Ancuţa Mihaela Rotar

Antibacterial activity and interactions of plant essential oil combinations against Gram-positive and Gram-negative bacteria

The aim of this study was to compare the antibacterial effects of several essential oils (EOs) alone and in combination against different Gram-positive and Gram-negative bacteria associated with food products. Parsley, lovage, basil, and thyme EOs, as well as their mixtures (1:1, v/v), were tested against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Salmonella typhimurium. The inhibitory effects ranged from strong (thyme EO against E. coli) to no inhibition (parsley EO against P. aeruginosa). Thyme EO exhibited strong (against E. coli), moderate (against S. typhimurium and B. cereus), or mild inhibitory effects (against P. aeruginosa and S. aureus), and basil EO showed mild (against E. coli and B. cereus) or no inhibitory effects (against S. typhimurium, P. aeruginosa, and S. aureus). Parsley and lovage EOs revealed no inhibitory effects against all tested strains. Combinations of lovage/thyme and basil/thyme EOs displayed antagonistic effects against all bacteria, parsley/thyme EOs against B. cereus, S. aureus, P. aeruginosa, and E. coli, and lovage/basil EOs against B. cereus and E. coli. Combinations of parsley/lovage and parsley/basil EOs exhibited indifferent effects against all bacteria. The combination of lovage/basil EO showed indifferent effect against S. aureus, P. aeruginosa, and S. typhimurium, and the combination parsley/thyme EO against S. typhimurium. Thyme EO has the highest percentage yield and antibacterial potential from all tested formulations; its combination with parsley, lovage, and basil EOs determines a reduction of its antibacterial activity. Hence, it is recommended to be used alone as the antibacterial agent.

Characterization of pine bud syrup and its effect on physicochemical and sensory properties of kefir

This study aimed to develop a value-added kefir by the addition of pine bud syrup. For this purpose, different concentrations of pine bud syrup [2, 4, 6, 8, and 10% (w/w)] were added to kefir formulation after the fermentation. The pine bud syrup used for kefir fortification is rich in polyphenols and terpenes and has a high antioxidant activity. The study was designed to evaluate the influence of pine bud syrup on the physicochemical and sensory properties of kefir. The addition of pine bud syrup resulted in an increase in total solids and a decrease in fat content, proteins, and pH. The kefir sample with 10% pine bud syrup was the most appreciated by sensory panelists. Its overall acceptability score was higher (6.71 points) than regular kefir (5.57 points). The addition of 10% pine bud syrup improved the texture and consistency of regular kefir.

Chemometric Comparison and Classification of Some Essential Oils Extracted from Plants Belonging to Apiaceae and Lamiaceae Families Based on Their Chemical Composition and Biological Activities

This study is focused on the comparison and classification of parsley, lovage, basil, and thyme essential oils (EOs) based on their chemical composition, total phenolic content, antioxidant and antibacterial activities by using appropriate chemometric methods: Principal component analysis (PCA) and hierarchical cluster analysis (HCA). The results showed that parsley, lovage, and thyme EOs are rich in monoterpene hydrocarbons, but basil EO is rich in oxygenated monoterpenes and phenylpropanoids, and that both PCA and HCA separated essential oils into two main groups of which one contains two sub-groups. β-Phellandrene was the major component identified in parsley and lovage EOs, estragole was the major component in basil EO, and p-cymene was the major component in thyme EO. Thyme EO showed the highest level of total phenolics, the highest antioxidant capacity, and exhibited the stronger antibacterial activity, results that were emphasized by both chemometric methods used. Among tested essential oils, the one of parsley was distinguished by a low total TPC, weak antioxidant activity, and weak antibacterial activity against S. enteritidis (ATCC 13076); lovage EO by low TPC, weak antioxidant activity, but moderate antibacterial activity; and basil EO by low TPC, moderate antioxidant activity, and weak antibacterial activity against L. monocytogenes (ATCC 19114).

The Evaluation of the Sensory and Microbiological Properties of the Yogurt Supplemented with Achillea melifolium and Solanum muricatum

This research explored the sensory characteristics and consumer acceptance of novel yogurt. The study aimed to develop a new type of yogurt through addition of microcapsules with Achillea melifolium infusion and jelly from the pepino fruit. The effect of yogurt supplementation with four different levels (0%,1%,3%,5%) of microcapsules with Achillea melifolium infusion (MI) and four levels (0%,3%,7%,11%) of pepino juice jelly (PJ) on sensory properties and the viability of lactic acid bacteria in yogurts during storage (21 days) at 4°C was evaluated. The yogurt supplementation with 3% microcapsules and 7% jelly significantly improves the stability of the lactic acid bacteria, that contained the recommended levels of 108 cfu/g lactic acid bacteria at the end of 21-days shelf life. All the yogurt samples, however, contained the recommended levels of (106–107 cfu/g) lactic acid bacteria at the end of 21-day shelf life.The yogurt with 3% microcapsules and 7% jelly was the most appreciated (6.78 points), followed by the classic yogurt (5.98 points). Total phenols content was 251 mg GAE/g for A. millefolium infusion and 117 mg GAE/g for pepino juice. The radical scavenging activity of A. millefolium infusion was 78% and for pepino extract 56.30%.

RESEARCHES CONCERNING THE PROTEOLITICAL MODIFICATIONS DURING THE FERMENTATION AND THE STORAGE OF DAIRY PRODUCT-SANA

In this study were followed biochemical modifications of dairy product-sana, during processing. The researches were focused on two main working directions: - appreciation of raw milk quality; - dairy product-sana amino–acids determination by gas chromatography method.