Effect of High-Pressure Food Processing on the Physical Properties of Synthetic and Biopolymer Films

Effect of High-Pressure Processing on the Packaging Properties of Biopolymer-Based Films: A Review

Suitable packaging material in combination with high-pressure processing (HPP) can retain nutritional and organoleptic qualities besides extending the product’s shelf life of food products. However, the selection of appropriate packaging materials suitable for HPP is tremendously important because harsh environments like high pressure and high temperature during the processing can result in deviation in the visual and functional properties of the packaging materials. Traditionally, fossil-based plastic packaging is preferred for the HPP of food products, but these materials are of serious concern to the environment. Therefore, bio-based packaging systems are proposed to be a promising alternative to fossil-based plastic packaging. Some studies have scrutinized the impact of HPP on the functional properties of biopolymer-based packaging materials. This review summarizes the HPP application on biopolymer-based film-forming solutions and pre-formed biopolymer-based films. The impact of HPP on the key packaging properties such as structural, mechanical, thermal, and barrier properties in addition to the migration of additives from the packaging material into food products were systemically analyzed. HPP can be applied either to the film-forming solution or preformed packages. Structural, mechanical, hydrophobic, barrier, and thermal characteristics of the films are enhanced when the film-forming solution is exposed to HPP overcoming the shortcomings of the native biopolymers-based film. Also, biopolymer-based packaging mostly PLA based when exposed to HPP at low temperature showed no significant deviation in packaging properties indicating the suitability of their applications. HPP may induce the migration of packaging additives and thus should be thoroughly studied. Overall, HPP can be one way to enhance the properties of biopolymer-based films and can also be used for packaging food materials intended for HPP.

Migration kinetic of silver from polylactic acid nanocomposite film into acidic food simulant after different high-pressure food processing

The migration study of nano-Ag migration from polylactic acid (PLA) films was studied. Samples treated by high-pressure food processing (0, 100, 200, 300, and 400 MPa pressure) were soaked in acetic acid solution and incubated at 20 °C for 90 days. At the end of storage, nano-Ag particles (AgNPs) migration from the PLA/AgNPs composite film treated under 200 MPa high pressure was the lowest. However, AgNPs migration was accelerated under 400 MPa high pressure. High-pressure processing (200 MPa) could cause denser structure and higher crystallinity degree in films than other treatments. Lower amount of AgNPs induced a decline in the intensity of specific characteristic peaks. The diffraction peak intensity of α-crystal for the film sample treated with 400 MPa was the lowest on day 60. The crystallization index of the PLA matrix changed with different high-pressure processing. The result indicated that appropriate high-pressure food processing could effectively suppress AgNPs migration from PLA-based film while contacting with acidic acid food simulant. PRACTICAL APPLICATION: The release of nanoparticles from food packaging material is a very important matter when the migration is concerned with regulatory and toxicity issues. The study described the migration kinetic of AgNPs from PLA nanocomposite film into acidic food simulant after different high-pressure food processing. The results indicated that the PLA/AgNPs nanocomposite film was safe for acidic food after high-pressure treatment.

Effect of high pressure processing on migration characteristics of polypropylene used in food contact materials

The migration of small molecular mass organic compounds from polypropylene (PP) copolymer films into food simulants during and after high pressure processing (HPP) was studied. An overlapping temperature profile was developed to isolate the pressure effect of HPP (700 MPa, 71°C, 5 min) from equivalent thermal processing (TP) at atmospheric pressure (0.1 MPa). Chloroform, toluene, methyl salicylate, and phenylcyclohexane were chosen as surrogate compounds, and were spiked into test polymer films at concentrations of 762-1152 mg kg^-1 by a solvent soaking technique. Migration (w/w) of surrogate compounds from loaded PP films into Miglyol 812 (a medium-chain triglyceride mixture) and 10% ethanol was quantified by headspace GC/MS during HPP and TP, and subsequent storage at 25°C for up to 10 days. HPP significantly delayed migration of the surrogates from PP into both food simulants relative to TP. The average migrations into Miglyol after TP and HPP were 92.2-109% and 16-60.6%, respectively. Diffusion coefficients estimated by migration modelling showed a reduction of more than two orders of magnitude for all surrogate compounds under high pressure at 700 MPa (AP' = 8.0) relative to equivalent TP at 0.1 MPa (AP' = 13.1). The relative T_g increase of PP copolymer under compression at 700 MPa was estimated as T_g+94°C. For 10% ethanol, average migrations after TP and HPP were 9.3-50.9% and 8.6-22.8%, respectively. During extended storage, migration into both simulants from HPP-treated samples was initially slower than that from untreated or TP-treated films. However, after 8-24 hours of storage, the differences in percent migration of selected surrogates were not significant (p > .05) among the treated PP films. Therefore, the physical changes of PP films that occur during HPP appear to be reversible with a return to their original dimensions and diffusion properties after decompression.

Effect of high-pressure processing on characteristics of flexible packaging for foods and beverages

High-pressure processing is an emerging food preservation technology that causes minimal product quality loss: Food packaged and high-pressure processed keep most of their nutritional qualities, in addition to extending their shelf life. However, the selection of packaging materials suitable for this technology becomes extremely important, since processing can cause changes in the visual aspects and in the physicochemical and mechanical properties of the materials, compromising the shelf life and safety of high-pressure processed foods somehow. Some studies have evaluated the effect of this technology on the properties and the migration and diffusion potential of intentional substances and of polymeric components in some flexible multilayer laminated packaging. Within this context, an important and relevant issue for industrial applications is knowing the possible effects of the parameters of high-pressure treatments, in low and high temperature, on the structure and morphology of materials that, in turn, can determine the relevant effects on the mechanical, barrier, and thermal properties and the migration and diffusion potential of intentional and non-intentional substances. Our study aims to make a literature review on the requirements of flexible packaging materials that can be used in high-pressure processing and the state of the art and the knowledge of the effects of different processing conditions on their properties.

Biodegradable Polymeric Capsules Obtained via Room Temperature Spray Drying: Preparation and Characterization

The aim of this contribution is to determine the relationship existent between the chemistry and/or viscosity of some biodegradable polymer solutions and the morphology of micro- and nanospheres resulted after spray drying the solutions at room conditions either in the presence or in the absence of an encapsulated aqueous material. Using dichloromethane as solvent, the following polyesters were used to prepare 2 wt% solutions: polyhydroxybutyrate (PHB), polylactic acid (PLA), poly(lactic- co-glycolic acid) (PLGA) and Eastar Bio GP (GP). A comprehensive thermal characterization was also performed on all polymers to verify the relationships existent between the structure of polyesters and certain important parameters, such as Tg, T m, Td. It was observed that a decrease in the solution viscosity triggers the formation of smoother microspheres. When the viscosity becomes low enough the sprayed solution can lead to the development of well defined nanospheres instead of microspheres. Additionally, it was found that in the presence of an aqueous core the micro- and/or nanocapsules coalesce into larger micrometric aggregates, due to the plasticizing effects of water on the polyester.