The use of natural antimicrobial compounds in food has gained much attention by the consumers and the food industry. This is primarily due to two major factors. First, the misuse and mishandling of antibiotics has resulted in the dramatic rise of a group of microorganisms including foodborne pathogens that are not only antibiotic resistant but also more tolerant to several food processing and preservation methods. In addition, increasing consumers’ awareness of the potential negative impact of synthetic preservatives on health versus the benefits of natural additives has generated interest among researchers in the development and use of natural products in foods. Essential oils are volatile, natural, complex compounds characterized by a strong odor and are formed by aromatic plants as secondary metabolites. The bioactivity properties of essential oils are generally determined by the major compounds present in them. They have been widely used for bactericidal, virucidal, fungicidal, antiparasitical, insecticidal, medicinal, and antioxidant applications. The biological activity of the oils can be compared with the activity of synthetically produced pharmacological preparations. Thus, essential oils are promising natural extracts that need further evaluation for possible application as supplement, preservatives, or antioxidants in food or pharmaceutical industries.

The Essential oil (EO) of Nigella sativa (black cumin) was extracted from the crude oil and the volatile constituents were characterized using gas chromatographic analysis. The EO was formulated in water-based microemulsion system and its antibacterial activity against six pathogenic bacteria was evaluated using the agar well diffusion method. This activity was compared with two other well known biologically active natural and synthetic antimicrobials namely eugenol and Ceftriaxone(®). Results showed that N. sativa EO microemulsion was highly effective against S. aureus, B. cereus and S. typhimurium even at the lowest tested concentration of that EO in the microemulsion (100.0 μg/well). Interestingly, the EO microemulsion showed higher antibacterial activity than Ceftriaxone solution against S. typhimurium at 400.0 μg/well and almost comparable activity against E. coli at 500.0 μg/well. No activity was detected for the EO microemulsion against L. monocytogenes and P. aeruginosa. Eugenol which was also formulated in microemulsion was less effective than N. sativa EO microemulsion except against P. aeruginosa. The synthetic antibiotic (Ceftriaxone) was effective against most of the six tested bacterial strains. This work is the first report revealing the formulation of N. sativa EO in microemulsion system and investigating its antibacterial activity. The results may offer potential application of that water-based microemulsion in controlling the prevalence of some pathogenic bacteria.

The aim of this study was to investigate some factors that can contribute to the formulation of aqueous-based carvacrol microemulsion that can potentially be used in food preservation or disinfection. For this purpose the capacity of formation of carvacrol microemulsion was first revealed by studying the phase behavior of that compound in five different non-ionic microemulsion systems. Factors affecting that phase behavior like the type of non-ionic surfactant and presence of solubilization enhancers were also studied. The fully dilutable microemulsion system that can incorporate high carvacrol amount, as revealed from the phase diagrams, was chosen for the antibacterial evaluation study. The same microemulsion system was re-formulated in a cationic form by substituting the non-ionic surfactant, Tween 20 (T20) with the cationic cetylpyridinium chloride (CPC). The disc diffusion method was used to evaluate the activity of these microemulsion systems against different pathogenic bacteria. Results of the phase behavior study showed that carvacrol is a challenging phenolic compound which did not lend itself easily for solubilization in a fully dilutable non-ionic microemulsion. Incorporation of some solubilization enhancers like propylene glycol (PG) or short chain alcohols can fulfill this purpose however high surfactant/carvacrol ratio (9:1) was still required to solubilize only 1.0 wt% carvacrol in dilutable microemulsion. The antibacterial evaluation study at that concentration revealed that non-ionic carvacrol microemulsion formulated with T20 and a solubilization enhancer did not exhibit better antimicrobial activity than the same concentration of carvacrol formulated in surfactant-free aqueous solution composed of water/PG (1:1). On the other hand, the CPC-formulated carvacrol microemulsion showed significantly higher antibacterial activity than T20-formulated microemulsion. Results of the current investigation shed the light on the solubilization capacity and phase behavior of carvacrol in non-ionic microemulsion and the potential of using cationic carvacrol microemulsion in disinfection and decontamination applications.

Background. Chlorella vulgaris alga is one of the most important additives for enhancing the nutritional content of conventional foods, hence positively affecting human health. This alga is known as a rich source of protein, fatty acids, fiber, essential vitamins and minerals. Also, it contains antioxidants, omega 3, antiviral and anticancer properties. The aim of this research is increasing the nutritional and potential therapeutic value of processed cheese by using Chlorella vulgaris alga, taking advantage of its high nutritional and health value. Materials and methods. The ingredients in the processed cheese blends were mature cheddar cheese, Ras cheese, butter, skimmed milk powder, Emulsifying salts (K-2394, S9s & S4), Chlorella vulgaris (in freezedried and slurry forms). Chemical, rheological and sensory evaluation properties were evaluated in processed cheese analogue (PCA) treatments when fresh and after three months of cold storage at 5-7 degrees C. PCA treatments were enriched with 2%, 4% and 6% dried Chlorella vulgaris powder in the cheese blends and 4% Chlorella vulgaris slurry. Results. The incorporation of alga into processed cheese led to an increase in their functional characteristics. The results of sensory evaluation of PCA samples demonstrated that 2% of alga addition was the best treatment, followed by 4%, but that the level of 6% was unacceptable to consumers. The studied alga enhanced the cheese analog with the high levels of selenium, zinc, iron, magnesium and potassium. Antioxidant activity in the cheese enhanced with Chlorella vulgaris was higher than the control sample. To improve some properties of PCA, other emulsifying salts (S9S and S4) were tested and the alga was added in the form of slurry with value of 4% into the cheese blend. Both S9S and S4 emulsifying salts were good and the S4 was the best for oiling off and meltability. Also, when using the slurry of Chlorella vulgaris, the granular texture of the cheese analog completely disappeared. Conclusions. The results showed that the alga indeed increased nutrition values and health benefits to the processed cheese, making it a substantial functional food. Therefore, we recommend supporting the manufacture of the processed cheese analogue with the addition of 2% Chlorella vulgaris alga in soft powder form and 4% Chlorella vulgaris alga in slurry form at the end of the processing.