ABSTRACT
The effectiveness of three natural compounds in slowing down the deterioration of microbial quality of Fior di latte cheese is addressed. In particular, the control of the growth of spoilage microorganisms and the determination of the Microbiological Stability Limit (MAL) were the main goals. A Central Composite Design (CCD) strategy was adopted to highlight possible combined effects between three essential oils: sage and two types of lemon. Results showed an increase in the MAL value for all cheese samples packaged with the antimicrobial compounds, compared with the control cheese. Moreover, the combinations of the three essential oils indicated that the substances can act in a synergistic or antagonistic way, depending on their concentrations. In particular, a synergistic effect was evident when the three compounds were used at about 3000 ppm.
Subject(s)
Cheese/microbiology , Enterobacteriaceae/drug effects , Food Microbiology , Oils, Volatile , Plant Oils , Pseudomonas/drug effects , Salvia officinalis , Anti-Infective Agents/pharmacology , Drug Antagonism , Drug Synergism , Food Preservation/methodsABSTRACT
This study explains how active coating can serve to prolong the shelf life of Fior di latte cheese. The active coating was prepared by dissolving, in two sodium alginic acid solutions (5 and 8% w/v), different concentrations of lysozyme (0.25, 0.50 and 1.00 mg ml-1)+50 mm of Ethylene-Diamine Tetraacetic Acid (EDTA). Samples of Fior di latte cheese packaged in brine and active brine (lysozyme+EDTA, at the above concentrations) were also used as controls. The quality decay of the Fior di latte cheese stored at 10 degrees C was assessed by monitoring the viable cell concentration of the main spoilage microorganism, as well as its sensory quality (i.e., external appearance, consistency, colour and flavour). The concentration of rod-or coccus-shaped Lactic Acid Bacteria (LAB) was also monitored to assess the effect of the proposed packaging strategies on the flora type of Fior di latte cheese. The results show that an increase in the shelf life equal to 104% was recorded for the coated samples, compared with controls packaged in brine without active compounds. This shelf life increase is slightly lower than that recorded with samples packaged in the active brine (151%), as a result of a more pronounced microbial proliferation; however, the coating could be a better packaging solution for the reduced weight of tray.
Subject(s)
Cheese/microbiology , Food Packaging/methods , Food Preservation/methods , Alginates , Colony Count, Microbial , Edetic Acid , Food Packaging/instrumentation , Glucuronic Acid , Hexuronic Acids , Hydrogen-Ion Concentration , Italy , Muramidase , Pseudomonas/cytology , Salts , Sensation , Solutions , Time FactorsABSTRACT
In order to have a deeper insight into the retinol isomerization phenomenon, in this work different milk samples have been analysed for their content of trans retinol and its cis-isomers, by means of reliable HPLC techniques. Levels of the different isomers and the degree of retinol isomerization (13-cis/all-trans ratio, %) have been monitored during milk storage at different temperatures and after addition of specific microorganisms. In raw milk stored at 4 degrees C for 96 h the degree of retinol isomerization shifted from 1.1 to 2.3%, while in raw milk stored at 22 degrees C for 24 h it increased from 1.1 to 12.7%. Among microorganisms tested in pasteurized milk, the most active in causing an increment in the 13-cis/all-trans ratio (%), from 3.4 to 33.4% in 8 h, was Streptococcus thermophilus. The results obtained demonstrated a relationship between microbial evolution and retinol isomerization. Therefore, the determination of retinol isomers is of importance not only for a more precise evaluation of vitamin A activity but also for the evaluation of the microbiological quality of milk.
