Impact of olive oil and potassium carbonate pretreatment on physico-chemical properties of sun-dried Sundar Khani raisins (Vitis vinifera L.)

Sundar Khani is native grape variety of Pakistan which has long berry length and significantly rich in taste and sweetness. There is limited literature on pretreatment and drying data for this valuable variety of Grapes. Current study was conducted to investigate the physio-chemical indices of potassium carbonate (K2CO3) and olive oil combined treatments followed by natural sun drying method. The effects of 2 % K2CO3 pretreatments alone and in combination with various amounts of pure olive oil (1 %, 2 %, and 3 %) were studied. The results showed that, physical attributes like raisin length, width, volume, weight and total replication weight increased under distilled water treatment, while, combination of 2 % K2CO3 + 3 % Olive oil significantly reduced the drying time, 2 % K2CO3 + 1 % Olive oil gave higher final yield, rehydration ratio was highest under dH2O treatment and greater decay loss was observed at 2 %K2CO3 + 2 % olive oil. Further, 2 % K2CO3 displayed higher ratios of total soluble solids, sugars and peroxidase enzyme activity as well as titratable acidity, anthocyanins, total phenols, flavonoids were maximum at 2 % K2CO3 + 2 % Olive oil pretreatment. In addition, 2 % K2CO3 + 3 % Olive oil increased the Catalase enzyme activity as well as achieved higher scores in the evaluation of sensory attributes particularly morphological form, color and overall acceptance. This study aimed to investigate the physicochemical indices of Sundar Khani grapes under different pretreatment and sun-drying conditions using K2CO3 and olive oil and it could be suggested that raisin production of Sundar Khani by using above mentioned treatments along with sun drying could have future scope both in export and industrial markets due to its incredible reduction in drying and processing time.