Sous Vide?
You might be curious to know what it is.
Just imagine cooking a food item, sealed in a vacuum package by putting it in warm water for loooooooong time (say hours)
What do you think? Is it feasible? Does this cooking technique exist? Why is it required?
YES, this technique is called Sous Vide. It is a French word that stands for ‘Under Vacuum’. It’s a low-temperature long time cooking method that is proven to be efficient in retaining taste, texture, and nutrients of the product.
Sous Vide is a topic of study since 1990. Many scientists have worked on this process and analyzed that it is a superior method for minimal processing of foods, bring more taste and nutrients to the product compared to traditional cooking.
There are two important steps in Sous Vide Cooking:
Vacuum Packaging of product before cooking in a heat-stable, food-grade packaging material
Precise control of temperature and time for the cooking.
Both the process gives various advantages to the food. Vacuum packaging enables food product to be cooked without loss of flavor volatiles and moisture, inhibits the growth of aerobic bacteria during storage and enhance shelf life by preventing re-contamination of food after cooking, Since there is a precise control of temperature during cooking, it gives more control over the doneness compared to traditional cooking, give more reproducibility (i.e. same taste can be achieved many times without variation) and pasteurize the product to make it safe at low temperature.
Effect of Sous Vide on Plant-based Foods:
When the vegetables are cooked traditionally, the majority of water-soluble and heat-labile nutrients are lost. The reason behind this is the disruption of the cell wall of vegetables in the rapid cooking method which causes the flavor loss and leaching of nutrients in water. When very high temperature is applied, the pectin, which is responsible for the intact structure of fruits and vegetables, become gelatinous and cause vegetables to be mushy. Sous Vide cooking has proven itself as an efficient way to retain the nutritional value, taste, and texture of the vegetables.
Since low temperature is used in Sous Vide, the cell wall of the vegetables remains intact and prevents nutrient loss. Moreover, it has been observed that the pectin material strengthens itself on slow cooking, say 50ᵒC for 30 minutes, and maintain the tender structure of the vegetable without getting them overcooked.
Sous Vide is proven to be beneficial in cooking legumes as it causes efficient gelatinization of starch granules and increases the digestibility of protein. It also eliminates the requirement of soaking legumes before cooking because slow cooking in vacuum pack creates the same impact as soaking. Since the cooking water is not discarded, the water-soluble nutrients remain in the final product (1).
For non-starchy vegetables, the cooking time is three times more than the traditional cooking, starchy vegetables take twice the time compared to rapid cooking and legumes take 3-6 hours for cooking depending on their variety (1).
Effect of Sous Vide on Meat:
Some meat cuts are tough in nature and require tenderness before consumption. The tenderness can be achieved by dissolving the collagen into gelatin along with reducing the inter-fiber adhesion. One of the ways of achieving tenderness is by mechanical treatment, in which needles are punctured into the tough cut to loosen the bonds between tissues. Another method is brining, in which meat is soaked into 3-10% salt solution for a couple of hours which causes the breakdown of collagen and make the meat tender. Such processes may cause pathogen contamination in the product. Sous Vide eliminates the requirement of all these processes. Researchers have found that cooking at 50-60ᵒC for 24hours cause tenderness in the tough cuts of meat (esp. beef). The reason behind this is proteolytic enzymes (activated due to moderate temperature) which decrease the strength of the myofibrils and weaken the connective tissues (3)
Besides tenderness, since the meat cuts are evenly heated in a water bath, there is a uniform cooking and color throughout the piece. Also, slow cooking doesn’t cause fiber contraction (as in case of rapid heating), therefore there is no water loss from the muscles that make the final product juicy (4).
Commercial applicability of Sous Vide:
There are debates for the commercial applicability of Sous Vide products. Sous Vide food, generally, are not protected by low water activity or pH or any preservative. They are only exposed to mild heat treatment during cooking followed by refrigerated storage for better shelf life and food safety (2)
Many researchers favor this technique due to the enhancement of flavor and nutritional profile of the product whereas other researchers oppose it because of the chances of an outbreak of anaerobic microbes’ esp. C. Botulinum. Since the products are vacuum packed and are preservative-free, there is a suitable environment for anaerobic microbes to grow and release toxins. Therefore, such products have a limited shelf life at refrigerated conditions (2)
There are two most popular Sous Vide cooking methods for industrial purposes. One is Cook-hold or Cook-serve in which ingredients are vacuum-sealed, pasteurized, and held at a temperature of 54ᵒC until serve. Such a method is applicable for restaurant chains as products can’t be held at warm temperatures for days. Another popular industrial method is Cook-chill or Cook-freeze method where ingredients are vacuumed packed and pasteurized followed by rapid chilling and chilled/frozen storage. These rapid chilled products have a different shelf life at different storage temperatures such as 90 days at <2.5ᵒC, less than 31 days at <3.3ᵒC, and less than 5 days at <7ᵒC.
Although Sous Vide is an older technique used by various chefs to make their special dishes, it has a wide range of industrial applications also. Sous Vide products are better than canned products in terms of nutritional value and taste. If an efficient cold chain can be maintained at all places, Sous Vide products has good potential to capture the market.
References:
Douglas E. Baldwin (2012). Sous Vide Cooking: A Review. International Journal of Gastronomy and Food Science, Volume 1, Issue 1
Sandra Caroline Stringer and Aline Metris (2017). Predicting Bacterial behaviour in sous vide food. International Journal of Gastronomy and Food Science.
P.E. Bouton, P.V. Harris (1981). Changes in the Tenderness of Meat Cooked at 50-65ᵒC. Journal of Food Science, Volume 46, Issue 2
http://sciencemeetsfood.org/science-behind-sous-vide-cooking-explain-friends/
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