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18 Dairy Fermented ProductsR.C. ChandanGlobal Technologies, Inc., Minneapolis, Minnesota, USA

18.1 Introduction

Microorganisms employed as starters for productionof cultured dairy foods are divided into two types, basedon the optimum temperature ranges at which they oper-ate (Hutkins, 2006; Stanley, 2003; Vedamuthu, 2013a).The lactic acid bacteria incubated at temperatures above35 C are referred to as thermophilic bacteria and thoseincubated at 2030 C are called mesophilic starters.Yogurt is derived by culturing with thermophilic cultures,which act in symbiosis with each other. In contrast, sourcream or cultured cream is obtained by fermentation withmesophilic lactococci and leuconostocs. Yogurt and sourcream do not involve whey formation and removal fromcurd. A notable exception is Greek yogurt, which hasgained particular attention in recent years (Kilara &Chandan, 2013).Cheese production involves removal of liquid whey,

leading to partial dehydration and concentration of cer-tain milk constituents. Most cheese varieties are producedwith mesophilic cultures, but certain varieties use thermo-philic bacteria. In addition, other microorganisms, likemolds and yeasts, characterize certain cheese varieties.During cheese making, lowering of pH and addition ofsalt confer a preservative effect, resulting in extensionof shelf life as well as safety for consumption. In cheese,the main milk components (proteins, fat, and minerals)are concentrated and protected from rapid deteriorationby spoilage microorganisms. For consumers, cheese pro-vides good nutrition, variety, convenience of use, portabil-ity, food safety, and novelty of flavors and textures.Modern packaging techniques confer evenmore extendedshelf life, allowing the movement of cheese over long dis-tances from the place of manufacture. There are some

400 varieties of cheese consumed throughout the world.The major varieties have distinctive flavor and textureascribed primarily to the use of milk of various domesti-cated animals, discrete microbial cultures, enzymes,and ripening conditions. Their processing proceduresinfluence final chemical composition resulting in distinctfermentation patterns, which in turn develop specificflavors and textures (Chandan & Kapoor, 2011a, 2011b).At the turn of the last century, developments in melting

processes, involving natural cheese of various ages, gavebirth to a line of processed cheese products with con-trolled flavor and texture, and extended shelf life. In addi-tion, various shapes, sizes, configurations, and slicedversions were created to provide varieties with novelapplications. The consumer can use these products asingredients in cooking of several dishes or as a ready-to-eat snack. These products are designed to be consumedas spreads or as slices in sandwiches, and function as a dipor topping on snacks.Various fermented dairy foods may be consumed in

original form or theymay bemixed with fruits, grains, andnuts to yield delicious beverages, snacks, desserts, break-fast foods, or a light lunch. A variety of textures andflavors are generated by selection of lactic acid bacteria.A combination of lactic acid bacteria and their strainsallows an interesting array of products to suit differentoccasions of consumption.This chapter discusses general technical aspects of the

manufacture of fermented dairy products with a focus onyogurt, sour cream, Cheddar, and process cheese. Othercultured milks and cheeses are not considered here inany depth. For more extensive treatment of variousaspects of fermented dairy products including cheese,the reader is referred to several literature resources

Food Processing: Principles and Applications, Second Edition. Edited by Stephanie Clark, Stephanie Jung, and Buddhi Lamsal. 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.

405

(Chandan & Kilara, 2011, 2013; Hill, 2009; Hutkins,2006; Law & Tamime, 2010; Pannell & Schoenfuss,2007; Tamime & Robinson, 2007).

18.2 Consumption trends

Trends in the production and consumption of fermenteddairy foods (e.g. yogurt, sour cream and dips, and naturalcheese) in the US are presented in Table 18.1. Productionand consumption of yogurt, sour cream, and cheese haveregistered significant gains in the time period of19602011. Yogurt production in 2011 was 4272 millionpounds with per capita consumption of 13.7 pounds. Thegrowth of yogurt has been especially remarkable duringthis period. However, compared to Sweden, with percapita consumption of 62.8 pounds, US consumption ismodest (Schultz, 2011). Sour cream production of 1264million pounds with per capita consumption of 4.1pounds has been fairly flat in recent years. Natural cheeseproduction of 10,597 million pounds and per capita con-sumption of 33.5 pounds has shown modest growth.Table 18.2 shows the trends in production and con-

sumption of some cheese varieties in the period20052011. Cheese production and consumption farexceed the production of yogurt and sour cream. The datain the table show that the per capita consumption of nat-ural cheeses has gone up. Process cheese products arederived from natural cheeses and contain water and other

food ingredients. Their consumption is relatively steadycompared to natural cheeses. The most popular individ-ual cheese variety in 2011 was Mozzarella, followed byCheddar cheese. The per capita consumption of all Italianvarieties grew.During 2011, the supermarket sales of natural cheeses

was 2271 million pounds (valued at $11,076 million).Cheddar cheese totaled 834 million pounds (valued at$3889 million), followed by Processed Americancheese (760 million pounds valued at $2583 million)and Mozzarella cheese (475 million pounds valued at$2190 million) (IDFA, 2012).

