Effect of pre-treatments and drying on nutrient content of orange fleshed sweet potatoes in Maswa District, Tanzania

Rural communities in Tanzania are increasingly suffering from food shortage and malnutrition. A household survey was conducted to determine the baseline situation in Maswa district, regarding production, processing and storage of orange fleshed sweetpotato roots and cowpea leaves. Chemical analysis was carried out on four sweetpotato varieties (Jewel, Karoti dar, Kabode and Ejumula) possessing different intensities of orange-flesh colour to establish levels of nutrients in fresh and processed products using standard methods of analysis (AOAC). Beta carotene was determined by the spectrophotometric method. Sweetpotato varieties were subjected to pre-treatments including blanching and boiling. Results of the baseline survey indicated that there was limited knowledge regarding nutritional excellence and blanching of orange fleshed sweetpotato. Michembe (fresh dried) was more preferred than matobolwa (boiled and then dried) sweetpotato. Fresh samples of sweetpotatoes had significantly low proximate composition (protein, fat, fiber and carbohydrate) compared to dried samples due to the fact that during drying food loses a significant amount of moisture resulting into concentrating other nutrients. There was a three-fold reduction in β-carotene content when fresh samples were dried. Boiled chips had more retention of beta carotene content compared to blanched chips. Results further showed that michembe had significantly low β-carotene content and low retention on storage compared to boiled and blanched chips after six months storage at room temperature. It is therefore recommended that blanching be introduced to rural communities during processing of orange fleshed sweetpotatoes to protect nutrients loss. Education on processing and nutritional excellence of orange fleshed sweetpotatoes should also be provided so as to reduce incidences of community malnutrition in and Tanzania.