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STUDY OF OIL DETERIORATION DURING CONTINUOUS AND INTERMITTENT FRYING

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Deep fat frying is a common method of food preparation leading to products of high palatability. Oxidative and thermal changes occurring in the oil during frying are dependent on the conditions of frying, the nature of food being fried as well as the composition of the oil. This study was undertaken to compare deterioration in refined groundnut oil during continuous frying and intermittent frying of poori, a traditional wheat based product. Continuous frying was carried out for eight hours with hourly replenishment with fresh oil to maintain the constant volume. Intermittent frying was done for two hours every day for four days without replenishment. Samples drawn at regular intervals were analyzed for Free Fatty Acid (FFA), Peroxide Value (PV), Anisidine Value (AV), Diene-Triene Values . Fresh oil and the samples drawn at the end of frying study were also analyzed for Oxidized Fatty Acid, Smoke point, Iodine Value (IV), Saponification Value, Unsaponifiable Matter (USM), Viscosity and Fatty Acid Composition. Among the parameters studied, AV (172.4), Diene Value (1.57), Oxidized Fatty Acids (2.5), and Viscosity (103.5) were higher in the oil subjected to 8 hours of intermittent frying as compared to the corresponding values of 93.0, 0.70, 0.23 and 85.3 respectively in the oil after 8 hours of continuous frying. Furthermore, decrease in IV Results show that continuous frying with periodic replenishment causes less damage to the frying oil than intermittent frying without replenishment.

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STUDY OF OIL DETERIORATION DURING CONTINUOUS AND INTERMITTENT FRYING

  1. 1. Amit K. Das 1 , R. Babylatha 2 , A. S. Pavithra 3 , R. Chetana 2 and Sakina Khatoon 2 * Departments of 1 Food Engineering, 2 Lipid Science & Traditional Foods and 3 Sensory Science Central Food Technological Research Institute, Mysore E mail: *sakoon_buri@yahoo.com R esults showed that c ontinuous frying with periodic replenishment caused less damage to the frying oil than intermittent frying without replenishment. <ul><li>D eep fat frying is a common method of food preparation leading to products of high palatability. Oxidative and thermal changes occurring in the oil during frying are dependent on the conditions of frying, the nature of food being fried as well as the composition of the oil. This study was undertaken to compare deterioration in refined groundnut oil during continuous frying and intermittent frying of poori , a traditional wheat based product. Continuous frying was carried out for eight hours with hourly replenishment with fresh oil to maintain the constant volume. Intermittent frying was done for two hours every day for four days without replenishment. Samples drawn at regular intervals were analyzed for Free Fatty Acid (FFA), Peroxide Value (PV), Anisidine Value (AV), Diene-Triene Values . Fresh oil and the samples drawn at the end of frying study were also analyzed for Oxidized Fatty Acid, Smoke point, Iodine Value (IV), Saponification Value, Unsaponifiable Matter (USM), Viscosity and Fatty Acid Composition. Among the parameters studied, AV (172.4), Diene Value (1.57), Oxidized Fatty Acids (2.5), and Viscosity (103.5) were higher in the oil subjected to 8 hours of intermittent frying as compared to the corresponding values of 93.0, 0.70, 0.23 and 85.3 respectively in the oil after 8 hours of continuous frying. Furthermore, decrease in IV Results show that continuous frying with periodic replenishment causes less damage to the frying oil than intermittent frying without replenishment. </li></ul><ul><li>D eep Fat Frying is a common method of processing foods particularly for the preparation of a large variety of snacks. </li></ul><ul><li>During frying thermal, physical and chemical degradation reactions take place resulting in the formation of numerous decomposition products that affect the functional, sensory and nutritional quality of the oil. </li></ul><ul><li>In India Ground nut oil is widely used as a frying medium. </li></ul><ul><li>  </li></ul>T he present study is planned to study the changes in Ground nut oil under normal frying conditions. <ul><li>The Intermittent Frying operation was carried out for 2 hours everyday continued upto 4 consecutive days. There was no replenishment of oil during the course of frying and the samples were drawn after each day frying. Conditions of frying were maintained similar to that of continuous frying. </li></ul><ul><li>To determine the quality of oil, following Physico-chemical characteristics were analysed: </li></ul><ul><ul><li>Free Fatty Acid (FFA) </li></ul></ul><ul><ul><li>Peroxide Value (PV) </li></ul></ul><ul><ul><li>Anisidine Value (AV) </li></ul></ul><ul><ul><li>Diene-Triene Values </li></ul></ul><ul><ul><li>Total Polar Component </li></ul></ul><ul><li>Fresh oil and oil samples drawn at the end of frying operation were also analyzed for </li></ul><ul><ul><li>Oxidized Fatty Acid </li></ul></ul><ul><ul><li>Smoke Point </li></ul></ul><ul><ul><li>Iodine Value (IV) </li></ul></ul><ul><ul><li>Saponification Value </li></ul></ul><ul><ul><li>Unsaponifiable Matter (USM) </li></ul></ul><ul><ul><li>Viscosity </li></ul></ul>T he authors are grateful to Dr. V. Prakash , Director, CFTRI for his keen interest in the study. The authors thankfully acknowledge support and encouragement from Dr. KSMS Raghavarao , Head, FE and Dr. B.R. Lokesh , Head, LSTF. A special thank to Mr. K.K. Bhat , Head, SS and Dr. K. Venkatesh Murthy , Sci, FE, for their valuable suggestions and encouragement during the study. F rying trials were conducted with 2 kg of refined ground nut oil in a stainless steel pan, heating the oil upto 180 o C and frying Poori in it. In a batch, 3 poories weighing about 60 g, were fried in 2 kg of oil. Every hour 10 batches of poories were fried During continuous Frying oil samples were drawn after every hour and the oil was replenished upto the initial quantity i.e., 2 kg at each interval of frying. The frying was continued upto 8 hours. <ul><li>M onitoring the chemical parameters during continuous frying revealed that the first hour of frying caused drastic changes in FFA, PV, AV, and Diene-Triene Value. At the end of first hour of frying FFA, PV and AV increased nearly by 5, 10 and 6.5 folds respectively. </li></ul><ul><li>As expected PV showed fluctuations whereas AV and Diene-Triene Value showed steady increase till the end of frying. </li></ul>Fig 1: Free Fatty acid Fig 7: Colour Profile of Continuous Frying Fig 8: Colour Profile of Intermittent Frying Error bar is on Standard Deviation of triplicate analysis Error bar is on Standard Deviation of triplicate analysis Error bar is on Standard Deviation of triplicate analysis Error bar is on Standard Deviation of triplicate analysis Error bar is on Standard Deviation of triplicate analysis <ul><li>Similar trend was also observed in the case of intermittent frying and oil deterioration was more pronounced on the first day. </li></ul><ul><li>Among the parameters studied, AV (93.0), Diene Value (0.70) Oxidized Fatty Acids (0.23) and Viscosity (85.3) were lower in the oil subjected to 8 hours of continuous frying as compared to the corresponding values of 172.4,1.57, 2.5, and 103.5 respectively in the oil after 8 hours o f intermittent frying </li></ul><ul><li>This was further substantiated by greater decrease in I.V. during intermittent frying. </li></ul>Diene Value Triene Value Fig 9: Overall Comparison Fig 10: Overall Comparison Table 1: Physico-chemical Characteristics The main attributes of oil deterioration for the samples drawn after 8 h of continuous frying as well as intermittent frying are relatively summarized along with the fresh oil. Figure 1 and 2 show that intermittent frying has remarkably greater effect on oil deterioration than continuous frying

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