Survival Analysis Applied to Sensory Shelf Life of Yogurts–II: Spanish Formulations

Sensory shelf lives of commercial Spanish yogurts stored at 10 °C were studied. Yogurts were strawberry flavored and differed in fat content (free and whole-fat) and consistency (stirred and set-style). Yogurts were tested between 0 and 90 d of storage by consumers who expressed acceptance or rejection of each sample and measured overall and attribute acceptability on a 9-point hedonic scale. Survival analysis statistics were used to estimate sensory shelf lives. Considering 25% of consumers rejecting the product, shelf lives varied from 38 to 69 d, depending on the composition, so if useful life were to be established using sensory criteria, a single shelf life for yogurt would not appear to be very appropriate. A log-linear model and a direct quantile comparison formula were introduced to analyze the effect of formulation on rejection time distributions and shelf life values, respectively. Fat-free yogurts had shorter shelf lives than whole-fat yogurts. Acceptability of yogurts measured on a 9-point hedonic scale varied less than percentage rejection over the storage times.