Thermal Food Processing

UHT Thermal Processing of Milk 323
for the presence of mesophylic bacteria according to European law. 1,124 About
14% of total milk samples analyzed were out of range, in particular, 25% from
great distribution, 17% from middle distribution, and none from small distribution.
The authors suggested that contamination could be due to heat-resistant
spores or after-packaging contaminations.
10.5.2 AFLATOXINS
The contamination of food with aflatoxins is a notorious problem. From epidemiological
studies it is known that aflatoxins are toxic and carcinogetic compounds.
Human exposure to aflatoxins can result from ingestion of contaminated
food. Aflatoxin M1 (AFM1), a hydroxylated metabolite of aflatoxin B1 (AFB1),
can be present in milk via animals consuming feed contaminated with AFB1.
AFB1 has been classified as class 1 or human carcinogen and AFM1 as class 2
or probable carcinogen. 125 Because milk represents a main constituent of the diet
of children and growing young, i.e., the population most at risk, it is necessary
to monitor the contamination of aflatoxin in milk. Current regulations for AFM1
in milk have been established by the Food and Agriculture Organization (FAO): 126
permissible levels range from 0.05 to 0.5 ppm.
Heat processing of milk should not affect the AFM1 concentration because
AFM1 is heat stable (decomposition temperature ranges from 237 to 306°C).
Nevertheless, published data on the effect of heat treatment on milk AFM1
levels seem to be contradictory. 127 This can be due to the fact that AFM1 is not
stable in milk (contamination disappeared after 6 days storage at 0°C), and not
all methods used to determine AFM1 have the same accuracy, precision, and
sensitivity.
Martins and Martins 128 investigated the occurrence of AFM1 in raw and UHT
commercial milk in Portugal. Only two UHT-treated milk samples exceeded the
limit of 0.05 ppm, while the other 68 UHT-treated milk samples had low AFM1
levels (from