Removal of Mycotoxins during Food Processing

Transcription

1 88 Removal of Mycotoxins during Food Processing Hisashi Kamimura Abstract In order to learn whether there might be a risk to human health from the intake of mycotoxins contaminating agricultural products, the stabilities of mycotoxins under various cooking conditions employed in daily life and the possibility of removal of mycotoxins during manufacturing processes were investigated. 1) Stability of mycotoxins against heat. By heating mycotoxins within the range of Ž, temperatures which are seen during a normal cooking process, we investigated the stability of mycotoxins against heat. When boiled ( Ž), mycotoxins remained almost 100% after 45 minute heating. As the temperature rose, such as when frying ( Ž), mycotoxins started decomposition. In the case of grilling (about 210 Ž), the nivalenol type of toxin rapidly decreased to 10% after 15 minute heating. In conclusion, we hypothesize that mycotoxins decompose as the temperature rise, but that part of the mycotoxins remains through ordinary cooking methods in terms of heating temperature as well as heating time. 2) Influence on mycotoxins by a cooking process. Mycotoxins were added artificially to raw materials, which were then processed. In the case of noodles, only 10 to 12% of the added aflatoxins were transferred into water. Other foods were made from spaghetti, barley, coix seed, popcorn which were naturally contaminated with deoxy nivalenol, nivarenol, zearalenone. The contents of these mycotoxins were essentially unaffected by cooking. These experiments indicate that there is a high probability of intake of mycotoxins from such cooked foods. 3) Influence of manufacturing process on mycotoxins. The possibility that mycotoxins may be removed in manufacturing processes was investigated. Edible oil (aflatoxins, Fusarium toxins) and cornstarch (fumonisins) at various stage of the manufacturing processes was examined to determine the fate of mycotoxins. Even when food materials are contaminated by mycotoxins, they can be completely removed during manufacture. Key words : aflatoxin, Fusarium toxin, food processing, removal Introduction Agricultural products which are used as food are always exposed to the danger of fungal contamination during their cultivation, harvest, transport and storage, when the foodstuff, temperature and humidity are suitable for the growth of certain fungi, there is always the danger of mycotoxin production. Among such fungi, some species of the genus Aspergillus, well-known aflatoxin producers, are frequently found. Natural infection by Fusarium sp. are observed as often as, or more often than, that of Aspergillus. Tokyo Metropolitan Research Laboratory of Public Health 24-1, Hyakunincho 3-chome, Shinjuku, Tokyo

2 89 Fig. 1 Stability of Mycotoxins to heat treatment : Zearalenone, c c c : Nivalenol type, c œ c œ c : T-2 type c c c c : Aflatoxin B1 and G1, c c c : Aflatoxin B2 and G2 Fusarium sp. affects various agricultural products and causes Bakanae disease of rice plant, stem wilt of broad bean, fusarium blight and so forth. Also Fusarium sp. harms kernels of wheat, barley, corn etc. and inhibits full growth of those kernels. Of these, Fusarium sp. has been treated mainly as a plant pathogen in the past. However, recently, it has been proved that Fusarium sp. produces trichothecene mycotoxins such as nivalenol, deoxynivalenol and T-2 toxin as well as other kinds of mycotoxin such as zearalenone and fumonisins. As the actual condition of contamination by fusarium mycotoxins over staple cereals became clear, the problem of fusarium mycotoxins became one of the most important dietary hygiene issues. Aflatoxins and fusarium toxins (deoxynivalenol, nivalenol, zearalenone, fumonisins and so on) have been detected in wheat, barely and their products, and also in nuts and seeds, spices, oil and their products and dairy products. Therefore, aflatoxins and fusarium toxins represent a potential food hygienic problem. In order to learn whether there might be a risk to human health from the intake of mycotoxins contaminating agricultural products, the possibility of removal of mycotoxins Table 1 Behavior of fusarium mycotoxins in the cooking process

