Effectiveness of the Purdue Improved Crop Storage bags for preservation of common dry beans "Phaseolus vulgaris L."

Abstract

Common dry bean Phaseolus vulgaris L. is a nearly “perfect food” because it is significant for promoting food and nutrition security, besides being a source of household income for rural and urban communities. Conversely, the safe storage of beans is still a big challenge for actors in the dry bean value chain across sub-Saharan Africa (SSA). The Purdue Improved Crop Storage (PICS) triple bag system is one of the proven hermetic technologies that effectively and safely store grains in SSA.The main objective of this study was to evaluate the effectiveness of the PICS bags for preserving the physicochemical, nutritional, culinary, and sensory characteristics of Nambale short (NS) and Yellow short (YS) dry beans during six months of storage. Before the quantitative study, a rapid appraisal took place to assess the knowledge, attitudes and practices of purposively selected consumers and traders within the Kampala district. The findings revealed that Nambale short and Yellow short beans were the preferred bean varieties by most consumers. The beans used in the experiment were sorted and solar-dried before filling them into either PICS or Polypropylene (PP) bags in triplicate. The bags were placed inside a rodent-proof mesh storage cage under typical local conditions for six months. Non-destructive sampling was done at 0, 3, and 6-month storage intervals to evaluate the quality characteristics of the beans but data for gas composition and temperature were collected at 0, 6, 12 and 24 hours (day 1), 12 and 24 hours (day 2), 24 hours (day 3 to 18), and 168 hours (day 19 to 180 for the remaining twenty-three weeks. At the end of six months of storage of NS and YS beans in either PICS or PP bags, results of a mixed-design ANOVA showed significant interaction effects between storage time*bag type*bean genotype on the means of oxygen (F (1.68, 13.48) =15.42, p<0.05), carbon dioxide (F (1.42, 11.39) =11.39, p<0.05), moisture content (F (2, 16) =17.46, p<0.05), invisible mould infestation (F (2,16) =3.76, p<0.05), insect infestation (F (2,16) =5.11, p<0.05), insect damage (F (2,16) =52.49, p<0.05), weight loss (F (2,16) =15.35, p<0.05), water holding capacity (F (2,16)=13.74, p<0.05), swelling capacity (F (2,16) =5.13, p<0,05) and swelling index (F (2,16) =11.67, p<0.05). For temperature (F (2.66, 21.30) =16.95, p<0.05), germination rate (F (2, 16) =11.12, p<0.05), hydration index (F (2, 16) =7.50, p<0.05), cooking time (F (2, 16) =257.53, p<0.05) and water uptake ratio (F (2, 16) =4.37, p<0.05), the significant interaction effect was between storage time*bag type. At the same time, there was a significant interaction effect between storage time*bean genotype for mean germination rate (F (2, 16) =6.82, p<0.05). On the other hand, the interaction effects were insignificant but time as a main effect was significant on the means of in-vitro protein digestibility (F (2, 16) =45.75, p<0.05), bean integrity (F (2, 16) =8.95, p<0.05), hydration capacity (F (2, 16) =713.89, p<0.05), HCl Extractable iron (F (2,16) =6.13, p<0.05) and HCl Extractable zinc (F (2, 16) =9.49, p<0.05). For sensory characteristics, both the interaction and main effects were insignificant. Further, significant correlations were observed between storage conditions and the quality characteristics as well as among the quality characteristics. Generally, at the end of six months, the losses in the quality characteristics of PICSNS & PICSYS combinations were lower than those registered in PPNS & PPYS. In addition, PICNS had significantly better quality characteristics compared to PICSYS beans throughout storage. The storage time was a significant factor in determining the effectiveness of PICS bags for preserving the quality of NS & YS beans against losses during storage. Keywords: Physicochemical, nutritional, culinary, and sensory characteristics of common dry beans; Post-harvest storage