β -GLUCAN - A FUNCTIONAL COMPONENT OF FOOD

β-Glucans are polysaccharides of D-glucose monomers linked by β-glycosidic bonds. They are found in cereals such as oat, barley, rye and wheat, mushroom and yeast cell walls having β (1→3), β (1→4) and β (1→6) glycosidic linkages. β-glucans are located throughout the starchy endosperm whereas in wheat the highest concentration is in the sub aleurone layer with little in the rest of the starchy endosperm. All 1, 3 configuration β glucans have the same biological potency whether they are derived from oats or yeast -the two major sources. These six-sided D-glucose rings can be connected to one another, on a variety of positions on the D-glucose ring structure. Some β-glucan compounds are continual repeats of D-glucose attached at a specific position. These unique carbohydrates often present unlike structures and contribute to dissimilar functions, which lead to disparate potential health benefits.

 β -glucans from oat, barley, and seaweed are primarily linear short β-(1, 3) segments with long β-(1, 4) branches. The forms from grains appear to function through a variety of mechanisms, such as reducing cholesterol reabsorption in the enterohepatic recirculation process, delaying absorption of dietary fat, and possibly enhancing intestinal fermentation by the microflora. As immune modulatory food ingredients, β-glucans are either soluble gel-forming components or insoluble particulates. These properties vary with the source and modification or degree of branching.

Sources of β Glucans:

Natural β -glucans are dietary supplement found in several common foods, including oats, barley, medicinal mushrooms  and organisms such as yeast, various fungi and in rye and wheat in lesser extent. It is located mainly in sub-aleurone, aleurone and bran parts of the grains. The richest concentrated source of β glucans is baker’s yeast cell wall. The major sources and its type are given as;

Oat: Oats possess high amounts of β-glucan in the form of soluble fiber, which helps lower cholesterol. This slows down the release of sugars into the bloodstream and extends the feeling of satiety after eating. Oat-derived β -glucan is linked to lower blood sugar and insulin levels in people with diabetes.

Barley: Barley β -glucan works by converting into a water-soluble gel, which facilitates the absorption of nutrients in the intestines while slowing digestion and trapping fats and carbohydrates. The feeling of fullness that results from slower digestion promotes diet control and weight loss by curbing hunger. 
Mushroom and Yeast: Mushroom and yeast β-glucan has the effect of aiding in the body's natural immune defenses by acting as an immune modulator. Two of the most common sources of these types of β-glucan are shitake mushrooms and Baker's yeast. Shitake-derived β -glucan blocked the progression of cancer cells; fight off infection naturally in the body. Yeast-derived β-glucan acts similarly to support the immune system. 

Functions of β Glucans:

β-glucans play a key role in some health-promoting properties, such as enhancement of immune function, protection against radiation exposure, cancer prevention and reduction of blood cholesterol and blood glucose levels. This also possesses several beneficial qualities, including the ability to fight off free radicals in a similar way to antioxidants.

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