Bisulfite is a highly reactive chemical that is commonly used in some foods and beverages because of its ability to inhibit both enzymatic and nonenzymatic browning, to inhibit growth of many microorganisms, and to act as an antioxidant and a reducing agent. Bisulfite has also been tested for its ability to degrade aflatoxin. Sodium bisulfite was hypothesized to react with the double bond on position 8,9 of the terminal furan ring to make it more water soluble. Aflatoxin B does not have this double bond; hence, degradation by bisulfite is not possible. The formation of sodium sulfonate (BS) was confirmed to be the major reaction product of aflatoxin with sulfonic acid.

Aflatoxin B was completely destroyed after soaking corn with aflatoxin levels in excess of 1900 ppb in 10% sodium bisulfite for 72 hours followed by filtering, drying, and incubation at 50°C for 21 days. Moisture, sodium bisulfite level, time, and temperature have significant effects on AFB degradation whereas AFB is not affected. Doyle and Marth observed that the presence of citric acid or methanol decreased the rate at which sodium bisulfite destroyed aflatoxins in a pH 5.5 buffered system. For aflatoxin levels of about 235 ppb in corn, lower concentrations of 0.5% and 1% sodium bisulfite were more effective at destroying AFB than NaOH or aqueous ammonia at the same level, while at 2% NaOH or aqueous ammonia were more effective than bisulfite. When figs contaminated with 250 ppb AFB were treated with 0.2% hydrogen peroxide minutes before a 1% bisulfite treatment, 57% more AFB was destroyed in 72 hours at 25°C than with bisulfite alone. Treatment of naturally contaminated groundnut cake with sodium bisulfite and sodium hydroxide separately decreased aflatoxin levels for up to 24 hours of storage, but samples showed an increase in total aflatoxin content after 10 and 20 days of storage at ambient temperature, most likely due to regrowth of fungus seen at longer time periods. Treatment of Aspergillus flavus inoculated groundnut cake with 1% sodium bisulfite at 10% moisture completely inhibited mold growth and aflatoxin production at room temperature.

Source:Aflatoxin and Food Safety Edited by Hamed K. Abbas CRC Press 2006

The beneficial effects of wine on human health may originate from their nonalcoholic components, such as flavanoids and phenols. Some phenolic compounds can be protective, whereas others have been found to be mutagenic at high doses in laboratory studies. Fazel and coworkers found that quercetin can induce mutation during in vitro culture of animal cells, but is an anticarcinogen in whole animal dietary studies. This anomaly may be due to the differences in the concentrations of quercetin used and the low level of metal ions and free oxygen found in the animal body. Subbaramaiah and coworkers observed that resveratrol, a member of the stilbene family found in wine, can inhibit the production of cyclooxygenase-2, thought to be important in carcinogenesis. As well, flavanols and flavones strongly reduce the action of the common dietary carcinogens such as the heterocyclic amines. In this regard, it is important to note that wines made from fruits such as cherry, blackberry and blueberry, and red grape show a very high complement of superoxide and hydroxyl radical scavenging ability due to the presence of several phenolic components.

The flavanoids are also strong inhibitors of calcium second messenger function in animal systems, and the biological activities of wines may, to a large extent, result from this activity. Recently, during in vitro culture, the flavonoid wine components have been shown to be specifically cytostatic and cytotoxic to MCF-7 cells, which are estrogen receptor positive breast cancer cells. Under similar conditions, the normal human mammary epithelial cells were unaffected. Thus, by enhancing the components in the wine that afford health beneficial effects, the functional food value of the wine can be enhanced. Even though moderate wine consumption is believed to be beneficial to cardiovascular health, its effect on breast cancer development is still controversial. Several biotechnological approaches such as in vitro culture, genetic engineering of grapes for enhanced secondary metabolite biosynthetic pathways, and conditions of fermentation could ultimately enhance the functional food value of the wine.

Several studies have shown that alkali treatment, using inorganic or organic bases, is an effective and economically feasible method of degrading aflatoxins. Alkalis cause the hydrolysis of the lactone ring in AFB; however, evidence suggests that the hydrolyzed lactone ring can close again under acidic conditions and regenerate back to AFB. Alkaline treatments have been studied for the destruction of aflatoxins because of the conditions used during the making of tortillas from corn. Treatment of corn with less than 0.5% calcium hydroxide decreased aflatoxin levels by 43%.

Reversion tests with acid treatment resulted in conversion back to the original concentration. Higher levels of calcium hydroxide did not improve aflatoxin degradation and resulted in a less sensory acceptable product that broke easily and had too strong of an alkaline flavor. Typical conditions of nixtamalization only raise pH levels in corn products to about 7.0. At these pH levels, the aflatoxin detoxification process can be reversed by acid treatment, resulting in the original AFB structure being reformed. Boiling 1600-ppb naturally contaminated corn with 3% NaOH at 100°C for 4 minutes decreased total AFB and AFB levels by 93%. A reversion level of 18% back to the original AFB structure was observed after treatment with acid. Further heat processing by autoclaving and deep frying at 196°C for 15 minutes to make a corn snack resulted in a product with acceptable levels of less than 20 ppb of aflatoxin for human food and nondetectable mutagenicity.

An earlier study used a combination of 2% calcium hydroxide based on sample weight followed by 0.5% methylamine to decontaminate peanut meal with aflatoxin levels of 400 ppb and found that the level was reduced to acceptable standards with no reversion. A study was conducted to determine the effects of nixtamalization on decontamination of corn co-contaminated with aflatoxin and fumonisin. Nixtamalization alone resulted in aflatoxin levels being decreased from 300 ppb to 5 ppb, and complete decontamination was achieved when combined with ammonium hydroxide. Fumonisin levels were reduced by 100% using this procedure, but it was not known whether the reduction was due to loss in the water soaking step or if chemical modification occurred. Extracts of tortillas made with the nixtamalized corn from the same study did not show teratogenic effects by the avian embryo assay, but mixed results were found in the mutagenicity assay by the Ames test.

Source:Aflatoxin and Food Safety Edited by Hamed K. Abbas
CRC Press 2006