FOOD PROCESSING AND PRESERVATION: CHILLED FOODS
Diagram
Low and slow in the pack, or cook normally then chill fast
Sous vide
Food is vacuum sealed in a pack, cooked low and slow in a water bath, then chilled and held cold until serving.
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Cook-chill
Food is cooked normally, by boiling, steaming or roasting, then portioned, blast chilled fast, and held cold until reheating.
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The key point
Both cook in or for a pack and chill for later service, but sous vide cooks in the pack at low temperature, while cook-chill cooks first and chills fast after.
Figure 1: Sous vide cooks low and slow in a sealed pack; cook-chill cooks normally and then chills fast. Drawn in our own style from Sun, Handbook of Food Safety Engineering, chapter on sous vide and cookchill processing.
Introduction
Sous vide and cook-chill both cook food and chill it for later service, but they cook in different ways. Sous vide seals the food in a vacuum pack and cooks it low and slow in a water bath, in the pack, then chills it and holds it cold. Cook-chill cooks the food normally, by boiling, steaming or roasting, then portions it, blast chills it fast, and holds it cold until it is reheated for service. Both depend on strict time and temperature control, because chilled cooked food can still grow microbes if it is held wrongly.
Sun gives a chapter to sous vide and cookchill processing. This article follows that book.
Quick comparison
Table 1: Sous vide compared with cook-chill
| Aspect | Sous vide | Cook-chill |
|---|---|---|
| Cooking | Low and slow, in a water bath, inside a vacuum sealed pack | Normal cooking: boiling, steaming, roasting, then portioning |
| Pack | Vacuum sealed before cooking, and cooked in the pack | Cooked first, then packed and chilled |
| Cooking temperature | Low, held for a long time | Normal cooking temperatures |
| Chilling | Chilled after cooking, in the pack | Blast chilled fast after cooking |
| Storage | Held chilled in the sealed pack | Held chilled in portions |
| Serving | Reheated in the pack, or finished and served | Reheated, usually by the caterer, before serving |
| Texture and flavour | Tender and even, with juices kept in the pack | Normal cooked texture, as in ordinary catering |
| Main risk | Low temperature cooking needs exact time and temperature control | Slow cooling lets microbes grow, so chilling must be fast |
| Scale | Suited to single portions and fine cooking | Suited to large scale catering: hospitals, schools, airlines |
| Typical foods | Steaks, fish, vegetables, sauces in single portions | Stews, sauces, rice, vegetables, plated meals in bulk |
Scientific explanation
Definition
Sous vide is the cooking of food sealed under vacuum in a pack, in a water bath at a low temperature for a long time, followed by chilling and cold holding until service. Cook-chill is the cooking of food by normal methods, followed by portioning, rapid blast chilling, and cold holding until reheating for service. Sun gives a chapter to both together, and that chapter is the source for this article.
Working principle
In sous vide, the vacuum pack keeps juices and flavour in, and the water bath holds the food at one even low temperature for hours, so the whole piece reaches the same temperature and stays tender. Because the temperature is low, the time must be long enough to kill the vegetative microbes of concern, and the food must be chilled promptly and kept cold. In cook-chill, the food is cooked through by normal heat, which kills vegetative microbes, and then it must be cooled fast, because the danger zone between hot and cold is where microbes grow. Blast chilling pulls the temperature down quickly, and the food is held cold until it is reheated for service.
Apparatus
The books used here name the water bath and vacuum sealer for sous vide, and the blast chiller for cook-chill. No laboratory apparatus for telling the two apart is named, because the distinction is in the process, not in a test.
Measurement procedure
The distinction is made from the process record: water bath temperature and time for sous vide, and cooking temperature, chilling time and holding temperature for cook-chill. The books used here give no worked calculation with numbers for this comparison, so none is given.
Factors affecting readings
For sous vide, the thickness of the piece and the bath temperature decide the time needed. For cook-chill, the portion size and the blast chiller decide how fast the food cools. In both cases, holding temperature and holding time decide safety, and reheating must be thorough.
Formulas and calculations
The books used here give no formula for this comparison, so no formula or worked calculation is given.
Industrial applications
- Sous vide is used in restaurants for steaks, fish and vegetables in single portions.
- Cook-chill is used in hospitals, schools and airlines for large scale catering.
- Sous vide is used for sauces and meats that must be tender and evenly cooked.
- Cook-chill is used for stews, rice and plated meals made in bulk and served later.
- Both are used to prepare food in advance and serve it later without cooking from scratch.
Advantages and limitations
- Sous vide: advantage: even, tender cooking with juices and flavour kept in the pack. Limitation: needs exact time and temperature control, and low temperature cooking is unforgiving if the time is short.
- Cook-chill: advantage: suits large scale catering and normal cooking equipment. Limitation: chilling must be fast, or microbes grow in the cooling food.
- Sous vide: advantage: portions are sealed, so there is no drying and no contamination after cooking. Limitation: needs a vacuum sealer and a water bath, and the pack must stay sealed.
FAQ
Is sous vide just slow cooking?
No. Sous vide seals the food under vacuum and cooks it at a low, even temperature in a water bath, in the pack.
Why must cook-chill food be chilled fast?
Because microbes grow fastest in the warm range between hot and cold, so slow cooling lets them multiply.
Do both need refrigeration?
Yes. Both are chilled foods and must be held cold until reheating and service.
Can sous vide food be served without reheating?
It is chilled after cooking, so it is reheated in the pack, or finished and served, before eating.
