**2. Lactic acid bacteria in dairy processing**

Milk is a highly perishable food raw material, therefore, its transformation in cheese or other form of fermented dairy product, provides an ideal vehicle to preserve its valuable nutrients (Table 1), making them available throughout the year. It is known that while unprocessed milk can be stored for only a few hours at room temperatures, cheeses may reach a shelf-live up to 5 years (depending on variety).

© 2013 Kongo, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Lactic Acid Bacteria as Starter-Cultures for Cheese Processing:

The starter-culture applied in this, so-called, natural fermentation, is usually a poorlyknown microflora mix that although having a predominance of LAB, may also contain non-LAB microorganisms, and its microbial diversity and load is usually variable over time. In fact, studies directed to characterize traditional cheeses show that those made from raw milk harbor a diversity of LAB (Bernardeau et al., 2008) depending on geographical region, where a few may show particular interesting technological features that upon optimization may have industrial applications (Buckenhiiskes, 1993). For example, because wild strains need to withstand the competition of other microorganisms to survive in their hostile natural environment, they often produce antimicrobials substances called bacteriocins (Ayad et al., 2002), which are natural antibacterial proteins that can be incorporated directly into fermented foods as such (food–grade) or indirectly as starter culture (Bernardeau et al., 2008). Although nisin is today the only bacteriocin that reached commercial status, approved worldwide as a natural food preservative, many other bacteriocins may soon reach similar status. Recently, our work (to be published) with LAB isolates from traditional portuguese raw-milk cheeses, revealed several lactobacilli having antibacterial activity against pathogens such as *Listeria monocytogenes, Staphyloccus aureus*, *Salmonella newport* and even *E.coli*. Future studies may allow us using these isolates or their metabolites, applied *in* 

Moreover, traditional cheeses also obtain their flavor intensity also from the non-starter lactic acid bacteria (NSLAB), which are not part of the normal starter flora but develop in the product, particularly during maturation, as a secondary flora (Beresford, et al., 2001). The isolation and optimization of wild-type strains from traditional products, to be used as starter cultures in cheese processing, is indeed a highly active field of research in Food

Cheese is made in almost every country of the world and there are more than 2000 varieties, made from milk of several mammals, processed industrially or by traditional methods

However, despite the large number of varieties, the basic steps required in any cheese processing are essentially the same, and slight variations in any of these steps may result in

**Milk treatment**. In large-scale cheese processing, the milk is heat-treated, e.g. 73 ºC for 15 seconds, to destroy pathogens and reduce microbial numbers, while in most traditional PDO raw-milk cheeses heat treatment is not applied. Also the milk may be standardized, i.e. the fat content may be increased or reduced, or the casein-to-fat ratio may be adjusted.

**Starter-culture addition**. The type of commercially available starter preparation to be used will be determined by the cheese recipe. As previously stated, large-scale processing relies on using defined, commercially available starters, while for traditional cheeses, a natural

*situ or ex situ* fashion, in applications where food safety is a concern.

**2.2. LAB food safety and cheese technology** 

products of different general quality (Figure 2).

fermentation (whey from the previous lot) is often used.

Science today.

(Figure 1).

Past, Present and Future Developments 5

Note: In cheese, these nutrients will appear at a concentration approximately ten times higher, while the water content decreases.

**Table 1.** Approximate composition of milk from various species of mammals

Fermentation with lactic acid bacteria (LAB) is a cheap and effective food preservation method that can be applied even in more rural/remote places, and leads to improvement in texture, flavor and nutritional value of many food products. LAB have a long and safe history of application and consumption namely in cheese processing (Aquilanti et al., 2006, Caplice & Fitzgerald, 1999, Giraffa et al., 2010, Ray, 1992; Wood, 1997; Wood & Holzapfel, 1995) thus being generally regarded as safe (GRAS). Increasing knowledge of LAB physiology, together with new developments in processing technology, is leading to their application beyond traditional starter culture application, namely in new food safety roles and direct health applications.

### **2.1. LAB as starter-cultures in cheese processing**

Cheese-making is based on application of LAB in the form of defined or undefined starter cultures that are expected to cause a rapid acidification of milk through the production of lactic acid, with the consequent decrease in pH, thus affecting a number of aspects of the cheese manufacturing process and ultimately cheese composition and quality (Briggiler-Marco et al., 2007).

