Food remaining inside the packaging of commercial foods can cause food loss. Therefore, packaging must be improved in the near future to reduce the food loss. To determine the key improvements necessary, the current trends in relation to food loss through residual foods and their causes should be clarified for each packaged food. In this study, we focused on a typical triangular rice ball called onigiri, which has been estimated to be sold multibillion times in Japan annually. We estimated the amount of food waste from the dried seaweed (nori) used to envelope the onigiri remaining between the layers of packaging film. The results obtained from five onigiri suggested that the average mass of food waste from nori remaining between the layers of the packaging film was 47.6 mg. Consequently, when the number of distributed onigiri per year in Japan was assumed to be 1.0, 2.5, and 5.0 billion, the amount of residual nori per year in Japan was predicted to be 47.6, 119.0, and 237.9 Mg (= tons), respectively. Because the certainty of opening the packaging was also suggested to affect the amount of residual nori, we also compared the shape and heat-sealing pattern of the packaging film before and after opening the product. However, the differences in the packaging films were not significant and did not affect the amount of residual nori. Thus, to reduce food waste from residual nori for similar onigiri products, the fundamental packaging design, including the mechanism for enveloping rice balls, must be reconsidered.

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