Improving the nutritional quality of pale cockroach proteins by reducing digestive protease inhibitors through enzymatic treatment

Insect proteins have been gaining attention, especially after the Food and Agriculture Organisation of the United Nations (FAO) recommended their consumption in human and animal food. Insects are excellent sources of protein, fibre, vitamins, fatty acids and minerals, as well as containing several essential amino acids similar to those found in meat. Enzymatic hydrolysis is the most common process used to obtain bioactive peptides, and can also be used to reduce allergenic compounds and digestive protease enzyme inhibitors found in various food matrices. Thus, the objective of this study was to evaluate the effects of enzymatic hydrolysis of proteins from pale cockroaches (Phoetalia pallida) on the reduction of digestive proteases (pancreatin, pepsin, and trypsin) inhibitors naturally present in this substrate. The pale cockroach hydrolysates were obtained according to an experimental mixture design, using FoodPro® PNL, FoodPro® 30L and FoodPro® PXT enzymes (IFF company), applied individually or in binary/ternary combinations. Fifty millilitres of protein dispersion (100 mg mL^-1) in phosphate buffer (100 mmol L^-1, pH 7) were added of proteases (100 U mL^-1) and incubated at 50°C under agitation of 100 rpm for 2 h for enzymatic hydrolysis. Subsequently, the hydrolysed dispersions were subjected to heat treatment (100°C for 20 min) to inactivate the enzymes and the supernatants containing the bioactive peptides were collected after centrifugation at 14 000 g at 5°C for 20 min. The inhibitory activity of digestive proteases was assessed using azocasein as a substrate in the presence of protein dispersions (5 mg/mL). The activity was expressed as relative percentage values, using as control an assay performed in the absence of protein dispersions (hydrolysed or not). The results showed that, in the presence of protein hydrolysates, the proteolytic activities of pancreatin and trypsin increased, ranging from 7.09 to 17.22% and from 1.06 to 9.74%, respectively. For these enzymes, no inhibitory activity were detected at the evaluated concentration. Conversely, pepsin activity decreased markedly, with 53.63% inhibition in the presence of the non-hydrolysed sample. Enzymatic hydrolysis attenuated this effect, reducing the inhibition to only 8% in the hydrolysates generated with the enzymatic treatment composed of 1/2 FoodPro® PNL and 1/2 FoodPro® 30L. It can be concluded that the enzymatic hydrolysis reduces the presence of protease-inhibiting compounds in pale cockroach, therefore, it is an excellent way to improve its nutritional quality.