![]() First, it influences the product's chemical, enzymatic and microbiological stability. The determination of Water activity is important in the production process and in the quality assurance process. Water Activity is measured in Aw units in the scale from 0 to 1, When Aw – 1, all of the water is available for hydration (as in distilled water), When Aw – 0, there is no water available at all. It describes the amount of water available for the hydration of materials. How water activity effects other parameters?īecause, I know the your doubt on Water activity vs Moisture got cleared after reading this article.Water activity defines the energy status of water in a substance or a system. Then, what are those factors which decide product quality or shelf life?Ībove mentioned four parameters are the ones that play their own major roles in deciding a shelf-life of a product. So, I guess, one more question has popped out in your mind. There are many other changes which occur in the product, which makes it less palatable and less enjoyable. Is it that, after that defined date, the product becomes microbiologically unsafe? Now, the thing you should always observe when you buy any edible product is to check it’s expiry date.Įvery edible product has its shelf life mentioned on its pack. Undoubtedly, I get a no, from most of you. Have you ever observed the text on any edible product that you have bought? When we say, product stability is less, the first thing which comes to our mind is the microbial spoilage. So, it is the water activity that is crucial, in deciding the product shelf-life, not the moisture content. For ex., If we say that a product is having 0.8 a w, we want to say that the product is equal to 80 g of free water as compared to 100 g of free water. ![]() In defining water activity, we actually compare the vapour pressure of a product with pure water but not with any other solvent or liquid. Pure water is 100% free and so is having maximum vapour pressure. The more the free water, more will be the vapour pressure. Vapour pressure is also dependent on free water. In a layman language, I can say that water activity is the indication of free water available. I don’t want people to remember water activity by its definition rather want to understand this term. Which is technically defined as the ratio of vapour pressure of water in product to vapour pressure of pure water. This free water can be expressed in terms of water activity (a w) So, a product with the same moisture content can have a different shelf life. Thus, we can say that the monolayer water doesn’t help in any of the above functions. So, it is quite evident that water, until and unless available, can not be utilized for any of the above functions. It acts as a solvent for many substrates, on which enzyme acts.Microbes grow because it acts as a solvent for many nutrients.Water is used by microbes for their growth.To explain this, I would ask another question – what is the role of water in deciding the shelf life of the product? Here, as we see that water is present in three different forms, a question arises,Īre all forms of water important in determining the product shelf life? The third form is ‘free’ water condensed within the capillary structure or in the cells of food. Once the monolayer is completely developed, water starts adhering to monolayer which has solutions of soluble components. ![]() The BET monolayer value, therefore, represents the moisture content at which the food is most stable. Typical examples include gelatin (11%), starch (11%), amorphous lactose (6%) and whole spray-dried milk (3%). When all sites are (statistically) occupied by adsorbed water, the moisture content is termed the BET (Brunauer–Emmett–Teller) monolayer value. Water is present in different forms in a product.Ī proportion of the total water is attached to the molecules of the product through bonding with specific sites like hydroxyl, carbonyl or other suitable groups present in food. The moisture content of the product is the total water present in the given product. Water Activity vs Moisture Content:- Moisture content: I would try to touch and explain following aspects in a simplified way :. ![]() So, I thought to discuss the most important aspect of food processing – Water, which is commonly known as moisture content among the food professionals. WATER: not only essential for ‘life’ but also for ‘product shelf life’ I think the answer to both the questions is NO. Let’s discuss about the difference between the terms water activity vs moisture…Ĭan any life on this earth neglect the importance of water?Ĭan any food professional neglect the importance of water in determining product shelf life?
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