12-11 |
A comparison of Weibull Hazard method and consumer acceptance in determining the shelf life of roasted peanuts stored at different temperatures and water activities |
C. M. LEE and A. V. A. Resurreccion. Dept. of Food Science & Technology, Univ. of Georgia, 1109 Experiment St., Griffin, GA 30223-1797 Shelf stability of roasted peanuts (RP) is an important quality factor in the confectionery industry and is affected by storage temperature and water activity. The Weibull Hazard method (WHM) is recommended over consumer acceptance tests (CT) for shelf life evaluation, but its validity requires further investigation. This research investigated the shelf life of RP stored at four temperatures of 23, 30, 35 and 40°C and three water activities, 0.33, 0.44 and 0.54 in a 4 x 3 factorial design. The specific objectives were to (1) determine the effect of temperature and water activities, and (2) compare the findings between WHM and CT. Untrained panelists evaluated samples stored for 20, 40, 60, 80, and 100% of expected shelf life using an acceptable/unacceptable rating scale according to the WHM. Samples packaged in nitrogen (99%) flushed bags and stored at 4°C served as control. Samples stored for 40 and 110% of expected shelf life were evaluated by consumers (n=50) for overall, aroma, flavor, appearance, color and texture acceptance using 9-point hedonic scales. Using WHM, less than 50% of each treatment per sampling time was rated unacceptable; thus, no accelerated phase was conducted and shelf life could not be determined. Likewise, when overall acceptance ratings was rated by consumers, only one sample was unacceptable (<5.0). Flavor acceptance ratings were more sensitive to changes. A prediction model (R2=0.734) was established and the shelf life of RP stored at 23, 30, 35, and 40°C was predicted as 85, 67, 54 and 43 days when stored at aw=0.33, as 99, 66, 45 and 25 days when stored at aw=0.44, and as 119, 66, 32 and 2 days, respectively, when stored at aw=0.54. WHM based on acceptable/unacceptable ratings over-predicted the shelf life of RP. Whereas consumer tests, using attribute acceptance ratings, provide more accurate prediction of shelf life.
Session 12, Sensory Evaluation: Methods and consumer testing
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