Combination of Homogenization, Citrus Extract and Vanillic Acid for the Inhibition of Some Spoiling and Pathogenic Bacteria Representative of Dairy Microflora
This research proposes the optimization of a preserving treatment (homogenization—high-pressure homogenization (HPH)—and some safe antimicrobial compounds) able to inhibit the spoiling and pathogenic microflora of milk. In the first phase, 16 strains, including lactobacilli and bifidobacteria, pseudomonads and enterobacteria, were studied in order to assess their resistance to homogenization (pressure ranging from 50 to 150 MPa for single-step treatments; multi-step treatments were performed at 150 MPa through two or three passes across the homogenizing valve). Lactobacilli and bifidobacteria were the most resistant microorganisms (as a threefold treatment at 150 MPa was required to achieve a cell reduction of 1–2 log cfu/ml), followed by pathogens and then by pseudomonas and enterobacteria. Then, a mixture design was further used to define combinations of homogenization (0–150 MPa pass−1), vanillic acid (0–0.24 %) and citrus extract (0–300 ppm), to control the growth of a mixture of pseudomonas, enterobacteria and lactic acid bacteria; results were used to build two successive models: a primary model for the estimation of the physiological parameters of the microorganisms, whose fitting parameters were used to build a secondary model (polynomial equation) to predict the effectiveness of the combinations of HPH, citrus extract and vanillic acid. Statistical analysis highlighted that a prolongation of shelf life by 4 days (evaluated by pseudomonas cell counts) could be achieved combining homogenization at 75 MPa with either 0.12 % of vanillic acid or 150 ppm of citrus extract.
Authors:
Antonio Bevilacqua, Daniela D’Amato, Milena Sinigaglia, Maria Rosaria Corbo
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