@article{zhang_jo_lopetcharat_drake_2020, title={Comparison of a central location test versus a home usage test for consumer perception of ready-to-mix protein beverages}, volume={103}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2019-17260}, abstractNote={Ready-to-mix (RTM) whey protein beverages are an expanding product category, and sensory properties strongly affect consumer acceptance and purchase intent. Because consumers themselves prepare RTM whey protein beverages, understanding possible gaps between central location test (CLT) and home usage test (HUT) results is critical. The objectives of this study were to compare results obtained from a CLT and a HUT and to identify the drivers of liking and disliking vanilla-flavored RTM whey protein beverages. Fourteen commercial vanilla-flavored RTM whey protein beverages were rehydrated with spring water at 15% solids (wt/vol) and evaluated by a trained panel (n = 8). Ten representative products were selected for consumer testing. Rehydrated beverages were subsequently evaluated by protein beverage consumers (n = 160) in a CLT. Nine representative products were selected for the HUT. Consumers prepared and evaluated individual beverages over 3 consecutive weeks, trying 3 samples each week. Overall liking and other attributes were scored by consumers in both tests. Data were evaluated by univariate and multivariate statistical analyses. Overall liking scores from the HUT were higher than scores from the CLT. The products with the highest and lowest overall liking scores were consistent between the CLT and HUT. More differences were observed among beverages by CLT compared with HUT when liking was averaged across all consumers. Both methods identified 2 distinct consumer clusters. Fruity flavor and sweet taste were drivers of liking, whereas cardboard flavor and bitter taste were drivers of disliking in both methods. The HUT exclusively identified thickness (viscosity) as a driver of liking and astringency as a driver of disliking. These results suggest that a CLT can be used to differentiate consumer acceptance among vanilla-flavored RTM whey protein beverages. A HUT should be used to provide more intensive insights for mouthfeel and mixing experience-related attributes.}, number={4}, journal={JOURNAL OF DAIRY SCIENCE}, author={Zhang, M. T. and Jo, Y. and Lopetcharat, K. and Drake, M. A.}, year={2020}, month={Apr}, pages={3107–3124} }
 @article{wherry_jo_drake_2019, title={Concentration of furfuryl alcohol in fluid milk, dried dairy ingredients, and cultured dairy products}, volume={102}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2018-15714}, abstractNote={Maillard reactions occur in dairy products during heat treatment. Furfuryl alcohol (FA) may be found in dairy products as a result of Maillard reactions. The recent posting in California Proposition 65 indicates that FA may be carcinogenic, and for this reason it is crucial to accurately measure FA concentrations in dairy products. The objective of this study was to identify an extraction and quantitation method for FA from dairy products and to determine FA concentrations in milk, dairy powders, and cultured dairy products. Solvent-assisted flavor extraction, solid-phase microextraction, stir bar sorptive extraction with gas chromatography-mass spectrometry and triple quadrupole mass spectrometry were compared for recovery of FA. Internal standards for the quantitation of FA (2-methyl-3-heptanone, furfuryl-d5 alcohol, 2,5-dimethylphenol, 5-methyl-2-furfuryl alcohol, and 5-methyl furfural) were also compared. Subsequently, fluid milk [high temperature, short time (HTST) and ultrapasteurized], whey protein isolates (3 mo-4 yr), whey protein concentrates (3 mo-4 yr), whole milk powders (1 yr), high and low heat skim milk powders (SMP; 0-8 yr), milk protein isolates (3 mo-3 yr), milk protein concentrates (3 mo-3 yr), Cheddar cheese (mild, medium, sharp, and extra sharp), mozzarella cheese (whole and part skim), cottage cheese (nonfat, low fat, and full fat), sour cream (nonfat, low fat, and full fat), traditional yogurt (nonfat, low fat, and full fat), and Greek-style yogurt (nonfat; n = 139 products total) were evaluated. Furfuryl alcohol was extracted from products by headspace solid-phase microextraction followed by gas chromatography-triple quadrupole mass spectrometry using a ZB-5ms column (30 m × 0.25 mm × 0.25 