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

Iulia Bleoancă,Daniela Borda,Elena Enachi

doi:10.3390/foods9070855

Iulia Bleoancă, Daniela Borda + Show 1 more

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https://doi.org/10.3390/foods9070855

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Abstract

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 < 0.05). TT films displayed slightly, but significant higher, antimicrobial activity (p < 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.

Highlights

Consumers’ increasing demand for minimally processed food products led to increased researchers’attention towards new ways to valorize the potential of plant-based extracts as preservatives for extending food shelf-life and insuring food safety
Appearance of the two sides of the WPC film was similar for high pressure-thermally treated films (HPT) and TT films
Combination of High pressure processing (HPP) and TT resulted in both denaturation via above referred mechanism and by forcing the water molecules inside the protein matrix, that exposed the hydrophobic core, followed by protein unfolding [32,33]

Summary

Introduction

Consumers’ increasing demand for minimally processed food products led to increased researchers’attention towards new ways to valorize the potential of plant-based extracts as preservatives for extending food shelf-life and insuring food safety. Essential oils (EOs), used conventionally as flavorings by the food industry are considered for new applications as antimicrobials and antioxidants and are generally recognized as safe (GRAS) by the United States Food and Drug Administration [1]. In the EU, Regulation 1334/2008 sets the maximum levels of certain substances present as flavorings in or on foods, EOs included. From the aromatic plants volatile profile, terpenes (C10) are representing 90% of the EOs but sesquiterpenes (C15) are frequently present [2]. Even though EOs have antimicrobial effect against a wide range of food related spoilage and pathogenic microorganisms, the required concentration is often too high and their intense odor may negatively interfere with food quality and consumers’

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