The Calculation of Optimal Osmotic Dehydration Process Parameters for Mushrooms by Employing: A Firefly Algorithm

Commercial agronomy represents a multi-billion dollar, worldwide enterprise. Within this industry, the annual global production of mushrooms currently exceeds 6 million tonnes [1]. As with many fresh fruits and vegetables, the high moisture content of mushrooms renders them highly perishable and, due to various enzymatic, microbial and chemical reactions, they commence deterioration immediately upon harvesting [2] [3]. Therefore, it becomes imperative to determine effective preservation methods that retain the overall quality and desirable features of the product. The preservation of many agricultural commodities has often been accomplished by employing various combinations of drying using heat processing and dehydration [2] [3] [4]. The dehydration of fresh produce generally extends their storage lives, decreases their shipping weights, and reduces the need for special packing requirements [2]. However, hot-air dried products conventionally processed using tray, vacuum, or cabinet dryer techniques have not received widespread acceptance due to the perceived diminished quality of the endproduct [2] [4] [5]. 

Recently, osmotic dehydration has been introduced as a practical alternative preservation approach that is capable of producing a higher quality final product [6]. In osmotic dehydration, fresh produce is immersed in a hypertonic solution where the water content from the cells of the produce is transferred into the solution due to the relative differences in their solute concentrations [6]. In this processing, osmotic dehydration removes a desired portion of the water from within the fresh produce resulting in a product of intermediate moisture content [7] [8]. Simultaneously, a corresponding transfer of solid materials (normally sugar and/or salt) occurs from the solution into the product [6] [9] [10]. In terms of final product quality relative to standard hot air drying methods, osmotic dehydration causes only minimal thermal degradation due to the low temperatures involved [6] [11] [12] [13].

Osmotic dehydration of fresh agricultural commodities can also be used as a pre-treatment to supplemental dry-processing because it improves many sensory, functional and nutritional properties [14]. The quality of the subsequent product is superior to one without pre-treatment due to (i) the improvements to texture of the fruits and vegetables, (ii) the stability of the colour pigmentation during storage, and (iii) increases in the solid gain transfer of sugar and salt from the hypertonic solution [2] [11]. Thus, in conjunction with other ensuing drying technologies, osmotic dehydration produces a superior quality, shelf-stable product for both local consumption and export markets. 

Water removal during the dehydration process is influenced by many factors such as type and concentration of osmotic agents, temperature, circulation/agitation of solution, solution-to-sample ratio, thickness of food material, and any pretreatments [4] [6]. While an expanding market currently exists for osmo-convective dehydrated fruits and vegetables in both domestic and world markets, only limited efforts have been undertaken to optimize the requisite osmotic process parameters [2] [11] [15] [16] [17] [18]. Specifically, an effective analysis of the mass transport occurring within the osmosis process measured in terms of water loss and solid (sugar, salt) gains is of considerable commercial and practical relevance [4] [6] [10].

In this study, the functional form of the osmotic dehydration process for mushrooms is constructed using a standard response surface technique [17] [18] [19] [20] [21]. The format of the resulting optimization model is shown to be a non-linear goal programming problem [15] [16] [17] [18]. This study employs the Firefly Algorithm (FA) [17] [22] [23] [24] to determine the optimal osmotic parameters for the mushroom dehydration case considered in [2]. It can be shown that the resulting osmotic process parameters produced by the FA are superior to those from the previous approaches.