Stress test methods : a potential approach to hurry up shelf-life tests on oat products
Abstract: The aim of this Master’s thesis was to find out more about the delimiting quality- and shelf-life parameters over time for liquid oat-based products. According to that, to present applicable subjective and objective shelf-life test approaches at accelerated conditions. The study aimed to gain a deeper knowledge concerning the general and accepted way of performing accelerated storage tests. This study focused especially on products, which suffer from quality failure caused by oxidation, such as liquid oat-based products. The main subject was to present a proper accelerating test method, with potential to be implemented on products with oxidation as the delimiting quality failure parameter to make the production of oat products more effective and economically desirable. Current shelf-life studies cover a long period in time, which prolongs the time and the total costs until new products finally can be launched on the market. An easy stress-test method is desirable to be able to accelerate shelf-life storage measurements in parallel to an actual shelf life-study lasting for the whole shelf-life period. This, in order to get a first indication of whether it is worth to continue with the shelf-life study or not and if the product has the possibility to last and keep a high quality for the whole test period or not. If possibility to implement these kind of accelerated tests, it would be a big advantage. The easiest, applie able accelerated approach to recommend, is the shelf-life experiments due to Q10-modeling, were two test temperatures in combination with correlation shelf-life estimations will generate a Q10-factor. The intention with Q10 -modeling is a way to state the increase in the rate of reaction, when the temperature is increased by 10°C. The value of Q10 can be calculated from data of almost every kind of storage test, even if the temperatures are not 10°C from each other. The test temperature should be within a range of 20-60°C. Common test temperatures are10°C apart and experiments should e.g. be conducted at 25, 35, 45 and 55°C. Temperatures of 25°C and 35°C are working as a suitable example, when dealing with autooxidation reactions. At least two test temperatures are required, but three or four is an ideal number for more precise shelf-life predictions. Experimental studies conducted within 60 days period of time seem generate good test results. The Q10-factor based on shelf-life experiments, are used further in order to calculate the activation energy (EA) for the reaction of interest. The acceleration factor (AF) factor is thereafter calculated by using mathematical equations. The AF factor converts the accelerated shelf-life estimation results back to normal storage conditions. There is most likely time and money to save with a proper accelerated study as it hopefully will give a hint and point out the measureable, limiting parameter and the weakness of a products shelf-life on an early stage. This initial data will give information whether the study should be ended on an early stage to save time and money, or to be continued at full-time length. An accelerated study cannot under any circumstances be the single deciding action to predict a products shelf-life. An accelerated shelf-life study should always be performed in parallel with a full-length study and together with a sensory evaluation program. The sensory evaluation program should be considered as the major limiting parameter, due to the consumers’ interpretation, acceptance and preferences.
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