CHEESE TECHNOLOGY

Module 8. Manufacture of different varieties of cheese

Lesson 19
SWISS CHEESE

19.1 Introduction

Swiss cheese originated in the Emme valley in Switzerland around the 15th century. It is known as Emmental cheese in the country of its origin. Besides the USA and Switzerland, many other countries such as Italy, Austria, Finland, Denmark, Germany and Argentina are known to make excellent Swiss cheese.

This cheese is a hard variety, known by the presence of shining eyes with smooth, waxy texture and sweet nutty taste with a mild flavor. It is reported that a specific grass available in the Emme valley produce typical cheese, this being the probable reason that no other country has duplicated exactly, the flavor and body characteristics of Emmental cheese from Switzerland. Swiss cheese should have a sliceable texture, regular round eye holes, dull to brilliant appearance, 45% min fat on dry matter basis, mild nut-like taste and should be minimum of 60 days old before consumption. Swiss cheese production ranks third in the world, next only to Cheddar and Mozzarella.

Table 19.1 Composition

19.2 Mechanism of Eye Formation

Most Swiss-type cheeses undergo a more or less pronounced propionic acid fermentation, which is brought about by propionic acid bacteria. They grow under anaerobic conditions, using calcium lactate as the substrate. The end products are the corresponding propionate, acetate, water and carbon dioxide.

Part of the CO₂ may be produced by dicarboxylation of amino acids (e.g. tyrosine and arginine) by enterococci due to high salt concentration and low pH (5.1 to 5.2) in the periphery of the cheese. It has been reported that 50% of the lactate is metabolized by propionibacteria and lactate fermentation is more intense in the centre than in the periphery.

To initiate propionic acid fermentation, the ripening temperature of the cheese must be raised approximately to 18-25°C for a certain period of time. The relative humidity (RH) of the curing room during hot curing (22°C/85% RH/6-8 weeks) influences the eye formation. Uneven RH results in uneven eye formation. The eyes are formed by the continuous production of CO₂ which diffuses out at weak points. They have 1.25–2.54 cm diameter and are spaced at 2.54 – 7.62 cm. As soon as the development of sufficient eyes is accomplished, the propionic acid fermentation is usually retarded by storing the cheese at lower temperatures. About 130 l of CO₂ is produced in 120-150 days in 80 kg Swiss cheese where 80 l of CO₂ diffuses out and 50 l of it remains in the eyes at 85 – 92% RH.

19.3 Method of manufacturing

Fig. 19.1 Steps of manufacture

19.4 Defects

19.4.1 Late fermentation

This occurs during ripening of cheese. The gas may form pin holes or the resulting eyes may appear in clusters. This defect is usually caused by lactate fermenting bacteria belonging to the genus Clostridium, strains of butyric acid bacteria, the name usually used by Swiss cheese makers for those organisms isolated from brown cheese. Among the various species like Clostridium tyrobutyricium, C. butyricum and C. sporogenes, it has been found that only C. tyrobutyricum produces brown cheese.

19.4.2 Bitter cheese

Streptococcus faecalis var. liquefaciens forms the major part of the ripening flora and is directly responsible for bitterness. Generally, this is not caused by a detrimental flora, but by some starter strains that may not contain enough peptidases to degrade the peptides produced by proteolysis. This may result from the higher proteolytic activity of the rennet at lower pH, which leads to accumulation of polypeptides including bitter ones. Cheese manufactured using temperatures higher than normal has a greater incidence of bitterness than those made by traditional methods.

19.4.3 Flavor defects

The most common among these are putrid, unclean, fermented, yeasty, rancid and fruity. Putrid flavor is probably caused by objectionable protein decomposition and the odor frequently resembles H₂S with equally offensive aromas. Large numbers of Clostridia and Micrococci have been found in such spoiled cheeses. Clostridium lentoputrescens is associated with a putrid flavor and with development of a white, crumbly conditions and large irregular eyes.

Rancid flavor is usually because of higher concentrations of butyric acid produced by C. butyricum or C. tyrobutyricum. Oxidative rancidity resulting from lipid oxidation also may occur. Use of lipolysed milk may also yield rancid cheese.

19.4.4 Color defects

Colored spots may be formed by the growth of pigmented propionibacteria in Swiss cheese. The round brown spots on the cut surface or eyes of cheese could be overcome by adding starter propionibacteria. This defect is most pronounced when cows are not on pasture and when milk contains fewer propionibacteria. Propionibacterium rubrum and P. theonii are brightly colored and may cause spots. Dark spots may be caused by other pigmented microorganisms.

Table 19.2 Defects in swiss cheese