Sensory Shelf-Life Test

The sensory shelf-life test is designed to validate the length of time that a product will remain the same “acceptable quality8” level or have “no change in desired sensory characteristics4” over that entire life of a product. Changes in sensory properties are very sensitive for consumers rejecting products. Some product properties are too complicate to measure objectively. Moreover, instrumental measurement alone cannot indicate consumer acceptability or rejection. It is very important to ensure no change in sensory properties since consumers want to pay for desired sensory characteristics at their acceptable level. Researchers, therefore, conducts a sensory shelf-life test by deciding on which sensory test to perform, how to organize a test, i.e. length of study, product storage condition and period, evaluated schedule7,8, and analysis method12.
 

Sensory Test Selection and Applications

 
A descriptive test can be done to measure quality changes11, while, at critical time point, performing hedonic testing can evaluate the impact of quality changes on consumers’ acceptability or preference5. A difference test may be used12 when the shelf-life criterion is the first detectable change in specific attribute (e.g. an occurrence of stale/off-flavor) or overall difference. Moreover, acceptance test or preference test alone has also been used6 to estimate shelf-life.
 

Examples of Test Organization and Analysis

 
To determine which approach to conduct a sensory shelf-life test depends on company resource flexibility, time line, product deterioration mechanism, factors affecting shelf-life, attributes to be measured, and action standards7,8.
 
For example, a study on shelf-life extension of salmon slices14, the samples were purchased from different markets, assigned to 5 treatments with one being a control, and stored at 1°C. At 0, 3, 6, 9, 12, and 15 days of storage, samples were cooked and examined by 15–semi-trained panelists for overall acceptability on appearance, odor intensity, salmon flavor, aftertaste, tenderness, juiciness, off-odor, and off-flavor using hedonic scales. Scores of greater than 4 were considered acceptable, while 3 or 4 was a borderline acceptability. Based on analysis of variance , no difference was found among the treatments. Although overall acceptability significantly decreased with storage time, the scores for each attribute rated over storage periods were in acceptable range. In conclusion, minor changes over storage period were observed and all treatments could extend untreated shelf-life of 8 days to 12-15 days.
 
Another study was conducted to evaluate consumer acceptability of minced meat stored at various temperatures and times3. Enough minced beef was divided into glass bottles, 30-grams each and frozen at -18°C. Bottles were randomly removed, thawed to 4°C at different time interval, and assigned to the following storage temperatures and times.
• 2°C: 0, 24, 48, 96, 144, 192, 240 hours
• 9°C: 0, 24, 48, 72, 96, 120, 144 hours
• 19°C: 0, 6, 12, 18, 24, 36, 48 hours
 
Increased temperature treatments were used to accelerate storage condition. With this test organization, 21 samples from all storage temperatures and times could be evaluated at the same time. Sixty consumers considered minced beef appearance and answered (yes/no) whether they would normally consume each sample. Predictive equations for estimating minced beef shelf-life were constructed based on survival analysis and Arrhenius model. With 50% consumer rejection and 95% confidence intervals, the predicted shelf-life at temperatures of 2, 9, and 19°C were 88, 44, and 17 hours, respectively. Additionally, predicted shelf-lives of minced beef stored at different temperatures with different consumer rejection percentages were successfully calculated.
 
Various applications2,10,13 and analyses1,6,9 of sensory shelf-life test have been published.
 
Since there are many ways to conduct sensory shelf-life testing, researchers should carefully and thoroughly design the study and consider its impacts8 before conducting each study.
 

References

 
1 Calle, M.L., Hough, G., Curia, A., and Gómez, G. 2006. Bayesian survival analysis modeling applied to sensory shelf life of foods. Food Quality and Preference, 17: 307-312.
 
2 Diez, A.M., Santos E.M., Jaime, I., and Rovira, J. 2009. Effectiveness of combined preservation methods to extend the shelf life of Morcilla de Burgos. Meat Science, 81: 171-177.
 
3 Hough, G., Garitta, L., and Gómez, G. 2006. Sensory shelf-life predictions by survival analysis accelerated storage models. Food Quality and Preference, 17: 468-473.
 
4 IFTS. 1993. Shelf life of Foods-Guideline for its Determination and Prediction. IFTS, London.
 
5 Garitta, L., Hough, G., and Sánchez, R. 2004. Sensory shelf life od Dulce de Leche. American Dairy Science Association, 87: 1601-1607
 
6 Giménez, A., Ares, G., and Gámbaro A. 2008. Survival analysis to estimate sensory shelf life using acceptability scores. Sensory studies, 23: 571-582.
 
7 Kilcast, D. 2006. What approaches does a leading consultancy firm use to estimate shelf-life when time schedules are short? In Workshop summary: Sensory shelf-life testing. Food Quality and Preference, 17: 640-645.
 
8 Kilcast, D., Subramaniam, P. 2000. Stability and Shelf-life of Foods. pp.1-22, 79-105. New York: CRC Press.
 
9 Ledauphin, S., Pommeret, D., and Qannari, El M. 2008. Application of hidden Markov model to products shelf lives. Food Quality and Preference, 19:156-161.
 
10 Manzocco, M. and Lagazio, C. 2009. Coffee brew shelf life modeling by integration of acceptability and quality data. Food quality and Preference, 20: 24-29.
 
11 Martinez, C., Mucci, A., Santa Cruz, M.J., Hough, G., and Sanchez, R. 1998. Influenze of temperature, fat content and package material on the sensory shelf-life of a commercial mayonnaise. Sensory Studies, 13: 331-346.
 
12 Munoz, A.M., Carr, B.T., and Civille, G.V. 1992. Sensory Evaluation in Quality Control. New York: Van Nostrand Reinhold.
 
13 Patsias, A., Chouliara, I., Badeka, A., Savvaidis I.N., and Kontominas, M.G. 2006. Shelf-life of a chilled precooked chicken product stored in air and under modified atmospheres: microbiological, chemical, sensory attributes. Food Microbiology, 23: 423-429.
 
14 Sallam, K.I. 2007 Chemical, sensory and shelf life evaluation of sliced salmon treated with salts of organic acids. Food Chemistry, 101: 592-600.