According to Codex Alimentarious yogurt is milk product obtained by fermentation of milk by the action of Symbiotic cultures of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.1
The definition about yogurt varies between the countries globally and the standard for this product depends on the local regulations mainly.
Some countries recognize the classic-style yogurt, in which Streptococcus thermophilus and Lactobacillus bulgaricus species are used only. In others the use of different Lactobacillus species is allowed. Furthermore, there could be difference in the requirement about the heat treatment of the product in order to call it yogurt.
Yogurt used to have shorter shelf life compared to what’s today on the market. Why is that?
There are several factors that make the longer shelf life of natural yogurts possible but basically it all goes to reduction in the contamination level of unwanted bacteria.
Improvements in the milking methods, raw milk quality, transportation of the milk to production facilities in cold chain and quality control of incoming milk ensure that the number of bacteria in the milk is kept at a minimum level.
Uncompromising hygiene in the dairies is one of the main factors for keeping the high quality of the end product. The processing of the milk is done in a closed system with improved production technology using standardized and safe starter cultures for the fermentation process. Furthermore the advanced knowledge about the fermentation these days enables producers to use the good bacteria from bioprotective cultures to keep the yogurt fresh for longer.
Another important step is the progress in maintaining the cold chain. In recent years the yogurt has been kept cool at the recommended storage conditions from the dairy, through the distribution, to the refrigerated shelves in the store. What’s more, even the improved performance of our home refrigerators plays important role here.
Is all yogurt probiotic?
No, it is not. The difference between the regular yogurt and the probiotic yogurt lies in the type of bacteria. Not all good bacteria used during fermentation are probiotics. The definition of probiotics is: “Live microorganisms that, when administered in adequate amounts confer a health benefit on the host”2
The probiotic effects are strain specific and probiotic products should deliver in line with the definition and the requirements of a true probiotic. For a yogurt to be called “probiotic”, it must contain live probiotic bacteria (as well as standard yogurt bacteria) throughout shelf life in sufficient amounts. The amounts should be linked to the claimed beneficial effect for which there is clinical documentation.
Both the regular and the probiotic yogurt contain starter cultures, but it is only the probiotic yogurt that has the addition of the bacteria with specific documented health benefits. The consumers therefore need to look for products with information about the specific probiotic strain and the cell count present.
Why sometimes yogurt could stay out of the fridge and do not spoil fast?
Years ago, most yogurts were fermented in the open containers without being sealed. The conditions in the chambers during the fermentation step allowed possible high rate of mold and yeast contamination in the final product leading to fast spoilage of the yogurt left at ambient temperature.
Nowadays, there are improvements to the production process. After the cultured milk enters the package, it is immediately sealed and sent to the fermentation chambers in closed containers. Fermentation rooms are now also heated with dry air and fresh air passed through positive-hepa filters. That is why the yogurt produced in a closed system has significantly lower risk of contamination by unwanted microorganisms from outside allowing longer shelf life and not getting spoiled even outside refrigerator for a certain time.
Furthermore, the use of standardized starter cultures and sometimes bioprotective cultures is helping a lot in keeping and improving the product quality.
1 Codex Alimentarious 243-2003
2 FAO/WHO. Joint FAO/WHO Working Group Report on Drafting Guidelines for the Evaluation of Probiotics in Food 2002
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