Evaluation of Frying Oil Quality

Evaluation of Frying crude embrocate tonusCHAPTER IILITERATURE REVIEWDeep Fat FryingDeep- fill in heat up is fundamentally a process which involves immersing a fodder item in a large quantity of anele or fat at graduate(prenominal) temperature, which is normally replenished and reuse numerous times before being disposed and it is by chance one of the most dynamic processes in all of food bear upon (Sumnu Sahin, 2008). Products of deep-fat heat come with desired sensory characteristics much(prenominal) as deep- fry food flavour, golden brown colour, and a crisp texture (Warner, Gupta, White, others, 2004). A crisp outer texture is an ultimate characteristic of most fried foods which is developed through rapid surface dehydration during frying and stool be controlled by changing a few variables, including crossing preparation, breading or batter formulation, frying procedures, and post-frying conditions (Banks, 1996).Deep-fat frying uses a large volume of facile such a s embrocate, fat, and paraffin which has highschool boiling point and buoyancy forces ar particularly efficient to homogenize the temperature along the vertical program line because oil and fat be highly thermo-expandable fluids (Achir, Vitrac, Trystram, 2008). Oil often makes up signifi smoket portion of the final food product, as much as 45% of the fall product although frying oils serves primarily as a heat exchange mean(a) (Erickson Perkins, 1996). According to Rossell (2001), frying is suitable in cooking all types of foods such as meat, fish as substantially as vegetables especially potatoes which be probably the food most associated with frying, as potatoes are used to produce both French fries and crisps.deep-fried food undergoes two correlated mass transfers which are water vergeination and oil uptake during frying (Bassama, Achir, Trystram, Collignan, Bohuon, 2015). Therefore, the nutritional value of the final product is significantly altered by the natur e of the frying oils as they are indeed differ markedly in terms of their fatty venereal infection and fat-soluble micronutrient composition (Chiou, Kalogeropoulos, Boskou, Salta, 2012). Oil is usually heated at high temperatures at 160-200C in the presence of air, and water vapour is released from the fried food during the discontinuous frying process resulting in undesirable changes that may legislate concurrently with desirable modifications, one such change being the firing of nutrients, and especially vitamins (Jurez, Osawa, Acua, Sammn, Gonalves, 2011). Due to thermal dissolution, chemical reactions like oxidation and hydrolysis advance, therefore causing changes of the functional, sensory and nutritional tint of the fat and may finally decease a point where it is impossible to prepare high fiber fried products and the frying oil will have to be dispose (Stevenson, Vaisey-Genser, Eskin, 1984). A few factors that affect rate of the oil decomposition are composit ion of the oil, the temperature and the length of frying, continuous or intermittent frying, type of fried food, and raw oil replenishment (Fan, Sharifudin, Hasmadi, Chew, 2013). In addition, according to Abdulkarim et al (2007), oils with high amount of oleic acid which is rich in monounsaturated fatty acid are more stable and slower to develop oxidative rancidity during shelf life.Quality of Frying OilThe shade of food may be defined as the composite of those characteristics that differentiate individual units of products acceptableness (Lawson, 1985). The initial feature of oil as well as its military capability during frying is influenced by all steps included in touch of the oil and can have a significant impact on the quality of fried food prepared with it (Orthoefer Cooper, 1996). Assessing frying oil quality is very important because a certain amount of oil is inattentive by food during frying and becomes part of the food (Rossell, 2001b). When compared with fresh oil, the libertine oil has an altered nutritional and toxicological profile (Perkins Kummerow, 1959). Therefore, determination of its quality is critical for reaching the desired shelf-life for the product, and undertakes the potential for creating health hazard (Gupta, 2005).Oil is used repeatedly at high temperatures, and miscellaneous chemical processes such as hydrolysis, polymerization, oxidation and fission take place resulting in the assemblage of products of decomposition that not only affect the quality of fried foods yet also to human health, especially when frying fat or oil is highly abused (Frankel, Smith, Hamblin, Creveling, Clifford, 