Flavor of cheese

In cheese making, the casein is separated from the liquid part of the milk — the whey. It is then pressed and stored until ripe. The flavors of cheeses arc caused mostly by esters created during the ripening. 

After the curd and whey are physically separated and the optimum pH level is reached, the curd is salted. Salt improves the flavor of cheese, retards microbial metabolism, and helps expel moisture from the curd. Salt is either added directly to the curd (Cheddar, Colby) or the preformed block of cheese is placed in a brine solution (almost all other cheese types). 

Lactones and methyl ketones contribute to the overall flavor of cheese. Their analysis normally requires solvent extraction, distillation, and derivatization. Various extraction procedures have been developed for the analysis of lactones by GC (Wong et ah, 1975). Methyl ketones have been analyzed by paper chromatography (Morgan and Anderson, 1956), spectrophotometry (Godinho and Fox, 1981), and gas chromatography (Keen and Walker, 1974 Manning, 1978). 

Marilley, L. and Casey, M. G. (2004). Flavors of cheese products Metabolic pathways, analytical tools and identification of producing strains. Int. J. Food Microbiol. 90,139-159. 

Lactones are cyclic compounds formed through the intramolecular esterification of a hydroxy fatty acid. 7-Lactones and 8-lactones, with fivesided and six-sided rings, respectively have been found in cheese (Jolly and Kosikowski, 1975 Wong et al., 1975 Collins et al., 2004). The origin of the precursor hydroxy fatty acids has been ascribed to a 8-oxidation system in the mammary gland of ruminants (see Fox et al., 2000), the reduction of keto acids (Wong et al., 1975) and/or the action of lipoxygenases and other enzymes present in members of the rumen microflora (Dufosse et al., 1994). Lactones have low flavor thresholds and while their aromas are not specifically cheese-like (their aromas have been described variously as peach, apricot and coconut ), they may contribute to the overall flavor of cheese (see Collins et al., 2004). 

Because of the high total flavor of cheese, the threshold levels of FFAs are higher than for milk or butter. In Cheddar cheese, ADVs of 2.8 3.0 meq/ 100 g fat are usually attained before rancidity is evident (Deeth and FitzGerald, 1975b). Various studies have shown that rancid Cheddar has 2 10 times more FFAs than good quality cheese (Bills and Day, 1964 Ohren and Tuckey, 1969 Law et al., 1976). 

Milk fat contains a number of different lipids, but is predominately made up of triacylglycerols (TAG) (98%). The remaining lipids are diacylglycerols (DAG), monoacylglycerols (MAG), phospholipids, free fatty acids (FFA) and sterols. Milk fat contains over 250 different fatty acids, but 15 of these make up approximately 95% of the total (Banks, 1991) the most important are shown in Table 19.1. The unique aspect of bovine, ovine and caprine milk fat, in comparison to vegetable oils, is the presence of high levels of short-chain volatile FFAs (SCFFA), which have a major impact on the flavor/aroma of dairy products. Most cheeses are produced from either bovine, ovine or caprine milk and the differences of their FFA profile are responsible for the characteristic flavor of cheeses produced from such milks (Ha and Lindsay, 1991). 

Although it is not possible to describe the flavor of cheese in precise chemical terms, very considerable progress has been made on the identification of flavor compounds in cheese and elucidation of the biochemical pathways by which these compounds are produced. It is generally recognized that the aroma of cheese is primarily in the volatile fraction while taste is largely in the aqueous phase until recently, most researchers focussed on the volatile fraction. Intervarietal comparisons should be a valuable approach toward identifying key flavor compounds. Although several such studies on the volatile compounds have been reported, there have been relatively few comparative studies on the aqueous phase. 

Specific flavor defects are frequently encountered in cheese. While the desirable flavor of cheese has been difficult to define precisely in chemical terms, the specific cause(s) of many defects has been established more or less definitively. The principal flavor defects in cheese are described below. 

