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

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

Foz do Iguaçu - Brazil

Congreso; CIGR - International Conference of Agricultural Engineering / XXXVII Congresso Brasileiro de Engenharia Agrícola; 2008

A modified version of the Global Stability Index (GSI) methodology proposed by ACHOUR (2006) applicable to follow the variation of multi-quality indices during Butter lettuce storage was developed. To study the loss of lettuce stability, physical indices 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 greenness index as total chlorophyll content (TC) and ascorbic acid content as a nutritional index were analyzed as a function of the storage time. In the presented modification the determination of the threshold values when the quality indices have not a defined standard limit of acceptability was proposed using a linear correlation with lettuce overall visual quality (OVQ) values. Also, the way to calculate the weighting factors in the case of multi-quality indices was developed. The proposed methodology allowed the determination of a Global Stability Index for each lettuce zone (external, middle and internal) that best describes its quality stability during storage time. In addition, a non linear model was found in order to describe the dependency of GSI and OVQ for external, middle and internal zones of lettuce. The advantage of the application of the modified GSI method with respect to the classical methods was the reduction in the number of experimental determinations.