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Rancidity and its measurement in bakeries


Fat and Oils are major ingredients for any baked goods . These oils and fats are bought in bulk by these bakery manufacturers . Chances of fat or oil being rancid becomes high if stored for a longer period .This rancid fat or oil can then effect the quality of baked items . Fat and oil can be checked for rancidity prior to production by instrument called rancimant .


What Is Rancidity?


Rancidity is a very general term and in its most general meaning, it refers to the spoilage of a food in such a way that it becomes undesirable (and usually unsafe) for consumption. When people say that a food has "gone bad," what they're usually talking about is rancidity. Most of the time, but not always, rancidity can change the odors or flavors of a food in such a way that it becomes very unpleasant to smell or taste.


While most any food can technically become rancid, this term applies particularly to oils. Oils can be especially susceptible to rancidity because their chemistry can make them exceptionally susceptible to oxygen damage. When food scientists talk about rancidity, they are often talking about a specific type of rancidity involving oxygen damage to foods, and this type of rancidity is called "oxidative rancidity." During the process of oxidative rancidity, oxygen molecules interact with the structure of the oil and damage its natural structure in a way that can change its odor, its taste, and its safety for consumption. Chemical reaction produces butryic acid which gives the foul smell and taste .


Rancidity is caused by hydrolysis and oxidation. Heat, moisture and exposure to light will increase these chemical reactions and thus increase the likelihood of the onset of rancidity. Anti –oxidant added in during dough preparation prevents or delays oxidation hence the rancidity of oil or fat .


How to measure the level of Rancidity?


Apparatus called Rancimat is used to calculate effect of antioxidant on oil and fat . Other methods like used for determination of rancidity are Peroxide value ( Primary Oxidation)and Anisidine value( Secondary Oxidation) in fat or oil .Peroxide value provides the extent of rancidity present in the oil.Peroxide value is found by formation of iodine when oil or fat are reacts with iodine ion. Totox value are also used to check the quality of oil and fat .


Totox Value = Anisidine value + 2x Peroxide value


The 743 Rancimat is an instrument with two separately thermostatted heating blocks, each holding up to four reaction vessels containing 2 to 10g of sample.This means that samples can be run at one or two different temperatures.


Up to four different instruments can be linked to a single PC via serial interfaces.Up to 32 samples at eight different temperatures can be measured.


The short-chain carboxylic acids formed by the oxidation at elevated temperatures are collected in the deionised water and the conductivity measured.


The conductivity time curve is shown live for each measuring point.


The induction time is determined automatically from the second derivative of the measuring curve.

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