Evaluation of Frying Oil Quality

Evaluation of Frying anele QualityCHAPTER IILITERATURE REVIEWDeep Fat FryingDeep- plump out heat is basically a process which involves immersing a forage item in a large quantity of fossil crude or fat at richly temperature, which is normally replenished and reused numerous times before being disposed and it is possibly one of the most dynamic processes in all of intellectual nourishment processing (Sumnu Sahin, 2008). Products of deep-fat heat come with desired sensory characteristics such(prenominal) as fried food flavour, golden brown colour, and a crisp texture (Warner, Gupta, White, others, 2004). A crisp satellite texture is an ultimate characteristic of most fried foods which is developed through rapid surface dehydration during fry and can be controlled by changing a few variables, including product preparation, breading or batter formulation, heat up procedures, and post- heat conditions (Banks, 1996).Deep-fat frying uses a large volume of liquid such as oil, f at, and paraffin which has steep boiling point and buoyancy forces ar particularly efficient to homogenize the temperature along the vertical direction because oil and fat ar risquely thermo-expandable fluids (Achir, Vitrac, Trystram, 2008). crude oil often makes up significant portion of the final food product, as much as 45% of the total product although frying oils serves primarily as a heat exchange medium (Erickson Perkins, 1996). According to Rossell (2001), frying is suitable in cooking all types of foods such as meat, fish as advantageously as vegetables oddly potatoes which are probably the food most associated with frying, as potatoes are used to produce both French fries and crisps.Fried food undergoes twain correlated mass transfers which are water injury and oil uptake during frying (Bassama, Achir, Trystram, Collignan, Bohuon, 2015). Therefore, the nutritional value of the final product is significantly abnormal by the nature of the frying oils as they are indeed differ markedly in terms of their fatty acid and fat-soluble micronutrient composition (Chiou, Kalogeropoulos, Boskou, Salta, 2012). Oil is unremarkably 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 occur concurrently with desirable modifications, one such change being the loss of nutrients, and especially vitamins (Jurez, Osawa, Acua, Sammn, Gonalves, 2011). Due to thermal decomposition, chemical reactions ilk oxidation and hydrolysis occur, thus causing changes of the functional, sensory and nutritional quality of the fat and may eventually transcend a point where it is impossible to prepare high quality fried products and the frying oil will have to be discarded (Stevenson, Vaisey-Genser, Eskin, 1984). A few factors that affect rate of the oil decomposition are composition of the oil, the temperature and the length of f rying, continuous or intermittent frying, type of fried food, and fresh oil replenishment (Fan, Sharifudin, Hasmadi, Chew, 2013). In addition, according to Abdulkarim et al (2007), oils with high enumerate 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 quality of food may be defined as the composite of those characteristics that differentiate individual units of products acceptability (Lawson, 1985). The initial quality of oil as well as its durability during frying is influenced by all steps included in processing 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 tot up of oil is absorbed by food during frying and becomes part of the food (Rossell, 2001b). When compared with fresh oil, the degraded oil has an altered nutritional and toxic ological profile (Perkins Kummerow, 1959). Therefore, ending of its quality is critical for reaching the desired shelf-life for the product, and reduces the potential for creating health hazard (Gupta, 2005).Oil is used repeatedly at high temperatures, and various chemical processes such as hydrolysis, polymerization, oxidation and fission take place resulting in the accumulation of products of decomposition that not only affect the quality of fried foods but in addition 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 fryer design and the nature of the operating conditions. For example, frying foods that contain high levels of egg solids can contribute to primaeval foaming repayable to leaching of lecithin into the frying oil and fats fro m 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 operator should ensure that the food being cooked are uniform in term of size and free 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 darkening and further deterioration of the frying fat. In addition, ensuring that all traces of detergents are upstage during rinsing is very important since this substance can catalyze fat breakdown when frying is resumed (Jacobson, 1967 Weiss, 1983). Oil quality can be maintained by swage rate which is described as the ratio of the total amount of fat in the fryer to the rate at which fresh fat is adde d to the steam boiler and daily turnover at 15-25% of the fryer capacity is recommended (CJ, 1967). Condition of the frying fat gets better when the rate of turnover is higher as appropriate turnover rate will replace lost 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 bargain for 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 operation 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 eventually reach a point where the oil needs to be discarded. Physical changes in oil that occur durin g heating and frying include increased viscosity, color, and foaming, decreased crumb point, development 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 th e frying medium. When oil is heated in air, it first shows a gain in weight 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 loss 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 absorption of the oil and iodine value of the oil may decrease later during frying due to the double bonds are consumed in various reactions. Hydrolysis is caused by moisture in fried foods resul ting 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).