Thyme Antimicrobial Effect in Edible Films with High Pressure Thermally Treated Whey Protein Concentrate

Abstract

<jats:p>Application of high pressure-thermal treatment (600 MPa and 70 °C, 20 min) for obtaining edible films functionalized with thyme extracts have been studied in order to evaluate the antimicrobial capacity of films structure to retain and release the bioactive compounds. The high pressure-thermally treated films (HPT) were compared with the thermally treated (TT) ones (80 ± 0.5 °C, 35 min). The film structures were analyzed and the sorption isotherms, water vapor permeability, antimicrobial activity and the volatile fingerprints by GC/MS were performed. The HPT film presented more binding sites for water chemi-sorption than TT films and displayed significantly lower WVP than TT films (p &lt; 0.05). TT films displayed slightly, but significant higher, antimicrobial activity (p &lt; 0.05) against Geotrichum candidum in the first day and against Bacillus subtilis in the 10th day of storage. The HPT film structure had ~1.5-fold higher capacity to retain volatiles after drying compared to TT films. From the HPT films higher amount of p-cymene and α-terpinene was volatilized during 10 days of storage at 25 °C, 50% RH while from the TT films higher amount of caryophyllene and carvacrol were released. During storage HPT films had a 2-fold lower capacity to retain monoterpenes compared to TT films.</jats:p>

Physicochemical and Antimicrobial Properties of Whey Protein-Based Films Functionalized with Palestinian Satureja capitata Essential Oil

“…Furthermore, no antimicrobial activity of the films was observed against E. faecalis ATCC 29212 even at the highest TEO1 concentration tested. The data presented in this paper are comparable to those obtained by Bleoancă et al [36] who produced films from high pressure thermally treated whey protein concentrate into which the extracts were added. The authors have demonstrated the ability of the film matrix to vehicular the bioactive molecules, as they were endowed with good antimicrobial properties as demonstrated by the inhibition zones towards three fresh food spoilage microorganisms such Torulopsis stellata, Geotrichum candidum, and Bacillus subtilis [36].…”

“…The data presented in this paper ar comparable to those obtained by Bleoancă et al [36] who produced films from high pre sure thermally treated whey protein concentrate into which the extracts were added. Th authors have demonstrated the ability of the film matrix to vehicular the bioactive mol cules, as they were endowed with good antimicrobial properties as demonstrated by th inhibition zones towards three fresh food spoilage microorganisms such Torulopsis stellat Geotrichum candidum, and Bacillus subtilis [36]. After 24 h at 37 • C, it was observed that the WP-based film itself was unable to inhibit bacterial growth (Figure 6).…”

Efficacy of Two Stabilizers in Nanoemulsions with Whey Proteins and Thyme Essential Oil as Edible Coatings for Zucchini

“…Anhydrous glycerol 8.0% ( w / w ) was added as a plasticizer to the resulting coating mixture. This formula was previously optimized by Bleoanca et al [ 24 ].…”

“…The samples were divided in half and two stabilizers were tested, one using Tween 20 (T) in a concentration of 0.9% ( w / w ) [ 24 ] and the other half using 0.18% ( w / w ) mix of gums (S), concentration previously optimized by our group (data not shown). Thyme ( Thymus vulgaris ) EO was added in a concentration of 2.5% ( w / w ) in all samples, considering the results of previous tests performed by our research group.…”

Use of Essential Oils and Volatile Compounds as Biological Control Agents

“…Bleoancă et al studied two different treatments for the formation of edible films containing thyme extracts. Both high-pressure-thermally treated films and thermally treated ones display different structures with different abilities to retain volatile compounds [ 16 ]. Finally, Kostoglou et al showed the promising potential of three plant terpenoids—carvacrol, thymol and eugenol—as anti-biofilms agents, as they showed significant anti-biofilm activities against Staphylococcus aureus and Staphylococcus epidermidis .…”