Effect of Blanching and Drying Temperatures on Various Physico-chemical Characteristics of Green Beans

Abstract

Fresh green bean samples (un-blanched and blanched) were dried at 50, 60 and 70 °C, followed by studying the effect of blanching treatment and drying temperature in various characteristics and storage study in HDPE and LDPE packaging material. The blanched dried green bean samples showed lower ash content but higher rehydration ratio, chlorophyll content and carbohydrate content than un-blanched dried green bean samples. No significant change in moisture, protein, fat and fibre content was observed after blanching. The green beans were dried up to the moisture content of 14±0.5 from an initial moisture content of > 90 %. The increase in the drying temperature reduced the drying time. Blanching treatment enhanced the drying rate, the kinetics parameter showed that the value of ‘k’ ranged from 0.008-0.013 and 0.009-0.015 /min in un-blanched and blanched samples respectively. The drying temperature caused decrease in color parameters, chlorophyll content, however RR was observed to increase with the drying temperature. The moisture, chlorophyll content, color values (L* a* b*) and rehydration ratio was observed to decrease with the storage. The better desirable quality attributes of green beans were retained in HDPE as compared to LDPE. In conclusion it was suggested that drying temperature effects the quality attributes of the green beans and also the packaging material also influence the storage stability of the dried green beans.