Effects Of Juice Processing On Oxalate Contents In Carambola Juice Products

Abstract

Effects of processing methods including pressing, enzyme-assisted extraction using Pectinex, lactic acid fermentation by Lactobacillus acidophilus, and alcohol fermentation by Saccharomyces cerevisiae on total and soluble oxalate contents of carambola juices were studied. Total and soluble oxalates were extracted by HCl 0.2M and Nanopure water, respectively for 20 min at 800C. The extracts were analyzed using ion exchange HPLC. An increase in juice yields (15.89 – 17.29%), as well as total oxalate (1.60 – 1.73 times) and soluble oxalate contents (1.16 – 1.49 times) were observed in enzymatic juices processed at different incubation periods, compared to pressed juice. At the same time, extension of enzyme incubation periods led to an increase in soluble oxalate contents in the products (p<0.05). The lowest and highest soluble oxalate contents were found to be 94.56 ± 2.71 (mg/100mL) after 90 min, and 120.85 ± 3.67(mg/100mL) after 180 min, respectively. Alcohol fermentation using Saccharomyces cerevisiae resulted in significantly lower amounts of total oxalate (37 – 58%) and soluble oxalate (39 - 59%) after 1–5 weeks of fermentation (p<0.05). Moreover, prolonged fermentation demonstrated better reduction of oxalate contents. Meanwhile, lactic acid fermentation using Lactobacillus acidophilus had no effects on total and soluble oxalate contents in carambola juices. Keywords: carambola, oxalate, Lactobacillus acidophilus, Saccharomyces cerevisiae, pectin, pectinase, juice processing, fermentation.