Chemistry Reference
In-Depth Information
binding sites due to Maillard reactions (Pappas and Rothwell, 1991). The
functional consequences, if any, of such a reduction in calcium binding have
not been investigated. In view of the reactivity of
-casein in Maillard reac-
tions, it is possible that such reactions may reduce the stability of casein
micelles such as occurs during storage and age gelation of UHT milk. Avail-
able evidence suggests that Maillard browning reactions do not contribute to
age gelation (Venkatachalam et al., 1993). However, the development of
Maillard crosslinks has not yet been examined in UHT milk and, therefore,
the possible role of Maillard reactions in age gelation cannot be discounted.
7.8.4. Formation of Toxic Compounds
7.8.4.1. Furan
The formation of furanic derivatives in Maillard reactions is well
described and the toxicology of furfural and HMF in particular is well
described (see Section 7.3.4). In early 2004, the US Food and Drug Admin-
istration (FDA) expressed concern at the presence of furan, a possible human
carcinogen, in a number of heat-treated foods (FDA, 2007). The presence of
furan and hundreds of furanic molecules in foods has been recognized for at
least 30 years. Most of these molecules derive from Maillard reactions (Maga,
1979; Crews and Castle, 2007).
The level of furan found in heated dairy products is relatively low
(generally
<
20 mgkg
-1
in infant formulas and evaporated milks compared
with products such as some soups and canned foods where levels
>
200 mg
kg
-1
have been reported) (M¨rk et al., 2006; FDA, 2007).
Maillard products such as furfural and furoic acid have been proposed
as furan precursors in heated foods (Crews and Castle, 2007). Systems
containing ascorbic acid yield the highest levels of furan, especially in the
presence of oxygen (Perez Locas and Yayalayan, 2004; Hasnip et al., 2006).
Removal of oxygen or addition of a reducing agent, such as sulphite, results in
lower furan levels (M¨rk et al., 2006). M¨rk et al. (2006) also noted that more
complex systems resulted in less furan formation, presumably due to compet-
ing reaction pathways; the intermediates 2-deoxyaldotetrose and 4-hydroxy-
2-butenal were proposed to yield furan from ascorbic acid/carbohydrate
pathways or polyunsaturated fatty acid oxidation, respectively.
7.8.4.2.
Acrylamide and Other Vinylogous Maillard Reaction Products
The discovery, in 2002, of high levels of the carcinogen, acrylamide, in some
thermally processed plant foods revealed a hitherto unknown Maillard pathway
with significant food safety implications (Friedman and Mottram, 2004; Skog and
