Assesment of the nutritional value, microbial quality and sensory acceptance of cookies enriched with edible longhorn grasshoper (ruspolia differens serville) flours from different processing methods

Abstract

Long-horned grasshopper (Ruspolia differens), an edible insect native to sub-Saharan Africa, is considered a delicacy by some communities in the region and contributes 5-10% of the protein intake. However, its full utilization as food across the different cultural constructs has been hampered by neophobia and disgust occasioned by uncommon food cultural practices, thereby limiting its potential to combat malnutrition in the region. Therefore, there is need to process and hide the insect into modern food products to improve its utilization. The current study investigated the effects of enriching cookies with differently processed R. differens flours on the nutritional composition, digestibility and volatile organic compounds profile, the microbial quality and the sensory acceptance on a 5-point hedonic scale. Blanched, boiled and toasted R. differens-based cookies demonstrated significantly (p<0.05) higher protein (10.90-11.09%) whereas deep-fried R. differens-based cookies exhibited higher fat (25.82%) and energy (514.69 kcal). The levels of essential amino acids; leucine (8.57-8.97 mg/g) and isoleucine (5.56-6.07 mg/g) were significantly (p<0.05) higher in blanched, boiled and toasted R. differens-based cookies than in control and deep-fried R. differens-based cookies. Omega-3 fatty acid, methyl (9Z,12Z,15Z)-octadecatrienoate (0.34-2.12μg/g) was only detected in the cookies integrated with the processed R. differens flours. Methyl hexadecanoate (5.02-10.58μg/g), methyl (9Z)-octadecenoate (11.55-17.20μg/g) and methyl (9Z,12Z)-octadecadienoate (0.19-12.10μg/g) were the dominant fatty acids in the different cookie types. Cookies supplemented with blanched and boiled R. differens exhibited significantly (p<0.05) higher levels of Fe (7.11-7.12 mg/100 g) and Zn (4.17-4.33mg/g). Pleasant aroma compounds; 2E,4E-dodecadienal, pentanal, and octanal, methyl pyrazine, furfurals, benzaldehyde, and 2-pentyl furan, were more pronounced in cookies prepared with boiled, toasted and deep-fried R. differens. The digestibility of R. differens based cookies and control cookies ranged between 71.23-80.41% and 88.22%, respectively. All the cookie types expressed permissible levels of total viable counts (>30 Log cfu/g), Staphylococcus aureus, Salmonella spp and yeast and moulds that are compliant with Kenya Bureau of Standards guidelines on insect-based products. Sensory evaluation suggested that panelists preferred the overall sensory characteristics of control (4.24) and deep-fried R. differens-based cookies (3.97) while lowly rating flavour of blanched R. differens-based cookies (3.17). Summarily, blanched and boiled R. differens-based cookies, expressed excellent nutritional profiles and digestibility. However, blanched R. differens requires masking of the objectionable flavours to enhance consumer preference.