2-6-nonadienal--(e-z)-isomer and n-hexanal

The dominant volatile off-flavor compounds of pea and soy milk were investigated by gas chromatography-olfactometry-mass spectrometry (GC-O-MS), sensory evaluation, and odor-activity values (OAVs), which led to the identification of their differences. We identified 11 aroma compounds as important odorants with OAVs greater than 1 in pea and soy milk. OAVs contribution rate demonstrated that 6 compounds contributed most to the characteristic off-flavor of pea milk, among which 2-methoxy-3-isopropyl-(5 or 6)-methyl pyrazine, hexanal, (E,E)-2,4-nonadienal, and (E,E)-2,4-decadienal contributed more than others. For soy milk, 1-octen-3-one, hexanal, (E,E)-2,4-nonadienal, and (E,E)-2,4-decadienal showed more important contributions. These odor-active compounds were divided into non-lipoxygenase (non-LOX) and LOX pathways based on their synthesis. Several endogenous enzymes that are important to the LOX pathway were identified by liquid chromatography tandem mass spectrometry (LC-MS/MS), and the contents of key off-flavor compounds were found to be related to the enzyme activities, while the lipid content was not an important factor.

Topics: Aldehydes; Chromatography, Liquid; Glycine max; Milk Substitutes; Odorants; Olfactometry; Pisum sativum; Soy Milk; Tandem Mass Spectrometry; Volatile Organic Compounds

Previous research has demonstrated that unit operations in whey protein manufacture promote off-flavor production in whey protein. The objective of this study was to determine the effects of feed solids concentration in liquid retentate and spray drier inlet temperature on the flavor of dried whey protein concentrate (WPC). Cheddar cheese whey was manufactured, fat-separated, pasteurized, bleached (250 ppm hydrogen peroxide), and ultrafiltered (UF) to obtain WPC80 retentate (25% solids, wt/wt). The liquid retentate was then diluted with deionized water to the following solids concentrations: 25%, 18%, and 10%. Each of the treatments was then spray dried at the following temperatures: 180 °C, 200 °C, and 220 °C. The experiment was replicated 3 times. Flavor of the WPC80 was evaluated by sensory and instrumental analyses. Particle size and surface free fat were also analyzed. Both main effects (solids concentration and inlet temperature) and interactions were investigated. WPC80 spray dried at 10% feed solids concentration had increased surface free fat, increased intensities of overall aroma, cabbage and cardboard flavors and increased concentrations of pentanal, hexanal, heptanal, decanal, (E)2-decenal, DMTS, DMDS, and 2,4-decadienal (P < 0.05) compared to WPC80 spray dried at 25% feed solids. Product spray dried at lower inlet temperature also had increased surface free fat and increased intensity of cardboard flavor and increased concentrations of pentanal, (Z)4-heptenal, nonanal, decanal, 2,4-nonadienal, 2,4-decadienal, and 2- and 3-methyl butanal (P < 0.05) compared to product spray dried at higher inlet temperature. Particle size was higher for powders from increased feed solids concentration and increased inlet temperature (P < 0.05). An increase in feed solids concentration in the liquid retentate and inlet temperature within the parameters evaluated decreased off-flavor intensity in the resulting WPC80.

Topics: Aldehydes; Alkenes; Cheese; Food Handling; Food Technology; Milk Proteins; Particle Size; Pasteurization; Taste; Temperature; Volatile Organic Compounds; Whey Proteins

Off-flavor of soymilk is a barrier to the acceptance of consumers. The objectionable soy odor can be reduced through inhibition of their formation or through removal after being formed. In this study, soymilk was prepared by three grinding methods (ambient, cold, and hot grinding) from two varieties (yellow Prosoy and a black soybean) before undergoing three heating processes: stove cooking, one-phase UHT (ultrahigh temperature), and two-phase UHT process using a Microthermics direct injection processor, which was equipped with a vacuuming step to remove injected water and volatiles. Eight typical soy odor compounds, generated from lipid oxidation, were extracted by a solid-phase microextraction method and analyzed by gas chromatography. The results showed that hot grinding and cold grinding significantly reduced off-flavor as compared with ambient grinding, and hot grinding achieved the best result. The UHT methods, especially the two-phase UHT method, were effective to reduce soy odor. Different odor compounds showed distinct concentration patterns because of different formation mechanisms. The two varieties behaved differently in odor formation during the soymilk-making process. Most odor compounds could be reduced to below the detection limit through a combination of hot grinding and two-phase UHT processing. However, hot grinding gave lower solid and protein recoveries in soymilk.

Topics: Aldehydes; Chromatography, Gas; Food Handling; Furans; Glycine max; Hexanols; Hot Temperature; Ketones; Lipoxygenase; Odorants; Solid Phase Microextraction; Soy Milk; Soybean Proteins; Taste; Volatile Organic Compounds