EFFECT OF SPROUTING AND ROASTING ON SHELLING AND FUNCTIONAL CHARACTERISTICS OF WATERMELON SEEDS

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2018-02
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The seeds which are often the waste part of the fruits have not generally received much attention with a view to being used or recycled rather than discarded. Interestingly the seeds of watermelon (Citrullus lanatus) have higher protein, fat, vitamins, minerals and other essential nutrient activity. It is therefore necessary to evaluate the functional properties, the nutritional and anti-nutrients contents of these fruits and their waste materials so that the knowledge derived can be used to encourage adequate consumption of fruits and reutilization of the seeds in possible value added applications. The inability to effectively shell watermelon in order to meet the requisite capacity necessary for industrial utilization has been a hindrance to its use for large scale production of various commodities. A variety of health and nutritional benefits can be obtained from sprouting. Roasting can enhance flavor through caramelization and maillard browning on the surface of the food. Therefore, the present work aimed at studying the effect of operational speed (1500, 1750 and 2000rpm) and seed conditions (15, 20 and 25% mc) on shelling of soaked and sprouted watermelon seeds in a centrifugal shelling device through the performance indicators i.e. capacity, shelling efficiency, broken percentage and whole kernel recovery. The effect of sprouting and roasting on functional and anti-nutritional qualities of watermelon seed kernel (WMSK) was also evaluated. Blended malt powder was prepared from sprouted ragi and watermelon seeds at different proportion of ragi:WMSK as 70:30, 60:40, 50:50 and 0:100 to assess the acceptability. The experiments have been conducted; data has been analyzed statistically using single factor and two-factor ANOVA and interpreted. Standardization of sprouting process indicated that a combination of 12h soaking in normal water followed by 48h sprouting period and 6h soaking in warm water (40ºC) followed by 48h sprouting period will result in more than 85% and 92% sprouting respectively. On sprouting, the fiber, ash and ascorbic acid was found to increase substantially from normal WMSK powder (8.01±0.36%, 5.95±0.40% and 29.52±0.94% respectively). On sprouting the WAC (135.37±0.60%), FAC (135.57±0.40%), ES (87.22±0.63%), FC (24.83±0.21%) and FS (18.77±0.40%) improved significantly. With increase in roasting time there was significant reduction in ascorbic acid as it is highly sensitive to heat. The roasted samples showed gradual decrease in WAC, FAC, FC and FS with increase in time of roasting and have significant difference from those of sprouted sample. On the contrary roasted sample was shown to have good emulsion stability. The unprocessed WMSK powder contained 311.99±0.80mg/100g oxalic acid and 411.27±1.54mg/100g phytic acid respectively. On sprouting the oxalic acid content and phytic acid content decreased significantly to 119.42±0.89mg/100g and 272.74±1.06mg/100g respectively. Dry heat treatment to roasted samples was not effective in reducing oxalic acid content and phytic acid content significantly. The shelling efficiency increased with a decrease in moisture content and increase in shelling speed. But the shelling efficiency of any combination was invariably higher in sprouted sample than soaked sample. On an average the percent broken was less in sprouted seed than soaked seed samples for any given set of process parameters. There was an increasing trend of breakage with increasing speed and decreasing moisture content. Maximum WKR of 66.53% was obtained at 20±1% moisture content at 2000 rpm for soaked sample where as WKR was maximum (69.13%) at moisture content of 20±1% and shelling speed of 1750 rpm for sprouted seed. Though the beverage prepared using only sprouted WMSK powder (S4) scored highest overall acceptability (8.02), the ANOVA revealed that there was no significant difference between S3 (ragi:WMSK, 50:50) and S4 (ragi:WMSK, 0:100). Considering the nutritional profile, the sample S3 (50:50) also has more balanced composition to be recommended for adult group of the society.
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