µm; Phenomenex Inc., Torrance, CA). Furfuryl-d5 alcohol was used as an internal standard. Each food was extracted in triplicate. Ultrapasteurized milks had higher levels of FA than HTST milks (122.3 vs. 7.350 µg/kg). Furfuryl alcohol concentrations ranged from 0.634 to 26.55 µg/kg in whey protein isolates, 2.251 to 56.19 µg/kg in whey protein concentrates, 11.99 to 121.9 µg/kg in milk protein isolates, and 8.312 to 49.71 µg/kg in milk protein concentrates, and concentrations increased with powder storage. High heat SMP had higher concentrations of FA than low heat SMP (11.8 vs. 1.36 µg/kg) and concentrations increased with storage time. Concentrations of FA in Cheddar and mozzarella cheese ranged from 2.361 to 110.5 µg/kg and were higher than FA concentrations in cottage cheese or sour cream (0.049-1.017 µg/kg). These results suggest that FA is present at higher levels in dairy products that have been subjected to higher temperatures or have been stored longer. Sour cream and cottage cheese had lower levels of FA. Compared with other studies on food products with reported levels of FA, such as coffee (200-400 µg/g), dairy products have very low levels of FA.}, number={5}, journal={JOURNAL OF DAIRY SCIENCE}, author={Wherry, B. M. and Jo, Y. and Drake, M. A.}, year={2019}, month={May}, pages={3868–3878} }
 @article{schiano_jo_barbano_drake_2019, title={Does vitamin fortification affect light oxidation in fluid skim milk?}, volume={102}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2018-15594}, abstractNote={Off-flavors in milk related to light oxidation form due to photoxidation of native riboflavin and tetrapyrroles, resulting in an array of lipid oxidation compounds. Recent work has established that fortification with water-dispersible vitamin A can result in off-flavors in fluid skim milk caused by vitamin A degradation products in the vitamin premix. The objective of this study was to determine the role of vitamin fortification on light oxidation of high temperature, short time pasteurized fluid skim milk. First, the aroma profiles and aroma-active volatile compounds in light-exposed vitamin premixes were determined by exposing the premixes to fluorescent (FL) or light-emitting diode (LED) light at 2,000 lx at 4°C for 0, 2, 4, 8, or 24 h. A trained panel (n = 6) documented aroma profiles of each vitamin premix at each time point. Headspace solid-phase microextraction followed by gas chromatography-olfactometry and gas chromatography-mass spectrometry (GC-MS) were performed to characterize aroma-active compounds in light-exposed vitamin premixes. In the second experiment, commercial vitamin premixes (vitamin A and vitamin D in oil and water matrices) were used to fortify skim milk (vitamin A: 3,000 IU/946 mL; vitamin D: 600 IU/946 mL). Skim milk was pasteurized, homogenized, and packaged in 946-mL high-density polyethylene jugs. Milks were exposed to FL or LED light at 2,000 lx at 4°C for 4, 12, 24, or 48 h. Controls with and without vitamins and light shielding were included. Riboflavin and vitamin A and D degradation were quantified via ultra-high-performance liquid chromatography. A trained panel (n = 8) documented sensory profiles of milks at each time point. Lipid oxidation volatile compounds were quantified via solid-phase microextraction with GC-MS. Vitamin degradation volatile compounds were quantified via solvent-assisted sorptive stir bar extraction with GC-MS. Riboflavin, vitamin A, and vitamin D degradation were consistent with that reported in previous studies. We found no effect of vitamin fortification on development of typical light oxidation-related off-flavors (cardboard and mushroom) or lipid oxidation-related volatiles (hexanal and heptanal). A perfumey/floral flavor was documented in the oil-based vitamin A-fortified milk, suggesting that light exposure affected the off-flavors contributed by water- versus oil-based vitamin fortification. These results show no evidence that vitamin fortification at current levels provides any protection against light oxidation-related off-flavors in fluid milk.}, number={6}, journal={JOURNAL OF DAIRY SCIENCE}, author={Schiano, A. N. and Jo, Y. and Barbano, D. M. and Drake, M. A.}, year={2019}, month={Jun}, pages={4877–4890} }
