Light Exposure Affects Milk Acceptability and Emotional Response of College Students

Wednesday, July 23, 2014
Exhibit Hall AB (Kansas City Convention Center)
Alexandra M. Walsh , Virginia Tech, Blacksburg, VA
Hayley Potts , Virginia Tech, Blacksburg, VA
Susan Duncan , Virginia Tech, Blacksburg, VA
Abstract Text:

Off flavors in fluid milk result from light exposure due to poor light-blocking characteristics of packaging materials. Even short periods of light exposure cause light-induced oxidation leading to noticeable differences in flavor.  There is no direct evidence that light-induced oxidation affects milk acceptability.  In this study, effects of fluorescent light exposure (2000 lux) on fluid 2% milk for periods of 8 and 168 hrs (7 days; 4°C) were determined on oxidative stability of milk, consumer acceptability of the product, and the resulting emotional response from the sensory experience. Oxidative stability was measured by thiobarbituric reactive substances (TBARS) and riboflavin (Rb) assays. Consumer (n=53) acceptability of the product was reduced, as measured with a 9-point hedonic scale and a check-all-that-apply emotional response scorecard.  TBARS assays showed significant increases in oxidation by-products by 168 hrs (p=0.006).  Rb decreased significantly, with 71% loss by 168 hrs.   Although there was no significant chemical evidence of oxidation by 8 hrs of light exposure, hedonic scores decreased significantly from 7.20 (like moderately) to 5.85 (below like slightly) (p= 0.008).  Acceptability decreased severely by 168 hrs of light exposure (p= 2.15 E-10) with light-exposed milk scoring only a 3.46 (between dislike moderately to dislike slightly).  Light-protected milk maintained a score of 7.0 over the 7 days of refrigerated storage. Emotion term selection reflected the acceptability change; across all milk samples the terms calm, content, good and satisfied were shared (≥ 20% frequency of the term used and < 8% difference in percent frequency between samples compared).  Unique terms for ‘liked’ samples (hedonic score: 6 - 9) included friendly, good-natured, happy, interested, peaceful, pleasant, pleased, quiet, safe, warm, and whole.  However, ‘disliked’ samples (hedonic score: 1 – 4; mostly light-exposed milk samples) exclusively shared the term disgusted. Milk that is protected from light maintains a high quality flavor with positive emotional responses whereas the influence of light degradation causes negative sensory and emotional responses.  The emotional and flavor acceptability of milk is particularly important in the 18-25 year old population focused on in this study.  This population is establishing independent selection, purchasing habits, and consumption of products that influence future health and well-being.  In the tested population, only 24% reported consuming any milk (whole, 2%, 1%, skim) more than once daily. The selection of milk packaging that protects milk nutrients and flavor quality is important consideration for increasing milk consumption.

Keywords: Milk, Emotion, Oxidation