Citric Acid for Mozzarella and Ricotta: How Much per Litre of Milk

Short answer: for homemade mozzarella, use 1½ teaspoons (about 7 g) of citric acid per 3.8 L (1 US gallon) of milk, which works out to roughly 1.9 g per litre. For ricotta, use 1 teaspoon (about 5 g) per 3.8 L of whole milk, roughly 1.3 g per litre. Both amounts come from tested University of California Cooperative Extension recipes; the gram figures are our conversion, so weigh rather than scoop when you can.

TL;DR: Mozzarella = 1½ tsp citric acid dissolved in 1 cup of cool water, added to cold milk before heating to 32 °C. Ricotta = 1 tsp citric acid stirred into milk heated to 93 °C. Use milk that is not ultra-pasteurized, and refrigerate fresh cheese within two hours.

How much citric acid per litre of milk?

Extension recipes are written for 1 US gallon (3.8 L). Most Canadian milk comes in 4 L bags or jugs, so the table also gives a 4 L column. The teaspoon-to-gram conversion assumes about 4.8 g per level teaspoon of citric acid, the same working figure we use in our other citric acid guides.

Cheese	Per 3.8 L (1 US gal)	Per 4 L	Per litre	Key temperatures
Mozzarella (30-minute method)	1½ tsp ≈ 7 g	≈ 7.5 g	≈ 1.9 g	Acidified milk to 32 °C, curds to 41 °C, stretch at about 57 °C
Ricotta (whole-milk)	1 tsp ≈ 5 g	≈ 5 g	≈ 1.3 g	Milk to 93 °C, then add acid off the heat
Ricotta top-up if whey stays milky	+⅛ tsp ≈ 0.6 g	+0.6 g	—	Wait a few more minutes after adding

Mozzarella also needs rennet: the extension recipe uses ¼ tsp of liquid rennet (about 20 drops) or ¼ of a rennet tablet per 3.8 L, dissolved in ¼ cup of cool, non-chlorinated water. Follow the label of your rennet if it states a different strength.

Why does mozzarella need citric acid?

In traditional mozzarella, bacterial cultures slowly acidify the curd over several hours until it can stretch. The quick home method replaces that step: citric acid lowers the milk's acidity directly, so the curd formed by rennet is ready to stretch in about half an hour. Too little acid and the curd will not stretch; too much and it turns crumbly and grainy. That is why measuring matters more than with most kitchen ingredients.

Ricotta works differently. There is no rennet: hot milk plus acid makes the proteins clump into soft curds. The extension recipe lists three interchangeable acids for 3.8 L of milk: ⅔ cup of lemon juice, ⅔ cup of white vinegar, or 1 tsp of citric acid. Citric acid gives the most neutral flavour and the most repeatable result, because its strength does not vary like lemon juice does.

How do you make mozzarella with citric acid, step by step?

1. Prepare. Clean and sanitize your pot, spoons and colander. Use a large non-reactive pot (stainless steel, not aluminium or cast iron).
2. Dissolve the rennet. Stir ¼ tsp liquid rennet into ¼ cup of cool, non-chlorinated water. Set aside.
3. Dissolve the citric acid. Stir 1½ tsp (about 7 g) of citric acid into 1 cup of cool, non-chlorinated water until fully dissolved, then pour it into the empty pot.
4. Add the milk. Pour in 3.8 L of milk quickly so it mixes with the acid solution.
5. Heat slowly to 32 °C (90 °F). Use a thermometer. Then take the pot off the heat.
6. Add the rennet. Pour in the rennet solution and stir gently top to bottom for about 30 seconds. Cover and leave undisturbed for 5 to 10 minutes.
7. Check the curd. It should look like custard, with a clean separation from clear whey. If it is soft or the whey is milky, wait a few more minutes.
8. Cut and heat. Cut the curd into 2.5 cm (1 inch) cubes, return to the heat and warm slowly to 41 °C (105 °F) while stirring gently. Off the heat, keep stirring 2 to 5 minutes; longer gives a firmer cheese.
9. Drain. Scoop the curds into a colander and press gently to release whey.
10. Heat and stretch. Microwave the curds for 1 minute, drain, knead, then repeat in 15 to 30 second bursts until the curd reaches about 57 °C (135 °F). Wear heat-resistant gloves. Stretch like taffy until smooth and shiny, adding salt (about 1 tsp) if you like.
11. Chill. Shape into balls, drop them into ice water, then refrigerate within two hours.

How do you make ricotta with citric acid?

1. Warm 3.8 L of whole milk gradually to 93 °C (200 °F) in a large pot. It can take up to an hour; remove it from the heat if it starts to boil.
2. Off the heat, stir in 1 tsp (about 5 g) of citric acid, ideally pre-dissolved in a little water, plus up to 2 tsp of salt if desired. Stir gently.
3. Leave the pot undisturbed for 10 minutes. You should see white curds and thin, yellowish whey.
4. If the liquid is still milky, add another ⅛ tsp of citric acid and wait a few minutes.
5. Strain through cheesecloth or a fine towel for 10 to 60 minutes, depending on how dry you want it.
6. Use right away, refrigerate in a sealed container for up to a week, or freeze for up to 6 months.

The extension recipe yields about 4 cups (roughly 800 g) of ricotta from 3.8 L of whole milk.

Which milk works best?

• Avoid ultra-pasteurized (UHT) milk. Both extension recipes specify milk that is not ultra-pasteurized; high-heat treatment changes the proteins and gives weak, mushy curds. In Canada, check the carton for "ultra-pasteurized" or long refrigerated shelf-life claims.
• Whole milk gives the best yield and texture for ricotta. Lower-fat milk works for mozzarella but makes a firmer, less creamy cheese.
• Use chlorine-free water to dissolve rennet. Chlorine can weaken rennet; let tap water stand or use bottled water.

What if the cheese does not work?

• Curd too soft, whey milky (mozzarella): give the rennet more time before cutting. If it never firms, the milk is likely ultra-pasteurized or the rennet has lost strength.
• Curd does not stretch: it may not be hot enough. Keep heating in short bursts until it reaches about 57 °C.
• Grainy, crumbly mozzarella: often too much acid. Weigh the citric acid next time instead of using heaped spoons.
• Small ricotta yield: make sure the milk really reached 93 °C before adding acid, and add the ⅛ tsp top-up if the whey stays cloudy.

If you enjoy cheese chemistry, the other citrate trick worth knowing is the silky melted-cheese sauce: see our guide to sodium citrate for cheese sauce (the 2-3% rule).

Sources

• UC Cooperative Extension Master Food Preserver Program — Cheesemaking Recipes (March 2020): mozzarella (1½ tsp citric acid per gallon) and ricotta (1 tsp citric acid per gallon, 200 °F) recipes.
• UCCE Master Food Preservers of Solano and Yolo Counties — Making Mozzarella Cheese: step-by-step method, rennet dilution and 135 °F stretching temperature.
• UCCE Master Food Preserver Program of Sacramento County — Making Soft Cheeses: Additional Recipes: same citric acid and rennet amounts, confirmed independently.