Analysis of antimicrobial whey protein‐based biocomposites with lactic acid, tea tree ( Melaleuca alternifolia ) and garlic ( Allium sativum ) essential oils for Edam cheese coating

Effect of Sheep's Whey Edible Coatings with a Bioprotective Culture, Kombucha Tea or Oregano Essential Oil on Cheese Characteristics

Films and coatings based on biopolymers have been extensively studied in recent years since they have less impact on the environment, can be obtained from renewable sources, have good coating and film-forming capacity, are biodegradable and can have interesting nutritional properties. In the present study, sheep's cheese whey powder (SCWP) was used to produce edible cheese coatings. Six types of cheese samples were produced: without coating (CON); treated with natamycin (NAT); with SCWP coating without antimicrobials (WCO); with SCWP coating with a commercial bioprotective culture (WFQ); with SCWP coating with kombucha tea (WKO); and with SCWP coating with oregano essential oil (WEO). At the end of the ripening period, all the cheeses were classified as full-fat and semihard, according to the Portuguese standard. The higher hardness and adhesiveness values of samples CON, WFQ and WKO were in line with the lower moisture in defatted cheese observed in these samples, indicating that future work should address the improvement of water vapor barrier properties of the whey-based coating. The samples treated with natamycin and with oregano essential oil presented significantly lower values for hardness. Differences were also observed on titratable acidity and aw, both between samples and because of ripening time. The color parameters of cheese samples also presented differences, chiefly in the rind, but the highest differences observed resulted from ripening time rather than between samples. In all cases, the counts of lactobacilli and lactococci surpassed log 7 CFU/g by the end of ripening. Regarding yeast and mold counts, the samples CON and WCO presented the highest values by the end of the ripening period (>log 4 CFU/g), while sample NAT presented the lowest value (ca. log 3 CFU/g). Samples WFQ, WKO and WEO presented values which were ca. 0.5 log cycles lower than samples CON and WCO. Hence, the use of SCWP alongside bioprotective culture, kombucha tea or oregano essential oil had a positive impact in the reduction of mold counts on cheese surfaces. Future work should also evaluate the joint use of different antimicrobials.

Controlled Release of Tea Tree Oil from a Chitosan Matrix Containing Gold Nanoparticles

Chitosan is a biopolymer that, due to its versatile bioactive properties, has applications in several areas, including food, medicine and pharmaceuticals. In the field of tissue engineering, chitosan can be used, for example, as a dressing to treat wounds or dermal damage, such as burns or abrasions. This work deals with the controlled release of tea tree oil from chitosan-based polymeric films and droplets containing gold nanoparticles (AuNP). AuNPs were successfully incorporated into the chitosan matrix using two different approaches. Both solutions were loaded with tea tree oil, and from these solutions, it was possible to obtain drop-cast films and droplets. The controlled release of oil in water was performed both in the films and in the droplets. The addition of AuNP in the controlled release system of melaleuca oil favored a release time of around 25 h. A series of experiments was carried out to investigate the effects of different reaction temperatures and acetic acid concentrations on the formation of AuNPs in the presence of chitosan. For this purpose, images of the AuNP films and droplets were obtained using transmission electron microscopy. In addition, UV-vis spectra were recorded to investigate the release of tea tree oil from the different samples.