Optimization of Low-cost Food Processing Techniques for the Development of Cowpea Leaves Soup Mixes

Abstract

Seasonality in the availability coupled with limited value addition practices of the cowpea leaves is great impediment to its utilization. The current study evaluated value addition approaches for the production of superior quality shelf-stable cowpea leaves based product to bridge limitation in the availability of the crop. The study was implemented using a desk review that identified optimized modern processing techniques for the vegetables; a field survey incorporating a mixed method convergent study design in the eastern and coastal arid and semi-arid lands (ASALs) in Kenya, Kitui and Taita Taveta Counties, to identify the trends and constrains in the utilization of cowpea leaves; and experimental study that utilized optimization approach in processing and evaluating product quality of cowpea leaves. The desk study established that hurdle technology, combining two preservation techniques, has the advantage of optimal retention of product quality than the use of a single preservation technique. The field study showed that the mean period of availability of fresh leaves in the areas was 4.8 ± 4.3 weeks in each cropping season. Sun-drying was the most utilized preservation technique among the households, 27.5%. Households in the coastal ASALs significantly (p < 0.05) consumed more of dried forms (odds ratio: 3.3) but less of boiled ones (odds ratio: 0.1) than those in the Eastern parts of Kenya. Involvement of households in the commercialization of cowpea leaves and sale of the preserved forms in the open-air market significantly increased the likelihood (p<0.001, OR=2.47 and p<0.001, OR=2.3; respectively) of utilization of the vegetables during scarcity. Marketing challenges, lack of access to inputs and inadequate postharvest technologies for preservation of the vegetables constrained the production and utilization of cowpea leaves. Optimal fermentation of the leaves was achieved at a sugar and salt concentrations of 5% and 2%, respectively, for 16 days; attaining a pH of 3.8 and titratable acidity of 1.22% with a desirability of 0.859; R2 for 0.89 and 0.60 for the model predicting pH and titratable acidity, respectively (p<0.001). Comparative analysis between optimally and locally processed dehydrated vegetables sourced from the farmer groups showed that, the optimally dehydrated cowpea leaves combined better retention of beta-carotene and the minerals than the latter (p<0.001). The optimal ratio for incorporation of dried cowpea leaves in soup mixes was established as 49%. Use of low-cost processing of processing (sun-drying) are half less costly than the mechanized techniques, the derivative benefits are lower. The most optimal technique, however, the solar-drying technique had the most optimal benefit-cost (1.55). The low-cost processing techniques imparted invariably similar quality parameters in terms of the physico-chemical attributes of the soup mixes. The keeping and sensory quality were, however, lower than the soup mixes processed through mechanized techniques (p<0.05). Cowpea leaves processed using modernized techniques had no significant (p>0.05) difference on the acceptability. The low-cost techniques provided alternative pathways for processing cowpea leaves soup mixes thus recommended in resource-constrained settings. Input of feasibility studies focusing on socio-determinants for uptake would be required for instituting dissemination approaches of these technologies.