Off-flavors

In addition to alcohoHc fermentation, a malolactic fermentation by certain desirable strains of lactic acid bacteria needs to be considered. Occasionally, wild strains produce off-flavors. Malolactic fermentation is desirable in many red table wines for increased stabiUty, more complex flavor, and sometimes for decreased acidity. Selected strains are often added toward the end of alcohoHc fermentation. AH the malic acid present is converted into lactic acid, with the resultant decrease of acidity and Hberation of carbon dioxide. Obviously this has more effect on the acidity the more malic acid is present, and this is the case in wine from underripe, too-tart grapes. Once malolactic fermentation has occurred, it does not recur unless another susceptible wine is blended. 

Chemical bleaching is never used on oils intended for edible use because it oxidizes unsaturated fatty acids to cause off-flavors. However, it does find wide usage for specialty linseed oil, for the paint industry, and fatty chemicals such as sorbitan esters of fatty acids and sodium stearoyl lactylate. Residual peroxide is destroyed by heating above its decomposition temperature. 

Analysis of Trace or Minor Components. Minor or trace components may have a significant impact on quaHty of fats and oils (94). Metals, for example, can cataly2e the oxidative degradation of unsaturated oils which results in off-flavors, odors, and polymeri2ation. A large number of techniques such as wet chemical analysis, atomic absorption, atomic emission, and polarography are available for analysis of metals. Heavy metals, iron, copper, nickel, and chromium are elements that have received the most attention. Phosphoms may also be detectable and is a measure of phosphoHpids and phosphoms-containing acids or salts. 

In addition to surfactant properties, emulsifiers are sometimes used to enhance the fat-replacer properties of hydrocoUoid systems. Off-flavors and legal restrictions limit use in this appHcation to a level below 0.5% of the finished product (41). 

Vacuum Treatment. Milk can be exposed to a vacuum to remove low boiling substances, eg, onions, garlic, and some silage, which may impart off-flavors to the milk, particularly the fat portion. A three-stage vacuum unit, known as a vacreator, produces pressures of 17, 51—68, and 88—95 kPa (127, 381—508, and 660—711 mm Hg). A continuous vacuum unit in the HTST system may consist of one or two chambers and be heated by Hve steam, with an equivalent release of water by evaporation, or flash steam to carry off the volatiles. If Hve steam is used, it must be cuUnary steam which is produced by heating potable water with an indirect heat exchanger. Dry saturated steam is desired for food processing operations. 

Irradiation. Although no irradiation systems for pasteurization have been approved by the U.S. Food and Dmg Administration, milk can be pasteurized or sterilized by P tays produced by an electron accelerator or y-rays produced by cobalt-60. Bacteria and enzymes in milk are more resistant to irradiation than higher life forms. For pasteurization, 5000—7500 Gy (500,000—750,000 tad) are requited, and for inactivating enzymes at least 20,000 Gy (2,000,000 rad). Much lower radiation, about 70 Gy (7000 tad), causes an off-flavor. A combination of heat treatment and irradiation may prove to be the most acceptable approach. 

Alitame (trade name Adame) is a water-soluble, crystalline powder of high sweetness potency (2000X, 10% sucrose solution sweetness equivalence). The sweet taste is clean, and the time—intensity profile is similar to that of aspartame. Because it is a stericaHy hindered amide rather than an ester, ahtame is expected to be more stable than aspartame. At pH 2 to 4, the half-life of aUtame in solution is reported to be twice that of aspartame. The main decomposition pathways (Fig. 6) include conversion to the unsweet P-aspartic isomer (17) and hydrolysis to aspartic acid and alanine amide (96). No cyclization to diketopiperazine or hydrolysis of the alanine amide bond has been reported. AUtame-sweetened beverages, particularly colas, that have a pH below 4.0 can develop an off-flavor which can be avoided or minimized by the addition of edetic acid (EDTA) [60-00-4] (97). 

Essential Oils. Volatile oils from plants are referred to as essential oils. The oils can be obtained through steam distillation, solvent extraction, or separation of the oils from pressed fmit. They consist of oxygenated compounds, terpenes, and sesquiterpenes. The primary flavor components of essential oils are oxygenated compounds. Terpenes contain some flavors but are often removed from the essential oil because they are easily oxidized (causiag off-flavors or odors) and are iasoluble. Essential oils are prepared from fmits, herbs, roots, and spices. 

Hypochlorite readily chlorinates phenols to mono-, di-, and tri-substituted compounds (163). In wastewater treatment chlotophenols ate degraded by excess hypochlorite to eliminate off-flavor (164). Hypochlorite converts btomoben2ene to cb1oroben2ene in a biphasic system at pH 7.5—9 using phase-transfer catalysts (165). 

Seafood. Citric acid is used in combination with other preservatives/antioxidants to lower the pH to retard microbial growth, which can lead to spoilage, formation of off-flavors, and colors on fish and other seafood products. 

Proposed IDE standards for caseiaate are hsted ia Table 4. la most cases the sodium salt is preferred for emulsificatioa the calcium salt is preferred for imitation cheese. Caseia and caseiaates must be stored carefliUy and evaluated for flavor before use ia products. Improperly manufactured or stored caseia—caseiaate has a very stroag, musty off-flavor. Excessive fat coateat, high lactose and moisture contents, and high storage temperatures contribute to undesirable flavor development. 

Isolated soy proteins have also been used in whipped toppings. Soy-protein-based toppings have a lower protein concentration than caseinate-based toppings. Formulations ate adjusted to protein levels, and higher protein levels can result in off-flavors. Typical formulations for a Hquid frozen, prewhipped product are given in Table 18. 

M. Orfanopoulos, iu G. Charalambous, ed., "Flavors and Off-Flavors," Proceedings of the International Flavor Conference, July, 1989, Elsevier Science Pubhshers B.V., Amsterdam, The Nethedands, 1989, pp. 865—872. 

Dried Whole Egg and Yolk. Dried plain whole egg and yolk products are either dried as is, or have the glucose removed to improve stabiHty and shelf life of the product. Glucose is removed before drying by use of glucose oxidase or by yeast fermentation (see Yeasts). Bacterial fermentation is not used because of off-flavor and off-odor development. 

Consumer acceptance of milk is strongly determined by its sensory characteristics. The development of off-flavor in milk as a result of lipolysis can reduce the quality of milk. The enzymatic release, by milk lipase, of free fatty acids (FFA) from triglycerides causes a flavor defect in milk described as rancid . Triglycerides in milk contain both long chain and short chain fatty acids, which are released at random by milk lipase. The short chains FFA, like butyric acid, are responsible for the off-flavor. 

In the Netherlands, milk from every farmer is tested twice a year for the extent of lipolysis, using the BDI method. However, the BDI method only detects long chain FFA, which does not induce off-flavor. On the other hand, headspace sampling does detect the short chain FFA. The aim of this study is to compare the BDI method to headspace sampling. 

Another factor requiring consideration is the presence or absence of light. Fats will develop off-flavors sooner in the presence of light than in the dark (1). It has also been observed that certain wave lengths of light will cause rancidity to develop in a shorter time than will other wave lengths (8,13). 

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