Spray-dried conjugated linoleic acid encapsulated with Maillard reaction products of whey proteins and maltodextrin

Thymol nanoemulsified by whey protein-maltodextrin conjugates: the enhanced emulsifying capacity and antilisterial properties in milk by propylene glycol

The objective of this research was to enhance the capability of whey protein isolate-maltodextrin conjugates in nanoemulsifying thymol using propylene glycol to improve antilisterial properties in milk. Thymol was predissolved in PG and emulsified in 7% conjugate solution. Transparent dispersions with mean diameters of <30 nm were observed up to 1.5%w/v thymol. In skim and 2% reduced fat milk, Listeria monocytogenes Scott A was reduced from ∼5 log CFU/mL to below the detection limit in 6 h by 0.1% w/v and 0.45% w/v nanoemulsified thymol, respectively, contrasting with gradual reductions to 1.15 and 2.26 log CFU/mL after 48 h by same levels of free thymol. In full fat milk, L. monocytogenes was gradually reduced to be undetectable after 48 h by 0.6% w/v nanoemulsified thymol, contrasting with the insignificant reduction by free thymol. The improved antilisterial activities of nanoemulsified thymol resulted from the increased solubility in milk and synergistic activity with propylene glycol.

Nanocapsular dispersion of thymol for enhanced dispersibility and increased antimicrobial effectiveness against Escherichia coli O157:H7 and Listeria monocytogenes in model food systems

Essential oils are marginally soluble in water, making it challenging to evenly disperse them in foods and resulting in an increased tendency to bind with food lipids and proteins, resulting in lowered antimicrobial efficacy. In the current study, free and nano-dispersed (ND) thymol were compared in terms of their antimicrobial efficacies against Escherichia coli O157:H7 ATCC 43889 and 43894 and Listeria monocytogenes strains Scott A and 101 in apple cider and 2% reduced-fat milk. Apple cider was adjusted to pHs 5.5 and 3.5, and antimicrobial tests were performed at 0.3-, 0.5-, 0.75-, and 1.0-g/liter thymol concentrations at 35, 32, 25, and 4°C. Overall, 0.5 and 1.0 g/liter thymol in nano-dispersion and along with free thymol were inhibitory and bactericidal, respectively, against bacterial strains under all treatment conditions. At pH 5.5, 0.5 g/liter ND thymol was bacteriostatic against L. monocytogenes and E. coli for up to 48 h. At pH 3.5, L. monocytogenes controls did not survive beyond 12 h but E. coli survived and was inhibited by 0.5 g/liter ND thymol after 12 and 48 h in apple cider. E. coli strains were significantly sensitive to 4°C and pH 3.5 (P < 0.05). When bacteria were tested in 2% reduced-fat milk at 35 or 32°C, ND and free thymol demonstrated inhibition at 4.5 g/liter. Thus, the current technology seems to be promising and novel, enabling thymol-containing nano-dispersions that are not only transparent but also effective against pathogens in food applications, especially in clear beverages.