Towards establishing the spoilage mechanisms of the long-horned grasshopper Ruspolia differens Serville

Unlike other foods of animal origin, the spoilage mechanisms of edible insects remain unknown. This research intends to establish the cause of spoilage of the long-horned grasshopper, Ruspolia differens , with high and low water activity ( a w ). To achieve this, fresh and spoiled raw and processed grasshoppers stored under different conditions were assessed for (i) fat oxidation, (ii) antioxidant levels, and (iii) volatile compounds which served as indicators for different spoilage mechanisms. Results indicate that the free fatty acid value (6.69% as oleic acid), peroxide value (2.66 mEq O 2 /kg) and p -anisidine value (1.04) of fresh R. differens are similar to those of spoiled raw ( a w = 0.98) and oven-roasted ( a w = 0.95) R. differens . The headspace of the latter only possesses volatile sulphur compounds (dimethyl disulphide and dimethyl trisulphide), indicating microbial spoilage. Conversely , the headspace of spoiled R. differens with low a w (< 0.60) only possess volatile aldehydes, ketones and organic acids, indicating oxidative rancidity. The latter have high acid (11.3% as oleic acid), peroxide (17.09 mEq O 2 /kg) and p -anisidine (11.84) values. Thus, water activity plays an important role in determining the kind of spoilage that R. differens will undergo.