1984 Fritsch, 1981). According to Stevenson et al (1984), the rate of formation of decomposition products vary with the food being fried, the oil being used, the choice of the pullet design and the nature of the operating conditions. For example, frying foods that contain high levels of crank solids can collapse to early foaming collectable to leaching of lecithin into the frying oil and fats from meat or chicken can diffuse into the oil during the frying process, thus contaminate the frying oils (Landers Rathmann, 1981 Weiss, 1983). Stevenson et al (1984) said that floozy should ensure that the food being cooked are uniform in term of size and renounce from excess surface water, crumbs or breading material to reduce fat breakdown caused by the food during frying.Cleanliness of the fryer is one of the factors to be considered in controlling fat breakdown as polymerized fat deposited on the fryer tends to catalyse the formation of more gum which contributes to foaming, color change and further deterioration of the frying fat. In addition, ensuring that all traces of detergents are take during rinsing is very important since this substance can catalyze fat breakdown when frying is resumed (Jacobson, 1967 Weiss, 1983). Oil quality can be hold by turnover rate which is described as the ratio of the tota l amount of fat in the fryer to the rate at which fresh fat is added to the kettle and daily turnover at 15-25% of the fryer capacitor is recommended (CJ, 1967). Condition of the frying fat gets better when the rate of turnover is higher(prenominal) as appropriate turnover rate will replace helpless of silicones due to adherence to the fried items and will keep the level of FFA small.Furthermore, quality of the oil at point of purchase contributes significantly to quality of used frying oil as illustrated in Table 1.Table 1 Quality limits for frying oilAdapted from Rossell (2001).Changes occurring during deep-fat fryingThere are three main factors that are important in frying operating theater which are the food to be fried, the oil used, and the characteristics of the process especially temperature and frying time (Blumenthal, 1991). Chemical reaction like oxidation and hydrolysis will affect the functional, sensory and nutritional quality of the oil which may ultimately reach a point where the oil needs to be discarded. Physical changes in oil that occur during oestrus and frying include increased viscosity, color, and foaming, diminish smoke point, training of off odors such as acrid and burnt, and development of off flavors in the fried food (Warner, 2002). Physical and chemical reactions that occur during frying are represented in Figure 1.Figure 1 Changes occurring during deep fat frying (Adapted from Fritsch 1981)Products of decomposition formed during frying can be divided into two classes which are volatile and non-volatile products. Volatile decomposition products include aldehydes, ketones, alcohol acids, esters, hydrocarbon, lactones and aromatic compounds are removed from frying medium by steam generated during frying (Stevenson et al., 1984). On the other hand, the non-volatile decomposition products eventually produce physical changes in frying oil such as increase in color, foaming, and viscosity (Perkins, 1967). Their formation is due largely to thermal oxidation and polymerization of the unsaturated fatty acids in the frying medium. When oil is heated in air, it first shows a gain in cant over as oxygen is absorbed, and its peroxide value may increase and when heating continues, the peroxides will decompose, and scission products start to distil off, leading to a net liberation in weight (Perkins, 1967 White, 1991). Hydroperoxides may undergo further degradation of three major types (a) fission to form alcohols, aldehydes, acids and hydrocarbons, thereby also contributing to the darkening of the frying oils and flavors (b) dehydration to form ketones and (c) free-radical formation of dimers and trimers, leading to polymers, all of which contribute to viscosity increase (Lalas, 2008). According to Artman (1969), conjugation of the double bonds and the accumulation of oxygenated products increases the ultraviolet light absorption of the oil and iodine value of the oil may falling off later during frying due t o the double bonds are consumed in various reactions. Hydrolysis is caused by moisture in fried foods resulting in the formation of free fatty acids (FFA), monoglycerides, diglycerides, and glycerols. FFAs may also be formed during oxidation due to cleavage and oxidation of double bonds (Perkins, 1967).