Rice Bran Oil Processing

By: Prashant Sahni *

The entrancing aroma of fresh made ‘puris’ on a lazy Sunday morning or the captivating savour of freshly fried ‘wadas’ on a mundane day can always be a treat for our taste buds and reminds us of our abysmal love for the fried foods. Average Asian cuisine and particularly delicacies from the Indian peninsula have their rendezvous with frying as an important part of their preparation. However, it is very essential to be wise in your choice while choosing cooking oil as it not only adds flavour to your dishes but also has a vital effect on your health. Stir-frying and deep frying operations can instil a huge amount of oil in the food. Therefore, it is essential to go for oil that not only improves the eating quality of your food but also makes your dishes nutritionally wholesome. With the paradigm shift in healthy eating, people are getting acquainted with healthy food choices. Rice bran oil is one such new entrant in the cooking oil category and is gaining a lot of importance because of its health benefits. Rice bran oil is recently being referred to as ‘Liquid Gold’. It is widely manufactured and marketed in various segments of the market and finding warming acceptance among different demographics.

Traditionally, many of the Asian countries, including India, were predominantly using rice bran for the purpose of cattle besides the measly amount of it is utilised recently for fibre enrichment. However, Japan realised the true potential of rice bran by extracting rice bran oil and marketing it as ‘Heart Oil’. Now, it is emerging as popular cooking oil among the masses, particularly because of its light nature and the high smoking point which makes it congenial with frying applications. Also, the production of rice bran oil offers huge prospects in India, since India, China, and Japan are the leading rice producers. More than half of rice is processed in small rice mills and this leaves approximately 20–25 million metric tons of bran available for oil production.

Rice Bran Oil is a Liquid Gold

Rice bran oil is rightly said to be liquid gold, owing to its excellent nutritional profile. Ideal cooking oil should have a well-balanced proportion of saturated, monounsaturated and polyunsaturated fatty acids and it should be free of trans-fats. Rice bran oil offers almost balanced fatty acid composition and contains 47 percent monounsaturated fats; 33 percent polyunsaturated fats; and 20 percent saturated fats. It is composed of 38.4 percent oleic acid; 34.4 percent linoleic acid; 21.5 percent palmitic acid; 2.9 percent stearic acid; 2.2 percent ?-linoleic acid; and 0.6 percent myristic acid. Besides having well balanced fatty acid composition rice bran oil constitutes various bioactive components which make it quite a paragon amongst the other cooking oils. Rice bran oil is a rich source of antioxidants especially oryzanol, tocopherols, tocotrienols, squalene, phytosterols and phytosteryl esters which not only contributes to the high bioactive potential of the oil but also confers it good oxidative stability and longer shelf life than other edible oils.

Important Steps in Rice Bran Oil Processing

Besides the plethora of health benefits of rice bran oil, it is important from a food processor’s point of view that rice bran oil requires good care and optimisation of extraction operation to allow the wholesomeness and optimal quality of finished products. Unlike other oils which are obtained from the oilseeds, rice bran oil is extracted from the bran obtained after milling of rice and presents a challenge in its processing. All the problems related to processing start with the deterioration of the quality of rice bran particularly due to lipase activity. Therefore, technological intervention is required to retain the natural integration of rice bran oil.

Stabilisation of Rice Bran: Besides having generic steps of oil extraction and refining, the heart of rice bran oil processing lies in the stabilisation of the rice bran. As aforesaid, rice bran contains lipase that starts hydrolysing the triglycerides immediately after removal of bran from the grain and results in a prolific increase in the free fatty acids. Various technologies of stabilisation include steam stabilisation, chemical stabilisation and extrusion technology. However, none of these technologies became popular due to various techno-commercial reasons.

Physical Refining: Physical refining offers an attractive solution to allow the retention of nutritional constitutes like oryzanol in the refined oil with a less detrimental effect on the environment and to earn more profit.

Degumming: Effective degumming is a pre-requisite for efficient physical refining of the oil. Water degumming is the most commonly employed method for the refining of edible oils; however, it is not effective in removing phospholipids to a desirable low level. Enzymatic degumming offers an efficient solution that allows hydrolysis of the phospholipids into water-soluble lyso-lecithin and its separation from the oil phase by centrifugation.

Winterisation: It is another important step in rice bran oil processing intended for removal of traces of wax and stearin to allow the oil to remain clear even at 0°C for offering a good export market. Rice bran oil form ?’ prime crystals. Therefore, the slow cooling cycle is recommended. Stearins obtained from winterisation of oil find its use in the shortening, frying oil and margarine oil formulations.

Utilisation of Rice Bran Oil in the Food Industry

Rice bran oil is occupying a prominent place in the market shelves as healthy cooking oil and is widely utilised as a functional ingredient in various food formulations particularly in the bakery and confectionery products for the replacement of shortening with healthy fats. Rice bran oil not only confers a good nutritional profile to these products but also enhances their storage stability. Rice bran is likely to have a stronger foothold in the years to come and it will be strongly recommended by dieticians, adopted by consumers and processed into versatile products. It will be used as part of food formulations by food the processing industry.

* PhD Scholar, Department of Food Science and Technology, Punjab Agricultural University, Ludhiana; Email: ftech.sahni@gmail.com

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