1. 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 70°C. The rate of coagulation increases as the temperature is raised to 90°C 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 90°C), the curd is removed with perforated scoops and placed in forms. After removing the first rise, the 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 acceptable because 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.

Procedure

1. Collect whey (pH > 6.1) and weigh it into a cylindrical vat. Sweeter whey (pH > 6.4) is preferred. Immediately heat the whey to 50°C to stop culture growth.
2. Add milk or skim milk (up to 25% of the total weight).
3. Heat in a jacketed vat (indirect heating) to 80 – 85°C with gentle agitation. Direct heating by steam injection from the bottom may be used in addition to indirect heating. Direct steam may help to float the curd, but it is not required.
4. Add citric acid (5% solution) or vinegar to induce maximum coagulation of caseins and whey proteins. The required amount for a 90:10 blend of whey and milk 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 20°C. Alternatively, add the acid slowly until the whey becomes clear. The ingredients we normally use in the Guelph pilot plant are 60 Kg of whey (pH > 6.4), 10 Kg milk or cream, and 600 mL of vinegar. The vinegar should be diluted in about 2 L of hot water and then added slowly to the hot whey/milk.
5. While adding the acid, continue heating with no or very little agitation to 90 – 95°C.
6. Hold the curd for an additional 10 min at > 90°C. 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 sanitized plastic sheet, cover the sheet with ice, and roll the drain table into a cold room (0 – 4°C). When the curd is cool, package in plastic tubs or wrap 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. Final pH after cooling should be 5.8 – 6.2.

An interesting alternate procedure is to use butter milk as the acidulant. Assuming the initial blend is about 90% whey and 10% milk, the required amount of buttermilk is about 10% of the weight of the whey/milk blend. Add the butter milk slowly and maintain the temperature at 85- 90ºC.

2. Gryphon Frying Cheese

Introduction

Gryphon frying cheese is a white, semi-soft cheese with a bland, slightly acid flavour and good sliceability. The cheese can be produced from whole milk or recombined milk by direct acidification at elevated temperatures. Milk is heated to 85°C 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.

Milk for Gryphon cheese is standardized to a protein to fat ratio of up to 1.2. This will increase the total solids of milk from about 12% to 14 – 15% 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 mold growth. The cheese is held in refrigerated storage for about 2 – 3 days to allow the curd to become firm and sliceable.

Gryphon Frying Cheese contains no added bacterial culture, so 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.

Gryphon Frying Cheese 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 or citric acid
• Skim milk powder
• Salt

Procedure

1. Standardize milk to a PF of 0.95 to 1.2 using skim milk powder or other sources of non-fat milk solids.
2. Heat the standardized milk to 85°C and hold for 5 – 15 min. Longer heat treatment increases cheese yield but imparts more cooked flavour to the cheese.
3. While the milk is warming, weigh the required citric acid monohydrate. The required amount of citric acid as a percent of the amount of milk can be estimated from the protein content of the milk as follows:

% Citric acid monohydrate = 0.09124 + 0.07075 (% Milk protein) 

Note: for anhydrous citric acid, multiply the result by 0.914.

4. Dilute the required amount of citric acid monohydrate with hot water (about 80°C) to form a 3.0% solution. The dilution helps ensure gradual acidification (no hot spots), which encourages formation of large aggregates of proteins, rather than small grainy particles. Slowly pump coagulant solution into the vat with gentle agitation (almost no agitation). Turn on steam to maintain high temperature. Hold for 10 – 15 min to allow curd to settle.
5. Open the gate and drain the 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 the cheese in the hoops overnight in a 2 – 4°C cooler.
11. Cut to desired portion sizes and vacuum or gas flush package.

3. Paneer

(contributed by Sunil Radhakrishnan, Guelph, MSc grad, 2004)

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) has the best body, flavour and texture, but it is also made from cow milk. Paneer pH is typically 5.7 – 6.0 and its composition when made from 6% fat milk is 57% moisture and 26% fat.

Procedure

1. Heat fresh milk to 82°C, hold for 5 min and cool to 70°C.
2. Prepare coagulant of 2% citric acid solution (generally, 2 – 2.5 g citric acid is required to coagulate one Kg of milk). Heat the coagulant to 70°C so the milk and the coagulant are at the same temperature. The quantity of coagulant added should be sufficient to give a clear whey separation. Agitate gently, when adding the coagulant to the milk to avoid breaking up the curds.
3. After the greenish white tinge of the whey is seen (pH 5.7 – 6.0), allow the curd to settle for 5 – 10 minutes.
4. Separate the curd and whey using a muslin cloth. Whey temperature should not fall below 63°C.
5. Fill cloth lined hoops and press for 15 – 20 min.
6. Remove pressed Paneer from the hoop, cut into required sizes and immerse in chilled water (4 – 6°C) or 5% brine solution (4 – 6%) for 2 – 3 hours to make it firm. After chilling treatment, the Paneer is surface-dried to remove free water and then vacuum or gas flush packaged into bags or tubs.
7. Store at 2 – 4°C (refrigeration temperature).

Note: 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.