Storage Time: Influence of Nano-ZnO and Soft-Sterilization on Biophysical and Quality Attributes of Canned Cowpea (Vigna unguiculata, TN 5-78)

Cowpea seeds can be cooked in the dried form, sprouted, or ground into flour. This study is to investigate effect of soft-sterilization and nano-ZnO treatment on canned cowpea (TN 5-78) biophysical and quality attributes during 10 months of storage. Cowpea was blanched, ultrasonicated with nano-ZnO solution 0.025% (w/v) added prior to canning at 110 ºC for 15 min and analyzed every 2 months up to 10 month at ambient storage. Total mold and yeast count were below the limits of detection for nano-ZnO treated samples and control over the storage period though, some colonies of mesophilic bacteria were observed in the untreated samples at the 8th and 10th month of storage. There are significant differences (P < 0.05) between the treated samples and untreated one at the 10th month of storage for the pea’s firmness. No significant differences was noticed between the samples from the initial analysis to the end of storage time for the leached solids percentage (P < 0.05). Moreover, slight change in protein content and pH values were also found. The overall acceptability score of nano-ZnO treated samples remained in a good range up to 10th month of storage whereas, untreated samples was under acceptation level. Therefore, ZnO nanoparticules combined with heat can be a possible alternative approach to can foods that the quality attributes are altered by conventional thermal sterilization.