Effect of Ageing , Moisture Contents and Storage Structures on Nutritional and Cooking Characteristics of Brown Rice during Storage

Rice is one of the important food crops forming staple diet to half of the world’s population. India stands first in area, second in production, followed and preceded by China on these two aspects [1]. The rice crop forms the basic economy activity directly or indirectly for about 150 million rural house-holds in India [2]. Though appearance of brown rice is not so good, but considering its nutritional importance, it is recommended to use brown rice in daily diets. Brown rice is wealth of nutrients that are contained in the bran layer. It is rich in dietary fibre, minerals oils, and vitamins particularly thiamine [3]. Moreover, brown rice contains large amount of insoluble fibre, which may prevent a variety of cancers. The process that produces brown rice removes only the outermost layer of the rice kernel and is the least damaging to its nutritional value. The complete milling and polishing that converts brown rice into white rice destroys 67% of the vitamin B3, 80% of the vitamin B1, 90% of the vitamin B6, half of the manganese, half of the phosphorus, 60% of the iron and all of the fiber and essential fatty acids [4] and [5]. The hulling process also breaks up cells in the outer layer, releasing lipase enzyme which catalyzes break down of the oil in the bran layer, liberating free fatty acids that cause rancidity and off flavour. Both of these factors are responsible for the short life and poor acceptability of brown rice among the masses [6]. Brown rice is less desirable due to its poor cooking and eating qualities [7]. An unusual property of rice is that its cooking and eating quality depends on its age after harvest. New rice swells poorly during cooking and gives out a thick and sticky gruel. These undesirable property gradually changes during storage of rice for a few months. This phenomenon of change in cooking and eating properties of rice during its storage is called ageing of rice. Ageing during storage results in numerous changes in the chemical and physical properties of rice [8] and [9]. For a stable supply, it is necessary to increase rice production and to minimise losses during post harvest process. Storage is the one of the most important processes, because inadequate storage causes qualitative and quantitative grain losses [10]. Nowdays in other countries, airtight storage of brown rice has been attractive as an economically viable and ecologically oriented storage system because it can preserve rice quality without refrigeration [11], [12] Abstract The nutritional and cooking characteristics of four month stored brown rice at 12%, 14% and 16% moisture contents (w.b) were studied. Brown rice was stored in different indigenous storage structures (mud bin, jute bag and polypropylene bag) at ambient conditions such as nutritional characteristics i.e. crude protein, crude fat and total carbohydrates and cooking quality includes elongation ratio and water uptake ratio (WUR) were studied for single variety of paddy (Sugandha). The experimental results showed that nutritional characteristics namely protein and carbohydrate content dropped slightly with the advance in storage periods. However the fat content decreased largely in jute bag followed by mud bin and polypropylene bag and same behaviour showed for protein and carbohydrate corresponding storage structures. The elongation ratio and water uptake ratio was improve with the advance in storage period. The elongation ratio and WUR was greatest increase in polypropylene bag followed by mud bin and then jute bag while moisture content taken into consideration elongation ratio was higher at 16% moisture content followed by 14% and 12% moisture content. While in case of water uptake ratio it was inverses in case of moisture content i.e. WUR was highest at lowest moisture content during storage.