Browning, non-enzymatic

MANZOCCO L, CALLiGARis s, MASTROCOLA D, NicoLi M c and LERici c R (2001) Review of non-enzymatic browning and antioxidant capacity in processed foods . Trends Food Sci Technol, 11 340-6. 

Microbial growth, enzymatic reactions, non-enzymatic browning (reaction between carbonyl and amino compounds), and lipid oxidation are the major deterioration mechanisms that limit the stability of low moisture (o intermediate moisture foods (o.6o < <0.85) and biological materials. 

To fulfill the needs for long term stability of a biological material, the optimum range of water activity lies between 0.20 and 0.35, This area represents the best compromise between lipid oxidation and non-enzymatic browning. Enzymatic browning is suppressed under these conditions, and growth of microorganisms is impossible. 

Delay non-enzymatic browning of fruits and some vegetables. 

Maillard reaction. The Maillard reaction is also known as non-enzymatic browning, non-enzymatic glycosylation, and glycation. It comprises the spontaneous reaction between carbonyl and amino compounds, such as sugars and proteins, respectively. It is especially well-known in the... 

Humic substances. Analogous to the reactions described above, humic substances (the polymeric pigments from soil (humus) and marine sediments) can be formed by both enzymatic and non-enzymatic browning. High concentrations of free calcium and phosphate ions and supersaturation with respect to hydroxyapatite can sustain in soil, because adsorption of humic acids to mineral surfaces inhibits crystal growth (Inskeep and Silvertooth, 1988). A similar adsorption to tooth mineral in a caries lesion can be anticipated for polycarboxylic polymers from either the Maillard reaction or enzymatic browning. 

Rodriguez-Saona, L., Wrolstad, R., Pereira, C. (1997). Modeling the contribution of sugar, ascorbic acid, chloro-genic acid and amino acids to non-enzymatic browning of potato chips. Journal of Food Science, 62, 1001-1005. 

Numerous review articles (1-20) and a number of books (21-26) have been devoted to the Maillard reaction, viz., the non-enzymatic browning reactions involving amino acids and reducing sugars. 

Volatile compounds formed by non-enzymatic browning reactions are of great importance for the sensory properties of heat-treated foods. 

Non-enzymatic browning reactions play a central role in the formation of food aroma and flavor, especially in heat-treated foods. The purpose of this work is to present sensory data, scattered in the literature, for volatile non-enzymatic browning reaction products and related compounds. The compilation has no pretensions to completeness and only a small part of the extensive patent literature has been covered. Anyhow, it is felt that a compilation of this kind, which has not been available hitherto, would be useful to workers in the field. 

The volatile compounds formed by the Maillard reaction are only one group of flavor compounds in foods. Schutte (1) presents a brief summary of the major classes and their modes of formation from precursors. Some of them can be formed by different pathways. An example is the furans, which can be formed by non-enzymatic browning reaction but also by biotransformation. 

The early scientific discoveries relating to heat induced aroma development can be traced to the work of Louis—Camille Maillard at the University of Nancy during the period of 1912 to 1936 (2). He published at least 8 papers on the subject of the reaction of sugars with amino acids. The Maillard Reaction, or so-called, non enzymatic browning reaction chemistry, has become the focus on a great amount of scientific work (3). 

If a nitrogen source is added, or if residual nitrogen-containing compounds are present, classical non-enzymatic browning (MaiHard) along with caramel ization can occur. Although the Maillard reaction is not the major emphasis of this review, it is difficult not to include it in discussions of carbohydrates and their degradation products. 

Heterocyclic compounds are primarily formed through non-enzymatic browning reactions. Recent studies of deep-fat fried food flavors led to the identification of pyrazines, pyridines, thiazole, oxazoles and cyclic polysulfides which had long-chain alkyl substitutions on the heterocyclic ring. The involvement of lipid or lipid decomposition products in the formation of these compounds could account for the long-chain alkyl substitutions. Model systems were used to study the participation of lipids in the formation of pyrazines, pyridines, thiophenes and cyclic polysulfides. 

T. Hofmann, W. Bors, and K. Stettmaier, Studies on radical intermediates in the early stage of the non-enzymatic browning of carbohydrates and primary amino acids, J. Agric. Food Chem., 1999, 47, 379-390. 

T. Hofmann, H. F. Erbersdobler, I. Kruse, and V. Faist, Molecular weight distribution of non-enzymatic browning products in Japanese soy sauce and studies on their effects on NADPH-cytochrome c-reductase and glutathione-S-transferase in intestinal cells, in G, 2002, 485 186. 

L. Vandewalle and A. Huyghebaert, The antioxidant activity of the non-enzymatic browning reaction in sugar-protein systems, Med. Fac. Landbouww. Rijksuniv. Gent., 1980, 45, 1277-1286, via Food Sci. Technol. Abstr., 1983, 15, 2A132. 

Figure 3-13 Proposed Browning Reaction Mechanism According to Burton and McWeeney. Source From H.S. Burton and DJ. McWeeney, Non-Enzymatic Browning Routes to the Production of Mel-anoidins from Aldoses and Amino Compounds, Chem. Ind., Vol. 11, pp. 462-463, 1964.

During the crushing process, ascorbic acid can be added to protect against oxidation. This prevents non-enzymatic browning until the juice is pasteurized. 

To prevent non-enzymatic browning, the fruit can be dipped in a 5% solution of citric acid (or in lemon juice). This is especially advisable in the case of sliced and diced apples where the acid content is low. The acid allows the light colour to be retained, while at the same time improving the taste of the pieces of apple. The colour of the fruit can be made even lighter by adding ascorbic acid to the dip. 

CIC Non-enzymatic-browning compounds 2,5- and 2,6-dimethyl pyrazines, trimethyl pyrazine impart the fresh, green, nutty character, 2-methyl-6,7-dihydro-5H-cy-clo-penta-pyrazine is responsible for the roasted-nutty note and 2,5-dimethyl-4-hy-droxy-furan-3(2H)-one supports the caramel like, sweet overall impression. 

Rinderknecht, H. and Jurd, L. (1958). A novel non-enzymatic browning reaction. Nature 181, 1268-1269. 

Bell, L.N. Kinetics of non-enzymatic browning in amorphous solid systems distinguishing the effects of water activity and glass transition. Food Res. Int., 28, 591,1996. 

Labuza, T.P., Warren, R., and Warmbier, H.C. The physical aspects with respect to water and non-enzymatic browning. Nutritional, Biochemical and Chemical Consequences of Protein Cross-linking, M. Friedman, ed.. Plenum Press, New York, pp. 379 -418,1977. 

Karmas, R., Buera, M., and Karel, M. Effect of glass transition on rates of non-enzymatic browning in food systems, J. Agric. Food Chem., 40, 873, 1992. 

Roos, Y. and Himberg, M.J. Non-enzymatic browning behaviour, as related to glass transition of a food model at chilling temperatures, /. Agric. Food Chem., 42,893, 1994. 

Schebor, C., Chirife, J., and Buera, M. Non-Enzymatic Browning in dehydrated potato and Starch Model Systems in relation to physical state. International Congress on Engineering and Food, J. Welti-Chanes, G.V. Barbosa-Canovas and J.M. Aguilera, eds., Technomic Rublishing Company, Inc., USA, pp. 309-313, 2001. 

Research projects in basic enzymology of polyphenol oxidase and the chemistry of non-enzymatic browning may lead to new browning inhibitors. Reviews on polyphenols oxidase (13) and on Maillard reactions (14) are available. The interest in enzymatic browning is aided by skin cancer research as melanins are the pigments involved in the coloring of human skin. 

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