The relevance of selecting the best in vitro test for antifungal screening of essential oils is sometimes overlooked. The minimal inhibitory concentration is usually determined using in vitro diffusion experiments. However, these data are mainly of interest when the essential oils are intended to be used as volatiles in the food packaging atmosphere. Data from both the in vitro diffusion and dilution experiments can be used for essential oil spray applications. The volatile behaviour of sprays, as well as the effect of touch, are essential considerations. If essential oils are to be used in a food matrix, such as bread dough, an in vitro dilution screening assay is required to predict antifungal activity when dispersed in a medium, ideally with adjusted pH, aw, media composition, and incubation temperature.
Impact Of Selected Chemical Charactersitics Of Cold-Pressed Oils
One of the most essential parameters used to measure oil quality is oxidative stability, which determines the oil’s resistance to oxidation. Unsaturated fatty acids oxidise during storage or heat treatment, causing their quality to deteriorate. Oils high in polyunsaturated fatty acids, particularly linolenic acid, are particularly susceptible to oxidation. Oils obtained by cold pressed technology in addition to triacylglycerides also contained lipid-accompanying compounds. As a result, its stability is determined not only by the composition of fatty acids, but also by the presence of antioxidants, primary and secondary oxidation products, metals, and other pollutants that may speed up or slow down the oxidation process.(1)
Thermal techniques can also be used to determine the oxidative stability of oil. Pressure differential scanning calorimetry (PDSC) is a good method for assessing the oxidative stability of vegetable oils in an accelerated mode; results are acquired faster due to the high temperature and pressure used. The fact that oil oxidation is an exothermic process is used in the PDSC approach. A reference sample is compared to the heat emitted during the oxidation of an oil sample. The difference in generated heat is graphed over time, from which the determined start time and maximal oxidation duration can be calculated. Both metrics are used to describe the oxidation of oil, although they relate to different stages of the oxidation process.
The products formed in the oxidation processhave an ad-verse effect on the human body; therefore, proper assessment of the oxidative stability is a decisive step in the safety assessment of oil. The methods for determining the oxidative stability of oils are numerous.