Nutrient Composition of Two Cricket Species (Scapsipedus icipe and Gryllus bimaculatus), and Effect of Extrusion Process Optimization on Nutritional, Functional and Sensory Properties of Maize-Cricket Porridge Flour

Abstract

Globally, there is growing interest in integrating cricket flour into plant-based foods to combat nutritional insecurity. However, data on the nutrient profiles of Scapsipedus icipe and Gryllus bimaculatus—the most widely consumed cricket species in Kenya— remains limited. Incorporating crickets into food matrices and using extrusion may impact the nutritional and functional properties of the formulated products. Optimal extrusion parameters for maximizing nutrient yield from various cricket species remain undefined. This study aimed to (i) determine the nutrient and anti-nutrient phytochemical composition of the two cricket species and compare them with published records of key animal and plant sources (ii) develop a nutritionally balanced maize-cricket formulation and evaluate the effect of extrusion on nutrient and functional properties of the formulated product using existing extrusion conditions (iii) determine the sensory attributes of porridges prepared with extruded and non-extruded maize-cricket flour blends and (iv) optimize the extrusion process parameters for attainment of optimal product in extruded maize-cricket porridge flour blends. Standard analytical methods were used to determine the nutrient composition of both cricket species. Maize-cricket blends were formulated using adult cricket powder, maize flour, and sugar. These were optimized using Minitab 20 software to meet the daily protein requirements of children aged 5-12 years. Three formulations containing 10%, 15%, and 20% cricket powder were prepared and processed both by extrusion and non-extrusion methods and samples subjected to nutritional and functional analysis. A semi-trained panel of 46 participants evaluated the sensory attributes of the porridge samples using a 9-point hedonic scale. Response Surface Methodology (RSM) through Box Benhenken design and the extreme vertices model of Mixture Design were employed to optimize extrusion process variables (barrel temperature, screw speed, and feed moisture) and formulation respectively, aiming to produce a porridge with significantly higher nutrient content from blends of S. icipe and G. bimaculatus with standard maize flour. Both cricket species, S. icipe and G. bimaculatus, demonstrated comparable protein content (56.8-56.9%) to animal sources and higher amino acid profiles to plant-based proteins. Their protein digestibility (80-88%) was similar to common plant foods but slightly lower than animal proteins. The cricket species were notably rich in essential minerals like iron, zinc, and potassium, significantly surpassing plant and animal sources. Calcium content was comparable to most sources, except kidney beans and eggs. Both cricket species offered higher levels of riboflavin, thiamine, and folic acid compared to conventional sources. Vitamin A was significantly higher in S. icipe compared to G. bimaculatus. Notable amounts of polyunsaturated fatty acids were found in (S. icipe (24.71%) and G. bimaculatus (19.16%), alongside saturated and monounsaturated fatty acids. Physicochemical properties of oils from both species revealed high similarity across most parameters, including refractive index, specific gravity, peroxide value, and saponification value (P = 0.1047, 0.0774, 0.3581 respectively). However, a highly significant difference was observed in acid values, with S. icipe (2.19 ± 0.36 mg KOH) exhibiting more than double the acidity of G. bimaculatus (1.10 ± 0.01mg KOH; P < 0.001). Additionally, G. bimaculatus demonstrated a slightly higher solidification temperature range (2–7°C) compared to S. icipe (2–5°C). These results suggest that while the primary chemical stability and density of the two lipids are comparable, they differ significantly in their free fatty acid content and thermal xxii behavior. Analysis of anti-nutritional factors in S. icipe and G. bimaculatus revealed significant differences in most phytochemical markers (P < 0.05). G. bimaculatus contained significantly higher levels of phytates (10.33 ± 6.00 mg/100g vs. 3.85 ± 0.44 mg/100g; P = 0.012) and tannins (1.56 ± 1.08 mg/100g), which were not detected in S. icipe (P = 0.003). Conversely, S. icipe exhibited a significantly higher concentration of total polyphenols (65.00 ± 1.79 mg/100g) compared to G. bimaculatus (48.00 ± 4.49 mg/100g; P = 0.021). No significant difference was observed in oxalate concentrations between the two species (P = 0.076). These findings indicate that while G. bimaculatus possesses a more diverse anti-nutritional profile, S. icipe is richer in total polyphenolic content. Extruded porridge flours incorporating cricket powder were significantly more desirable in terms of appearance (P = 0.003), texture (P = 0.001), and mouthfeel (P = 0.028) compared to non-extruded counterparts. Consumer preference was most desirable with the addition of cricket powder at a 10% enrichment level. Taste, texture, and thickness were the most influential sensory attributes with a desirability rate of 21%, 26.6% and 17.2% respectively. The addition of cricket powder at different levels resulted in varying changes in the proximate composition, functional, and pasting properties of the porridge. While some properties like ash, dry matter, and P2 temperature remained unchanged (P = 0.657, P = 0.295, P = 0.851 respectively), protein digestibility increased at the 10% substitution level. Hydration properties improved, and bulk density decreased with increasing cricket powder levels. Extrusion reduced pasting properties, except for P2 temperature (P = 0.851). Optimal extrusion conditions were determined to be a barrel temperature of 120°C, a screw speed of 40 rpm, and a feed moisture content of 12%. Under these conditions, blends with S. icipe achieved a higher protein content (7.7%) with greater reliability (93.8% (d=0.9377)) compared to G. bimaculatus blends (5.8%) with a reliability of 43.5% (0.4347). In conclusion, both cricket species in this study were found to have significant levels of protein, minerals, fat and vitamins. When compared to conventional food sources using the Kenya Food Composition Tables, both species were shown to have either similar or higher values for protein, mineral, vitamins and fat. The extruded corn-cricket porridge evaluated in this study containing 16.52 g/100g of crude protein with an in vitro digestibility of 54.5%, provides 9.00 g of digestible protein per 100 g serving. Based on WHO/FAO (WHO/FAO/UNU, 2007) guidelines, this represents a substantial contribution to the daily requirements of school-going children, meeting approximately 49.1% of the RNI for a 5-year-old and 23.5% for a 12-year-old. Therefore, it is recommended to policy makers as a viable option to be added into the food basket for school meals in Kenya.