < 0.05) than the TB. Cumulative MUFA was greater ( < 0.05) in USUGrain compared with both USUGrass and USUBFT, which were similar ( > 0.05). Strecker aldehydes, ketones, pyrazines, and methional were affected ( ≤ 0.036) by muscle and found to have a greater concentration in GM compared with TB. Overall, consumers determined that USUGrain GM and TB had similar ( > 0.05) quality ratings. However, within forage-finished beef, the GM was perceived more frequently ( < 0.05) to be of premium quality and the forage-finished TB was more frequently ( < 0.05) rated as having unsatisfactory quality. These findings were in agreement with ratings of tenderness and overall liking. Therefore, in the context of our consumer group grilled GM and TB steaks, grain-finished beef provided more uniform quality and eating experience compared with forage-finished beef.

Strecker Aldehyde Formation in Wine: New Insights into the Role of Gallic Acid, Glucose, and Metals in Phenylacetaldehyde Formation.

Strecker degradation (SD) leading to the formation of phenylacetaldehyde (PA) was studied in wine systems. New insights were gained by using two full factorial designs focusing on the effects of (1) pH and (2) temperature. In each design of experiments (DoE) three factors, glucose, gallic acid, and metals at two levels (present or absence), were varied while phenylalanine was kept constant. The obtained results gave a clear indication, with statistical significance, that in wine conditions, the SD occurs in the presence of metals preferentially via the phenolic oxidation independent of the temperature (40 or 80 °C). The reaction of the amino acid with the o-quinone formed by the oxidation of the gallic acid seems to be favored when compared with the SD promoted by the reaction with α-dicarbonyls formed by MR between glucose and phenylalanine. In fact, kinetics results showed that the presence of glucose had an inhibitory effect on PA rate of formation. PA formation was 4 times higher in the control wine when compared to the same wine with 10 g/L glucose added. By gallic acid quinone quantitation it is shown that glucose affects directly the concentration of the quinone. decreasing the rate of quinone formation. This highlights the role of sugar in o-quinone concentration and consequently in the impact on Strecker aldehyde formation, a promising new perspective regarding wine shelf-life understanding.