Powder characteristics, moisture sorption isotherm, and shelf-life prediction of freeze-dried recombinant Lactococcus lactis NZ3900-fermented milk powder

Abstract

There is an increasing trend toward delivering therapeutics such as vaccines using lyophilized, food-grade recombinant live cultures. The addition of protectants and proper packaging could improve the properties and stability of the powder. Hence, this study was aimed to investigate the powder characteristics, moisture sorption isotherm, and shelf-life prediction of the freeze-dried recombinant Lactococcus lactis NZ3900-fermented milk powder with protectants (1:1 maltodextrin:trehalose) in vacuum packaging. The freeze-dried fermented milk powder with protectants demonstrated good flow and rehydration properties with 0.98 flow stability, 4350 g/mm cake strength, 4.45 mm cohesion index, and 89% dispersibility. The freeze-dried fermented milk powder displayed a type III isotherm curve with a predicted shelf-life of 33.7 and 46.3 days in aluminum polyethylene and 4-ply retortable polypropylene–polyamide–aluminum–polyethylene terephthalate, respectively, at 38 °C and 90% RH. The good characteristics of freeze-dried recombinant L. lactis-fermented milk powder with protectants display its potential as a powder product for vaccine delivery.

Keywords:

• Freeze-drying
• fermented milk
• food-grade culture
• genetically-modified food
• moisture sorption isotherm
• shelf-life prediction

Acknowledgments

The authors would like to thank Paul Etim Effiong for the construction of Lactococcus lactis NZ3900 harboring pNZ8149 expressing USP45-139A-68V-TTD used in this study.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.

Additional information

Funding

This work was supported by the UCSI Research Excellence & Innovation Grant (REIG) under REIG-FAS-2020-003.