Design fabrication and evaluation of walnut bleacher

Abstract

The aim of the present study was to design, fabricate, and evaluate a walnut bleaching machine. The machine consists of a feed hopper, rotating drum, motor, reduction gear, belt and pulley system, pump, storage tank, lever, delivery chute, and a control box. The bleaching process is achieved by simultaneous chemical and mechanical action. In order to assess the performance of the machine, acidified sodium chlorite, sodium hypochlorite, and hydrogen peroxide were used as bleaching agents in 2 and 3% concentrations for 5 and 7 min of time. The result of the performance tests showed the significant effects of bleaching agent and bleaching time on all the performance and color parameters with the exception of damaged walnut percentage. Treating inshelled walnuts with 3% sodium hypochlorite +0.2% HCl (T5) for 7 min followed by rinsing in plain water resulted in attractive and bright shell appearance of walnuts. Further, highest bleaching efficiency (94.69%), fully bleached walnut percentages (94.19), and lowest partially bleached walnut percentage (5.47) were recorded when T5 was used as bleaching agent for 7 min in bleacher. Practical applications Dark shell colored and stained walnuts have poor consumer acceptability. In India, crude methods are employed to remove these shell stains, which compromise the shell integrity, thus leading to moisture ingress into kernels. This results in kernel darkening, mold growth, and oxidative rancidity in walnuts. However, for improving the surface appearance, the walnuts after dehulling are required to be processed. Therefore, a walnut bleaching machine was developed and various chemical bleaching agents were investigated to study their effects on surface cleaning of inshelled walnuts. A technology of this nature can be useful to walnut growers and processors.