L Fat assays

Fat quality is best assessed by measurement of moisture, impurities and individual fatty acids. However, there are a number of less extensive tests that can be used to give some idea of fat composition and quality. Fat titre is a measure of hardness, and simply relates to melting point. The break-point between tallows and greases is about 40°C. The higher the melting point, the more saturated the fat. Titre should obviously be consistent for an individual class of fat or fat blend from any one supplier. Iodine value can also be used as a measure of hardness. Each double bond (unsaturated) will take up a molecule of iodine, and so higher values mean a greater degree of unsaturation, which in turn should relate to lower titre (Table 2.20). Iodine value is greatly influenced by levels of palmitic, oleic and linoleic acid in most fats and oils. Generally, as titre increases by 10 units over the range of 50 - 100, then palmitic acid content decreases by about 2%. Also as a rule of thumb iodine value = 0.9 x % oleic acid + 1.8% x linoleic acid.

Table 2.20 Iodine value and titre of common fats

Iodine Value

Titre°C

Tallow

45

45

Lard

65

40

Poultry fat

80

35

Vegetable oil

120

15

A major concern with the quality of fats and oils, is rancidity or the potential for rancidity. Rancidity is an irreversible oxidative process, that is autocatalylic, meaning that breakdown products fuel further degradation. Rancid fats will be less palatable, less digestible, and in extreme cases, the process of oxidative rancidity can continue in the body of the bird following consumption of these fats. The Initial Peroxide Value (IPV) is often used to measure degree of rancidity upon delivery of a fat. An IPV in excess of 18 - 20 meq is cause for concern. If a fat is not stabilized with an antioxidant, there is potential for subsequent rancidity during storage. This potential can be measured by creating extreme conditions for rancidity, namely bubbling pure oxygen through the heated sample for 24 hr, and re-measuring peroxide value. As a word of caution, peroxide build-up is time dependent, since after reaching a peak, there is a breakdown of peroxides to other indigestible compounds. Therefore fats that have finished oxidizing can show a low peroxide value, but have very poor nutritive value. Such samples are best detected by their 'rancid smell'.

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Pregnancy Diet Plan

Pregnancy Diet Plan

The first trimester is very important for the mother and the baby. For most women it is common to find out about their pregnancy after they have missed their menstrual cycle. Since, not all women note their menstrual cycle and dates of intercourse, it may cause slight confusion about the exact date of conception. That is why most women find out that they are pregnant only after one month of pregnancy.

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