Nutrient composition and consumer acceptability of soybean-sweet potato based complementary food fortified with longhorn grasshopper (Ruspolia differens)

Traditional complementary foods in most sub-Saharan African countries are deficient in protein, essential minerals and vitamins resulting to sub-optimal growth and increased premature deaths among children below five years of age. This calls for action to develop home based enrichment of traditional complementary foods through advances in available low cost animal protein like edible insects. Longhorn grasshopper (Ruspolia differens) commonly known as senene in Tanzania is among most consumed edible insects by societies around Lake Victoria crescent. This study was was aimed at developing a nutritious, shelf stable and acceptable complementary food from soybean, sweet potatoes and longhorn grasshoppers. Ethnography study was conducted to understand indigenous technologies on processing methods, preservation, shelf-life, nutritional knowledge and traditions towards senene consumption among the Haya tribe in Kagera region of Tanzania. Senene-based complementary flour product was formulated from germinated, dried, roasted soybeans flour mixed with toasted senene and sweet potatoes flour at different ratios. The formulations were: CF1 (25% senene: 35% soybeans: 40% sweet potato), CF2 (20% senene: 40% soybeans: 40% sweet potato) and CF3 (15% senene: 35% soybeans: 50% sweet potato). Proximate composition, minerals (calcium, iron and zinc), vitamin A, phytic acid analyses and microbial analysis were done using standard methods. Consumer acceptability and shelf life studies were also carried out on formulated flours. Data analysis was done using SPSS for interviews and R for chemical, microbial and sensory data. The origin of senene remained an unsolved puzzle among most of respondents. Five varieties of senene were identified with harvesting for household consumption being done through wild collection. Traditionally made traps were used for commercial harvesting. Deep frying was the most preferred processing method while smoking was the most preferred preservation method, with shelf-life of up to 12 months. Traditions and taboos associated with senene consumption were identified, most of which favoured men while leaving out women and children. Chemical analysis showed significant 24 fold reduction of phytic acid after 72 h germination of soybeans (p<0.05). All three formulations had nutrients and energy levels superior to commonly used flour from the market and contained ideal composition, meeting Codex standards and above WHO recommendations for complementary foods (p<0.05). Toasted senene had the highest retinol content of 390 μg /100g while fresh sweet potatoes had the highest βcarotene content of 182 RAE (p<0.05). Microbial counts were significantly higher for fresh senene with 6.5log cfu/g. Processed senene and flour samples were free from E. coli and Salmonella spp contamination as required by Codex and EAS standards. CF1 was most liked flour with significantly highest score of 4.4 out of 5 on hedonic scale. Formulated products did not pose strange sensory attributes (p<0.05). Quantitative descriptive analysis (QDA) showed that CF1 had higher intensity scores in aroma, colour and hands feel while CF3 in whiteness and appearance. Principle Component Analysis (PCA) showed variation between products to be mainly explained by aroma, hand feel and colour on one side and attributes appearance and whiteness on the other side along PC1. Partial Least Square Regression showed that both mothers and students preferred CF1 for its colour, hands feel and aroma also CF2 and CF3 for their whiteness and appearance. All flours were shelf stable for five months. Indigenous technologies for harvesting, processing and preserving senene exist and maybe improved to fit current food processing standards hence promote commercialization of the edible insect for food and nutrition security. Exploitation of senene as a source of nutrients for complementary food formulation will be useful for the resource poor farmers.