The idea was to reduce wastage during cooking, but as a bonus both flavour and consistency were much better than with traditional preparation. Further development of the technique showed that it was possible to retain the good flavour of the product for 2 to 5 days if it was stored chilled after the heat treatment. Sous vide technology thus opened up possibilities of safeguarding flavour and aroma, reducing wastage in cooking and at the same time extending the shelf life of the chilled finished dish or individual components, for use by restaurants, mass catering and also the retail market.
Sous vide technology has been used in Norwegian food production for the last two decades and we now have extensive experience of using it in the restaurant and catering sector. We also see today that the same production techniques are being used with treatment at much higher temperatures and the products are being sold through national supermarket chains with shelf lives of several weeks.
The products are heat treated under controlled time and temperature conditions, followed by rapid chilling (from 90°C to <3°C within 90 minutes). The products are then stored chilled (<4°C) until being reheated for serving. The method allows for ready meals with a fresh effect that can be kept for a certain period, usually up to about 21 days.
Cook-chill
When the cook-chill method first came into use it was the taste and juiciness of the product that was the primary consideration. These should be safeguarded, because they are among the most important reasons for consumers choosing such products. Other important criteria are that preparing the food should be quick and that it should be healthy and safe. But even if all these factors are satisfied, the price must still be related to the consumer's perception of the product's quality. To achieve this, it is not enough to be more efficient than the average consumer is in his or her kitchen. One must be able to compete with cafes and other catering outlets in order to be able to sell the products in the supermarkets. For the mass caterers, the challenge is to be as efficient as a production kitchen that uses industrial methods.
The way the cook-chill method works is that the product is heat treated using a time and temperature which suits the raw materials and the desired product quality. The product is then rapidly chilled before packaging and further refrigerated storage (<4°C). One of the problem areas when using this method is that chilling with air is slow and involves the risk of introducing micro-organisms. For safety reasons therefore, shelf life is limited to 7 days or less.
Pasteurisation
Pasteurised and mild heat treated products often cross over somewhat and there is no clear boundary between these terms. Pasteurised products have previously usually been associated with long shelf life in the chill chain, such as for fish cakes, fish pudding and a number of dairy products. Today we can see a wide spectrum of different pasteurisations that range from milk pasteurisation (72oC for 15 sec) to ultra high temperature (UHT) pasteurisation at up to 140oC for a few seconds. Pasteurising conditions are often chosen so as to achieve special effects for the product, such as long shelf life or high nutritional content.
Pasteurisation describes a process of heat treatment of various products, especially foods, to ensure that they do not contain pathogenic or other bacteria, viruses and enzymes. The method was developed by and is named after the French scientist Louis Pasteur.
Several factors are involved in actualising products with extended shelf life. The trend towards ever fewer and more specialised production plants in the food industry means that products must be transported over greater distances than before. Increased shelf life can therefore give significant savings in terms of distribution frequency and cost. The trend towards low volume niche and specialised products is also a factor - for some of these products, a long shelf life is essential for achieving financially acceptable production and distribution. This is even more important where these products are often sold through channels other than the normal supermarket type outlets. And since extended shelf life is achieved by optimising hygiene standards throughout the production chain, this technology also automatically helps to secure another important goal: the best possible product quality and safety.
Further description
