Design and Development of Desheller cum Pulper for Wood Apple Fruit (Limonia acidissima) and By-product Utilization of Shell

Abstract

The wood apple fruits (Limonia acidissima) belonging to the family “Rutaceae” has extensive phytochemical and nutraceutical composition contributing to various health benefits. The wood apple fruit is a “Minor Forest product” native to India and Sri Lanka. The post-harvest processing of the whole wood apple fruit is essential for utilization of fruit pulp and development of value-added products. However, due to the lack of proper process technology, the fruit is currently processed by traditional manual operations using hammer or stone for breaking the fruit and spoon for scooping the pulp. The existing manual process is laborious, tedious, time consuming, causes contamination, wastage and can lead the product to be unsuitable for development of value-added products. Hence, this urges the need to develop an equipment and process technology for wood apple fruits to reduce these traditional process problems and drudgery. The continuous-automated equipment of wood apple fruits for deshelling, pulping and seed removal were designed, developed and evaluated for optimum utilization of fruits. The engineering properties of the fruits were analyzed for design and development of equipment. The average mass of the fruits was 232 g and the maximum dimensions of the fruits were 8.86, 8.42 and 8.21 cm for longitudinal axis (LD), intermediate axis (ID), and short dimensional axis (SD), respectively. The wood apple desheller cum pulper equipment was designed using Creo elements V5.0 software that will be suitable for all sizes of the fruit. The equipment was fabricated with stainless steel (SS304) for fruit contact parts and mild steel for the support structure of the equipment. The developed equipment consists of cutting unit, conveyor with cups, pulping unit, deshelling unit and seed removal unit. The cutting units cuts the fruit into two halves that is transported by the conveyor cups to the pulping unit by limit switch, PLA sensors and sequential timer arrangements that permit the conveyor cups to stop at accurate location. The pulp in the shell is loosened and conveyed by gravity to the desheller that separates shell from the pulp fraction. The seed removal unit separates the seeds from one end and the pure pulp from the outlet chute. The performance of the equipment was evaluated and optimized. The optimum deshelling efficiency (98.9 %), pulping efficiency (85.8 %), pulp yield (35.97 %), overall effective throughput capacity (29.6 kg/hr) and minimum overall equipment loss (10.5 %) were achieved with 600 rpm vibratory screen speed and 16.3 rpm of seed removal unit screw speed. The overall throughput capacity of equipment was 83 kg/h. The cost-economic analysis of equipment was performed and found to be ₹ 1,60,000 (per unit) for fabrication. Additionally, the cost of processing to produce 1 kg of pulp is ₹ 103.4, break-even point is 2214 kg, and the pay-back period will be 0.5 years which suggested the economic feasibility for utilization of the equipment. The by-product of wood apple fruit, the wood apple shell has revealed to have various groups of functional compounds such as polyphenols, flavonoids, minerals, protein and antioxidant property from the chemical and phytochemical analyses. However, utilization of the shell in food formulations has seen limited applications due to lack of proper process methodology and value addition methods. Hence, this necessitates the development of a process methodology for optimum utilization and application of the bioactive compounds from the wood apple shell in food formulations. In the current work, the bioactive compounds from the wood apple shell were extracted using specific and combined cold-plasma ultrasound assisted extraction and the obtained shell extract was incorporated as a natural antioxidant in edible oil by emulsification (water-in-oil and oil-in-water emulsion) with encapsulation of oil-in-water emulsion by spray drying, as oil is prone to rancidity and as there is consumer resistance against the use of synthetic antioxidants. The cold plasma treatment (20 min time, 15 KV voltage) prior to ultrasound-assisted extraction (15 min time, 50% amplitude, 5 feed/solvent ratio) has significantly higher enhancement of antioxidant activity (90 DPPH% and 93 ABTS%), phenols (63.84 mg GAE/g DW), and flavonoids (6.03 mg Quercetin/g DW) content compared to specific extraction techniques. The Fourier transform infrared spectroscopy and Gas chromatography-mass spectroscopy of shell extract has confirmed the various polyphenols and antioxidant compounds. The shell extract incorporated in sunflower oil by water-in-oil emulsion at varied shell extract concentrations (0.5 & 1 %) and oil (70 to 90 %) has observed efficient results at 0.5 % extract and 80 % oil concentration at 4°C than 25°C temperature during 28 days storage with lower mean particle size, homogeneous narrow distribution of particles and no observation of creaming, oxidation stability, and has high viscosity. Whereas the oil-in water emulsions at core concentration of extract (0.5&1 %) and sunflower oil (10 to 30 %) have shear-thickening behaviour, homogeneous nano particle size with stable formulation exhibiting efficient results at 1 % extract with 10 % oil concentration co-encapsulated with greater oxidative stability of PV ≤10 meq O2/kg oil throughout 28 days with encapsulation efficiency of 88.6 %. The current study suggests that the wood apple desheller cum pulper is economically feasible and can be commercially utilized by rural, small and medium scale industries for development of value-added products. Additionally, the shell extract can be acceptable as a natural antioxidant replacing synthetic antioxidant and the co-encapsulates developed can be utilized as functional ingredients in food, pharmaceutical and cosmetic formulations.