In spite of extensive and intensive research over the last 40 years, the flavor of cheese remains elusive. While very considerable qualitative and quantitative information is available on the aromatic and flavorful compounds in many cheese varieties is now available, it is not yet possible to fully define cheese flavor in chemical terms. Extensive comparative studies of the volatile and nonvolatile low molecular weight compounds, both of cheeses of different quality characteristics of the same variety and between varieties should be useful. Numerous studies on cheese flavor have been published but the number and diversity of cheese, both with respect to the range of quality attributes and cheese types analyzed in such studies, have been rather limited. Although expensive, such a large-scale study appears... 

Traditionally fermented dairy products have been used as beverages, meal components, and ingredients for many new products [60], The formation of flavor in fermented dairy products is a result of reactions of milk components lactose, fat, and casein. Particularly, the enzymatic degradation of proteins leads to the formation of key-flavor components that contribute to the sensory perception of the products [55], Methyl ketones are responsible for the fruity, musty, and blue cheese flavors of cheese and other dairy products. Aromatic amino acids, branched-chain amino acids, and methionine are the most relevant substrates for cheese flavor development [55]. Volatile sulfur compounds derived from methionine, such as methanethiol, dimethylsulflde, and dimethyltrisul-fide, are regarded as essential components in many cheese varieties [61], Conversion of tryptophan or phenylalanine can also lead to benzaldehyde formation. This compound, which is found in various hard- and soft-type cheeses, contributes positively to the overall flavor [57,62]. The conversion of caseins is undoubtedly the most important biochemical pathway for flavor formation in several cheese types [62,63]. A good balance between proteolysis and peptidolysis prevents the formation of bitterness in cheese [64,65],... 

The taste and flavor of cheeses depend on microorganisms playing a major role in ripening. From the high-quality Soviet cheese and from cheese milk 25 strains of propionic acid bacteria were isolated (Alekseeva et al., 1973a), of which 17 strains represented P. freudenreichii, and the others were P. acidipropionici and P. Jensenii thus the principal strain of Soviet cheese is P. freudenreichii. In addition, propionic acid cocci were also isolated at an early stage of cheese ripening (see Section 1.2.2). 

Carbonyls are quite important to the flavor of cheeses. The TNO-CIVO compilation of volatiles in foods lists 29 carbonyls as having been identified in Cheddar cheese at that time. Carbonyls (methyl ketones) may arise in fermented prodncts iiutiaUy via lipase activity of the starter cnlture. Dairy products contain a significant quantity of a-keto acids which are readily hydrolyzed from the triglyceride by microbial lipases and then decarboxylated to form odd carbon nnmber methyl ketones. 

Basil (Sweet Basil). Basil consists of the brown, dried leaves and tender stems of Ocimum basilicum L. (Labiatae), an aimual native to India, Africa, and Asia, and cultivated in Egypt, southern Erance, Morocco, the Mediteranean countries, and the United States. Basil is one of the oldest known herbs, and it is reported that there are perhaps 50—60 poorly defined Ocimum species which can only be identified according to their chemical components. The flavor of the basihcum type is warm, sweet, somewhat pungent, and pecuhar, ie, methyl chavicol and linalool. It is used with meats, fish, certain cheeses, and tomato-based salads. The fresh leaves are ground and known as pesto with pastas. It is the main component of the Hqueur Chartreuse. 

Soybean-based ice cream products, technologically feasible, are generally not in use because of flavor problems. An acceptable ice cream has been made by replacing 50% of the nonfat milk soHds with a dried soy protein isolate made up of cheese whey (21). Chocolate flavor has been widely used to mask the flavor of soybean proteins in ice cream (see Flavors and spices). 

Free glutamates exist in certain cheeses (such as parmesan), in tomato products, and in soy sauce. These products are often used to enhance the flavor of meat dishes. Proteins can be hydrolyzed by heat, releasing free glutamates. Cooked meats, especially grilled meats, get some of their taste from free glutamates. 

In addition to producing fertilizers, phosphoric acid is used to add the familiar tart flavor to carbonated sodas, beer, some jellies and jams, and some types of cheese. Because it dissolves iron... 

