نوع مقاله : مقاله پژوهشی
گروه علوم و صنایع غذایی، دانشکده کشاورزی، دانشگاه زنجان
عنوان مقاله [English]
Introduction: Bread is an important part of the Iranian families' diet. Due to the ease of mold growth, especially Aspergillus flavus on raw materials, it is possible to produce aflatoxin from these types of molds on the bread. The production of Mycotoxins in foods and feeds is a problem of major concern in all over the world. So, the most important microbial concern and challenge associated with bread are fungal infections and their toxins such as aflatoxins that include G2, B2, B1, and G1. There are several ways to reduce aflatoxin from foodstuffs including physical methods (cleaning, heating, radiation) chemical methods (chemical compounds, ozone gas) and biological methods (using bacteria, yeasts). Also, various studies have shown that the best and most reliable method for detoxification of contaminated foods with mycotoxins is the use of effective microbial species, such as Saccharomyces cerevisiae, which is an essential ingredient in the formulation of breads. Saccharomyces cerevisiae, also known as ‘’baker's yeast’’, is one of the most widely commercialized species and one of the effective adsorbent, rich in protein (40-45%), whose biological value is high and is also rich in vitamin B complex. This microorganism is used as active dry yeast in baking, which does not require refrigeration and had a longer shelf-life and better temperature tolerance than fresh yeast that would rise twice as fast, cutting down on baking time. The optimum temperature for growth of S. cerevisiae is 30–35 °C. With the respect that wheat in the silage during storage may be subjected to optimum temperature and humidity, conditions which is favorable for the growth of fungi and aflatoxin production in flour and bread, so S. cerevisiae can be used in baking for detoxification (via surface adsorption) and generating the carbon dioxide by the fermentation which is used as a leavening agent in bread and other baked goods. The leavening step is an essential stage in the fermentation of dough. S. cerevisiae does not only induce and increase the volume of dough through gas incorporation but helps creating the desired flavor and texture. Also, Saccharomyces cerevisiae is used as a probiotic in humans and animals. Especially, a strain Saccharomyces cerevisiae var. boulardii is industrially manufactured and clinically used as a medication. Investigations confirm that Saccharomyces cerevisiae var. boulardii is effective in reducing the risk of antibiotic‐associated diarrhea in children and adults.
So, the aim of this project is to investigate the effect of traditional fermentation, conventional baking and IR baking methods on the rate of aflatoxin reduction in lavash bread.
Material and methods: In this research, the effect of instant yeast of bread was investigated on the reduction of aflatoxin during fermentation of Lavash bread dough at 28 Degree Centigrade for 1 hour. For this reason, 100 kg of flour with 100 kg of water, 2% salt and 1.5% yeast were mixed for about 5 minutes until became uniform dough, then fermented at 28˚ C for 1 hour Afterwards covered with a translucent cloth, and allowed secondary fermentation was occurred for 2 minutes and then followed by baking in the oven for 25 seconds at 200 degree centigrade as Iranian National Standard No. 5 procedure. Besides, the performance of the infrared Turbo wave device was compared to conventional method for reducing the amount of total aflatoxin during the baking of the lavash bread.
Results and discussion: The results showed that the amount of reduced total aflatoxin in the fermented samples was 87.4% compared to the control samples before fermentation. Also, the effect of Lavash bread baking methods by infrared and a traditional manner showed 90.33% and 89.95% on the reduction of the amount of total aflatoxin respectively. It can be interpreted that Saccharomyces cerevisiae changes the structure of aflatoxin with its degrading enzymes such as acetyltransferase and reduces its toxic properties. Also, due to the presence of beta-glucan and manan as the binding agents in the cell wall of Saccharomyces cerevisiae; it is able to attach these kinds of toxin molecules to its cell wall and block them. Also, yeast can be effective in adsorption the aflatoxins to its cell wall which in the baking stage, due to the denaturation of yeast cell-wall proteins, the absorbed toxins on the yeast cell surface decomposed and destroyed under the heating action.
Conclusion: It can be concluded that fermentation is a necessary stage in the production of breads to create a good quality from the point of good texture, organoleptic concern, extending the shelf life of food product and ensures the safety of the bread and health of consumers. Because fermented bakery product has shown that has not toxins in higher amount than standard limit and Mycotoxins due to fermentation decomposes. On the other hand, baking can also decompose Mycotoxins structures. There are many kinds of baking machines which has different effect on the bread quality. So, new technologies such as infrared radiation helps to rapid heat transmission in baking stage therefore, it may influence on the fast degradation of toxic compounds. In this article in addition of investigation on fermentation effect on decreasing Aflatoxin amount, the conventional method of baking compared with Infra-red baking effect on omitting Aflatoxin compounds. But we found that although the amount of Aflatoxin in irradiated baked bread is lower than conventional baked bread, statistically the effect of baking method with infrared rays and conventional methods has similar effect for the destruction of aflatoxin in bread. Therefore, in spite of other differences between Infrared method and conventional method of baking, they do not differ in their effects on destruction of Mycotoxin among baking stage. As a result, the fermentation process with the active bread yeast function among suitable time and temperature plus baking stage can guarantee the health of bread.