A natural sap from mature coconut palm known as coconut neera is enriched with essential minerals and vitamins. Rapid microbial fermentation affects neera processing industries because it spoils the physicochemical properties. There are various methods in preservation that extend the shelf life of coconut neera. The addition of nisin is one of the methods which protect neera against fermentation. Therefore, the study is focused to identify the effective combination of nisin (50 ppm) with preservatives like sodium benzoate (500, and 1000 ppm), and calcium carbonate (2500, and 3000 ppm) at two different combinations in neera. At the end of 21 d, 3000 ppm calcium carbonate with 50 ppm nisin in N4 treatment had an effective reduction of 120 × 105 CFU/ml and 143 × 102 CFU/ml for total bacteria and total yeast count. The reduced microbial survival resulted in the pH of 10.45 ± 0.05, total soluble solids of 15.43 ± 0.12 °Brix, and total acidity of 1.11 ± 0.04 mg/ L, at this combination. The treatment of nisin with 3000 ppm calcium carbonate demonstrated the high red fluorescence bacterial cells than the treatment of nisin with 1000 ppm sodium benzoate. Additionally, the microorganisms in N4 treatment precipitated 65.34% Ca2+ from 79.96% in XRF intensity analysis. The synergistic effect of nisin and calcium carbonate explored their antimicrobial activity against the heterogeneous microbial population in coconut neera. The concentration of 3000 ppm calcium carbonate and nisin 50 ppm preserves the physicochemical and sensory qualities, up to 21 d at 4°C, and offer hope for the industrial-scale implementation.

Aim In this study, the effect of frozen storage on the inhibition of microbial population in coconut neera for shelf life extension was analysed. Methods and Results The aliquots of fresh neera were frozen at −6 and −20°C. The microbial reduction and chemical qualities were analysed during storage days, and were compared with the control. The highest reduction in microbes was obtained at −20°C for lactic acid bacteria, yeast and total viable count. Moreover, the fluorescence cell staining and cell density analysis exhibited a decline at −20°C, however it showed higher at −6°C. At the end of 28 days, neera exhibited a pH of 5·37, total soluble solid of 14·0 °Brix and total acidity of 0·82 mg l−1 at −20°C. Besides, color, viscosity, total protein and ethanol showed a less difference with control and better sensory attribute up to 21 days at −20°C. Conclusions Frozen storage at −20°C resulted in a better inhibition of lactic acid bacteria, which preserves neera from the metabolic conversion. The physicochemical qualities of neera were preserved for a longer period when stored at −20°C than at atmospheric storage. Significance and Impact of the study Frozen storage reduced microbial population and preserves the chemical properties with acceptable sensory attributes and increases the shelf life of coconut neera, making it fit for consumption.