Soybean fishy flavors

Omega-3 acids are considered essential to human health, but eannot be manufactured by the human body and must therefore be obtained from food. These acids are naturally present in most fishes and certain plant oils such as soybean and canola, which are foods that people rarely consume in large quantities. Moreover, the direct addition of omega-3 fatty acids to many foods is prevented due to some characteristics (fishy flavors, readily oxidized), which together reduce the sensory acceptability of foods containing fatty acids, limit shelf life, and potentially reduce the bioavailability of the acids. Encapsulation responds to the challenges of omega-3 fatty acid delivery and extends the reach of its health benefits. 

The frying performance of new varieties of low-linolenic acid soybean oils was compared to that of cottonseed oil (Table 12.10). The decrease in linolenic acid to 2 and 0.8% in the soybean oils improved the flavor quality and the oxidative stability of the potato chips. Although the total polar content of the cottonseed oil was higher, no differences were observed between the low linolenic acid soybean oils. Potato chips fried in ultra-low linolenic acid and stored for 7 weeks had significantly higher flavor quality, lower fishy flavor and lower hexanal than the low-linolenic acid soybean oil. In another study, low-linolenic acid and high-oleic soybean oils and their mixtures were compared with cottonseed oil (Table 12.11). The high-oleic acid soybean oil and its... 

Polyunsaturated fatty acids in vegetable oils, particularly finolenic esters in soybean oil, are especially sensitive to oxidation. Even a slight degree of oxidation, commonly referred to as flavor reversion, results in undesirable flavors, eg, beany, grassy, painty, or fishy. Oxidation is controlled by the exclusion of metal contaminants, eg, iron and copper addition of metal inactivators such as citric acid minimum exposure to air, protection from light, and selective hydrogenation to decrease the finolenate content to ca 3% (74). Careful quality control is essential for the production of acceptable edible soybean oil products (75). 

Sensory evaluation provides information most closely associated with the quality of food lipids. Flavor or odor defects may be detected by panelists before they are recognised by chemical or instrumental methods. For example, the fishy and grassy taste produced in linolenic acid-containing oils such as soybean oil occurs at very low levels of oxidation only detected by sensory analyses. The limitations of this method are poor reproducibility and high cost of panelists and the necessary facilities. The recommended approach is to use more reproducible chemical or instrumental methods to complement or support the sensory analyses (Frankel 1998). 

The U.S. Department of Agriculture (USDA) quality standards for soybean oil state that soybean oil shall be clear and brilliant when held at 70-85°F and shall be free from sediment, such as metal, wood, dirt, glass, paint, insects, insect parts, or any other foreign material (Anonymous, 2005). In addition, the oil shall have a bland odor and flavor and shall be free of beany, rancid, painty, musty, metallic, fishy, putrid, or any orher undesirable odor and/or flavor and have a light viscosity and no heavy oily mouthfeel. Table 15.4 lists the analytical requirements for a RBD and... 

Sensory evaluation is a specialized discipline, using trained panels to measure and analyse the characteristics of food lipids evoked by the senses of taste, smell, sight and mouth feel. Sensory analyses are those most closely associated with the quality of food lipids, but their usefiilness is limited because they are costly and require a well-trained taste and odor panel and the proper facilities. However, sensory analyses provide sometimes ausefiil approach to identifying flavor or odor defects in the processing of food lipids that caimot be detected by other more objective chemical or instrumental analyses. For example, certain flavor defects characterized as grassy or fishy in linolenate-containing oils such as soybean and low-erucic rapeseed (canola) oils (Chapter 1) occur at such low levels of oxidation that they can only be detected by sensory analyses. The old term flavor reversion for soybean oil is based on the characteristic of this oil undergoing flavor deterioration at unusually low levels of oxidation that cannot be measured by peroxide value determination. Oils derived from fish... 

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