CHANGES IN QUALITY ATTRIBUTES OF LONGAN JUICE DURING STORAGE IN RELATION TO EFFECTS OF THERMAL PROCESSING

Abstract

ABSTRACT Longan juice is accepted gradually by consumers due to its unique succulent, sweet and aromatic flavor. The effects of thermal processing (91C, 20 min) on quality related attributes (color, translucency, total soluble solids, total acidity, reducing sugars, ascorbic acid, phenolic compounds, protein and pectin) of longan juice during storage at low temperature were investigated. The heat‐treated longan juice had a higher translucency and lower concentrations of pectin, phenolic compounds and proteins of longan juice, compared with the nonheat‐treated juice. Furthermore, the thermal processing maintained higher concentrations of total soluble solids and total acidity but a lower ascorbic acid concentration. However, the thermal processing had no significant effects on reducing sugar concentration. Overall, the thermal processing maintained effectively color appearance and nutritional attributes such as total soluble solids and total acidity of longan juice during storage at low temperature. These results suggest that the thermal processing exhibits a potential for quality maintenance of longan juice. PRACTICAL APPLICATIONSBrowning and turbidity are the major factor to influence quality of fruit juice during storage. Thermal processing is generally applied to improve quality and extend shelf life of fruit‐related products. In this study, application of thermal processing exhibited potential for quality maintenance of longan juice in terms of evaluations of color, translucency and concentrations of total soluble solids, total acidity, reducing sugars, ascorbic acid, phenolic compounds, protein and pectin. The information obtained from this study could be used as a guideline for designing thermal processing to control the quality of longan juice.