 @article{jo_carter_barbano_drake_2019, title={Identification of the source of volatile sulfur compounds produced in milk during thermal processing}, volume={102}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2019-16607}, abstractNote={Volatile sulfur compounds in ultra-pasteurized (UP) milk are the major contributors to sulfur/burnt and eggy flavors, and these flavors are disliked by consumers. Previous research has established distinct differences in flavor profiles of fluid milk processed by high temperature, short time pasteurization (HTST) and UP by direct steam injection (DSI-UP) or indirect heat (IND-UP). An understanding of the contribution of the individual milk proteins to sulfur off-flavors would clarify the source of sulfur flavors in UP milks. The objective of this study was to determine the source of volatile sulfur compounds in fluid milk with a specific focus on the comparison of heat treatment effects on milks by HTST and UP. Formulated skim milks (FSM) were manufactured by blending micellar casein concentrate and serum protein isolate (SPI). Three different caseins as a percentage of true protein (FSM95, FSM80, and FSM60) were formulated to determine the source of sulfur/burnt and eggy flavors. Freshly processed micellar casein concentrate or SPI were blended to achieve a true protein content of about 3.2%. Raw skim milk served as a control. Skim milk and FSM were pasteurized at 78°C for 15 s (HTST) or 140°C for 2.3 s by IND-UP or DSI-UP. The experiment was replicated twice. Sensory properties of milks and FSM were documented by descriptive sensory analysis. Volatile sulfur compounds in milks and FSM were evaluated using solid-phase microextraction followed by gas chromatography-triple quadrupole mass spectrometry combined with a sulfur selective flame photometric detector. The FSM with higher SPI as a percent of true protein had higher sensory sulfur/burnt and eggy flavors along with elevated concentrations of hydrogen sulfide and carbon disulfide compared with skim milk or FSM with lower proportions of SPI. Sulfur compounds including dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, dimethyl sulfoxide, and methional were not associated with sulfur/burnt and eggy flavors, which suggests that these compounds may not specifically contribute to the sulfur/burnt and eggy off-flavors of UP milks. Sensory panelists found higher overall aroma impact, and cooked, sulfur/burnt, and eggy flavors for DSI-UP, followed by IND-UP and HTST. The combination of sensory and instrumental methods used in the current study effectively identified that milk serum proteins are the source of sulfur compounds in milk, and further confirmed the contribution of hydrogen sulfide and carbon disulfide to eggy and sulfur/burnt flavors, respectively.}, number={10}, journal={JOURNAL OF DAIRY SCIENCE}, author={Jo, Y. and Carter, B. G. and Barbano, D. M. and Drake, M. A.}, year={2019}, month={Oct}, pages={8658–8669} }
 @article{jo_benoist_barbano_drake_2018, title={Flavor and flavor chemistry differences among milks processed by high-temperature, short-time pasteurization or ultra-pasteurization}, volume={101}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2017-14071}, abstractNote={Typical high-temperature, short-time (HTST) pasteurization encompasses a lower heat treatment and shorter refrigerated shelf life compared with ultra-pasteurization (UP) achieved by direct steam injection (DSI-UP) or indirect heat (IND-UP). A greater understanding of the effect of different heat treatments on flavor and flavor chemistry of milk is required to characterize, understand, and identify the sources of flavors. The objective of this study was to determine the differences in the flavor and volatile compound profiles of milk subjected to HTST, DSI-UP, or IND-UP using sensory and instrumental techniques. Raw skim and raw standardized 2% fat milks (50 L each) were processed in triplicate and pasteurized at 78°C for 15 s (HTST) or 140°C for 2.3 s by DSI-UP or IND-UP. Milks were cooled and stored at 4°C, then analyzed at d 0, 3, 7, and 14. Sensory attributes were determined using a trained panel, and aroma active compounds were evaluated by solid-phase micro-extraction or stir bar sorptive extraction followed by gas chromatography-mass spectrometry, gas chromatography-olfactometry, and gas chromatography-triple quad mass spectrometry. The UP milks had distinct cooked and sulfur flavors compared with HTST milks. The HTST milks had less diversity in aroma active compounds compared with UP milks. Flavor intensity of all milks decreased by d 14 of storage. Aroma active compound profiles were affected by heat treatment and storage time in both skim and 2% milk. High-impact aroma active compounds were hydrogen sulfide, dimethyl trisulfide, and methional in DSI-UP and 2 and 3-methylbutanal, furfural, 2-heptanone, 2-acetyl-1-pyrroline, 2-aminoacetophenone, benzaldehyde, and dimethyl sulfide in IND-UP. These results provide a foundation knowledge of the effect of heat treatments on flavor development and differences in sensory quality of UP milks.