Humidity Maillard reaction

A thorough study of the aromas produced from over 400 model Maillard reaction systems vas performed (44). Combinations of 21 amino adds and 8 sugars were evaluated under different conditions of temperature and humidity. Table II lists beefy or meaty aromas produced from thermal interactions between glucose and eight amino acids. 

At high temperatures and humidities, dextrates may react with substances containing a primary amino group (Maillard reaction). Also incompatible with oxidizing agents. 

Lactitol as the monohydrate is nonhygroscopic and is stable under humid conditions. It is stable to heat and does not take part in the Maillard reaction. In acidic solution, lactitol slowly hydrolyzes to sorbitol and galactose. Lactitol is very resistant to microbiological breakdown and fermentation. Store in a well-closed container. When the compound is stored in an unopened container at 25°C and 60% relative humidity, a shelf-life in excess of 3 years is appropriate. 

Free amino- and guanidino-groups. As a model system of protein-sugar Maillard reaction, a powdered sample containing ovomucoid and glucose was incubated at 50 C and 65% relative humidity for various periods from 2 to 20 days. The incubated samples were dissolved in 50 mM Tris-HCl buffer, pH 8.0 and used for chemical and biochemical analyses. 

The presence or activity of water in foods may also enhance the rate at which deteriorative chemical reactions occur. Some products may become rancid through free radical oxidation even at low humidities and thus become unacceptable. Labile nutrients such as vitamins and natural color compounds are oxidized more rapidly when stored at low moisture levels. Enzyme-mediated hydrolytic reactions may reduce the quality of the food product. Other reactions such as the Maillard type of nonenzymatic browning may be enhanced by the presence of higher levels of water. On the other hand, water content is crucial for the textural characteristics and the sensory perception of foods. A food may be found unacceptable by consumers simply because it does not satisfy their textural (sensory) anticipation. 

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