Process And Product Optimization And Storage Characteristics Of Canned Peanut Soup Base

ABSTRACT Peanut soup is very popular in Ghana and the entire West Africa region. It is largely prepared and consumed both at the domestic and commercial scales. Due to the long and tedious nature of preparing the soup, there was the need to develop a shelf stable condensed canned peanut soupbase which could be reconstituted to create convenience in peanut soup preparation. Previous work/studies done established a process flow chart for the canned peanut soup-base through selection of suitable peanut variety; ingredient formulation and evaluation of the thermal processes. This study sought to optimize the production process of a canned peanut soup-base; conduct a shelf life study; determine proximate composition of product and to evaluate the canned peanut soup-base for consumer acceptance. The central composite rotatable design for three variables (i.e. K=3) was used to optimize the processing variables of the peanut soup base. The variables and their levels were roast temperature (130˚C - 150˚C), roast time (30-60 minutes) and retort (thermal process) time (45-65 minutes). The canned peanut soup-base obtained from the 16 experimental runs was used to prepare peanut soup. The quality of soups after the canning were evaluated by a 20 member sensory panel using a balanced incomplete block design for b=20, t=16, λ=1, N=80. An accelerated shelf life test was used for the estimation of the product shelf life for a period of 8 weeks at storage temperatures of 27˚C and 55˚C. Product attributes evaluated during this study included pH; peroxide value; free fatty acids content and colour (L-Value). Proximate analyses of the product were also conducted. Fifty peanut soup consumers were randomly selected and were given the canned peanut soup to prepare and evaluate the product in their homes, using a pre-tested questionnaire. iii Results showed that the colour (L-value) of the peanut paste was affected by the roast temperature-time combinations for the peanuts. Roasted peanut colour was highly dependent on the roasting temperature and time. The higher and longer the roasting temperature and time, the darker the peanut roast colour. The total colour change (∆E*) of product after retorting showed significant differences (p < 0.05) with respect to the different retorting times. It ranged from 2.18 for 38 min retort time to 6.08 for 72 min. Using the free fatty acid content of products after 5 weeks of storage as the cut-off spoilage indicator, the shelf life of the canned peanut soup base was estimated to be sixty-seven (67) weeks. The proximate analyses of the canned peanut soup base revealed that the product had moisture content of 64% with crude fat, crude protein, crude ash and carbohydrate been 21.81%, 6.54%, 2.27% and 5.48% respectively. The results from the study indicate that an acceptable canned peanut soup-base could be obtained from roasting peanuts at 125˚C for 28 minutes to obtain a paste of light roast colour and retorting the product for 55 minutes. The canned peanut soup base product obtained would be stable on the shelf for more than a year, and would still be acceptable to consumers. This could be used to establish the shelf-life (best before date) for the product. Also evaluation of canned peanut soup base revealed that close to 90% of consumers liked the product and are looking forward to seeing it on the market.