Abstract
This research investigated the microbial quality and the protein contents of Thai commercial frozen products of silkworm (Bombyx mori), bamboo caterpillar (Omphisa fuscidentalis), and field cricket (Gryllus bimaculatus). Total mesophilic aerobic counts were about 8-8.4 log cfu/g, while lactic acid bacteria numbers were up to 5.2 log cfu/g samples. Yeasts and mold as well as Enterobacteriaceae numbers were found to be no more than 6.3 and 6.6 log cfu/g, respectively, while Clostridium spp. enumeration detected 3.2-3.6 cfu per gram frozen insect samples. The protein content in cases of cricket and bamboo caterpillar after the Soxhlet defatting method and the Folch lipid extraction combined with isoelectric point precipitation were similar when compared at pH 3.5 or pH 4.5. In contrast, the protein yield from silkworm was higher at pH 3.5 in the Soxhlet defatted sample, as opposed to the Folch method treated sample where higher protein yield was obtained at pH 4.5. Furthermore, 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP) of field cricket subcritical water (121 or 135°C for 15 or 30 minutes) hydrolysates were also measured on a pilot basis. These tests revealed higher antioxidant activities in treated samples than in the untreated control. The highest DPPH radical scavenging activity and FRAP values were detected in samples treated at 135°C, while the protein content of these samples was lower than that of the untreated control. These results indicate that hydrolytic compounds of proteins and probably other types of cricket materials are possibly involved in the antioxidant activities of the treated defatted cricket samples.
Highlights
It is widely accepted that the human population on planet Earth would reach 9 billion by 2050, and one of the huge challenges of the 21st century is to produce enough food for everyone
In Thailand, several kinds of edible insects are consumed as deep-fried snacks including bamboo caterpillar (Omphisa fuscidentalis), silkworm (Bombyx mori), and field cricket (Gryllus bimaculatus), which are available at supermarkets in uncooked, frozen packages
Prior quantitative microbial analyses on field cricket and bamboo caterpillar are lacking; comparing our data to published findings on other edible insects, it can be concluded that the three frozen insect samples had moderate microbial load in the specific microbe groups that were investigated
Summary
It is widely accepted that the human population on planet Earth would reach 9 billion by 2050, and one of the huge challenges of the 21st century is to produce enough food for everyone For this reason, global interest towards alternative and novel food sources has been increased including the recent “rediscovery” of edible insects, especially in western societies. In Thailand, several kinds of edible insects are consumed as deep-fried snacks including bamboo caterpillar (Omphisa fuscidentalis), silkworm (Bombyx mori), and field cricket (Gryllus bimaculatus), which are available at supermarkets in uncooked, frozen packages. These frozen products are generally perceived by Thai customers as safe, studies assessing the microbial load of these are lacking. Protein extraction procedures after two different kinds of lipid removal methods were investigated, potentially aiding technological processes aiming to extract and purify insect proteins from the above
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