Application of the General Stability Index to assess the Quality of Butter Lettuce during Postharvest storage by a multi-quality indices analysis

MARÍA R. ANSORENA; MARÍA G. GOÑI; MARÍA V. AGÜERO; SARA I. ROURA; KARINA C. DI SCALA

JOURNAL OF FOOD ENGINEERING

Año: 2008

0260-8774

A modified version of the Global Stability Index (GSI) methodology applicable to follow the variation of multi-quality indices during Butter lettuce storage at optimal conditions was developed. To study the loss of lettuce stability, physical indices such as relative water content (RWC), water content (WC), free water (FW), bound water (BW) and the ratio free to total water (FW/TW), together with total chlorophyll content (TC) as a greenness index and ascorbic acid content (AA) as a nutritional index were analyzed as a function of the storage time. In the present modification, the determination of threshold values when the quality indices do not have a defined standard limit of acceptability was proposed using a linear correlation with lettuce overall visual quality (OVQ) values. Also, a method to calculate the weighing factors in the case of multi-quality indices was developed. The proposed methodology allowed the determination of a GSI for each lettuce zone (external, middle and internal) that best describes the stability of its quality during storage time. In addition, models were found in order to describe the dependency of GSI with OVQ and storage time for external, middle and internal zones of lettuce. The advantages of the application of the modified GSI method with respect to the classical real time shelf life testing were the reduction in the number of experimental determinations as well as the estimation of the maximum storage time through the presented models.