}, number={5}, journal={JOURNAL OF DAIRY SCIENCE}, author={Jo, Y. and Benoist, D. M. and Barbano, D. M. and Drake, M. A.}, year={2018}, month={May}, pages={3812–3828} }
 @article{jo_benoist_ameerally_drake_2018, title={Sensory and chemical properties of Gouda cheese}, volume={101}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2017-13637}, abstractNote={Gouda cheese is a washed-curd cheese that is traditionally produced from bovine milk and brined before ripening for 1 to 20 mo. In response to domestic and international demand, US production of Gouda cheese has more than doubled in recent years. An understanding of the chemical and sensory properties of Gouda cheese can help manufacturers create desirable products. The objective of this study was to determine the chemical and sensory properties of Gouda cheeses. Commercial Gouda cheeses (n = 36; 3 mo to 5 yr; domestic and international) were obtained in duplicate lots. Volatile compounds were extracted by solid-phase microextraction and analyzed by gas chromatography-olfactometry and gas chromatography-mass spectrometry. Composition analyses included pH, proximate analysis, salt content, organic acid analysis by HPLC, and color. Flavor and texture properties were determined by descriptive sensory analysis. Focus groups were conducted to document US consumer perception followed by consumer acceptance testing (n = 149) with selected cheeses. Ninety aroma-active compounds in Gouda cheeses were detected by solid-phase microextraction/gas chromatography-olfactometry. Key aroma-active volatile compounds included diacetyl, 2- and 3-methylbutanal, 2-methylpropanal, methional, ethyl butyrate, acetic acid, butyric acid, homofuraneol, δ-decalactone, and 2-isobutyl-3-methoxypyrazine. Aged cheeses had higher organic acid concentrations, higher fat and salt contents, and lower moisture content than younger cheeses. Younger cheeses were characterized by milky, whey, sour aromatic, and diacetyl flavors, whereas aged cheeses were characterized by fruity, caramel, malty/nutty, and brothy flavors. International cheeses were differentiated by the presence of low intensities of cowy/barny and grassy flavors. Younger cheeses were characterized by higher intensities of smoothness and mouth coating, whereas aged cheeses were characterized by higher intensities of fracture and firmness. American consumers used Gouda cheese in numerous applications and stated that packaging appeal, quality, and age were more important than country of origin or nutrition when purchasing Gouda cheeses. Young and medium US cheeses ≤6 mo were most liked by US consumers. Three distinct consumer segments were identified with distinct preferences for cheese flavor and texture. Findings from this study establish key differences in Gouda cheese regarding age and origin and identify US consumer desires for this cheese category.}, number={3}, journal={JOURNAL OF DAIRY SCIENCE}, author={Jo, Y. and Benoist, D. M. and Ameerally, A. and Drake, M. A.}, year={2018}, month={Mar}, pages={1967–1989} }
 @article{yeh_schiano_jo_barbano_drake_2017, title={The effect of vitamin concentrates on the flavor of pasteurized fluid milk}, volume={100}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2017-12613}, abstractNote={Fluid milk consumption in the United States continues to decline. As a result, the level of dietary vitamin D provided by fluid milk in the United States diet has also declined. Undesirable flavor(s)/off flavor(s) in fluid milk can negatively affect milk consumption and consumer product acceptability. The objectives of this study were to identify aroma-active compounds in vitamin concentrates used to fortify fluid milk, and to determine the influence of vitamin A and D fortification on the flavor of milk. The aroma profiles of 14 commercial vitamin concentrates (vitamins A and D), in