Effects of different heat treatments on lysozyme quantity and antimicrobial activity of jenny milk

Abstract

Thermal treatments are used to improve milk microbial safety, shelf life, and biological activity of some of its components. However, thermal treatments can reduce the nutritional quality of milk, affecting the molecular structure of milk proteins, such as lysozyme, which is a very important milk component due to its antimicrobial effect against gram-positive bacteria. Jenny milk is characterized by high lysozyme content. For this reason, in the last few years, it has been used as an antimicrobial additive in dairy products as an alternative to hen egg white lysozyme, which can cause allergic reactions. This study aimed to investigate the effect of pasteurization and condensation on the concentration and antimicrobial activity of lysozyme in jenny milk. Furthermore, lysozyme quantity and activity were tested in raw and pasteurized milk after condensation at 40 and 20% of the initial volume. Reversed-phase HPLC was performed under fluorescence detection to monitor lysozyme in milk samples. We evaluated the antimicrobial activity of the tested milk against Bacillus megaterium, Bacillus mojavensis, Clavibacter michiganensis, Clostridium tyrobutyricum, Xanthomonas campestris, and Escherichia coli. Condensation and pasteurization did not affect the concentration or antimicrobial activity of lysozyme in jenny milk, except for B. mojaventis, which showed resistance to lysozyme in milk samples subjected to heat treatments. Moreover, lysozyme in jenny milk showed antimicrobial activity similar to synthetic antibiotics versus some gram-positive strains and also versus the gram-negative strain X. campestris.

Biological Investigations and Spectroscopic Studies of New Moxifloxacin/Glycine‐Metal Complexes.

“…The mechanism is based on the ability of tested compounds to reduce the DPPH radical (deep violet) into a neutral stable molecule (pale yellow). [57,58] Stock radical solution of DPPH was prepared by dissolving 20 mg of DPPH in 15 ml ethanol and adjusted at 0.44 mg/ml. Test Procedures.…”

A Preliminary Assessment of HTST Processing on Donkey Milk

“…As a consequence, attention began to be paid to donkey milk transformation, in particular to its fermentation by lactic acid bacteria [ 13 , 14 , 15 , 16 , 17 ], to its storage [ 18 , 19 , 20 ], and to its sanitization [ 20 , 21 , 22 ]. Actually, the growing interest in donkey milk as a food for sensitive consumers, such as infants with allergies or immunocompromised elderly people, implies strict regulations for food safety [ 12 ].…”

“…Regional and National guidelines specific to donkey dairy farming exist in Italy and Greece [ 12 ]. Holder pasteurization [ 21 , 22 ], spray drying [ 19 , 23 ], lyophilization [ 15 , 19 ] and, more recently, high-pressure processing [ 21 , 22 , 23 , 24 ] have been tested, and some of the resulting products can be found on the market, especially powders. Due to the increasing number of small dairy donkey farms in Italy, farmers need more sophisticated and reliable processing devices, in order to guarantee a safe product of high quality, and to increase their market share beyond the local region.…”

Impact of Rodenticides on the Coagulation Properties of Milk

“…This ensured a more consistent comparison of control and experimental samples, but also excluded many of the variables intrinsic to a farmstead. We mitigated this problem by approximating the natural variations in bulk milk coagulation properties with real world data from cows and other sources of milk, such as buffalo, donkey, goat, sheep, and Jenny [ 32 , 33 , 34 ]. A logical next step would involve testing milk samples collected from bulk storage tanks in situ to validate the approximated bulk milk variations and the observed effects of rodenticide contamination.…”