Evaluation of the chemical composition of the antioxidant and antimicrobial properties of the essential oil of Thymus Kotschyanus or Kohlik Oti in laboratory environment and food model

Master's Thesis

Field of Health and Food Safety

Abstract:

Context: Essential oils and extracts obtained from medicinal plants with antimicrobial, anticancer and antioxidant compounds are of special importance as new and natural medicinal compounds both in the field of health and treatment of diseases and protection of raw and processed foods.

Aim: To determine the chemical composition, antioxidant and antimicrobial properties of the essential oil of Thymus Kotschyanus or Kohlik Oti plant in a laboratory environment and food model

Methodology: In this study, the essential oil of Kohlik Oti plant was prepared and identified by GC-MS, and the amount of phenolic and flavonoid compounds of the essential oil was determined using the standard method and its antioxidant property was determined by the DPPH method. The antimicrobial properties of essential oil against E.coli O157:H7 bacteria in culture medium and food model of buttermilk along with physico-chemical and sensory parameters of buttermilk were investigated during a period of 14 days. Findings: The results of essential oil analysis showed that thymol with 51.1% has the highest amount among essential oil constituents. The amount of phenolic compounds was 82±6.43?g/mL and the amount of flavonoids was 30.79±0.5?g/mL of essential oil. The evaluation of the antioxidant test showed that the IC50 of the essential oil was 32.35 ?g/mL and its MIC, which was determined by the microdilution method, was 470 ?g/mL of the essential oil. The essential oil has strong antimicrobial properties and in low concentrations added to the buttermilk, it destroyed the studied E.coli O157:H7 bacteria in the first days. Based on the obtained results, essential oil does not cause significant changes in the physicochemical properties of buttermilk, except for the total solids, where buttermilk without essential oil has a significant difference with buttermilk containing 100 and 200 ppm of essential oil in terms of this characteristic, and buttermilk with 50 ppm of essential oil has the best taste and has a higher acceptability among judges.

Conclusion: According to the results obtained, it can be Kohlik Oti was used in low concentrations in the production of buttermilk, and more studies should be done on it for use in other industries, and also the essential oil has good antioxidant power, so it can be used in combination with other preservatives to protect food from all kinds of oxidative systems.

Keyword: Essential oil, kohlik oti, antioxidant activity, antimicrobial activity, buttermilk

Introduction

One ??of the problems in food is the oxidation of oils. Oxidation is considered one of the most important and well-known causes of lipid corruption during their storage or processing. Edible vegetable oils containing high amounts of unsaturated fatty acids are very prone to oxidation. This process is not only associated with the spread of pungent taste, unpleasant aroma and discoloration, but also reduces the nutritional value of oils and fats and by producing some toxic and dangerous compounds, it exerts adverse effects on human health. However, to prevent the oxidation of oils in the food industry, synthetic antioxidants are used, which themselves have harmful effects on the human body (Zhang et al, 2010). Also, the presence of microorganisms and especially bacteria in food is very important in terms of health and public health, as well as in terms of food quality control. In addition, food spoilage due to the growth of microorganisms is still considered as a problem in the food industry. One of the ways to prevent the growth and control of bacteria in food is to use preservatives and antimicrobial compounds. In order to prevent the growth or kill some harmful microorganisms, chemical preservatives were used for a long time. But today, due to the increasing level of awareness and public concerns about the side effects of chemical preservatives, the tendency to consume products without preservatives or with natural preservatives is increasing.Therefore, in recent years, many studies have been conducted on natural preservatives such as essential oils and natural extracts. Extracts and essential oils of medicinal plants and their components have known antibacterial effects (Burt, 2004). Their many uses in order to control the growth of food pathogenic bacteria or the cause of spoilage have led to their use as food preservatives. Because essential oils and plant extracts and many food items are used to create a pleasant taste, the simultaneous presence of their antimicrobial properties can encourage their use for this purpose. The US Food and Drug Administration FDI [1] has also recognized the use of essential oils as food additives that are generally safe GRAS [2] (Oussalah et al, 2007). Today, food safety is an important public health issue and it is estimated that 30% of people in industrialized countries suffer from food-borne diseases. Therefore, new methods are still needed to reduce or eliminate food pathogens as much as possible with the combination or existing methods. One of the methods of producing healthy food is to use materials with natural structure. The use of essential oils and plant extracts as antibacterial and antifungal additives is one of these methods. (Bhurinder et al, 2001 and Reiter et al, 2009). Essential oils or essential oils (volatile or ethereal oils) are aromatic oily liquids obtained from different parts of a plant (flowers, blossoms, seeds, leaves, branches, bark, shrubs, wood, fruits and roots). Essential oils can be obtained by pressure, fermentation, distillation or extraction, but the steam distillation method is generally used to produce essential oils. According to an estimate, about 3000 types of essential oils are known, of which about 300 types are commercially important, especially for the purpose of perfume and seasoning trade, and some of them have antimicrobial properties. In addition to the antimicrobial properties of essential oils or their compounds, their antiviral, antifungal, anti-poisoning, anti-parasitic and anti-insect effects have also been determined. For example, in Canada, the cost of treating diseases caused by consuming meat contaminated with food pathogens is over 500 million dollars per year. In 1999, the Centers for Disease Control and Prevention reported that 76 million people in the United States get sick every year from foodborne pathogens. Such diseases lead to 225,000 hospitalizations and 5,000 deaths annually. According to the assessment of the United States Department of Agriculture (USDA), the medical costs and economic losses caused by discarding food that cause food diseases are in the range of 6.5 to 34.9 billion dollars per year (Rajhan, 1378). One of the ways to control the growth of pathogenic bacteria in food is to use preservatives and antimicrobial compounds. Adding chemicals to preserve food is usually based on preventing microbial growth or killing and destroying groups of harmful microorganisms (Bhurinder et al, 2001). deal of interesting applications in fresh and processed food preservation, Pharmaceuticals, alternative medicine and natural-based therapies.

Objective: Determine of chemical composition, antioxidant and antibacterial properties of Thymus Kotschyanus essential oil in vitro and food model.

Methods: the chemical compositions and its value of Thymus kotschyanus were determined with set Gas chromatography-Mass spectrometry.