Abstract
In our study, we assessed whether the addition of basil, fennel, oregano, rosemary, and chili can improve oxidative stability and sensory properties of flaxseed oil (FO) during 180 days of storage or induce oil contamination by microorganisms. Results showed that addition of spices and herbs in FO affected the hydrolytic changes, but far less than 2% of free fatty acids after storage, which was in line with regulations. Further, the addition of spices and herbs in FO decreased peroxide value (even up to 68.7% in FO with oregano) vs. FO whose value increased during storage, indicating increased oxidative stability and prolongation of shelf life of infused oils. The antioxidant activity of the infused oils ranged from 56.40% to 97.66%. In addition, the phenol content was higher in all infused oils (6.81-22.92 mg/kg) vs. FO (5.44 mg/kg), indicating that herbs and spices could scavenge free radicals and inhibit lipid peroxidation, while sensory analysts showed that FO infused with chili had the lowest bitterness intensity. According to the presence of certain microorganisms, results highlighted the need to develop new methods for inactivating microorganisms that would not only provide a microbial safety, but also preserve the beneficial properties of the oils/products.
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Key Points
Today, a number of compounds are known to have antioxidant properties, but only some of them can be used to prolong the shelf life of oils, since the selection of natural antioxidants to prevent lipid oxidation is challenging and depends on multiple factors such as fatty acid profile of the oil, minor components present in the oil, and structure of the antioxidants. The antioxidant activity of spices and herbs has been increasingly investigated, and food manufacturers are trying to replace synthetic antioxidants with natural compounds, which, in addition to slowing oxidation processes, also have a positive effect on consumer health and good image among consumers. Some natural antioxidants; i.e., plant-derived compounds such as carnosol, rosmanol, rosmariquinone, and rosmaridiphenol, may be up to four times as effective as butylated hydroxyanisole (BHA), and equal to butylated hydroxytoluene (BHT) due to synergism with other preservation methods, and are also reported to be superior in terms of safety, prevention of nutrition-related diseases, and improvements of physical and mental well-being of consumers.
Herbs and spices do not normally raise health concerns in humans, but they can be contaminated with microorganisms that can cause spoilage, whose growth during food storage increases or may allow the transmission of pathogenic bacteria, such as Salmonella spp., E. coli, Campylobacter, and Shigella spp., through the feces of birds or animals or by Clostridium botulinum present in the soil, which can be dangerous for the consumer. The aim of this study was to increase the oxidative stability of flaxseed oil by using natural antioxidants such as rosemary, oregano, basil, fennel, and chili based on beneficial health effects and the Mediterranean climate, as well as to evaluate the sensory properties of flaxseed oil infused with different spices and herbs. In addition, regarding the mentioned potential biological hazards that herbs and spices bear, microbiological testing of infused oil was also carried out to determine whether added herbs or spices contaminated the oils.
The panelists evaluated flaxseed oil samples with the addition of 5% spices and herbs in the form of macerate, and the results represent the sum of the panelists’ ratings. During the second, fourth, and six months of storage, chili had the lowest bitterness intensity. Rosemary had the lowest scores during 180 days of storage due to its high concentration of phenolic compounds and strong intensity of bitterness Flaxseed oil with fennel and oregano had similar results regarding bitterness intensity. Flaxseed oil with fennel was rated at the beginning of the preparation, as well as flaxseed oil with rosemary. Intense flavor and aroma respective to bitterness of flaxseed oil with oregano, which also had a high phenol content as rosemary, made it more bitter than others. Certain infused oils would be less accepted among consumers precisely because of the strong aroma intensity of the added herbs and spices, and that flaxseed oil with chili might be well accepted by consumers. The reason for this could be obtained higher scores, lower phenol content, and knowledge of this spice, its taste, and its use in the preparation of meals.
Furthermore, it should also be noted that the results of the sensory testing might have been different if flaxseed oil with basil had been included in the testing, but it was excluded due to the increased number of microorganisms. The obtained results of the sensory analysis of the infused oils were significant, because the intensity of bitterness can affect consumers’ acceptance of the product.