Thermal Food Processing

324 Thermal Food Processing: New Technologies and Quality Issues
In Brazil, Garrido and coworkers 132 investigated the presence of M1 and M2
aflatoxins in 60 UHT and 79 pasteurized commercial milk samples collected from
supermarkets. None of the milk samples were found to be contaminated with
aflatoxin M2, but aflatoxin M1 was detected in 29 samples (20.9%) at levels of
50 to 240 ng/l. Occurrence of aflatoxin M1 was high in both commercial pasteurized
and UHT milk. The contamination level, according to MERCOSUR
Technical Regulations, should not be considered a serious public health problem,
even if in some cases it exceeded the limit (50 ng/l) permitted by the EU.
10.5.3 CHEMICAL CONTAMINATION
Environmental contamination caused by human activities (industrial processing,
packaging procedures, accidents during transport, storage before consumption)
can affect milk safety. Chemical pollution, in particular by organic substances
(e.g., polychlorinated biphenyls (PCBs)), is one of the major problems. This is
a well-known concern, and worldwide, quality control structures focus on identifying
hazards and periodically surveying milk all along the supply chain. While
data on chemical contamination of breast milk are abundant in the international
scientific literature, food chain monitoring results are seldom published. This is
unfortunate, as availability of these results would be useful for the whole scientific
community.
Milk and cheeses, collected from Washington, D.C., area retail stores, have
been analyzed for polychlorinated dibenzo-p-dioxin and dibenzofuran contamination.
133 Contaminants were identified and quantified, and expressed in international
toxic equivalent (I-TEQ). Milk contamination ranged from 0.05 to 0.12 I-
TEQ. Similar values have been observed in milk collected in rural areas with no
apparent sources of contamination. 134 In particular, the I-TEQ values found for
the Washington milk samples are higher than the I-TEQ values of German milk. 135
In Italy, Fabietti and coworkers 136 examined 35 commercial milk samples for
the presence of the principal aromatic hydrocarbons (benzene, toluene, ethylbenzene,
xylenes). Milk samples were collected from different dairies and included pasteurized
whole, semiskimmed, and skim milk, and UHT whole and semiskimmed milk.
Levels of the two most common aromatic hydrocarbons (benzene and toluene) were
relatively low (0.12 to 100 µg/kg), while levels of ethylbenzene and total xylenes
(meta + ortho + para) were below the detection limit of 0.05 µg/kg. Benzene and
toluene levels were higher in whole and semiskimmed milk than in skim milk. No
differences were observed between pasteurized and UHT milk with similar fat
contents. Results indicate that levels of aromatic hydrocarbons in commercial milk
in Italy are similar to those found in other foods and are sufficiently low to consider
milk safe from the point of view of chemical contamination. 136
10.6 SENSORY QUALITY
UHT milk, either freshly prepared or stored, has a sensorial characteristic called
cooked note. Stale and oxidized flavors occur due to formation of aldehydes
and ketones.