Yoghurts, from mass consumption to industrial uses
Yoghurt is a peculiar fermented milk
The European Union recognizes the appellation Yoghurt (also written yogurt), however manufacturing regulations of this product vary among European countries.
France considers indeed that live ferments should be kept alive in the yoghurt, for it to be proper for consumption, Germany and Spain, on the contrary, use heat treatments to kill these exact same ferments and still call the resulting product yoghurt. In France, dairy produce that underwent a heat treatment after fermentation are not allowed to be called yoghurts. French regulations also prevent addition of other bacteria and of various ingredients such as gelatine , pectin, modified starch…
In France, the only product that may be called yoghurt (Codex 2003) is milk fermented by two specific bacteria: Lactobacillus bulgaricus and Streptococcus thermophilus. These live ferments must be abundantly present in the finished product (at least 10 million bacteria per gram). Lactobacillus bulgaricus develops sourness in the yoghurt whereas Streptococcus thermophilus influences flavours and organoleptic properties.
Storage and preservation conditions of such products are well defined in order to maintain bacteria alive: a temperature between 0°C and 6°C and a short shelf life.
Yoghurt manufacturing technology
Two types of yoghurt exist:
- Set yoghurts whose fermentation happens in jars: these are usually plain yoghurts or flavoured yoghurts.
- Stirred yoghurts whose fermentation happens in tanks before stirring and packaging: these are creamy yoghurts plain or with fruits.
These two types of yoghurt may be manufactured whether from partially or totally skimmed milk (3,5%, 1,0% or 0% fat).
Steps to manufacture a yoghurt:
A. Prepare and treat milk
- Enhance dry matter content: dry matter content of the milk that is going to be used is a critical factor, because it will define viscosity and texture of the finished product. Enhancement is made either by concentration (evaporation or reverse osmosis) or more often by addition of skimmed milk powder, milk proteins or lactoserum. Powdering is usually followed by filtration and deaeration.
- Heat treatment: this treatment aims at eliminating pathogens and unwanted substances that could later on help development of ferments.
- Homogenisation: this treatment occurs for fat milk. It prevents ascent and coalescence of fat during gelation, it restricts draining by enhancing water retention and it improves texture.
- Lactic ferment seeding
- Incubation: for both firm or stirred yoghurts, incubation occurs at a temperature between 42°C and 45°C and lasts between 2h30 and 3h30. This step aims at giving a sour taste to yoghurts.
- Fermentation stop: fast cooling to stop fermentation and storage in a cold-room.
High-quality nutritional and physiological properties
While a yoghurt jar may have the same nutritional value as a glass of milk, it may also have way better nutritional qualities thanks to the milk component modifications happening during yoghurt fermentation.
Average yoghurt composition (for 100g of yoghurt) is:
- 4 to 5 grams of glucides
- 0 to 3,5 grams of lipids (lipid content depends of the initial milk)
- 4 grams of protids
- Calcium, minerals, vitamins
Generally speaking, yoghurt brings:
- Dairy calcium
- Proteins (partially digested during lactic fermentation)
- B-vitamins (B2, B12, B3, B5 and B6)
- A and D vitamins
- Minerals (phosphorus, potassium)
- Micronutrients (iodine, zinc)
During fermentation, milk composition is modified. Some of these modifications allow yoghurt to have a better nutritional value than plain milk.
Some studies show that yoghurts also have nutritional and physiological properties that are particularly interesting:
- Better lactose absorption: thanks to live lactic bacteria in the yoghurt, absorption of lactose is easier for people lacking lactase. Countrary to popular belief, yoghurts are not to be prohibited from alimentation for lactose intolerants. In 2010, the European Food Safety Authority (EFSA) confirmed that live ferments in yoghurts help to digest lactose.
- Easier digestion of proteins: yoghurt is more digest than non-fermented milk and contains twice as many free amino acids.
- Easier digestion of fat: homogenisation for fat milk improves digestibility by increasing size of globules.
- Antimicrobial activity: yoghurt prevents gastrointestinal infections. Besides lactic acid, yoghurt bacteria produce antimicrobial substances and prebiotics, including oligosaccharides.
- Immune system stimulation: yoghurt has proved to have immunoregulatory effects. Increase of interferons and immunoglobulins production and B-lymphocytes activation are allocated to Lb.
- Preventive action against cancers of the digestive tract: lactobacilli are believed to modify bacterial enzymes that could lead to carcinogens (inducing cancerous tumors) in the digestive tract, inhibiting as a result creation of these precancerous substances.
- Hypocholesterolemic action: numerous studies have shown that yoghurt consumption have a hypocholesterolemic effect.
Yoghurts are amongst the 3 dairy produce whose daily consumption is recommended by the French national programme for nutrition (PNNS).
Yoghurt, both a consumer product and an industrial ingredient for food preparation
Many kinds of yoghurt exist in order to satisfy various tastes:
- Plain yoghurt (set): manufactured from semi-skimmed milk for the simplest version, it is called light or 0% if made from skimmed milk and may also be made from whole milk.
- Stirred yoghurt: manufactured from a process close to the firm yoghurt, the product is stirred after seeding in order to get a creamy texture.
- Sweetened, flavoured yoghurts or with fruits: sugar, sweetener, flavour, fruit pieces or coulis may be used to diversify yoghurt tastes.
- Yoghurt drinks: manufacturing process is the same as a stirred yoghurt, a whipping step is added to obtain a more liquid texture.
Adding other ingredients (apart from live ferments) is allowed while keeping the name yoghurt, as long as these additional ingredients are authorised by regulations.
Functional properties of yoghurt in industrial formulations
As an ingredient, yoghurt may be used for food preparations. Yoghurt enhances the taste of the products, it may also provide a more consistent texture and may sometimes be substituted for cream.
Application in ready-cooked dishes:
- Taste enhancer: peculiar taste, slightly sour.
- Ingredient for texture: yoghurt gives consistency and better resistance to cold sauces.
- Lower caloric content for some formulations.
Discover the range of yoghurts offered by FIT
- Stirred yoghurts 0% fat:
- Whole milk yoghurts:
- 3,5% fat
- Container (aseptic bags): 250 kg and 1000 kg
- 2,9% fat
- Light yoghurts 0% fat:
- Container (aseptic bags): 250 kg and 1000 kg
- Creamy yoghurts 5% fat:
*EFSA (European Food Safety Authority). 2010. Scientific Opinion on the substantiation of health claims related to live yoghurt cultures and improved lactose digestion (ID 1143, 2976) pursuant to Article 13(1) of Regulation (EC) No 1924/20061. EFSA Journal 8:1763.
Ingredient for texture
Lower caloric content for some formulations