Process optimization and product characteristics of white kenkey (nsiho)

Abstract

Kenkey, is a maize based sour, stiff dumpling, and it is among the most common fermented cereal food products in Ghana. There are several types of kenkey, and while some are made from whole maize grains others are produced using degermed/and dehulled maize grains. The kenkey types made using dehulled maize grains are less popular and have largely remained at the level of “ethnic food”, restricted to very few socio-cultural communities. Current trends in urbanization, and the increasing popularity of kenkey among consumers, require larger scale production with consistent quality. The study was carried out to examine the traditional white kenkey process and to optimize the key processing variables in order to obtain reproducible quality white kenkey that will be acceptable to native and non-native consumers. A survey was conducted in three white kenkey production districts to collate information on production, vending and consumption practices. The sensory profile and consumer acceptance of different types of kenkey and other fermented maize products in Ghana were investigated. A total of two hundred consumers including 110 Ghanaians and 90 internationals were used for the consumer test. Traditional white kenkey types were analyzed for their physicochemical, textural, microstructure and sensory characteristics. Physicochemical analysis involved determination of pH, titratable acidity, sugars, lactic acids, minerals, vitamins and amino acids using high performance liquid chromatography procedures. The textural characteristics of white kenkey randomly obtained from traditional processors were determined using instrumental (texture analyser) and consumer assessments. The effects of processing variables of steeping time (12, 30 and 48 h) and dough fermentation time (0, 12 and 24 h) on the physicochemical properties of white kenkey were determined. A (three variable) Box-Behnken design was used to optimize the processing variables of steeping time, steeping temperature, and fermentation time on white kenkey quality parameters of moisture, pH, titratable acidity, glucose and lactic acid content. The optimum region of the process variables was obtained by hedonic tests on the white kenkey using balanced incomplete block design (for k= 5, b= 21, λ=2, r =7) Quantitative Descriptive Analysis (QDA) was conducted on white kenkey made from within and outside the optimum region of the process variables, as well as white kenkey obtained from vendors using a panel of 18 trained members. Consumer acceptance study was conducted using 65 consumers for white kenkey obtained from the optimum region and traditionally processed white kenkey obtained from vendors. The results of the survey showed that there were two main types of white kenkey, nonsweetened white kenkey and sweetened white kenkey to which sugar is added during production. All three procedures involved steeping of dehulled maize grains which is then milled into a meal. In the (procedure at Atimpoku), the meal was not fermented any further but precooked, moulded into balls wrapped in leaves and steamed. In the (procedure at Anum), the meal was kneaded into dough and allowed to ferment for 12hours, the fermented dough (70%) is precooked and mixed with the remaining dough, moulded into balls and steamed. Three classes of behaviours of consumers were identified. Those who liked all the products 'all likers' (36%), those who preferred the white kenkey 'white likers' (30%) and those who preferred Banku 'banku likers' (34%). Sensory attributes important for the white likers were whitish colour, fruity odour, smooth and nonsticky texture, a less sour product without a pronounced fermented odour, and a bland taste. The white kenkey samples randomly obtained from vendors contained 70 – 77 % moisture, 0.58-0.88 g/100 g ash, 0.09-0.19 g/100 g fat, 2.45-2.84 g/100 g protein, vitamin B1 of 17-47 g/100 g, had pH of 4.07 –4.54, titratable acidity 0.42-0.60% lactic acid, 2-28 mg/g glucose, and 0.6-2 mg/g lactic acid. The amino acids lysine, methionine, Gaba and Ornitine values were less than 0.2 g/100g. Steeping time of maize was complimentary to fermentation time since both influenced the conversion of glucose by lactic acid bacteria into lactic acid. Generally, the longer steeping and fermentation times gave higher levels of glucose and lactic acid in the white kenkey. However, whilst steeping increased glucose level, dough fermentation reduced it. The intensity of whiteness (L) in white kenkey diminished as steeping time increased. On the other hand, fermentation time improved whiteness of kenkey. High aflata (i.e ratio of precooked to uncooked dough) produced kenkey with softer texture, whilst reducing the aflata ratio increased the hardness and stickiness of white kenkey. Consumers preferred white kenkey made using high aflata ratio and steamed for longer periods. The optimization studies showed that processing variables had significant effects on the physicochemical and sensory characteristics of white kenkey. The optimum region for the process variables at which the most acceptable kenkey was obtained were steeping time of 30-45 h at 30-35ºC temperature followed by 12 h dough fermentation. Consumer acceptance test indicated no significant difference in acceptance between the traditionally processed white kenkey samples and those obtained from the optimum region. White kenkey samples of higher quality potential has been identified. The process for production of white kenkey has been standardized, saving production time