Textural and sensory characteristics of whole and skimmed flavored set-type yogurt during long storage

A study of refrigerated storage (10 degrees C for 91 d) of whole and skimmed flavored set-type yogurt was made. Comparison with storage at 20 degrees C for 21 d and 30 degrees C for 3 d (accelerated) was also carried out. Refrigerated storage yogurts were assessed by a trained panel and by a consumer panel. Trained-panel scores were correlated to instrumental data, and the acceptability data for long storage were studied using consumer criteria. In all cases, after-storage pH values barely changed over storage time, indicating that the yogurt samples did not develop much acidity under any of the storage conditions studied. The profile of the instrumental texture curves obtained corresponded to a firm gel, which broke after a plunger penetrated the sample, and the firmness values of the whole yogurt were lower than for the skimmed yogurt under all the storage conditions studied. From a microbiological point of view, the viability of the yogurts was adequate at the different storage times and temperatures studied, although those stored at 10 degrees C for long periods would not comply with some countries' minimum requirements. Logistic regression of the data from a 50-consumer sensory evaluation showed that the probability of the whole yogurt being accepted after 91 d storage at 10 degrees C was around 40%, whereas for the skimmed yogurt it was only 15%, largely because the skimmed yogurt developed certain negative attributes at an earlier stage of storage than the whole yogurt.