The earliest productions of cheeses were based on the spontaneous fermentation, resulting from the development of the microflora naturally present in the raw milk and its environment. The quality of the end product was a reflex of the microbial load and spectrum of the raw material. Spontaneous fermentation was later optimized through backslopping, i.e., inoculation of the raw material with a small quantity of whey from a previously performed successful fermentation, and the resulting product characteristics depended on the best-adapted strains dominance (Leroy & De Vuyest, 2004). Today, backslopping is still used to produce many artisanal raw-milk cheeses, namely those bearing the PDO (Protected Designation of Origin) status, which are considered to be an important source of LAB genetic diversity, as well as being crucial from an economic and even ecologic point of view, since production of said cheeses (usually processed on a small-scale) contributes to local employment and maintains people functioning as "guardians of local environment" in regions that otherwise would be deserted.

The starter-culture applied in this, so-called, natural fermentation, is usually a poorlyknown microflora mix that although having a predominance of LAB, may also contain non-LAB microorganisms, and its microbial diversity and load is usually variable over time. In fact, studies directed to characterize traditional cheeses show that those made from raw milk harbor a diversity of LAB (Bernardeau et al., 2008) depending on geographical region, where a few may show particular interesting technological features that upon optimization may have industrial applications (Buckenhiiskes, 1993). For example, because wild strains need to withstand the competition of other microorganisms to survive in their hostile natural environment, they often produce antimicrobials substances called bacteriocins (Ayad et al., 2002), which are natural antibacterial proteins that can be incorporated directly into fermented foods as such (food–grade) or indirectly as starter culture (Bernardeau et al., 2008). Although nisin is today the only bacteriocin that reached commercial status, approved worldwide as a natural food preservative, many other bacteriocins may soon reach similar status. Recently, our work (to be published) with LAB isolates from traditional portuguese raw-milk cheeses, revealed several lactobacilli having antibacterial activity against pathogens such as *Listeria monocytogenes, Staphyloccus aureus*, *Salmonella newport* and even *E.coli*. Future studies may allow us using these isolates or their metabolites, applied *in situ or ex situ* fashion, in applications where food safety is a concern.

Moreover, traditional cheeses also obtain their flavor intensity also from the non-starter lactic acid bacteria (NSLAB), which are not part of the normal starter flora but develop in the product, particularly during maturation, as a secondary flora (Beresford, et al., 2001). The isolation and optimization of wild-type strains from traditional products, to be used as starter cultures in cheese processing, is indeed a highly active field of research in Food Science today.

### **2.2. LAB food safety and cheese technology**

4 Lactic Acid Bacteria – R & D for Food, Health and Livestock Purposes

3.0 3.3 4.6 3.5 3.8

**Table 1.** Approximate composition of milk from various species of mammals

3.75 6.0 9.0 3.0 6.0

and direct health applications.

Marco et al., 2007).

**2.1. LAB as starter-cultures in cheese processing** 

environment" in regions that otherwise would be deserted.

Fat Casein Lactose Albumin Ash Water %

> 0.4 0.7 1.1 1.7 0.7

0.75 0.84 1.0 1.5 0.75 87.3 84.5 79.6 84.8 85

4.75 4.6 4.7 5.5 4.5

Note: In cheese, these nutrients will appear at a concentration approximately ten times higher, while the water content

Fermentation with lactic acid bacteria (LAB) is a cheap and effective food preservation method that can be applied even in more rural/remote places, and leads to improvement in texture, flavor and nutritional value of many food products. LAB have a long and safe history of application and consumption namely in cheese processing (Aquilanti et al., 2006, Caplice & Fitzgerald, 1999, Giraffa et al., 2010, Ray, 1992; Wood, 1997; Wood & Holzapfel, 1995) thus being generally regarded as safe (GRAS). Increasing knowledge of LAB physiology, together with new developments in processing technology, is leading to their application beyond traditional starter culture application, namely in new food safety roles

Cheese-making is based on application of LAB in the form of defined or undefined starter cultures that are expected to cause a rapid acidification of milk through the production of lactic acid, with the consequent decrease in pH, thus affecting a number of aspects of the cheese manufacturing process and ultimately cheese composition and quality (Briggiler-

The earliest productions of cheeses were based on the spontaneous fermentation, resulting from the development of the microflora naturally present in the raw milk and its environment. The quality of the end product was a reflex of the microbial load and spectrum of the raw material. Spontaneous fermentation was later optimized through backslopping, i.e., inoculation of the raw material with a small quantity of whey from a previously performed successful fermentation, and the resulting product characteristics depended on the best-adapted strains dominance (Leroy & De Vuyest, 2004). Today, backslopping is still used to produce many artisanal raw-milk cheeses, namely those bearing the PDO (Protected Designation of Origin) status, which are considered to be an important source of LAB genetic diversity, as well as being crucial from an economic and even ecologic point of view, since production of said cheeses (usually processed on a small-scale) contributes to local employment and maintains people functioning as "guardians of local

Animal

Cow Goat Ewe Camel Buffalo

decreases.

