Optimization of the processing conditions and quality characteristics of watermelon jams using response surface methodology

Optimization of the processing conditions and quality characteristics of watermelon jams using response surface methodology

E Afoakwa, O Oguseye, G Annor, J Ashong

Water melon (Citrullus vugaris) is a fruit grown for its thirst quenching property rather than for ant nutritional value. It consists of 92% water and 8% sugar, so it is aptly named. Its high water content makes it impracticable to use this fruit for jam, but because it is seasonal, processing the fruit into jam is a means of keeping this out of season produce available throughout the year. This study sought to investigate the effect of sugar concentration and pH balance on the chemical, physiochemical and physical properties of watermelon jams. Through the response surface methodology (RSM), the effect of refractive index, soluble solids, pH, total acidity, moisture, ash, total carbohydrate, hardness and colour with respect to sugar concentration and pH were determined. Response surface models were generated using regression analysis and used to plot graphs for each of the indices studied. The results revealed that inclusion of 60% sugar improved the soluble solids content, texture, colour and gel set of the jam. Inclusion of sugar concentration above 60% did not increase soluble solids content of the jam and resulted in jams of sticky consistency which is unacceptable from the standpoint of the consumer. The low sugar jams failed to set and had unacceptable texture, colour and soluble solids content. Sugar significantly contributes to the quality of the jam but above 60% sugar concentration, the quality of the jam is not improved. Acid had significant effect on the gel set, texture, total acidity and pH of the finished jam. All the pH levels studied resulted in jams of acceptable pH when analyzed. The optimal conditions required achieving the optimum soluble …

2006

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English