1. ACCELERATED OXIDATION TRIALS FOR SHELF LIFE ESTIMATION BY: DIPANSHU CHINWAN FSTC 605

2. CONTENTS ▪ Introduction ▪ Classical approach (ASLT) ▪ Steps (ASLT) ▪ Methods ▪ ASLT at Low temperature ▪ Method ▪ Results ▪ Conclusion

3. INTRODUCTION ▪ Shelf-life is “the amount of time that a food product is considered acceptable for consumption when stored at the appropriate storage conditions.” ▪ Shelf-life studies can come in many different forms, including accelerated studies. ▪ In these studies, accelerated conditions (i.e. elevated temperature) are applied to eligible products to predict product shelf-life at typical storage conditions. ▪ This process is performed using the Q 10 value. ▪ The Q 10 value of a product is the temperature quotient for a 10°C temperature difference.

4. ▪ The most prominent spoilage concern for products eligible for accelerated shelf-life studies is rancidity. ▪ Hydrolytic Rancidity ▪ Oxidative Rancidity ▪ Accelerated studies best suited for products with more than 6 month of shelf life.

5. CLASSICAL APPROACH (ASLT) ▪ Factor: Temperature ▪ Effect on lipid oxidation is best analyzed in terms of overall activation energy. ▪ Assumption ▪ E A is the same in both, the absence and presence of antioxidants. ▪ Limitations ▪ Data at 60-65°C shows that such tests lead to sizeable, but predictable, underestimation of shelf-life extensions by antioxidants for room temperature. ▪ In comparison, data collected at 98-100°C are much less predictable. ▪ Temperature range should not be exceed in ASLT studies for foods.

6. STEPS (CLASSICAL ASLT) 1.Select a suitable method for testing the food product under consideration. 2.A sample is placed under the conditions of the test and the induction period is measured. 3.Translate the value for the induction period obtained into actual product shelf-life in months of storage. Four parameters are manipulated in ASLT procedures to speed up the oxidation and development of rancidity in foods or oils.

7. OTHER PARAMETERS ▪ Oxygen pressure ▪ Reactant contact ▪ Addition of catalyst * The effect of these factors is much less important than that of temperature. In accelerated stability tests, a product may be released based on accelerated stability test, but the real-time testing must be done in parallel to confirm the shelf-life prediction.

8. ASLT METHODS FOR PREDICTING OXIDATIVE STABILITY ▪ The Schaal Oven Test (SOT) ▪ 50 g samples held in 250 ml beakers maintained at 63°C. ▪ Samples smelled daily until rancidity point was reached. ▪ The temperature called for in this method is much lower than in most other ASLT procedures. ▪ Oxygen Absorption Methods (OAM) ▪ 100 to 1000mg samples of lipid are kept in 30 ml flasks connected to mercury manometers. ▪ These are connected to a pressure recorder. ▪ The sample is kept at atmospheric pressure in oxygen at 100°C. The end- point was taken as the time when a marked drop in pressure occurred. ▪ Use of a higher temperature acts as a limitation for this method.

9. ▪ Active Oxygen Method (AOM) ▪ 20 milliliter samples of lipid are kept in 1in × 8in glass tubes and clean dry air at 2.33 cm 3 /sec is bubbled through. ▪ The temperature is maintained at 97.8°C. ▪ Periodically about 0-2ml samples are withdrawn and the peroxide value (PV) is determined until it reaches 120 meq/kg. ▪ The main problem with this method is the high temperature used. Generally, an arbitrary multiplying factor is used, based on previous experience, to give an estimate of the shelf-life at room temperature. ▪ The ASTM Oxygen Bomb Method (OBM) ▪ 15-30 g of lipid is added to a glass container which was fitted into the bomb. ▪ The oxygen pressure used was either 65 or 115 psia and the temperature 99°C. ▪ The induction period was taken as the time to reach the mid-point of the first hour during which a pressure drop of at least 2 psia/h was obtained.

10. ACCELERATED TRAILS AT LOW TEMPERATURES ▪ Free radical generation (FRG) assays. ▪ Azo-initiators with analytical equipment that is widely used for antioxidant research such as the oxidative stability instrument and the oxygen bomb. ▪ Use of initiators instead of high temperatures to increase the rate of oxidation. ▪ Lower temperature of analysis reduces differences between the reaction kinetics of the assay and those of the oxidation during actual shelf life. ▪ Theoretically, apolar azo-initiators gave a good potential to mimic the natural oxidation process.

11. METHOD/STEPS ▪ Preparation of the initiator ▪ Antioxidants ▪ Matrix preparation ▪ Quantification of 2-thiobarbituric acid (TBA) Reactive Substances ▪ Quantification of Peroxide Value ▪ Measurement of Oil Stability Index ▪ Measurement of Oxygen Consumption with OB

12. RESULTS ▪ A combination of both OSI and OB methods were combined with the use of free radical source to reduce the standard operating temperature of 98°C.

16. CONCLUSION ▪ The combination of free radical generation with existing analytical equipment results in a straightforward assay that is easy to apply in practice. ▪ The oxidation process in the FRG assay proceeds much more quickly than in non-accelerated studies. ▪ The main advantage of FRG assays applied on complex food matrices is the improved ability to rapidly compare the qualitative performance of several antioxidants in an accelerated test. ▪ Use of lower temperatures in FRG assay method prevents unwanted effects caused at high temperatures.

17. REFERENCES ▪ Labuza, j. O. (1977). Accelerated shelf-life testing for oxidative rancidity in foods--a review. Food Chemistry. ▪ Bateman. L. 0954). Olefin oxidation. Quart. Reviews, 8, 147-67. ▪ Joyner, n. T. & Mcintyre, j. E. 0938). The oven test as an index of keeping quality, oil and soap, 15, 184--6. ▪ Sylvester, n. D., Lam pitt, l. H. & Ainswortii, a. N. (1942). Determination of the stability of oils and fats, J. Sot'. Chem. Ind., 61, 165-9. ▪ King, a. E., Roschen, h. L. & Irwin, w. H. (1933). An accelerated stability test using the peroxide value as an index. Oil and soap, 10, 105-9. ▪ Stefaan m. O. Van dyck. (2005). Free radical generation assays: new methodology for accelerated Oxidation Studies at Low Temperature in Complex Food Matrices. Journal of Agricultural and Food Chemistry, 887-892. ▪ Tian, K.; Dasgupta, P. K.; Shermer, W. D. Determination of oxidative stability of lipids in solid samples. J. Am. Oil Chem. Soc. 2000, 77, 217-222 ▪ Frankel, E. N. Stability methods. In Lipid Oxidation; The Oily Press Ltd.: Dundee, Scotland, 1998; Vol. 10, pp 99-114.

18. QUESTIONS ???