Physical and sensory attributes are important factors that influence food acceptance and choices. In this study, sensory and texture properties of nonfat yogurts made from reconstituted skim milk powder (SMP) fortified with SMP as a control, whey protein isolate (WPI), yogurt texture improver (TI), and sodium caseinate (NaCn) were investigated over a 12-d storage period. Viscosity and syneresis were measured as physical quality parameters. Descriptive sensory analysis was carried out for each sample to determine the profiles of the products. Consumer acceptance testing (n = 143 consumers) was also conducted to measure the acceptability of yogurts; panelists were asked to rank their preference for the different yogurt samples. Differences among physical and sensory attributes of yogurts were defined. Addition of WPI improved the physical properties of yogurts, resulting in the highest viscosity and the lowest syneresis. On the other hand, yogurt with WPI did not have desirable sensory properties. The descriptive panel indicated that yogurt with WPI had the lowest fermented flavor attribute. In general, yogurts fortified with NaCn and TI displayed better physical and sensory properties than did control and WPI-fortified yogurts. Consumer testing showed that yogurts with NaCn and TI were not different from the control with regard to their flavor acceptability. Yogurts fortified with NaCn and TI were the most preferred samples by Turkish consumers.

Application of aroma extract dilution analysis (AEDA) on the volatile components of low-, medium-, and high-heat-treated nonfat dry milks (NDM) revealed aroma-active compounds in the log(3) flavor dilution (log(3) FD) factor range of 1 to 6. The following compounds contributed the highest log(3) FD factors to overall NDM flavor: 2,5-dimethyl-4-hydroxy-3(2H)-furanone [(Furaneol), burnt sugar-like]; butanoic acid (rancid); 3-(methylthio)propanal [(methional), boiled potato-like]; o-aminoacetophenone (grape-like); delta-decalactone (sweet); (E)-4,5-epoxy-(E)-2-decenal (metallic); pentanoic acid (sweaty); 4,5-dimethyl-3-hydroxy-2(5H)-furanone [(sotolon), curry]; 3-methoxy-4-hydroxybenzaldehyde [(vanillin), vanilla]; 2-acetyl-1-pyrroline and 2-acetyl-2-thiazoline (popcorn-like); hexanoic acid (vinegar-like); phenylacetic acid (rose-like); octanoic acid (waxy); nonanal (fatty); and 1-octen-3-one (mushroom-like). The odor intensities of Furaneol, butanoic acid, methional, o-aminoacetophenone, sotolon, vanillin, (E)-4,5-epoxy-(E)-2-decenal, and phenylacetic acid were higher in high-heat-treated samples than others. However, the odor intensities of lactones, 2-acetyl-1-pyrroline, and 2-acetyl-2-thiazoline were not affected by heat treatment. Sensory evaluation results also revealed that heat-generated flavors have a major impact on the flavor profile of NDM.

Nonfat dry milk (NDM) is widely used both as an ingredient in other preparations and for direct consumption. Flavor quality of NDM is a critical parameter because it can directly impact final product quality. Flavors can be formed in NDM during subsequent storage. Identification of compounds responsible for storage-induced flavors is necessary to correlate sensory quality with potential sources of the flavors. Six NDM samples were selected for volatile flavor analysis based on sensory analysis and storage time. Volatile components were extracted by direct solvent extraction/high vacuum distillation. Volatile extracts were separated into neutral/basic and acidic fractions and analyzed by gas chromatography-olfactometry (GCO) and aroma extract dilution analysis (AEDA). A variety of aldehydes, ketones, and free fatty acids were responsible for generation of flavors in stored NDM. The following compounds exhibited high aroma impact by AEDA: 3-(methylthio)propanal (boiled potato); o-aminoacetophenone (corn tortilla); 2,5-dimethyl-4-hydroxy-3(2H)-furanone and 2-methyl-3-hydroxy-4H-pyran-4-one (burnt sugar); butanoic acid (cheesy); pentanoic acid (sweaty); acetic and hexanoic acids (sour/vinegar); octanoic, decanoic, and dodecanoic acids (waxy); p-cresol (cowy/barny); 3-methylindole (fecal); dimethyl trisulfide (cabbage); (E,E)-2,4-decadienal (fried/fatty); furfuryl alcohol (rubber/vitamin); phenylacetic acid (rose-like); and 1-octen-3-one (mushroom).

