Effect of black cumin essential oil on physicochemical, microbial and sensorial characteristics of ultrafilterated Feta cheese

Black cumin is one of the most important and valuable herbal plants that are wildly found in regions of Iran with dry weather such as Kerman, Fars, Isfahan and Yazd. Black cumin seed in traditional medicine is used as anti- flatulence, anti-diarrhea, antipyretic, blood fat and cholesterol reducer, anti-allergic and digestive enhancers. Essential oils are oily liquids that are obtained from different parts of the plant. Different compounds in the essential oil of black cumin include cumin-aldehyde, gamma trypinene, paracymon and other active ingredients, which are often terpene compounds and have numerous uses as anti-bacterial and antioxidant agents. In recent years, consumers have become more concerned with the health issues and are looking to eat foods with higher functional characteristics, as well as higher nutritional value. Therefore, it can be suggested that essential oil of Cumin as a natural and vegetable preservative was used in food. Because cheese is a nutritious environment for the growth of microbes, it always has microbial degeneration.

Identification of essential oil compound was performed by GC/MS chromatography. In order to evaluate the effect of Black Cumin essential oil on physicochemical, microbial and sensory properties of cheese, different percentages of Black Cumin essential oil (0, 0.05, 0.1% and 0.15%) were added to cheese. Iranian white cheese production was done by ultrafiltration method in Arjan Fars Company. Cheese sample were analyzed at days 3, 30 and 60 of storage time. Acidity, pH, fat, protein and dry matter were measured according to National Standard No. 2852, 2852, 8785, 1811, 1753 respectively. To measure the inhibition of free radicals of DPPH, method of Rezai et al(2012) was followed. Microbial characteristics were performed according to the standard microbial milk and dairy products number 2406. The color analysis was performed based on Hosseini et al (2019) method. The parameters of color include L* (lightness), a* (redness) and b* (yellowness) were measured. The sensory attributes were evaluated by 9 panelists. A five-point hedonic scale rating (1= very bad, 2=bad, 3= neither bad nor good, 4= good, 5= very good) was carried out. Data analyzed with SPSS: 22 software and Means were compared with Duncan multiple range test (p<0.05).

The analysis of black cumin essential oil with GC/MS chromatography showed that the main ingredients of it were α-Thujene, p-Cymene, Linalool, Thymoquinone, Carvacrol and Longifolene. The results showed that Changes in essential oil percentage had significant effect (p<0.05) on acidity, pH, IC50. With increasing essential oil percentage, an increase in the level of acidity and decrease in the level of IC50 and pH was observed. Changes in essential oil percentage had no significant effect(p<0.05) on protein, fat, salt and dry matter content of cheese. The results showed that storage period had no significant effect (p<0.05) on protein, fat and salt content. Increasing the essential oil percentage of cheese significantly decreased the L* index and increased the b* index. The microbial analyses showed no microbial contamination (coliforms, sataphylococcus aureus, mold and yeast) was found during the storage time therefore, the essential oil of Cumin can be used as a natural preservative in cheese production. Analyses of the sensory characteristics during storage time showed that the addition of essential oil to cheese did not have any significant effect on color and texture but had a significant effect on taste and acceptance of cheese. In all treatments, the taste score changed significantly with time (p <0.05). Over time, the flavour rating began to increase until the twentieth day, and then decreased to the end of the storage time. In general, the treatment containing 0.05% Black Cumin essential oil has the highest acceptance in sensory evaluation and since its other characteristics were standard, it was selected as the best treatment.