Chapter 7
Flavor Interaction with Casein and Whey Protein
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A. P. Hansen and D. C. Booker Department of Food Science, North Carolina State University, Raleigh, NC 27695
Processed milk protein-containing food products tend to retain less of the original perceived flavor as observed by sensory measurements. As the protein content of processed foods are increased to compensate for the reduction of fat, the potential exists for a corresponding reduction of flavor intensity due to flavor compound interactions with proteins. The purpose of this study was determine the extent of interaction between milk proteins and typical flavor compounds when the latter are mixed into ice cream during its manufacture. The model flavor compounds chosen for this study were vanillin, benzaldehyde, citral, and d-limonene. By fractionating the ice cream into fat, casein, and whey portions, one can determine the relative flavor concentration in each. Through quantitation of the amount of flavor in each fraction, the losses due to protein binding can be measured. The effect of these interactions upon sensory perception was also determined.
The acceptance of food products by the consumer is based on the sensory attributes of flavor, color, and texture. The aim of the food industry is to produce foods that are stable and have a good flavor and texture. One of the most important attributes of an acceptable food is the flavor as perceived by the consumer at the time of consumption. The term "flavor" denotes the characteristics which stimulate taste, smell, thermal and tactile sensations. The flavor chemist is concerned with the compounds that contribute characteristic taste and aroma of foods. The common characteristics of food flavors are: (1) they consist of many components, some present in high proportions; (2) they exert their influence at extremely low levels; (3) they are highly specific with respect to molecular configuration; and (4) they tend to be volatile. Natural and artificial flavor systems contain a vast number of compounds
0097-6156/96/0633-0075$15.00/0 © 1996 American Chemical Society
In Flavor-Food Interactions; McGorrin, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1996.
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F L A V O R - F O O D INTERACTIONS
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which contribute to the overall aroma and taste of a particular food. For example, chocolate and peanut flavors contain over 250 and 230 flavor compounds, respectively, some of which are more important than others to the characteristic flavor of the food. Simpler flavor systems, such as imitation vanilla and cherry flavors, also contain a variety of flavor compounds; however, each contains a sensory-dominating flavor component (vanillin and benzaldehyde, respectively) that contributes the characteristic taste and aroma. Vanillin (1) is the principal component of vanilla extract, which is used widely by the food industry as a flavoring agent, specifically in confectionery products and beverages (7). Benzaldehyde (2) is a compound present in almond, cherry, and cinnamon-type oils, as well as in the essential oils of many flowers (2).
OH 1
2
Citral has a strong lemon-like odor with a bittersweet taste. Commercially the product is a mixture of cis- and rrans-isomers, geranial (3a) and neral (3b). d~ Limonene (4) is one of the most widespread terpenes found in citrus peels. It is often used in frozen dairy desserts to produce a pleasant lemon-like odor.
3a
3b
4
Flavor Loss Small changes in the levels of flavor compounds in food products can alter their sensory properties and render the flavor of the product unacceptable to the consumer. Flavor changes in food products have been attributed to several factors including light, processing conditions, ingredients, and packaging materials. Flavor loss can occur due to interactions between flavor compounds and other food ingredients. Protein-containing food products that are processed at high
In Flavor-Food Interactions; McGorrin, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1996.
Downloaded by UNIV OF PITTSBURGH on December 24, 2014 | http://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/bk-1996-0633.ch007
7.
HANSEN & B O O K E R
Flavor Interaction with Casein & Whey Protein77
temperatures tend to retain less of the original perceived flavor (3). Hansen and Heinis (3) reported that vanillin flavor intensity, as measured by a 12-member trained taste panel, declined from 0.32 (moderately less than reference) to 0.15 (much less than reference) as the whey protein concentrate (WPC) level increased from 0.12% to 0.5% in flavored protein solutions. They later reported similar losses of benzaldehyde and d-limonene as W P C levels in flavored protein solutions increased from zero to 0.5% (4). Milk proteins are often added to lowfat frozen dairy desserts to impart smoothness and help to prevent weak body and coarse texture. Since 1988, protein-based fat substitutes have been available which simulate the mouthfeel of fat (5). In August 1991, a new version of a protein-based fat substitute was introduced which contained 100% whey protein. As the protein content of food is increased to compensate for the reduction of fat, the potential exists for reduction of flavor intensity due to flavor compound interactions with proteins. Even a small degree of interaction between flavor compounds and ingredients or packaging materials can reduce the amount available for sensory perception. Numerous studies have been conducted on the interaction of flavor compounds with β-lactoglobulin (β-lg) (6-9). β-Lactoglobulin readily binds certain alkanes, 2-alkanones, free fatty acids, triglycerides, and aromatic hydrocarbons (69). In addition to the primary binding site, β-lg is thought to contain other hydrophobic areas capable of undergoing interactions with apolar molecules (7-10). The purpose of this study was determine the extent of interaction between milk proteins and typical flavor compounds when the latter are mixed into ice cream during its manufacture. The model flavor compounds chosen for this study were vanillin, benzaldehyde, citral, and
