McCarthy K S, Lopetcharat K, Drake M A
Department of Food, Bioprocessing and Nutrition Sciences, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh 27695.
Nouveau Centric Co. Ltd., Bangkok 10250, Thailand.
J Dairy Sci. 2017 Mar;100(3):1702-1711. doi: 10.3168/jds.2016-11417. Epub 2017 Jan 11.
Milk consumption in the United States has been in decline since the 1960s. Milk fat plays a critical role in sensory properties of fluid milk. The first objective of this study was to determine the change in percent milk fat needed to produce a detectable or just noticeable difference (JND) to consumers in skim, 1%, 2%, and whole milks. The second objective was to evaluate how milk fat affected consumer preferences for fluid milk. Threshold tests were conducted to determine the JND for each reference milk (skim, 1%, 2%, and whole milk), with a minimum of 60 consumers for each JND. The JND was determined for milks by visual appearance without tasting and tasting without visual cues. Serving temperature effect (4, 8, or 15°C) on tasting JND values were also investigated. The established JND values were then used to conduct ascending forced-choice preference tests with milks. Consumers were assigned to 3 groups based on self-reported milk consumption: skim milk drinkers (n = 59), low-fat milk drinkers (consumed 1% or 2% milk, n = 64), and whole milk drinkers (n = 49). Follow-up interviews were conducted where consumers were asked to taste and explain their preference between milks that showed the most polarization within each consumer segment. Descriptive sensory analysis was performed on the milks used in the follow-up interviews to quantify sensory differences. Visual-only JND were lower than tasting-only JND values. Preference testing revealed 3 distinct preference curves among the consumer segments. Skim milk drinkers preferred skim milk and up to 2% milk fat, but disliked milk higher in fat due to it being "too thick," "too heavy," "flavor and texture like cream," "too fatty," and "looks like half and half." Low-fat milk drinkers preferred 2% milk up to 3.25% (whole milk), but then disliked higher milk fat content. Whole milk drinkers preferred whichever milk was higher in milk fat regardless of how high the fat content was, distinct from skim and low-fat milk drinkers. The findings of this study provide insights on sensory characteristics of milk fat in fluid milk and consumer sensory perception of these properties. These results also provide insights on how the industry might adjust milk fat references for adjusting milk sensory properties to increase milk preference and remain within the standards of identity of milk.
自20世纪60年代以来，美国的牛奶消费量一直在下降。乳脂肪在液态奶的感官特性中起着关键作用。本研究的首要目标是确定脱脂奶、1%、2%和全脂奶中，乳脂肪百分比的变化达到多少时，消费者能够察觉到或刚好能注意到差异（JND）。第二个目标是评估乳脂肪如何影响消费者对液态奶的偏好。进行了阈值测试，以确定每种参考牛奶（脱脂奶、1%、2%和全脂奶）的JND，每种JND测试至少有60名消费者参与。通过不品尝只看外观以及不看外观只品尝的方式来确定牛奶的JND。还研究了饮用温度（4℃、8℃或15℃）对品尝JND值的影响。然后使用确定的JND值对牛奶进行递增式强制选择偏好测试。根据消费者自我报告的牛奶消费量，将他们分为3组：脱脂奶饮用者（n = 59）、低脂奶饮用者（饮用1%或2%的牛奶，n = 64）和全脂奶饮用者（n = 49）。进行了后续访谈，要求消费者品尝并解释在每个消费者群体中表现出最大差异的牛奶之间的偏好。对后续访谈中使用的牛奶进行了描述性感官分析，以量化感官差异。仅通过视觉的JND低于仅通过品尝的JND值。偏好测试揭示了不同消费者群体之间有3条明显的偏好曲线。脱脂奶饮用者更喜欢脱脂奶和乳脂肪含量高达2%的牛奶，但不喜欢脂肪含量更高的牛奶，因为觉得它“太浓稠”“太油腻”“味道和质地像奶油”“脂肪太多”以及“看起来像对半混合的奶”。低脂奶饮用者更喜欢乳脂肪含量为2%至3.25%（全脂奶）的牛奶，但不喜欢更高的乳脂肪含量。全脂奶饮用者更喜欢乳脂肪含量更高的牛奶，无论脂肪含量有多高，这与脱脂奶和低脂奶饮用者不同。本研究结果为液态奶中乳脂肪的感官特性以及消费者对这些特性的感官认知提供了见解。这些结果还为该行业如何调整乳脂肪参考标准以调整牛奶的感官特性，从而提高牛奶偏好并保持在牛奶的身份标准范围内提供了见解。
