Nutrient profile, prebiotic potential of edible cricket, and effect of cricket-based porridge on growth, haemoglobin and fatty acid levels of school children

Abstract

There is a steady increase in the world population and therefore more pressure on available natural resources such as land and water. Animal rearing contributes to pollution through greenhouse gas emission causing climate change, making it hard to continue depending on commonly available animal protein as a major source of protein. Therefore, there is a need for alternative animal protein source such as insects. This study aimed at determining the nutrient composition, the prebiotic potential of chitin from the farmed crickets, and their utilization to improve growth, haemoglobin and fatty acid levels of children in Kenya. The specific objectives for this study were; to determine the optimum harvesting age of crickets based on nutrient composition, to evaluate the potential of cricket chitin as a prebiotic, for selected probiotic bacteria, develop a cricket-based porridge and determine its consumer acceptability, and to evaluate the effect of cricket-based porridge on the growth, haemoglobin and essential fatty acids levels of school going children. Crickets (Acheta domesticus) were obtained from Jomo Kenyatta University of Agriculture and Technology (JKUAT) cricket farm and nutrients profiles for 13 weeks were determined using standard methods. Cricket chitin was used as a prebiotic on selected probiotic bacteria. In the evaluation, bacterial media supplemented with 0%, 1%, 5%, 10% or 20% chitin were prepared following the standard procedure. Probiotic and pathogenic bacteria were cultured for 0, 6, 12, 24, and 48 hours and bacteria colony forming units counted. To assess consumer acceptability, and sensory evaluation of cricket-based porridge, different flour containing either: maize millet (MMP), maize millet with skimmed milk (MP10) or cricket powder (CP5) at 5%, CP10 at 10% or CP20 at 20% were developed. Sensory evaluation was done using a 7 hedonic scale. Randomized control trial, with three arms, was set up to evaluate the acceptability of the porridge by children and the effect of cricket porridge on children growth, haemoglobin, and essential fatty acid levels. Children (n=138) aged 3-4.5 years were recruited and fed with either maize millet (MMP), maize millet with skimmed milk (MP10) or cricket powder [CP5] for 6 months with monthly follow-up. Food acceptance was evaluated for the first 4 weeks of the trial, anthropometric and morbidity data were collected monthly from baseline to end line. Blood samples were collected using the finger prick method at baseline and endline for determination of haemoglobin and fatty acid levels. Crude protein means ranged from 36.0–60.0g/100g, chitin 2.20- 12.40g/100g, crude fat 12.00– 25.00g/100g, over the 13 weeks period, the change was significantly different (P≤0.05) over time. Mineral concentration was optimum at week nine with magnesium ranges of 1.30- 11.30mg/100g, calcium 1.40-19.70mg/100g and zinc 0.20 -16.60mg/100g. Crude fat content 25g/100g was optimum at weeks 9 and 10. All chitin concentrations significantly increased the population of probiotic bacteria (P≤0.05) while decreasing the population of pathogenic bacteria. During growth, there was a significant pH change (P≤0.05) in the broth media with the growth of all probiotic bacteria. Inhibition zones from probiotic bacteria growth supernatant against Salmonella typhi were most apparent at 16 mm and statistically significant in comparison with a 10% chitin concentration (P≤0.05). Pathogenic bacteria were suppressed most in the presence of chitin and probiotic bacteria. The results clearly demonstrate the prebiotic potential of chitin from farmed crickets. In the developed flour, microbial quality showed that the flour was safe for human consumption since there was no contamination of flour by enteric bacteria, with total bacteria counts, yeast and moulds in the flour having counts below the maximum acceptable limits. Maize millet porridge, milk based porridge, and cricket-based porridge 5% had the highest acceptability amongst the participants. There was a significant difference in appearance (P=0.02), taste (P<0.001), texture (P=0.01) and the general acceptability (P<0.001) of all the developed porridge. Therefore cricket-based porridge (5%) compared well with milk-based porridge hence used for the intervention. Consumer acceptability of cricket porridge was >75% in the first week and by the fourth week, all the children were able to accept cricket porridge to 100%. By four weeks of the intervention, all the children were able to develop a liking for the cricket porridge. All children in the three arms improved in anthropometric indices, weight for age Z score improved from -1.0 to 0.39, 035 and 0.41 in MMP, MP10 and CP5 respectively. There was a significant difference in haemoglobin levels at baseline and end line in all trial arms (P≤0.05). In conclusion, farmed cricket should be harvested between weeks 9, 10 and 11 when the protein, mineral, and fat content is optimum. Additional benefits can be obtained from cricket chitin which serves as a prebiotic, leveraging on the wide consumer acceptability of cricket as an additive in porridge. Cricket-based porridge was shown to improve the nutritional status of children, there is need therefore to develop cricket-based products for child feeding. Crickets would then be used as an animal source protein to supplement the commonly available animal protein sources. Further research to exploit the pharmaceutical potential of cricket chitin should be conducted and more parents educated on the use of crickets as an animal source protein to improve child nutrition.