Cheese is made in almost every country of the world and there are more than 2000 varieties, made from milk of several mammals, processed industrially or by traditional methods (Figure 1).

However, despite the large number of varieties, the basic steps required in any cheese processing are essentially the same, and slight variations in any of these steps may result in products of different general quality (Figure 2).

**Milk treatment**. In large-scale cheese processing, the milk is heat-treated, e.g. 73 ºC for 15 seconds, to destroy pathogens and reduce microbial numbers, while in most traditional PDO raw-milk cheeses heat treatment is not applied. Also the milk may be standardized, i.e. the fat content may be increased or reduced, or the casein-to-fat ratio may be adjusted.

**Starter-culture addition**. The type of commercially available starter preparation to be used will be determined by the cheese recipe. As previously stated, large-scale processing relies on using defined, commercially available starters, while for traditional cheeses, a natural fermentation (whey from the previous lot) is often used.

Lactic Acid Bacteria as Starter-Cultures for Cheese Processing:

**Figure 2.** Common steps to most cheese making processes

for many unwanted bacteria, thus increasing the end product safety.

body (firmness) and texture of the cheese.

curd and to increase its safety and shelf life.

to mat together.

to maintain the curd in the form of separate particles.

**Coagulation**. During coagulation, modifications on the milk protein complex occur under defined conditions of temperature and by action of a coagulant agent, which changes the physical aspect of milk from liquid to a jelly-like mass. Various coagulants are available, e.g. lemon juice, plant rennet or more commonly a proteolytic enzyme such as chymosin (rennin) or – due to high demand from the cheese industry - proteolytic enzymes from the mould *Rhizomucor miehei* obtained via biotechnology*.* These enzymes have an acidic nature, meaning they have optimum activity in a slightly acidic environment. Therefore, the action of LAB in this phase is crucial as they are required to rapidly release enough lactic acid, to lower the milk pH from 6.7 to near 6.2, (thus creating an appropriate environment for optimum activity of rennin) and later to pH 4.5 as the processing proceeds, creating an inhospitable environment

Ripening

Milk treatment

Coagulation

Whey draining

Salting/Pressing

**Cutting the coagulum**. The resulting coagulum may be cut with appropriate knives into curd particles of a defined size, e.g. 1–2 cm, or it may be transferred into containers or cheese moulds. The cutting or ladling of the coagulum is a very important step in the manufacture of some cheese varieties as it determines the rate of acid development and the

**Heating or cooking the curds**. Heating (37–45 ºC, depending on the type of cheese) the curds and whey affects the rate at which whey is expelled from the curd particles and the growth of the starter microorganisms. During heating, the curds and whey are often stirred

**Whey removal**. After heating and stirring, and when the curd particles have firmed and the correct acid development have taken place, the whey is removed allowing the curd particles

**Milling the curd**. In cheeses such as Cheddar, when the curd has reached the desired texture, it is broken up into small pieces to enable it to be salted evenly. Milling the curd can be done either by hand or mechanically. Salting is usually done to enhance the taste of the

Past, Present and Future Developments 7

**Figure 1.** (Top) - Brine salting of cheeses in a large-scale plant processing 20 tons of cheese a day. (Bottom) - Small-scale unit processing 50 Kg per day of a traditional PDO cheese

Lactic Acid Bacteria as Starter-Cultures for Cheese Processing: Past, Present and Future Developments 7

