Mycotoxin contamination in foodstuffs: decontamination of aflatoxin M1 in bovine milk by clay materials

Mycotoxines are widespread toxic substances produced by moulds in human and animal foodstuffs. Some of them, such as aflatoxin B1 (AFB1), are very toxic even in small amounts, but the modern approach to the problem (and the link with public health) started only in the 60s. The presence of aflatoxin M1 (AFM1), in milk and dairy products is also a problem of crucial interest. AFM1 is resistant to thermal and chemical treatments, so mineral sorbents are highly advisable. Clay minerals are suitable, but only a few data are available, as most studies deal with AFB1 (absent in milk). The capacity of clay materials to remove or attenuate the contamination of AFM1 in bovine milk was studied, also considering the effects of these clays on the nutritional properties of milk (in terms of protein, fat and lactose). In order to make the experiments transferable for practical use, only clays available from the market were tested, as well a very simple clay-milk interaction procedure was used. Some bentonites and a kaolin were selected for the experimental work. In particular, different bentonites were selected in order to partially accomplish the wide crystal-chemical features of smectite. Kaolin was less effective than bentonites, but was still able to detoxify contaminated milk, even using a little amount of kaolin (2.4% of the milk suspension). The detoxification role of the bentonites used was variable, but still very efficient: contaminated bovine milk (up to about 80 ng/L) was purified to safe levels (50ng/L for adults and 25ng/L for lactants), with moderate alteration of the nutritional properties of milk; moreover, the bentonite residue in the purified milk was very low (0.4%). The protein was more sensitive to clay adsorption compared to fat and lactose, and the decrease of protein in the treated milk increased with the clay-milk ratio. Among bentonites (beidellite-montmorillonite, ferruginous and saponite types), a saponite clay showed the highest sorbent capacity, in agreement with theoretical consideration about its higher cell surface (available for AFM1) and higher hydrophobicity. Isothermal adsorption procedures for the two more effective bentonites were also carried out in water. The collected data show an effective and safe use of clays in the detoxification of milk (and dairy products) contaminated by AFM1. The climatic changes observed in the last decades point to a wider diffusion of mycotoxines and health effects, and push toward the search for safe, cheap and accessible food treatments.