Investigation of using egg shell powder for bleaching of soybean oil

Abstract

Egg shell that accounts about 11% of egg weight is one of the industrial wastes that in this research has been used for soybean oil bleaching. The effects of using 1% and 2% of five different types of adsorbents; egg shell powder, egg shell ash, acid activated egg shell powder, acid activated egg shell ash and commercial bleaching earth have been investigated on the bleaching of neutralized soybean oil. The peroxide value, free fatty acid, chlorophyll, carotenoids, metals (copper and iron) and oil retention were determined. Egg shell structure was investigated. According to the results, the bulk of the egg shell consists of calcium and some other compounds such as magnesium, iron and manganese while silicate is the main composition of commercial bleaching earths. The results indicated that soybean oil bleaching with 2% egg shell powder reduced carotenoids and chlorophyll contents up to 82.56% and 46.33%, respectively. Also using of adsorbents based on egg shell reduced significantly (p < 0.05) the peroxide value, free fatty acid contents and oil retention as compared to commercial bleaching earth. It might be concluded that egg shell powder as an industrial waste can be employed as an adsorbent and regarded as a good alternative for bleaching of edible oils due to its high efficiency to remove undesirable components (pigments, iron, copper, oxidation products and free fatty acids) from neutralized oils and environmental protection against acid pollution.