both oil-soluble and water-dispersible forms, were evaluated by sensory and instrumental volatile compound analyses. Orthonasal thresholds were determined for 8 key aroma-active compounds in skim and whole milk. Six representative vitamin concentrates were selected to fortify skim and 2% fat pasteurized milks (vitamin A at 1,500-3,000 IU/qt, vitamin D at 200-1,200 IU/qt, vitamin A and D at 1,000/200-6,000/1,200 IU/qt). Pasteurized milks were evaluated by sensory and instrumental volatile compound analyses and by consumers. Fat content, vitamin content, and fat globule particle size were also determined. The entire experiment was done in duplicate. Water-dispersible vitamin concentrates had overall higher aroma intensities and more detected aroma-active compounds than oil-soluble vitamin concentrates. Trained panelists and consumers were able to detect flavor differences between skim milks fortified with water-dispersible vitamin A or vitamin A and D, and unfortified skim milks. Consumers were unable to detect flavor differences in oil-soluble fortified milks, but trained panelists documented a faint carrot flavor in oil-soluble fortified skim milks at higher vitamin A concentrations (3,000-6,000 IU). No differences were detected in skim milks fortified with vitamin D, and no differences were detected in any 2% milk. These results demonstrate that vitamin concentrates may contribute to off flavor(s) in fluid milk, especially in skim milk fortified with water-dispersible vitamin concentrates.}, number={6}, journal={JOURNAL OF DAIRY SCIENCE}, author={Yeh, E. B. and Schiano, A. N. and Jo, Y. and Barbano, D. M. and Drake, M. A.}, year={2017}, month={Jun}, pages={4335–4348} }
 @article{smith_campbell_jo_drake_2016, title={Flavor and stability of milk proteins}, volume={99}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2016-10847}, abstractNote={A greater understanding of the nature and source of dried milk protein ingredient flavor(s) is required to characterize flavor stability and identify the sources of flavors. The objective of this study was to characterize the flavor and flavor chemistry of milk protein concentrates (MPC 70, 80, 85), isolates (MPI), acid and rennet caseins, and micellar casein concentrate (MCC) and to determine the effect of storage on flavor and functionality of milk protein concentrates using instrumental and sensory techniques. Spray-dried milk protein ingredients (MPC, MPI, caseins, MCC) were collected in duplicate from 5 commercial suppliers or manufactured at North Carolina State University. Powders were rehydrated and evaluated in duplicate by descriptive sensory analysis. Volatile compounds were extracted by solid phase microextraction followed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry. Compounds were identified by comparison of retention indices, odor properties, and mass spectra against reference standards. A subset of samples was selected for further analysis using direct solvent extraction with solvent-assisted flavor extraction, and aroma extract dilution analysis. External standard curves were created to quantify select volatile compounds. Pilot plant manufactured MPC were stored at 3, 25, and 40°C (44% relative humidity). Solubility, furosine, sensory properties, and volatile compound analyses were performed at 0, 1, 3, 6, and 12 mo. Milk proteins and caseins were diverse in flavor and exhibited sweet aromatic and cooked/milky flavors as well as cardboard, brothy, tortilla, soapy, and fatty flavors. Key aroma active compounds in milk proteins and caseins were 2-aminoacetophenone, nonanal, 1-octen-3-one, dimethyl trisulfide, 2-acetyl-1-pyrroline, heptanal, methional, 1-hexen-3-one, hexanal, dimethyl disulfide, butanoic acid, and acetic acid. Stored milk proteins developed animal and burnt sugar flavors over time. Solubility of MPC decreased and furosine concentration increased with storage time and temperature. Solubility of MPC 80 was reduced more than that of MPC 45, but time and temperature adversely affected solubility of both proteins, with storage temperature having the greatest effect. Flavor and shelf stability of milk proteins provide a foundation of knowledge to improve the flavor and shelf-life of milk proteins.}, number={6}, journal={JOURNAL OF DAIRY SCIENCE}, author={Smith, T. J. and Campbell, R. E. and Jo, Y. and Drake, M. A.}, year={2016}, month={Jun}, pages={4325–4346} }