Effect of conventional bulk and some retail packaging materials on quality of dried mopane worm (Imbrasia belina)

Abstract

In this study, the effect of conventional bulk and selected retail packaging materials, and duration of storage was investigated on physicochemical, microbial stability and sensory quality of traditionally processed dried mopane worm under two storage conditions. The samples were analysed for changes in physicochemical (ash, moisture, fat, protein, and colour), microbiological (yeast, and mould and coliform count), and sensory colour, taste, texture and overall acceptability) qualities every 30 days for 120 days. The changes in the quality of traditionally processed and sun-dried mopane worm (MW) were evaluated using a 2 x 2 x 5 factorial experimental design comprising packaging materials, storage temperature and storage time with three replications. Results obtained from the experiment were subjected to ANOVA. Where significant ANOVA results were obtained mean separation was done using Tukey test at 5 % level significance. The first part of this study assessed the effects of conventional bulk packaging materials, storage temperature and time on the quality and shelf life of dried mopane worm. The two-way and three-way interactions among treatments significantly affected L*, a*, b* and ΔE* qualities of dried MW throughout the experimental period. The levels of L*, a*, b* decreased HST2. Whereas the values of a*, and b* increased in all treatments. The three-way interactions between packaging material, storage temperature and time significantly (p < 0.05) affected fat content, fat content decreased in PPT1, PPT2 and HST1, but increased in HST2 with increasing storage time. The three-way interaction did not significantly (p >0.05) affect moisture, ash, protein content; microbial count; and sensory colour, taste, texture and overall acceptability qualities. Moisture content decreased among treatments with increasing storage time. The decreasing moisture content resulted in a decreased yeast and mould count in HST2 during storage. The two-way interaction between storage temperature and time significantly (p < 0.05) affected moisture, fat content, sensory colour, taste, texture and overall acceptability qualities during storage. The liking scores for colour, taste, texture and overall acceptability decreased in HST1 and HST2. However, the two-way interaction between packaging material and time insignificantly (p > 0.05) affected moisture, protein content, microbial count and sensory colour, taste texture and overall acceptability qualities. The protein content of dried MW increased among treatments during storage. The second part of this study assessed the effects of selected retail packaging materials, storage temperature and time on the quality and shelf life of traditionally processed and sun-dried mopane worm. The two-way and. three-way interactions among treatments significantly (p < 0.05) affected L*, a*, b*, ΔE* qualities of dried MW. The levels of L*, a*, b* and ΔE* decreased in all treatments with increasing storage time. The three-way interaction significantly (p < 0.05) affected sensory texture qualities of dried MW during storage, but did not significantly (p > 0.05) affect ash, moisture, fat, protein content, microbial yeast, and mould, and sensory colour, taste, texture and overall acceptability. The liking scores for colour, taste, texture and overall acceptability were higher in HDPET1 than in HDPET2. The two-way interaction between storage temperature and time significantly (p < 0.05) affected ash content, moisture content and overall sensory acceptability. The moisture content decreased among the treatments with increasing storage time. Higher moisture content was reported in both LDPET1 and HDPET1 of dried MW samples during storage period. However, the two-way interaction between storage temperature and time did not significantly (p > 0.05) affect fat and, protein content; yeast, mould and coliform count; as well as sensory colour, taste and texture qualities. The yeast and mould count decreased in LDPET2, HDPET1 and HDPET2 with increasing storage time. The two-way interaction between packaging material and time, and packaging material and storage temperature had no significant (p > 0.05) effect on ash count, moisture content, fat content, protein content, yeast count, mould count, coliform count, sensory colour, taste, texture and overall acceptability of dried MW. Ash content increased among treatment with increasing storage time. Only the two-way interaction between packaging material and time significantly (p < 0.05) affected and overall acceptability. Therefore, it was concluded that for conventional bulk packaging the PP was better than HS packaging material while for retail packaging HDPE was better than LDPE in preserving the nutritional and sensory quality of traditionally processed dried MW .