A standardized descriptive language for skim milk powder and dried dairy ingredients was developed. The lexicon was initially identified from a large sample set of dried dairy ingredients (138). A highly trained descriptive panel (n = 14) refined terms and identified references. Dried dairy ingredients (36) were then evaluated using the developed language. Twenty-one descriptors were identified for dried dairy ingredients. Seventeen flavors and tastes were identified in skim milk powders (27) with nine jlavordtastes observed in all skim milk powders. Dried dairy ingredients were differentiated using the language (P <0.05). There were flavors common to all dried dairy ingredients while other flavors were specific to particular products.

The objectives of this study were to determine the volatile components responsible for the sensory perception of nutty flavor in Cheddar cheese. Cheddar cheeses with and without nutty flavors were selected by descriptive sensory analysis. Volatile aroma components from Cheddar cheeses with and without nutty flavors were isolated and characterized using solvent extraction with high vacuum distillation, dynamic headspace analysis, gas chromatography-olfactometry, and gas chromatography-mass spectrometry. More than 50 aroma-active compounds were detected in Cheddar cheeses. Consistent differences were observed between nutty and not nutty Cheddar cheeses. Strecker aldehydes were detected in higher amounts in Cheddar cheeses with nutty flavors compared with Cheddar cheeses without nutty flavors. Strecker aldehydes, dimethyl sulfide, and propionic acid were evaluated in young and aged Cheddar cheese models for nutty flavor by descriptive sensory analysis. Dimethyl sulfide and propionic acid did not contribute to nutty flavor in Cheddar cheese. The addition of Strecker aldehydes to young (<4 mo old) Cheddar cheese models resulted in nutty/malty flavor perceived by sensory analysis. When Strecker aldehydes were incorporated into aged (>9 mo old) Cheddar cheese models, nutty flavor perception increased. Strecker aldehydes contribute to nutty flavor in aged Cheddar cheese.

Chevre-style goat cheeses were characterized by descriptive sensory analysis as exhibiting sweet dairy flavors as well as a characteristic waxy/animal flavor. Aroma-active compounds (> 80) with high intensities identified by gas chromatography/olfactometry and gas chromatography/mass spectrometry included 2,3-butanedione (buttery), 1-octen-3-one (mushroom), o-aminoacetophenone (grape), lactones (coconut, peach), octanoic acid (sour/waxy), as well as 4-methyl and 4-ethyl octanoic acids (waxy/animal). Subsequent sensory analysis with model cheese systems confirmed that 4-methyl and 4-ethyl octanoic acids were responsible for the characteristic waxy/animal flavor.

Fresh Cheddar cheese whey batches from 2 processing plants and 4 starter culture rotations were extracted with diethyl ether followed by isolation of volatiles by high-vacuum distillation. Odorants were evaluated by gas chromatography-olfactometry (GCO) and aroma extract dilution analysis (AEDA). 2,3-butanedione (buttery), hexanal (green), 2-acetyl-1-pyrroline (popcorn), methional (potato), (E,E)-2,4-decadienal (frying oil) and (E,E)-2,4-nonadienal (frying oil) were potent neutral/basic aroma-active compounds identified in all whey samples. Odor intensities of hexanal, (E,E)-2,4-nonadienal, 2,3-butanedione, and (E,E)-2,4-decadienal were variable. Short-chain volatile acids were predominant in acidic fractions and their intensities differed among the whey samples. GCO findings agreed with quantitation results. Liquid whey aroma components are influenced by starter culture rotation.

Rennet casein, produced by enzymatic (rennet) precipitation of casein from pasteurized skim milk, is used in both industrial (technical) and food applications. The flavor of rennet casein powder is an important quality parameter; however, the product often contains an odor described as like that of animal/wet dog. Two commercial rennet casein powders were evaluated to determine the compounds responsible for the typical odor. Aroma extracts were prepared by high-vacuum distillation of direct solvent (ether) extracts and analyzed by gas chromatography-olfactometry (GCO), aroma extract dilution analysis (AEDA), and GC-mass spectrometry (MS). Odorants detected by GCO were typical of those previously reported in skim milk powders and consisted mainly of short-chain volatile acids, phenolic compounds, lactones, and furanones. Results of AEDA indicated o-aminoacetophenone to be a potent odorant; however, sensory descriptive sensory analysis of model aroma systems revealed that the typical odor of rennet casein was principally caused by hexanoic acid, indole, guaiacol, and p-cresol.