3 90 during cooking and manufacturing processes were investigated. Influence of Cooking Process on Mycotoxins Stability of the Mycotoxins against Heat By heating the mycotoxins within the range of Ž, temperatures which are seen during a normal cooking process, we investigated the stability of mycotoxins against heat. The result of this research appears in Fig. 1. The temperature for boiling and frying is around 100 to 150 Ž, which can rarely decompose mycotoxins. At the temperature for deep frying, that is 180 Ž, mycotoxins decompose gradually. At the temperature for grilling, 210 Ž, trichothecene type toxins can be decomposed within 30 minutes. It became clear that within the usual cooking time at home, mycotoxins can not be decomposed by either boiling, deep-frying or grilling. In conclusion, we hypothesize that mycotoxins decompose as the temperature rise ; but that part of the mycotoxins remains through ordinary cooking methods in terms of heating temperature as well as heating time. Table 2 Purification process of edible oil Fig. 2 Diagram of neutralization process of crude oil

4 91 Table 3 Analytical results of mycotoxins in commercial edible oil Behaviors of Mycotoxins after Cooking As previous research on mycotoxin contamination in foods on the market shows, fusarium mycotoxins, such as nivalenol, deoxynivalenol, and zearalenone are frequently detected in wheat, barley and corn as well as in food products made from them. We cooked those foods which had been proved to be contaminated. Table 1 shows the results. First, we added water to the pressed barley in which nivalenol, deoxynivalenol and zearalenone had been detected. After boiling the pressed barley for 15 minutes, we observed ppb of nivalenol, which was 282 ppb before cooking. On the average, 224 ppb of nivalenol was detected, which was slightly lower before cooking. We had the same result with deoxynivalenol as well as zearalenone. With these, we hypothesize that nivalenol, deoxynivalenol, and zearalenone hardly decompose in water when boiled. We had similar results when boiled coix seed (seed of Coix lacryma jobi var. ma-yuen) and spaghetti, and reached the hypothesize that, when boiled, the fusarium mycotoxins does not decompose in water and remains almost completely in food. In case of popcorn, we added oil to the popcorn in which deoxynivalenol had been detected. After popping, the popcorn for 5 minutes, we observed ppb of deoxynivalenol, which was 196 ppb before cooking. When popped, the mycotoxin is found not to be decomposed by cooking. Influence of Manufacturing Process on Mycotoxins Edible Oil The refining processes are shown in Table 2. Edible oil is manufactured as follows. The refining process are divided into 3, neutralization process using alkali solution, decoloring and deodorization. Crude oil after suction usually contain many impurities such as free fatty acid and non-glycerides. In the neutralization process, sodium hydroxide was added and stirred for 10 minutes at 60 Ž to remove impurities. In the decoloring process to remove pigments and trace ingredients, activated clay was added to the oil and stirred for 15 minutes at 110 Ž. In the deodorization process, for removal of aldehydes and ketones, the oil were heated to 240 Ž under reduced pressure between 2 and 5 mmhg, then subjected to vacuum

5 92 Fig. 3 Distribution of fumonisins in wet milling process Fig. 4 Manufacturing process of butter-peanut (Fried peanut) steam distillation for 120 minutes. We treated oil through the whole manufacturing processes and then the fate of mycotoxins was examined. The flow-sheet of the neutralization process is shown in Fig.2. In the neutralization process, crude oil was mixed with alkali, stirred, centrifuged to remove foots and washed with warm water until ph showed neutral. When oil and foots layer were separated, a major of mycotoxins was found to have moved to the foots layer. And further after washing with water, mycotoxins were found to have moved exclusively into the washing. Therefore, even if the crude oil is contaminated with aflatoxins and other mycotoxins, they can be completely removed after neutralization process. The results of the contamination survey on 60 samples from edible oils are shown in

