Product development of pawpaw (Carica Papaya) - solar drying of pulp and papaya ketchup preparation using gravity concentration method

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Fresh ripe solos papaya varieties obtained from commercial papaya farm in Accra (red variety) and the Biochemistry Department. KNUST (yellow variety), was used for this study. The research was carried out to study the effects of slice thickness and drying time; effects of some pretreatment methods and the effects of packaging types and storage time on the sensory and nutritional qualities of solar dried papaya fruits and the effects of treatment levels; process types and storage time on the qualities of papaya ketchups prepared using gravity concentration method. The study revealed that drying time and slice thickness significantly (p < 0.05) affected moisture, ash, crude fibre, vitamin C and microbial load. The combined effects of drying time and slice thickness affected all monitored quality attributes. The study also showed that nutritional changes stabilised at 72 hours of drying and slice of 10 mm thickness was most suitable for solar drying of papaya fruits. Pretreatments significantly (p<0.05) affected all parameters monitored with the exception of crude fibre and certain nutritional and sensory properties were enhanced and/or maintained significantly as compared to control samples (no pretreatment). Though all pretreatments had significant effect (p<0.05) in maintaining nutritional and sensory qualities as compared to control samples, metabisulphite and ascorbic acid pretreatments were more preferred for solar drying of’ papaya fruits. The study also revealed that packaging material and storage time significantly (p<0.05) affected the moisture, ash, vitamin (S and microbial load during storage. High density polyethylene pack was more suitable for storing solar dried papaya fruits. No significant difference (p>0.05) existed between the two papaya varieties used on all the nutritional and sensory attributes monitored with the exception of vitamin C content and colour. Results of the papaya ketchup showed that increasing treatment levels significantly (p<0.05) affected moisture, ash, pH, titratable acidity, total soluble solids (TSS), vitamin (S and some minerals. Protein, calcium and iron contents were not affected significantly with increasing treatment level. Process A (prior blanching) and process B (no blanching) significantly (p<0.05) affected only the vitamin (S and Potassium content of the Ketchups. Increasing treatment levels and processes had no significant effect on the sensory attributes monitored except for sharpness. Results of the ketchups also showed that storage time significantly (p<0.05) affected moisture, pH, TSS and vitamin C except titratable acidity. It can be concluded that the combined effects of pretreatment and solar drying can be used to preserve papaya fruits. Also Papaya can be used to produce wholesome ketchup with good sensory and nutritional qualities.
A Thesis Submitted to the Department of Biochemistry and Biotechnology (KNUST) in Partial Fulfillment of the Requirement for the Award of the Master of Science (M.Sc.) Degree in Food Science and Technology, 2004