**Figure 2.** Common steps to most cheese making processes

6 Lactic Acid Bacteria – R & D for Food, Health and Livestock Purposes

**Figure 1.** (Top) - Brine salting of cheeses in a large-scale plant processing 20 tons of cheese a day.

(Bottom) - Small-scale unit processing 50 Kg per day of a traditional PDO cheese

**Coagulation**. During coagulation, modifications on the milk protein complex occur under defined conditions of temperature and by action of a coagulant agent, which changes the physical aspect of milk from liquid to a jelly-like mass. Various coagulants are available, e.g. lemon juice, plant rennet or more commonly a proteolytic enzyme such as chymosin (rennin) or – due to high demand from the cheese industry - proteolytic enzymes from the mould *Rhizomucor miehei* obtained via biotechnology*.* These enzymes have an acidic nature, meaning they have optimum activity in a slightly acidic environment. Therefore, the action of LAB in this phase is crucial as they are required to rapidly release enough lactic acid, to lower the milk pH from 6.7 to near 6.2, (thus creating an appropriate environment for optimum activity of rennin) and later to pH 4.5 as the processing proceeds, creating an inhospitable environment for many unwanted bacteria, thus increasing the end product safety.

**Cutting the coagulum**. The resulting coagulum may be cut with appropriate knives into curd particles of a defined size, e.g. 1–2 cm, or it may be transferred into containers or cheese moulds. The cutting or ladling of the coagulum is a very important step in the manufacture of some cheese varieties as it determines the rate of acid development and the body (firmness) and texture of the cheese.

**Heating or cooking the curds**. Heating (37–45 ºC, depending on the type of cheese) the curds and whey affects the rate at which whey is expelled from the curd particles and the growth of the starter microorganisms. During heating, the curds and whey are often stirred to maintain the curd in the form of separate particles.

**Whey removal**. After heating and stirring, and when the curd particles have firmed and the correct acid development have taken place, the whey is removed allowing the curd particles to mat together.

**Milling the curd**. In cheeses such as Cheddar, when the curd has reached the desired texture, it is broken up into small pieces to enable it to be salted evenly. Milling the curd can be done either by hand or mechanically. Salting is usually done to enhance the taste of the curd and to increase its safety and shelf life.

**Ripening.** Finally, for most cheeses, the resulting mass is molded and put to ripening for periods that may vary from 15 days to one, two or more years. Ripening is a slow phase, crucial for the development of aroma and flavor, brought about by the action of the many enzymes released by LAB. During ripening the protein in cheese is broken down from casein to low molecular weight peptides and amino acids. Proteolysis is the major – and certainly the most complex of biochemical events that take place during ripening of most cheese varieties and LAB play an important role in it. This happens while the cheeses are stored in the curing cabinets and in some cases in caves, usually with temperature and humidity controlled (Figure 3).

Lactic Acid Bacteria as Starter-Cultures for Cheese Processing:

During coagulation, the initial step of casein hydrolysis is performed by chymosin (milk coagulant) and proteinases from starter lactic acid bacteria, starter moulds and other microorganisms. The further degradation of high molecular weight peptides produced at the initial step, is subsequently catalised to low molecular weight peptides by

**Figure 4.** Simplified view of the biochemical changes that lead to texture and flavour changes in cheeses.

**Figure 5.** General pathways leading to intracellular meatabolites, and their degradation routes to potential flavour compounds. More specifically, pathways from methionine to flavour compounds (methanethiol, thioesters, sulphur compounds) are shown (Adapted from Kranemburg et al., 2002).

Primary proteolysis in cheese is defined as changes in β-, γ-, s-caseinpeptides, and other minor proteins that are detected by PAGE (Figure 6). Primary proteolysis leads to the

endopeptidases from LAB during ripening (see Fig. 4 and 5).

Past, Present and Future Developments 9

**Figure 3.** Cheese ripening in cabinets with controlled temperature and humidity.

During coagulation, the initial step of casein hydrolysis is performed by chymosin (milk coagulant) and proteinases from starter lactic acid bacteria, starter moulds and other microorganisms. The further degradation of high molecular weight peptides produced at the initial step, is subsequently catalised to low molecular weight peptides by endopeptidases from LAB during ripening (see Fig. 4 and 5).

8 Lactic Acid Bacteria – R & D for Food, Health and Livestock Purposes

humidity controlled (Figure 3).

