Swiss Cheese

Swiss (Emmentaler) cheese was first made in the fifteenth century in the Emmental Valley. Swiss type cheese made in other areas are known by local names: Gruyere (Switzerland), Allfauer Rundkase (Bavaria), Battlematt (Switzerland), Fontina (Italy), Traanon (Switzerland) and Samso (Denmark). Swiss is traditionally made in large 50 kg wheels.

The distinctive feature of Swiss cheese is the formation of eyes by the gas forming bacteria Propioni bacterium shermanii. The manufacturing procedure is designed to provide the right chemical composition for the growth of P. shermanii and the right texture (sufficient elasticity) for bubble formation. Important manufacturing parameters are: (1) high dipping pH (about 6.3) which promotes retention of minerals; (2) high cooking temperature (52C) which promotes mineral retention and the loss of both moisture and lactose by syneresis; (3) high final pH (5.3 - 5.4) and mineral content which promote elasticity. The final pH is influenced by the amount of Lactobacillus helveticus which is added in the starter because this organism is able to metabolize both glucose and galactose.

Standards: 40% moisture, 27% fat.

Procedure

  1. Standardize milk to P/F = 1.1 by removing cream or adding skim milk. Do not add skim milk powder. Pasteurize.
  2. Add starters through a fine mesh screen, especially if the starter was made with reconstituted skim milk. Use 0.1% S. thermophilus, 0.1% L. helveticus and 0.005% Propioni bacterium shermanii. Ripen briefly (10 - 15 min.) at 37C.
  3. Measure 190 ml rennet per 1,000 kg milk. Dilute the rennet with 10 volumes of water and add the mixture to the milk.
  4. Cut when curd is firm using 1/4" (6.4 mm) knives. Continue cutting until curd size is reduced to the size of rice grains. If curd is forming clumps, cut more vigorously and begin agitation as soon as rice grain particles are achieved. Cutting speed is increased as the curd becomes less fragile. Too much cutting initially will cause dusting. The cutting process should take about 5 min. Do not allow the curd to clump.
  5. Stir out the curd with vigorous agitation until the curd is firm and resilient when gently pressed (30 - 60 min.). There should be little acid development at this point (pH 6.55 - 6.50).
  6. Cook the curd from 37C to 52C in 30 min. Heat slowly at first ( 1 - 1.5C in 5 min.). Rapid heating causes "case hardening" with traps moisture and acid inside the curd particles. Curd cooked too slowly may also be too acid. Continue vigorous agitation to prevent matting until the pH is 6.3 - 6.4. Experienced cheese makers look for the proper `grip' before removing the whey. Curd pH should not be less than 6.3 at whey separation.
  7. Stop agitation, allow the curd to settle and pump the whey into the moulding vat until the discharge pipe is beneath the surface of the whey. During this time check pump and pipes for air leaks. Shut off the pump and resume vigorous agitation to break up clumps. Then, pump the curd and whey into the moulding vat. Be careful to match output with input so that the curd is always covered in whey. When the make vat is nearly empty, recycle whey back into it to transfer all curd without drawing air. Make sure that the curd fills the vat evenly and forms a level surface under the whey.
  8. Cover the surface of the cheese with a double layer of cloth and place the press plates on top. At this stage loose curd must not be added to the curd mass. Add weights and let stand for 15 - 30 min. and then drain the whey from the moulding vat. Let stand for 1 hr. Remove the press plates and the surface cloth and also remove all loose curd particles and protruding edges. Then replace the cloths, cover with terry cloth to help dry the surface, position the press plates and add the weights. Press for 12 - 18 hrs. at room temperature (at least 22 C).
  9. Remove the press plates and cloths, and cut the cheese into blocks. Cheese pH at this time should be 5.2 - 5.4.
  10. Place the curd in the brine (at least 23%) and liberally salt the surface. Brining requires 48 hrs. with frequent agitation.
  11. After brining, immerse the cheese in the brine to remove salt particles from the surface and then store at 10C to dry the surface. Vacuum the blocks in pouches sufficiently large to permit expansion (15 - 20%) during eye formation.
  12. Store at 10C for 8 - 10 days for cooling and pre-ripening. Then, transfer to the warm room (23C) for curing and eye formation.
  13. When eye development is complete (2 - 3 weeks), place the cheese in the finishing cooler (2 - 5C) to stop eye development and to firm the cheese in preparation for cutting. Flavour development continues in the finishing cooler.

Acid development and ripening

Drainage in the press is affected by the rate of acid development which in turn is affected by the curd temperature and the activity of the organism. At dipping, the temperature is too high for any of the organisms to grow but as soon as the curd cools 49C, S. thermophilus begins to grow. The rods (L. helveticus) begin to grow about 5 h after dipping when the temperature in the cheese is about 45C and growth factors have been provided by the metabolism of the cocci. The following morning the temperature of the curd should be about 36C. Too rapid cooling does not allow enough acid development. The pH changes during curing are:

Time pH
21 hrs 5.00 - 5.15
15 days 5.20 - 5.25
30 days (eye formation) 5.30 - 5.35
75 days 5.45 - 5.55
6 months 5.50 - 5.60
9 months 5.60 - 5.90

The numbers of both rods and cocci decrease rapidly during the first 15 - 30 days of curing. Propioni bacteria multiply rapidly to about 100 million/g during 6 - 8 weeks. Propioni bacteria ferment lactic acid and produce propionic acid, acetic acid, water and carbon dioxide. Eyes formed by carbon dioxide production should be 1.9 - 2.5 cm in diameter and should be spaced 2.5 - 7.6 cm apart. The number of eyes depends on the rate of gas production. If gas is produced too rapidly the cheese will be overset with many small eyes. Little or no gas production causes a `blind' cheese. Any factor causing weakness or brittleness of the curd will result in defective eyes.

Defects

  1. Glasler: brittle curd resulting in defective or too few eyes.
  2. Pressler: pin holes due to contamination with Aerobacter aerogenes or Bacillus polymyxa.
  3. Nissler: Clusters or nests of holes due to lactose fermenting clostridia or an accumulation of fat in the area.
  4. Late gas formation: due to Clostridium butyricum or Clostridium lentoputrescens. These organisms, especially the latter, produce stinker cheese, and are inhibited at pH<5.3.

Yield: 7.5 - 9 kg per 100 kg of standardized milk.