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Sir:
Fats and oils in foods are oxidized during processing, circulation, and preservation. This reaction causes deterioration in taste, flavor, odor, color, texture, and appearance, and a decrease in the nutritional value of the foods (1 ). Furthermore, the reaction can induce food poisoning. Therefore, from a food quality and food safety perspective, this oxidation reaction must be suppressed. Instant noodles are a fried food, and therefore instant noodles contain a lot of fat and oil. In 1964 and 1965, Japan had a food poisoning epidemic caused by the degradation of the fat and oil in instant noodles (2). Many people who ate the degraded instant noodles developed acute symptoms such as diarrhea, nausea, emesis, abdominal pain, fatigue, and headache, but fortunately, no one died. After the incidents, the Ministry of Health and Welfare, currently the Ministry of Health, Labor and Welfare, in Japan set standards for instant noodles in the Food Sanitation Law to protect against food poisoning and to control the quality of instant noodles. In that law, peroxide value (PV) and acid value (AV) were chosen as useful indices to control food safety and quality, and the standard values of PV and AV were set at no more than 30 mequiv/kg and 3, respectively. These values were chosen because they indicate the initial stage of fat and oil deterioration. After setting these values, there have been no reported cases food poisoning caused by instant noodles in Japan.
At the initial stage of fat and oil deterioration, the reasons for measuring PV and AV are very different because of the different mechanisms underlying the formation of hydroperoxide and FFA from fat and oil. Hydroperoxide is formed by the oxidation of fat and oil, whereas FFA are formed by the hydrolysis of fat and oil. PV is an index to quantify the amount of hydroperoxide in fat and oil. Several studies have reported that secondary oxidized oil products are generally toxic (3). Also, weakly oxidized fat and oil at levels of only 100 mequiv/kg of PV are neurotoxic (4)....