**Ripening.** Finally, for most cheeses, the resulting mass is molded and put to ripening for periods that may vary from 15 days to one, two or more years. Ripening is a slow phase, crucial for the development of aroma and flavor, brought about by the action of the many enzymes released by LAB. During ripening the protein in cheese is broken down from casein to low molecular weight peptides and amino acids. Proteolysis is the major – and certainly the most complex of biochemical events that take place during ripening of most cheese varieties and LAB play an important role in it. This happens while the cheeses are stored in the curing cabinets and in some cases in caves, usually with temperature and

**Figure 3.** Cheese ripening in cabinets with controlled temperature and humidity.

**Figure 4.** Simplified view of the biochemical changes that lead to texture and flavour changes in cheeses.

**Figure 5.** General pathways leading to intracellular meatabolites, and their degradation routes to potential flavour compounds. More specifically, pathways from methionine to flavour compounds (methanethiol, thioesters, sulphur compounds) are shown (Adapted from Kranemburg et al., 2002).

Primary proteolysis in cheese is defined as changes in β-, γ-, s-caseinpeptides, and other minor proteins that are detected by PAGE (Figure 6). Primary proteolysis leads to the

formation of large water-insoluble peptides and smaller water-soluble peptides (Fox, 1993, Mooney *et al.,* 1998). Secondary proteolysis products include those peptides, proteins and amino acids soluble in the aqueous phase of cheese and are extractable as the water-soluble nitrogen (WSN) fraction. The WSN fraction is a complex mixture of large, medium, and small peptides and amino acids. These components result from the action of milk clotting enzymes, milk proteases, starter LAB and contaminating microorganisms (Rank *et al*., 1985).

Lactic Acid Bacteria as Starter-Cultures for Cheese Processing:

**Figure 7.** Evolution of pH (average standard deviation) in experimental cheese made with a starter

**Figure 8.** Evolution of physicochemical parameters (average ± standard deviation) throughout ripening

culture of authoctonous São Jorge cheese LAB isolates.

of cheeses made with an experimental starter culture.

Past, Present and Future Developments 11

**Figure 6.** Evolution of proteolysis via urea-polyacrylamide gel electrophoresis in São Jorge cheeses from dairies A and B, by 1, 15, 30, 60, 90 or 130 days of ripening. Lanes 1, 8 and 15, Na- caseinate; lanes 2-6: cheese A; lanes 9-14: cheese B (Kongo et al., 2012).

Typical cheese pH values measured at 3–7 days after manufacture are 4.9–5.5 in most firm and hard ripened varieties, and 4.4–4.8 in fresh lactic and most soft ripened varieties (Table 2 and Figures 7 and 8).


**Table 2.** Typical pH *vs* time profiles for several cheese varieties (time is in minutes unless otherwise noted).

Lactic Acid Bacteria as Starter-Cultures for Cheese Processing: Past, Present and Future Developments 11

10 Lactic Acid Bacteria – R & D for Food, Health and Livestock Purposes

2-6: cheese A; lanes 9-14: cheese B (Kongo et al., 2012).

Swiss type

2 and Figures 7 and 8).

Operations

noted).

formation of large water-insoluble peptides and smaller water-soluble peptides (Fox, 1993, Mooney *et al.,* 1998). Secondary proteolysis products include those peptides, proteins and amino acids soluble in the aqueous phase of cheese and are extractable as the water-soluble nitrogen (WSN) fraction. The WSN fraction is a complex mixture of large, medium, and small peptides and amino acids. These components result from the action of milk clotting enzymes, milk proteases, starter LAB and contaminating microorganisms (Rank *et al*., 1985).

**Figure 6.** Evolution of proteolysis via urea-polyacrylamide gel electrophoresis in São Jorge cheeses from dairies A and B, by 1, 15, 30, 60, 90 or 130 days of ripening. Lanes 1, 8 and 15, Na- caseinate; lanes

Typical cheese pH values measured at 3–7 days after manufacture are 4.9–5.5 in most firm and hard ripened varieties, and 4.4–4.8 in fresh lactic and most soft ripened varieties (Table

Add starter 0 6.60 0 6.60 0 6.60 0 6.60 0 6.60 Add rennet 15 6.60 35 6.55 30 6.55 75 6.50 60 6.50 Cut 45 6.55 70 6.50 75 6.50 115 6.4 300 4.80 Drain or dip into forms 150 6.35 100 6.45 195 6.3 130 NA 360 5.0 Milling NA NA NA NA 315 5.45 NA NA NA NA Pressing 165 6.35 130 390 5.40 NA NA NA NA Demoulding 16 h 5.30 8 h 5.40 10 h 5.20 24 h 4.6 NA NA Minimum pH 1 wk 5.20 1 wk 5.20 1 wk 5.10 1 wk 4.4 NA NA Retail 6 mo 5.6 6 mo 5.6 4 mo 5.3 6 wk 4.4 2–14 d 5.2 **Table 2.** Typical pH *vs* time profiles for several cheese varieties (time is in minutes unless otherwise

Gouda Cheddar Feta Cottage

Time pH Time pH Time pH Time pH Time pH

**Figure 7.** Evolution of pH (average standard deviation) in experimental cheese made with a starter culture of authoctonous São Jorge cheese LAB isolates.

