Chemical properties of lipids

food technology

1. CHEMICAL PROPERTIES OF LIPIDS Anchal Awana B.Tech Food Technology Section – A Roll no - 18

2. IODINE VALUE It is the number of grams of iodine or iodine compound absorbed by 100g of oil/fat .

3. Objectives:- It is direct representation of the degree of unsaturation of the oil /fat(higher the IV, higher the degree of unsaturation) Iodine is used to halogenate double bond

4. Principle :- 1] fatty acids reacted with halogen (iodine) resulting in the addition of the halogen at the C=C double bond sites. CH 2 ₌ CH 2 † ICl CHI− CHCl 2] the excess of iodine monochloride is treated with potassium iodide. ICl † KI KCl † I 2 3] the liberated iodine estimated by titration with sodium thiosulfate solution . I 2 † 2Na 2 S 2 O 3 Na 2 S 2 O 6 † 2NaI

5. Calculations:- Iodine value = 12.69(B-S)N ⁄ W Where, B = volume in ml of standard sodium thiosulphate solution required for the blank . S = volume in ml of standard sodium thiosulphate solution required for the sample. N = normality of the standard sodium thiosulphate solution W = wt in g of sample

6. Methods to determine the iodine value of fats and oils:- 1] Hubl’s method : carbon tetrachloride solution of substance is treated with solution of iodine and mercuric chloride in ethanol. 2] Wiji’s solution: iodine monochloride in glacial acetic acid is used. 3] Dam’s solution: solution of glacial acetic acid is use containing pyridine ,bromines and conc. Sulphuric acid.

7. Limitations :- It does not take into account the number and configuration of double bonds per molecule( only the total number of double bond is recorded)

8. Oil/fat Iodine number Milk fat Olive oil Coconut oil Palm oil Cocoa butter Rice bran oil Grape seed oil Beef fat Lard Peanut 30-35 80-88 8-11 44-51 35-40 99-108 124-143 Approx.50 Approx.60 84-105

9. PEROXIDE VALUE The peroxide value is figure used for determining the peroxide oxygen .It is expressed in mill equivalent of active oxygen per 1kg of fat . Methods to determine the PV:- Fourier transform infrared spectroscopy(FTIR) Iodometric titration Ferric ion complexes

10. Principle :- Peroxide value is a measure of the peroxides contained in the oil. the peroxides present are determined by titration against thiosulphate in the presence of KI starch is used as an indicator . Calculation:- PV( milli equivalent peroxide /kg sample) = S × N × 1000 ⁄ g sample. where, S = ml sodium thiosulphate(test-blank) N = normality of sodium thiosulphate

11. Factors that affect the rate of oxidation are the following :- amount of oxygen present degree of unsaturation of the lipids presence of antioxidants presence of prooxidants ,especially copper and some organic compounds such as heme-containing molecules and lipooxidase nature of packaging material light exposure temp. of storage

12. Steps of determining the peroxide value Weigh the sample accurately Dissolution of lipids in chloroform Acidification with acetic acid Addition of KI Incubate for 5 min Titration with sodium thiosulphate ROOH † 2H + † 2KI † I 2 † ROH † H 2 O † 2K + I 2 † 2Na 2 S 2 O 3 Na 2 S 2 O 6 † 2NaI

13. Oil/fat PV( meq /kg) Olive oil Sunflower oil Cocoa butter Maize oil Rapeseed oil 7.99 7.10 3.32 4.21 3.82

14. RESEARCH Blending of oil on storage stability and sensory characteristics of a ready to eat extruded snack By – Dr. Sridevi Gutta and Dr. Kavita Waghray Taking the nutritional evaluation of six different oil blends was conducted using sesame oil as control. The oil blends selected were rice bran, cottonseed, palmolein , mustard, and corn in the ratios of 80:20 and 20:80 with sesame. These oil blends were used by making a ready to eat (RTE) extruded snack and store it 2months to examined the changes in chemical and sensory characteristics. RESULT- Near significant changes were observed in the oil extracted from the fried product in comparison to control. Sensory evaluation of the ready to eat(RTE) extruded snack indicated that it was chemically acceptable up to two months of storage.

15. References :- Deman Florin Thomas Alfred, 2002 Springer Lipid Oxidation : Measurement Methods Analysis of Foods