Heat-acid precipitated cheese

Ricotta Cheese

Ricotta cheese is made from heat-acid precipitation of proteins from whey or whey-milk blends. The best Ricotta is made from very sweet whey (pH 6.4 - 6.5) without any addition of milk or acid. During heating whey proteins begin to coagulate at about 70C. The rate of coagulation increases as the temperature is raised to 90C and a thick layer of curd forms on the surface of the whey. When coagulation is complete and the curd is firm (after 10 - 20 min. at 90C), the curd is removed with perforated scoops and placed in forms. After removing the first rise, addition of acid (to about pH 5.9) will induce a second rise of coarser curd. If the pH is correct the whey should become clear.

It is now uncommon to make Ricotta cheese from whey only because: (1) Sweet whey with pH>6.4 is not always available; (2) the traditional hand skimming process of removing the floating curd is hot and tedious; and (3) yields are low. All of these problems are avoided or reduced by adding milk or skim milk before heating. Whey pH as low as 6.1 is then acceptable, the curd can be recovered by mechanical means and the yield is increased. The following is a procedure for the manufacture of Ricotta cheese from blends of milk and whey.

Thanks to John van Esch for some fine tuning of the following procedure:

Procedure

  1. Collect whey (pH>6.1) and weight it into a cylindrical vat. Sweeter whey (pH>6.4) is preferred. Immediately heat the whey to 50C to stop culture growth.
  2. Add milk or skim milk (up to 25% of the total weight).
  3. Heat by direct steam injection from the bottom of the vat to 80-85C without agitation.
  4. Add citric acid (5% solution) to induce maximum coagulation of caseins and whey proteins. The required amount is about 140 g citric acid monohydrate per 1,000 kg of whey-milk blend. The required amount can be determined exactly by titrating a sample of the blend to pH 5.9-6.0 at 20C. Alternatively, add the acid slowly until the whey becomes clear.
  5. Continue heating WITHOUT agitation to 90-95C.
  6. Hold the curd for an additional 15 min. at >90C. Then scoop the curd into the forms using perforated ladles. Fill the forms in rotation until they are level full.
  7. Cover the forms with a clean cloth, place chopped ice on the cloth, and roll the drain table into a cold room (0 - 4C). When the curd is cool it can be packaged in plastic tubs or wrapped in wax paper for immediate sale.

Notes: Ricotta cheese may also be creamed and/or pressed before packaging. A cured, dry Ricotta type cheese called Myzithra is made in Greece.

Queso Blanco (Frying Cheese)

Introduction

Queso Blanco is a white, semi-soft cheese with a bland, slightly acid flavour and good slice ability. The cheese can be produced from whole milk or recombined milk by direct acidification at elevated temperatures. Milk is heated to 85C and held for 5 min followed by the addition of a citric acid solution. The curd is formed as a result of co-precipitation of casein and the whey proteins. Rennet curd is made from milk which has not been heated in excess of pasteurization temperatures (72C/16 s) and contains only the casein fraction of milk protein. Whey proteins constitute approximately 20% of the total milk protein, and their co-precipitation with casein leads to substantially higher yields in Queso Blanco compared to Cheddar and other rennet coagulated cheese.

Milk for Queso Blanco manufacture is standardized to a protein to fat ratio of 1.2. This will increase the total solids (TS) of milk from about 12% to 14-15% TS and produce yields of 16-18% (16-18 kg cheese per 100 kg milk).

After draining, the curd is salted hot and agitated manually or with forking agitators, hooped, and pressed. Chilling the curd overnight allows easier handling before packaging. Vacuum packaging is necessary to prevent mould growth. The cheese is held in refrigerated storage for about 2-3 days to allow the curd to become firm and sliceable.

Since Queso Blanco contains no added bacterial culture, it is important to avoid contamination of the curd. Contamination will result in sour, unclean flavours upon storage.

An alternate packaging system which minimizes contamination is to extrude the hot salted curd into sausage casings.

Queso Blanco normally contains 52-53% moisture, 22-24% protein, 16-18% fat, 2-3% lactose, 2.5% salt, and has a pH of 5.3-5.5.

Materials 

  • Raw milk or recombined milk
  • Citric acid monohydrate C4H8O5.H2O
  • Calcium chloride dihydrate CaC2.2H20
  • Skim milk powder
  • Salt

Procedure

  1. Standardize milk to a P/F of 1.2 using skim milk powder.
  2. Weight out the required citric acid monohydrate. Dilute the required amount of citric acid monohydrate to form a 1.5% solution. The required amount of citric acid as a percentage of milk weight is calculated as:
    % citric acid monohydrate = 0.09124 + 0.07075 (% milk protein)
  3. Heat standardized milk to 85C and hold for 5 min.
  4. Slowly pump coagulant solution into the vat and agitate slowly. Turn on steam to maintain high temperature. Hold for 10-15 min to allow curd to settle.
  5. Open gate and drain whey.
  6. Trench and stir curd to allow maximum drainage.
  7. Salt curd directly in the vat and mix thoroughly for uniform distribution. 
    Weight of salt = 2.0% of expected yield
    Expected % yield = 4.83 (% milk protein) -3.64 
  8. Hoop while still hot.
  9. Press for 3-4 hours at 75 kPa (11 lbs/in2)
  10. Chill hoops overnight.
  11. Vacuum package.

Paneer (contributed by Sunil Radhakrishnan)

PANEER has been made in India for generations, mainly in the home. Milk is coagulated by lime juice, citric acid solution, sour whey, or lactic cultures. Citric acid solution generally gives a cleaner flavour to the Paneer than sour whey which may give off flavours and odours. Lime juice as a coagulant imparts a good flavour to the Paneer. Paneer made from 6% fat buffalo milk (in India) is supposed to be of the best body, flavour and texture. Paneer can also be made from cow's milk. Paneer pH is typically 5.7-6.0 and its composition when made from 6% fat milk is 54/7% moisture and 26% fat.

Procedure

  1. Take cow's milk in a pre-sterilised stainless steel vessel and heat it to82C and hold for 5 min. After holding, cool slightly to 70C.
  2. Prepare coagulant of 2% citric acid solution (generally, 2 - 2.5g citric acid is required to coagulate one kg of milk). Heat the coagulant to 70C so the temperature of the milk and the coagulant is the same. The quantity of coagulant added should be sufficient to give a clear whey separation wherein the colour of the whey tends to be a greenish white tinge. When adding the coagulant to the milk (at 70C), there should be very slow stirring so as not to break up the curd mass.
  3. After the greenish white tinge of the whey is seen (pH: 5.7 - 6.0), a final slow stir is given and the curd allowed to settle for about 5 - 10 minutes. Then the whey is drained out through a muslin cloth and the coagulated curd collected within the cloth. During this period, the whey temperature should not fall below 63C.
  4. Fill cloth lined hoops and press for 15- 20 min. Pressing can be done by a manual press.
  5. Remove pressed Paneer from the hoop, cut into required sizes and immerse in chilled water (4- 6C) or 5% brine solution (4- 6%) for 2 - 3 hours to make it firm. After chilling treatment, the Paneer is surface-dried to remove extra free water and then vacuum-packaged in HDPE (high density polyethylene) bags.
  6. Store at 5 - 8C (refrigeration temperature).

Notes:

Since moisture is high, Paneer is prepared and consumed immediately due to shelf-life problems. It can be cut conveniently into cubes, fried in oil and added in vegetable salads or garnished in curry preparations. Some people apply corn flour paste and barbecue it.