Soy Protein Fortification of a Low fat Dairy Based Ice Cream.

Abstract

Since the inception of the 1998 FDA approved health claims linking soy and health, soy protein has been investigated as a potential ingredient in many foods. Products containing soy protein have been characterized as having beany or woody off-flavors, which are unacceptable to many American consumers. Frozen dairy dessert products, in comparison, are appealing to many consumers and may potentially serve as carriers for functional ingredients such as soy protein. Understanding the flavor and sensory impact of soy protein in a dairy-based frozen dessert is important in designing soy fortified dairy products with high market acceptability. The goals of this research are to identify and characterize aroma active compounds contributing to off flavors in soy protein fortified dairy-based frozen desserts, and assess associated sensory impacts.

Descriptive sensory analysis was conducted on frozen dairy dessert mixes formulated with 0, 2, and 4% soy protein isolate (SPI). Duplicate samples (750g) containing an internal standard were distilled by high vacuum transfer followed by extraction of the distillate with diethyl ether. Extracts containing volatile compounds were separated into neutral-basic and acidic fractions and analyzed by gas chromatography-mass spectroscopy (GC-MS) and gas chromatography-olfactometry (GC-O) and aroma extract dilution analysis (AEDA). Comparison of retention indices, odor properties, and GC-MS data against reference standards was performed for identification of compounds. SPI fortified dessert mixes displayed different textural and color properties in comparison to the 0 % SPI control. Soy fortification increased mouth viscosity and mouthcoating. Green/grassy and doughy/fatty flavors increased in intensity with added SPI. GC-O analysis revealed higher concentrations of hexanal (green), (Z)-4-heptanal (fishy/oily), 2-acetyl-1-pyrroline (nutty/popcorn), and (E,E)-2,4-decadienal (fatty/frier oil) in the SPI fortified samples compared to controls. Consumer testing revealed lower acceptability of SPI fortified ice creams in conjunction with lower intensities of pleasing ice cream flavors with added SPI. Chocolate flavored SPI fortified ice creams received higher acceptability scores than vanilla flavored SPI fortified ice creams. Consumers indicated a general knowledge of the healthfulness of low fat dairy desserts and soy foods. This information will aid in the design and optimization of an acceptable soy fortified low fat dairy ice cream.