18.3 Production of starters for fermenteddairy foods

Fermented milk foods with desirable characteristics offlavor, texture, and probiotic profiles can be created byformulating the desired chemical composition of themilk substrate mix, judicious selection of lactic acidbacteria (starter), and fermentation conditions(Chandan, 1982; Chandan & Nauth, 2012; Chandan &Shahani, 1993, 1995). A starter is made up of one ormore strains of food-grade microorganisms. Individualmicroorganisms utilized as a single culture (single or mul-tiple strains), or in combination with other microorgan-isms, exhibit characteristics impacting the technology ofmanufacture of fermented milks.

Table 18.1 Total production and per capita sales of yogurt, sour cream and natural cheese in the US in recent years

Year

Yogurt Sour cream and dips Cheese (natural)

Total production Per capita sales Total production Per capita sales Total production Per capita sales

1960 44 0.2 Not available 0.9 1478 Not available1970 172 0.8 Not available 1.1 2201 11.41980 570 2.5 480 1.8 3984 17.51990 1055 4.2 625 2.5 6059 24.62000 1837 6.5 914 3.2 8258 29.832005 3058 10.3 1309 4.4 9189 31.742006 3301 11.1 1256 4.2 9525 32.62007 3476 11.5 1313 4.4 9777 33.62008 3570 11.8 1274 4.2 9913 33.02009 3832 12.5 1275 4.2 10,074 32.22010 4181 13.5 1270 4.1 10,443 33.12011 4272 13.7 1264 4.1 10,597 33.5

Million pounds. Pounds.Adapted from: IDFA (2012).

406 Food Processing: Principles and Applications

Modern industrial processes utilize defined lacticacid bacteria as starters for fermented dairy products.For detailed descriptions of starter cultures, the readeris referred to Stanley (2003), Hutkins (2006), and Veda-muthu (2013a, 2013b). Table 18.3 summarizes some of

the microorganisms used in the manufacture of yogurtand cultured cream.The most common lactic acid bacteria employed for

fermented dairy foods are: Lactobacillus delbrueckii subsp.bulgaricus, Streptococcus thermophilus, Lactobacillus aci-dophilus, Lactococcus lactis subsp. lactis, and Lactococcuslactis subsp. cremoris. They are responsible for the acidictaste arising from lactic acid elaborated by their growth.Leuconostoc spp. are used for typical flavor in sour cream.In cheeses, Lactococcus lactis subsp. lactis/cremoris,Lactobacillus helveticus, Lactobacillus delbrueckii subsp.bulgaricus, and Streptococcus thermophilus are employedfor acid and distinct flavor development, while Propioni-bacterium shermanii secretes propionate, a natural shelflife extender. Furthermore, it is possible to deliverhealth-promoting microflora to the consumer of the food.In this regard, yogurt cultures, Lactobacillus delbrueckiisubsp. bulgaricus (LB), Streptococcus thermophilus (ST),Lactobacillus acidophilus, Lactobacillus casei, and Bifido-bacterium species are notable examples.The cultures used in themanufacture of natural cheeses

are shown in Table 18.4. The cultures are used to providedistinct flavor and textural attributes to a particular cheesevariety. The metabolic products of culture growth leave adiscrete profile on the sensory properties of cheese. In thisregard, in addition to bacteria, edible molds extendcolor and flavor characteristics, typical of the variety ofthe cheese (blue, Roquefort, stilton, Camembert, Brie,Gorgonzola).Adequate production of lactic acid is essential for low-

ering the pH to a level where critical flavor compounds(acetaldehyde, diacetyl and other compounds) are formedin sufficient quantity. Factors interfering with proper aciddevelopment will retard or prevent adequate flavordevelopment. The culture may be incapable of producingadequate amounts of flavor due to a change in fermenta-tion pattern induced by oxygen tension or due to a changein the balance of various bacterial cultures. In certain

Table 18.3 Cultures used for production of yogurt

and sour cream

Yogurt Cultured/sour cream

Required by FDAregulations

Lactococcus lactis subsp. lactis

Streptococcusthermophilus

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