Vegetable oils: Effects of processing, storage and use on nutritional values

Abstract

At the present time, vegetable oils are the source of most of the visible fat in the U.S. diet. They are used as salad and cooking oils, in salad dressing, margarine and shortening. Processing methods include extraction, refining, hydrogenation and interesterification. During storage and use, the products are exposed to oxygen and/or heat, particularly during frying. Processing, storage and use are related to changes in composition, nutritive value and physical characteristics of vegetable oils. Refining removes undesirable minor components present in crude oils. Refined polyunsaturated vegetable oils are the primary dietary source of tocopherols. Hydrogenation modifies physical characteristics and improves sensory and oxidative stability. This process converts some of the polyunsaturated fatty acids to new fatty acid isomers. Although the biochemical effects of these isomers are still being studied, long‐term animal feeding trials and human experience have demonstrated that the partially hydrogenated oils in margarines and shortenings are wholesome foodstuffs. Abusive overheating of fat in air sharply decreases its palatability and nutritive value and may create minor amounts of carcinogenic materials. However, long‐term animal feeding studies with properly used frying fats have revealed little, if any, effect on life span and incidence of pathological conditions.

Effects of prefrying times on the nutritive value of canned tilapia meat

“…Heating the oil to high frying temperatures leads to formation of polymers as the reaction products condense. As these reactions take place, the sensory and nutritional qualities of the fat change and the oil can no longer be used to produce high-quality foods (Landers and Rathman, 1981;Paulose and Chang, 1973;Witchwoot et al, 1981). In the present investigation, the frying oil was replaced with fresh oil after each frying process, avoiding the possible detrimental effect of the deteriorated oil on the tilapia meat so that the changes of nutritive value of canned tilapia meat would be solely from the prefrying process.…”

Explorative spectrometric evaluations of frying oil deterioration

“…The compounds that result from this process are large molecules formed by carbon-to-carbon and/or carbon-to-oxygen-to-carbon bridges among several fatty acids (19). Marked increases in such oligomer compounds contribute to increases in fat viscosity, foaming, and color darkening (20).…”

Food use and health effects of soybean and sunflower oils.

“…However, RBD oils retain small amounts of trace components which are often measured as unsaponifiable materials, free fatty acid (FFA), and trace metals. In one report, the FFA concentration in fresh RBD oils was approximately 0.07% in both SBO and SFO, which is similar to most good quality edible vegetable oils [8]. Other research studies report FFA values of less than 0.07% in fresh SBO [18,19] and SFO [5].…”

“…The P:S ratio is about 4.0 for SBO and 6. 4 consumed in the United States [8]. Only safflower oil has a higher PUFA level than SBO and SFO.…”

“…Refined SBO and SFO are composed mainly of triacylglycerols, about 99% for SBO and 99.2% for SFO [8]. Typical FA distributions for SBO and SFO are shown in Table 1.…”