Since antiquity, animal milks have been converted by empirical processes to a wide variety of cheeses. With the development of microbiology as a scientific discipline, the critical role of microorganisms - bacteria, fungi, yeasts - in cheese began to be understood. Today, more than 650 cheese types are recognized and the flavor(s) of cheese has (have) now been investigated for more than a century.33 Typically, the situation is complex and the literature is enormous. For instance, more than 200 volatiles occur in Cheddar cheese. In a listing of 58 of these volatiles, 7 are sulfur compounds dimethyl sulfide (DMS),... 

Drying chamber shape predominantly is either conical or flat-bottomed. The flat-bottomed dryers remove the powder as it falls to the floor of the dryer by use of a rotating pneumatic powder discharger that functions as a vacuum cleaner. These dryers subject the product to significantly more heat than do the cone-bottomed dryers. While for many types of dry flavorings this additional heat is insignificant, thermally labile materials (e.g., natural flavorings - tomato, cheese, and numerous fruit juice based products) may suffer from the additional heat. 

Exploration of this method for controlled release of enzymes to produce flavors of importance in cheese ripening has been pioneered by Kirby and Law (1986), and was recently the subject... 

The development of a rancid flavor in milk and some other fluid products is usually undesirable and detracts from their market value. In contrast, the popularity of certain dairy products, notably some varieties of cheese, as well as some confectionery items containing milk as an ingredient, is thought to be partially due to the proper intensity of the rancid flavor. Hence, knowledge of the factors involved in the development of rancidity is of great practical importance to several industries. 

Lawrence et al. (1984) suggested that all types of cheese can be best classified by their calcium content and pH. According to this classification scheme, the extent of acid production at various stages of cheese manufacture ultimately influences the body and texture of cheese. Cheeses can, therefore, be classified by manufacturing procedure rather than by flavor. 

The use of homogenized milk for cheesemaking has been reviewed by Peters (1964). The advantages of homogenized milk in the manufacture and ripening of cheese are (1) lower fat losses in whey and therefore a higher yield, (2) reduced fat leakage of cheese at room temperatures, and (3) increased rate of fat hydrolysis and, therefore, desired flavor production in blue cheese. 

The activity of rennet in some maturing cheese is essential for normal cheese ripening. The practice of using less rennet in making cheese with concentrated milk has shown that the cheese does not develop characteristic sharp flavors (Chapman et al. 1974). The role of rennet in flavor development of cheese is to produce peptides that are degraded subsequently by the bacterial flora of the cheese. 

Amino acids are generally not considered to be important flavor components of several varieties of cheese, although they are important precursors of a variety of flavor components volatile sulfur compounds, amines, aldehydes, and ammonia (Adda et al. 1982 Aston and Dulley 1982 Forss 1979 Langsrud and Reinbold 1973). Free proline levels in Swiss cheese are important in producing the typical sweet cheese flavor. Cheeses with a proline content of < 100 mg/100 g cheese lacked the sweet flavor, while levels of >300 mg/100 g produced a cheese of excessive sweetness (Mitchell 1981). 

Excessive or insufficient acid development during manufacture can produce variability in the moisture content of cheese and defects in flavor, body, texture, color, and finish (Van Slyke and Price 1952). The rate of lactose fermentation varies with the type of cheese, but the conversion to lactic acid is virtually complete during the first weeks of aging (Van Slyke and Price 1952 Turner and Thomas 1980). Very small amounts of lactose and galactose may be found in cheese months after manufacture. (Huffman and Kristoffersen 1984 Turner and Thomas 1980 Harvey et al. 1981 Thomas and Pearce 1981). Turner and Thomas (1980) showed that the fermentation of residual lactose in Cheddar cheese is affected by the storage temperature, the salt level in the cheese and the salt tolerance of the starter used. 

Green, M. L. and Manning, D. J. 1982. Development of texture and flavor in cheese and other fermented products. J. Dairy Res. 49, 737-748. 

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