YOGURT PRODUCTION
Yogurt is a fermented milk product with a custard-like consistency which differentiates
it from other fermented milk products. The Code of Federal Regulations defi nes it as the
food produced by culturing cream, milk, partially skimmed milk, or skim milk used alone or
in combination with a characterizing bacterial culture that contains the lactic acid-producing
bacteria, Lactobacillus bulgaricus and Streptococcus thermophilus. Yogurt is more nutritious than
many other fermented milk products because it contains a high level of milk solids in addition to
nutrients developed during the fermentation process. In the U. S. market place, yogurts fi t into
four major niches based on fi nal product properties: children’s yogurt (extremely mild and sweet),
breakfast yogurt, dessert yogurt and health yogurt (high acid with a pH value as low as 3.5).
Typical yogurt manufacturing entails the following:
1. The process begins with milk with a fat level from 2.0-3.5%.
2. The serum solids content of the milk is increased to 10.5-11.5% through a standardization
process by adding condensed skim milk or nonfat dry milk.
3. Milk is homogenized and heated to 185o
to 195o
F (85-90.5o
C) for 30 to 60 minutes for
pasteurization.
- The high heat treatment improves the body of the yogurt and limits whey expulsion.
4. The milk is cooled to 104 to 106o
F (40 to 41o
C) and is inoculated with a lactic acid producing
culture.
5. Acid production is monitored and data (time/temperature/pH) is recorded.
6. The inoculated milk is incubated in a vat (stirred) or placed in consumer-sized sterile
packages (set) to incubate in a temperature controlled environment.
- To attain yogurt with a pH of 4.0 the cooling process should begin when the
fermenting milk reaches a pH of 4.3-4.4.
7. To extend the shelf life of the product, yogurt can be heat treated after culturing is complete,
destroying viable microorganisms.
Flavoring Options: Flavoring can be added to the chilled fermented yogurt. This is referred
to as Swiss-style yogurt. Sundae-style yogurt results when fruit or fruit fl avoring is added
to the bottom of the consumer package, followed by the inoculated base, and then incubated
until the predetermined acidity level is attained. Flavoring ingredients can also be added after
pasteurization or ultra-pasteurization.
Several optional ingredients can also be added to yogurt as specifi ed in the Code of
Federal Regulations.∗
All ingredients used for production must be safe and suitable. Before the
addition of any bulky fl avors, the yogurt must contain not less than 3.25% milk fat, and not less
than 8.25% milk solids non fat (MSNF), and must have a titratable acidity of not less than 0.9%,
expressed as lactic acid. The ingredients can be homogenized but must be pasteurized or ultrapasteurized
prior to the addition of bacterial culture.
Published by:
The Northeast Center for Food Entrepreneurship at the New York State Food Venture Center, Cornell University,
http://www.nysaes.cornell.edu/necfe/
This publication is for educational purposes only. 01/07
Cornell University is an Equal Opportunity/Affi rmative Action Educator and Employer
Major quality control points for yogurt manufacture include:
Ingredients:
- Use of milk that is of good initial quality, free from antibiotics.
- Storage of milk at proper temperatures and for no longer than predetermined time periods.
- Use of high quality ingredients (to be added after heat treatment) which conform to
microbiological criteria with respect to quality and absence of pathogens.
Process:
- Ensuring that milk is correctly standardized and that the materials used for standardization are
of good quality.
- Ensuring that appropriate pressure is used during the homogenization process.
- Ensuring that heat treatments are correctly applied and equivalent to pasteurization.
- Verifying that fermentation proceeds to a predetermined acidity (pH) level.
- Ensuring that the product cools according to a predetermined pattern
- Ensuring that handling is limited to avoid contamination of and damage to the fi nal product.
- Ensuring even distribution of added ingredients and consistent fi lling.