**Figure 8.** Evolution of physicochemical parameters (average ± standard deviation) throughout ripening of cheeses made with an experimental starter culture.

During processing, the pH history of the cheese is a good indicator of the actual product safety. For example a 'slow vat' allows more time at high pH for undesirable bacteria to grow, while during cheese ripening, unwanted bacteria may grow due to an acidity neutralization resulting from secondary microflora growth such as moulds. For most ripened varieties the combination of a low pH and ripening time, which leads to moisture decrease in the cheese, will in general cause a gradual decline of all groups of bacteria due to increasing inhospitable conditions inside the cheese.

Lactic Acid Bacteria as Starter-Cultures for Cheese Processing:

cheeses and cultured milk products. In traditional cheeses the natural starter cultures may

On the other hand, cheeses manufactured in a standard (large-scale) processing manner, are considered as safer because of the application of pasteurization and following the standard hygienic practices, including the HACCP. Traditional cheeses have their own specific processing methods, namely the common use of raw milk, however the hygienic procedures

> Mesophilic starter used for many cheese types. Used in Gouda, Edam, sour cream and lactic butter. Mesophilic starter used for many cheese types.

Thermophilic starter used for yogurt and many cheese types

particularly hard and semi hard high-cook cheeses.

Used in fermented milks and high-cook cheese.

particularly hard and semi hard high-cook cheeses

Limburger and as a cheese ripening adjunct culture.

Used in Gruyère and Emmental cheeses. Used in Gruyère and Emmental cheeses.

**Table 3.** Main bacteria associated with cheeses or other fermented products (From: Broome et al., 2003).

Mesophilic culture used for Edam, Gouda, fresh cheese, lactic

Used in smear surface-ripened cheeses, Camembert, Stilton and

*Lb. helveticus* Thermophilic starter for fermented milks and many cheese types

Thermophilic starter for yogurt. and many cheese types, particularly hard and semi hard high-cook cheeses.

and HACCP approaches adapted to their specificities should be applied as well.

**Main uses / Other comments**

*Lb. acidophilus* Probiotic adjunct culture used in cheese and yogurt.

*Lb. casei* Cheese ripening adjunct culture. *Lb. plantarum* Cheese ripening adjunct culture. *Lb. rhamnosus* Cheese ripening adjunct culture.

butter and sour cream.

harbor many different species and strains.

**Species / subspecies** 

**Lactococcus** *Lc. lactis* subsp.

*Lc. lactis* subsp. *lactis* biovar diacetylactis *Lc. lactis* subsp.

*Streptococcus Sc. thermophilus*

*Lactobacillus*

*Lb. delbrueckii* subsp. *bulgaricus*

*Lb. delbruecki*i subsp. *lactis*

**Leuconostoc** *Ln. mesenteroides* subsp. *cremoris*

*Brevibacterium Brev. linens*

*Propionibacterium Prop. Acidipropionici Prop. freudenreichii*  subsp. *shermanii*

*lactis*

*cremoris*

Past, Present and Future Developments 13

The pH history of a cheese and the hygienic practices applied in its manufacture are thus key factors to guarantee safe products. Thus, the isolation of autochthonous LAB intend to be used for development of specific starter cultures with improved acid production and other antimicrobial activities may be an excellent way towards reaching the goals of simultaneously obtaining safe traditional cheeses, still bearing their unique flavors.

Nowadays, western consumers still enjoy artisan cheeses thanks to their outstanding gastronomic qualities; however, in most industrialized countries the large-scale cheese processing is the most important branch of the food industry. In such cases, there is a strong need to control the fermentation process towards maximum efficiency in terms of yields and standardization of the end product. This, and the need to fulfill the safety assurance of the final product, is usually achieved by, among other improvements, adding a high dosage of pure LAB selected starter cultures, commercially available (today's world starter culture market is more than US\$1 billion), as well as by heat treating the raw milk, most commonly by pasteurization.
