Application of hurdle technique to preserve fresh scraped coconut at ambient and refrigerated storage

Abstract

Studies were conducted to preserve freshness of scraped coconut by applying the Hurdle Technique. The preliminary experiment was carried out to identify suitable humectant (to reduce water activity to <0.94) and the level of acidulent to be added (to reduce the pH to <4.5). The main study consisted of simple mixing of blanched scraped coconut with a combination of additives comprising of sodium chloride (as humectant), citric acid (as acidulent), tri sodium citrate (as buffer), and sodium benzoate 0.05% (as anti microbes) and Butylated Hydroxy Anisole (BHA), 0.02% on fat basis (as antioxidant), equilibrate for two hours, packing in LDPE/Nylon flexible pouches. The packed samples were stored at ambient (30±2°C) and refrigerated (5±2°C) temperatures for a period of three months and were analyzed for physico-chemical and sensory properties. It was found that use of sodium chloride at 3% and citric acid at 0.3% was effective as humectant and acidulent respectively. During storage it was found that coconut in ambient storage showed significant (p<0.05) increase in free fatty acids and Thiobarbituric acid values after the first month, this could be due to the photo oxidation of fat in the transparent pouches. Low free fatty acids and TBA values were observed under refrigerated conditions. Colour measurements ("L" and "b" values) showed a significant (p<0.05) difference after the first month of storage at ambient temperature and remained unchanged within the study period under refrigerated conditions. Microbiological studies showed that the total plate count in the coconut is not significant under both storage conditions within three months period and thereby indicating the hurdles to be effective against microorganisms. Sensory evaluation showed that the product remained acceptable up to one month at ambient temperature and minimum of three months at refrigerated temperature.The results indicated that application of combination preservation technique on fresh coconut gratings would extend the shelf life by one month at ambient conditions and by three months at refrigerated conditions.