6 93 Fig. 5 Distribution of aflatoxins in butter-peanut process Table 3. Aflatoxins were detected in 5 out of 8 peanut oil samples. Three of them contained B and G groups and the other two contained only B group. No mycotoxins were detected in any of the other oil samples, such as cotton seed oil, safflower oil, olive oil or salad oil. As the contaminated peanut oils were indicated as fragrant, we examined the properties of these oils. So, aflatoxins contaminated oils were not done neutralization process. Cornstarch Cornstarch is manufactured as follows. The manufacturing processes of corn starch are shown in Fig.3. Corn is cleaned, and steeped in hot water added 0.2% of sulfur dioxide at hours. The object of steeping is to prepare corn for subsequent separation of starch and by-products by wet milling. The actual milling operating is carried out on steeped corn in several stages. The object of the milling process is to provide for as complete separation of component parts of corn kernels. After milling, we get corn starch, sugar and corn oil. And also we get corn steep liquor, germ, fiber and gluten using for feed. Corn is often found contaminated with fumonisins. The fate of fumonisins was examined in manufacturing processed of corn starch made of fumonisin-contaminated raw corn. From the raw corn, 2.59 ppm of fumonisin B1 and 0.45 ppm of fumonisin B2 were detected, however, no fumonisins were found in the corn starch. On the other hand, the content of (umonisins in feed, fumonisin B1 was 0.02 ppm in corn steep liquor, 0.15 ppm of fumonisin B1 and 0.05 ppm of B2 were detected in germ, respectively. And 0.45 ppm of B1 and 0.25 ppm of B2 in fiber, and 0.72 ppm of B1 and 0.28 ppm of B2 in gluten were detected, respectively. Fried Peanut As previous research on mycotoxins contamination in foods on the market shows, aflatoxin are frequently detected in peanut and its products. The manufacturing processes

7 94 of fried peanut are shown in Fig. 4. Shelled peanuts are steeped in hot water of 90 Ž for 4 or 5 minutes, then treated with coat splitting machine to separate shells and kernels. Kernels are selected by several persons' eyes to remove worm-eaten, discolored or broken ones. After selection, kernels are dried by drying machine to control the water content as 25 to 30%. Then kernels are fried at 145 Ž for about 10 minutes and subjected to flavoring. After flavoring, kernels are further selected to exclude damaged ones which could not be picked up during the sorting process after coat splitting. The fate of aflatoxins was examined in manufacturing processed of fried peanuts made of aflatoxin-contamination raw peanuts from America which belong to florunner species. The result of this research in Fig.5. From the raw peanuts, 0.24 to 2.38 ppb of aflatoxin B1 was detected, however, the content of aflatoxin B1 after steeping was 0.73 ppb in kernels and 0.03 ppb in the water. After coat splitting, the content of aflatoxin B1 was 0.50 ppb in kernels, 0.66 ppb in coats and 0.64 ppb in damaged kernels. After frying, the oil contained 0.42 ppb of aflatoxin B1i however, fried kernels contained only trace of aflatoxin B1 and no aflatoxins were found in the end-products. From this investigation, it became clear that the content of aflatoxin decreases in the steeping and coat splitting processes and also that selection process is effective to decrease of toxin amount. To prevent secondary contamination of products, it is important to change water frequently in the steeping process and to change oil in the frying process. Conclusion From these research results, we conclude that many types of mycotoxin do not decompose by ordinary cooking methods conducted at home, and that they remain in food and accumulate in human bodies. In the case of some food products, even when mycotoxins are detected in primary materials, it can be removed in manufacturing process and does not remain in final product. Prevention of mycotoxin contamination depends on handling of agricultural products at various stages from harvesting to storing. People in agriculture must be made more aware of how important it is to prevent mycotoxin contamination, and the same heightened awareness is also essential for those in food manufacturing. References 1) Kamimura, H., Nishijima, M., Saito, K., Ibe, A., Naoi, Y. (1978) Procsperityand degradation of trichothecene mycotoxins by food processing Proc. Jap. Assoc. Mycotoxicol., 8, 14. 2) Kamimura, H., Nishijima, M., Saito, K., Yasuda, K., Ibe, A., Nagayama, T., Ushiyama, H., Naoi, Y. (1979) The decompositiorn of trichothecene mycotoxins during food processing J. Food Hyg. Soc. Japan, 20, ) Kamimura, H. (1987) Survey of mycotoxins contamination in commercial foods and foodstuffs, and fate of mycotoxins during food processing Proc. Jap. Assoc. Mycotoxicol., 26, 13. 4) Kamimura, H., Tabata, S., Tamura, I., Yasuda, K., Ushiyama, H., Nishijima, M., Nishima, T. (1987) Survey of Fusartum mycotoxins contamination in cereals and foodstuffs, and fate of mycotoxins during food processing J. Food Hyg. Soc. Japan, 28, ) Kamimura, H. (1996) Contamination of mycotoxins in foods and removal of mycotoxins during food processing Mycotoxins, 43, 27. 6) Kamimura, H. (1997) Influence on nivalenol by food processing Mycotoxins, 45, 17.