Characterization of enzyme naringinase and the production of debittered low alcoholic kinnow (Citrus raticulata blanco) beverage.

Naringin, the bitter flavonone glycoside and primary bitter component in citrus fruit juices can be hydrolysed by naringinase enzyme into tasteless component, naringenin. A rapid detection test for naringinase producing microorganisms using FeCl3 has been developed. Naringin an inducer in kinnow juice, mutated yeast Clavispora lusitaniae and induced the production of crude enzyme naringinase with the activity of 0.0135 IU/ml. The parameters optimized for naringinase production were pH (4), temperature (50°C), naringin (0.8%) and rhamnose concentration (0.6%) with high substrate activity Km value of 1.00 mM and Vmax value of 28.56 mM. Divalent cations Cu2+ and Ca2+ competitively inhibited enzyme activity where as Mn2+ and Zn2+ stimulated enzyme activity of 0.0103 IU/ml and 0.0079 IU/ml, respectively. The debittering of kinnow (Citrus reticulata blanco) juice by Clavispora lusitaniae mutant prompted for utilization of kinnow juice for the production of low alcoholic naturally carbonated fermented kinnow beverage. Technology for the production of low alcoholic naturally carbonated fermented kinnow beverage with yeast Clavispora lusitaniae under optimized fermentation conditions were developed. Microbiological, physiochemical and sensory evaluation of kinnow beverage with 40 percent juice revealed pH 4.2, TSS 10.5°B, acidity 0.53%, ascorbic acid 9.2 mg/100ml, reducing sugar 8.83 percent, total sugars 9.4 percent, limonin 1.7 ppm, naringin 120.8 ppm, ?-carotene 0.26µg/l, alcohol 0.28% (w/v), CO2 1.09 bar and plate count 9.3x108 cfu/ml, ranked highest for taste 7.9, aroma 8.5, colour 7.8, astringency 8.25 and overall acceptability 7.8 during storage period of 70 days under refrigerated conditions (4°C). The percentage decrease in limonin and naringin on storage was 54 and 64.8 percent, below the threshold level of limonin (6 ppm) and naringin (600 ppm) respectively.