POST HARVEST PROCESSING OF STAR GOOSEBERRY FRUITS
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Date
2018-02
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Abstract
Star gooseberry (Phyllanthus acidus), a close relative of amla (Phyllanthus emblica) belonging to family Grossulariaceae (Gooseberry family) is one of the earliest known tribal fruit being grown in abundance in India. The fruits are seasonal and perishable in nature due to high moisture content for which lots of fruits are getting wasted every year. Therefore, there is a necessity to develop a process technology to preserve the nutritional and medicinal values of the star gooseberry fruits in form of value added products for effective utilization throughout the year. The knowledge related to shape and physical dimensions, is useful in machine development for primary processing of fruits. The present investigation aimed at determining the physical and mechanical properties of star gooseberry fruits and seeds for different groups based on size. Hand operated grader and deseeding device was developed and tested for performance indicators such as capacity, deseeding efficiency, pulping efficiency, pulp loss and juice loss. The optimization of this osmo-convective process aimed at finding levels of sugar concentration (SC), immersion time (IT) and solution to product ratio (STP) for maximum possible water loss (WL), minimum ascorbic acid loss (AAL), targeted total phenolics (TP) Solute Gain (SG) employing Box-Behnken response surface design. Value added four variants of RTS beverage were prepared and the biochemical and sensory quality characteristics have been studied. The software MINITAB was used for the generation of response surface plots and optimization of process variables. Data analysis was carried out through ANOVA for interpretation of results.
Overall analysis of results indicated that a star gooseberry fruit lot may be classified into three distinct groups based on the size (Big, Medium and Small). All the three categories of fruits closely relate to oblate shape. The dimensions were measured as major and minor diameter and the values for big, medium and small are 2.5±0.14, 1.87±0.13; 2.1±0.16, 1.67±0.13 and 1.49±0.17, 1.13±0.1 cm respectively. No significant difference in properties such as particle density (PD), seed to pulp ratio and compressive and penetration force could be observed among the categories. The effectiveness of top, middle and bottom trays of the grader was found out to be 89.54%, 54.3% and 55.37% respectively. No significant difference could be observed in deseeding speed between big and medium fruits with average values of 390 and 386fruits/h respectively. The performance indicators such as capacity (2.29±0.18)kg/h, deseeding efficiency (93%), pulping efficiency (82%) for big fruits, were significantly higher than those of medium fruits. The pulp loss was found to be more (21±3.7 %) during deseeding of medium fruits. Therefore, it is suggested that the bigger size fruits should be preferred to be deseeded as it offers higher recovery and less loss of fruit pulp. Multiple regression analysis of experimental values for osmo-convective drying revealed that the proposed second order models for water loss, solid gain, ascorbic acid loss, and total phenolics were adequate and satisfactory with 0.96, 0.97, 0.92 and 0.93 as coefficient of determination respectively. The optimum conditions obtained for SC, IT and STP were 58 º Brix, 3.5 h, and 2:1 respectively. Corresponding to these values of process variables, the value of WL, SG, AAL and TPC were 36.14 %, 7.51 %, 36.91%, 1.99 mg GAE / g of DM. The overall desirability was 0.93. For deseeded fruits the set of optimum process variables were 52 º Brix, 2h, and 2:1 for SC, IT and STP respectively with the overall desirability of 0.84. The value of WL, SG, AAL and TPC were predicted to be 50.54 %, 9.35 %, 35.98% and 2.1 mg GAE / g of DM. RTS beverage using fresh syrup and ginger juice was highly accepted beverage with a score of 8.78±0.28 for OA. Followed by this, the RTS beverage prepared using residual osmotic syrup scored (7.71 for OA) and may be recommended which otherwise would be a huge food waste leading to environmental problem. After 3 months of storage, the beverage samples stored under both refrigerated and ambient conditions have undergone changes, but the changes in refrigerated sample are not significant, except the ascorbic acid content. The microbial load i.e. total bacterial and total mould count was analyzed to be within the safe limits. Therefore, the study recommends the RTS beverage to be stored in HDPE bottles in refrigerated storage conditions.