Shelf life prediction of packaged cassava-flour-based baked product by using empirical models and activation energy for water vapor permeability of polyolefin films

Modification of poly(L-lactic acid)-based films and evaluation of physical and antibacterial properties by using multivariate data analysis

The aim of this study is to prepare new packaging materials with improved physical and antimicrobial properties that prevent the growth of microorganisms. Poly(L-lactic acid) (PLA) based packaging films were prepared by the solvent-casting method using spruce resin (SR), epoxidized soybean oil, an essential oil mixture (calendula and clove oil), and silver nanoparticles (AgNPs). The AgNPs were synthesized by the polyphenol reduction method, using spruce resin dissolved in methylene chloride. The prepared films were tested for antibacterial activity and physical properties, such as tensile strength (TS), elongation at break (EB), elastic modulus (EM), water vapor permeability (WVP), and UV-C blocking effect. The addition of SR decreased the water vapor permeation (WVP) of the films, whereas the addition of essential oils (EOs) increased this property due to their higher polarity. The morphological, thermal, and structural properties were characterized using SEM, UV-Visible spectroscopy, FTIR, and DSC. The agar disc well method showed that SR, AgNPs, and EOs imparted antibacterial activity to the PLA-based films against Staphylococcus aureus and Escherichia coli. Multivariate data analysis tools, such as principal component and hierarchical cluster analysis, were used to discriminate PLA-based films by simultaneously evaluating their physical and antibacterial properties.

Effect of powdering on critical water activity estimate from dynamic dewpoint isotherm of a crispy starch-based snack: a case study with fish cracker

The moisture sorption isotherm (MSI) and critical water activity (a _w,crit ) of a dry food determine the moisture barrier properties required of packaging for desired shelf life of starchy dry food. These can be obtained with the novel rapid dynamic dewpoint isotherm method (DDI), but with such rapid measurement incomplete equilibration is of concern, and this relates to suitable particle size of the sample tested. Further, an MSI curve without clear inflection point can make it difficult to extract the a _w,crit. The objective of this work was to investigate the effects of particle size of a starch based snack on its MSI and on a _w,crit . A novel model to fit the MSI data was also created to obtain the a _w,crit . Fish cracker samples were prepared in three particle sizes (< 180 µm, 250-425 µm, and ~ 3000 µm) and tested at 25 and 35 °C for MSI using DDI. The sample comminution by grinding had clear and consistent effects, with finer particles absorbing more moisture. For this crispy snack, the rapid dense measurements enabled estimating the critical point that was robust against a 10 °C temperature change with about 200 µm particle diameter. This suggests near complete equilibration by the lack of rate effects from temperature, which were seen with larger particles. The results indicate that powdering dry crispy foods enables proper DDI measurements, while without powdering the isotherms can be degraded by particle size effects. The broken-stick type model fit the data extremely well and showed the critical transition clearly as a jump discontinuity in the derivative (slope).

Effect of Clay Nanofillers on the Mechanical and Water Vapor Permeability Properties of Xylan-Alginate Films

In this study, xylan–alginate-based films were reinforced with nanoclays (bentonite or halloysite) by the solvent casting technique. The effect of the nanoclay loadings (1–5 wt %) on various properties—mechanical, optical, thermal, solubility, water sorption, and water vapor permeability (WVP)—of the xylan–alginate films were examined for their application as food packaging materials. A 5 wt % loading of either bentonite or halloysite resulted in a 49% decrease of the WVP due to the impermeable nature of the silicate layers that make up both bentonite and halloysite. Thermal stability and solubility of the nanocomposite films were not significantly influenced by the presence of the nanoclays, whereas the optical properties were significantly improved when compared to neat xylan–alginate blend. In general, films reinforced with bentonite exhibited superior mechanical and optical properties when compared to both halloysite-based nanocomposite and neat films.