Problems with flavor development

Over the past few years, many advances have been made in the area of microwave product development with items such as popcorn, pizza, and frozen entrees. However, products such as baked goods have met with limited success. To date, many of the texture-related problems have been solved, but the majority of flavor-related problems (particularly flavor development during baking) have not. 

One of the major problems associated with the flavor development of microwave products results from the fact that the reduced time/temperature relationship during baking is not conducive to the formation of a crisp, outer crust or many of the Maillard compounds associated with a conventionally baked flavor. These microwave baked products thus have a different flavor character from conventionally baked products and are typically judged "inferior by consumers. 

Another area of interest to optimize the encapsulation efficiency of food flavors and oils by SD is the submicronization of the droplets oil of the emulsion. It has been well documented that emulsion droplet size has a pronounced effect on the encapsulation efficiency of different core materials by SD (Jafari et al., 2008). The findings clearly show that reducing emulsion size can result in encapsulated powders with higher retention of volatiles and lower content of unencapsulated oil at the surface of powder particles. The presence of oil on the surface of the powder particles is the most undesirable property of encapsulated powders, and it has been pointed out as a frequent problem with the quality of spray-dried products. This surface oil not only deteriorates the wettability and dispersability of the powder, but it is also readily susceptible to oxidation and to the development of rancidity. 

Although faux fats are widely used these days, they have yet to be perfected. One of the biggest problems with carbohydrate- and protein-based fat substitutes is that they decompose at high temperatures and therefore can t be used for frying foods. Another problem is that fat substitutes often alter the flavor of foods. Most aromatic chemicals, which greatly affect flavor, are soluble in fat, so the taste lasts much longer in foods made with real fat than in those that use substitutes. However, newly developed fake fats appear to counter some of these disadvantages. 

WOF is a problem associated with the use of precooked meat products such as roasts and steaks. The term WOF was first used by Tims and Watts (2) to describe the rapid development of oxidized flavors in refiigerated cooked meats. Published evidence indicates that the predominant oxidation catalyst is iron from ntyoglobin and hemoglobin, which becomes available following heat denaturation of the protein moiety of these complexes. The oxidation of the lipids results in the formation of low molecular weight components such as aldehydes, adds, ketones and hydrocarbons which may contribute to undesirable flavor. 

With the advent of noncorrodible dairy equipment, oxidative deterioration in fluid milk as a result of copper contamination has decreased significantly, although it has not been completely eliminated (Rogers and Pont 1965). However, the incidence of spontaneous oxidation remains a major problem of the dairy industry. For example, Bruhn and Franke (1971) have shown that 38% of samples produced in the Los Angeles milkshed are susceptible to spontaneous oxidation Potter and Hankinson (1960) have reported that 23.1% of almost 3000 samples tasted were criticized for oxidized flavor after 24 to 48 hr of storage. Significantly, certain animals consistently produce milk which develops oxidized flavor spontaneously, others occasionally, and still others not at all (Parks et al. 1963). Differences have been observed in milk from the different quarters of the same animal (Lea et al. 1943). 

The problem of developing desirable meat flavor in the presence of vegetable protein has been clearly demonstrated in the literature. Physical measurements after heating a meat model system with soy proteins have shown a dramatic reduction in the concentration of alkyl pyrazine compounds due to interaction with the soy proteins. These interactions have been defined in terms of stoichiometry and binding energies from measurements on pure standards of the methyl pyrazines. 

Many problems associated with successfully identifying and simulating the flavors characteristic of conventionally baked foods have yet to be overcome in the development of new microwave products. This study addresses these problems by identifying compounds most important to the characteristic flavors of white cake batter, microwave and conventionally baked cake. Gas chromatography, mass spectrometry, and odor analysis by sniffing indicated that compounds such as diacetyl, C4-C10 aldehydes, C4-C10 alcohols, C8-C11 dienals, 3-octen-2-one, and 7-octen-4-ol were common to all three flavor systems. Conventional cake was found to contain higher levels of isopentenal and furfural than microwave cake. 

Off-flavors in food packages are not only a legal but also often an economic problem, when market recalls have to be made. This chapter describes the different kinds, origins and development of off-flavors and deals with solutions for off-flavor problems arising from interactions between packaging and food. The text covers the sensory and analytical methods used for off-flavor-investigations and describes several case studies. 

There were several new developments during the 1970s. Of particular importance was the purification and characterization of a lipoprotein lipase (LPL) and the acceptance of the postulate that this was the major, if not the only, lipase in cows milk (Olivecrona, 1980). Similarly, the elucidation of the lipase system in human milk as consisting of an LPL and a bile salt-stimulated lipase, and the possible role of the latter in infant nutrition, were noteworthy (Fredrikzon et al, 1978). Also, microbial lipolysis assumed substantial significance with the widespread use of low-temperature storage of raw milk and the recognition that heat-stable lipases produced by psychrotrophic bacteria were a major cause of flavor problems in stored dairy products (Law, 1979). 

These specialists utilize highly trained judges and sophisticated test designs and analysis to solve sensory problems. Consumer testing in most industry applications now is done with consumers. Even with the continuing development of instrumentation to replace the human judge, sensory analysis continues to expand its contribution to flavor analysis. 

Background. As an analytical technique, tandem mass spectrometry is just entering its second decade of development. The variety of reported applications belies its relative youth. Tandem mass spectrometry (MS/MS) grew out of early work which used metastable ion transitions in order to establish ion structures and interrelationships. After extensive applications to ion structural studies, its usefulness in direct catplex mixture analysis became apparent with the early work of Cooks (1-3). Its successes in problem solving are summarized in a recent book edited by McLafferty (4). New, with several ccnmercial instruments available, MS/MS is being evaluated for application in several new areas, including biochemical analysis, forensic chemistry, and food and flavor analyses. The principles of MS/MS will be surmarized in the first part of this chapter. The second part of the chapter will deal with the reported applications of MS/MS to flavor analysis. 

An increasing problem is lipolysis in butter fat after manufacturing, which is caused by thermoresistant hpase enzymes that are created in the milk or cream by psycho-trophic bacteria or by residual native lipases that sirrvive pasteurization. Based on a determination of the lipase activity in cream, the keeping quality of manufactured butter in regard to hpolysis can be predicted with reasonable accirracy. A similar prediction for sweet cream butter can be based on lipase activity in the serum phase (71). The characteristic lipolytic flavors that can develop in milk products are primarily associated with the short- and medium-chain fatty acids that are relatively abundant in milkfat they have lower flavor threshold values than the long-chain fatty acids. As a result of improvements in the quality of raw milk and the standards of processing, lipolytic rancidity is seldom present in the fat source before its use in recombination (72). 

In response to the problems associated with the handling of unsalted butter, a new milkfat product was developed in New Zealand to combine the superior flavor of butter with the ease of handling of AMF. Initial shipments of this product, fresh frozen milkfat for recombining (FFMR) were favorably received, and FFMR quickly became established as the preferred alternative to unsalted butter (72). 

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