Suwimol Chockchaisawasdee

Water Sorption Isotherm of Pea Starch Edible Films and Prediction Models

The moisture sorption isotherm of pea starch films prepared with various glycerol contents as plasticizer was investigated at different storage relative humidities (11%–96% RH) and at 5 ± 1, 15 ± 1, 25 ± 1 and 40 ± 1 °C by using gravimetric method. The results showed that the equilibrium moisture content of all films increased substantially above aw = 0.6. Films plasticized with glycerol, under all temperatures and RH conditions (11%–96%), adsorbed more moisture resulting in higher equilibrium moisture contents. Reduction of the temperature enhanced the equilibrium moisture content and monolayer water of the films. The obtained experimental data were fitted to different models including two-parameter equations (Oswin, Henderson, Brunauer–Emmitt–Teller (BET), Flory–Huggins, and Iglesias–Chirife), three-parameter equations Guggenhiem–Anderson–deBoer (GAB), Ferro–Fontan, and Lewicki) and a four-parameter equation (Peleg). The three-parameter Lewicki model was found to be the best-fitted model for representing the experimental data within the studied temperatures and whole range of relative humidities (11%–98%). Addition of glycerol increased the net isosteric heat of moisture sorption of pea starch film. The results provide important information with estimating of stability and functional characteristics of the films in various environments.

Physical and mechanical properties of a new edible film made of pea starch and guar gum as affected by glycols, sugars and polyols

The influence of different plasticizers (glycols, sugars and polyols) on the moisture sorption, mechanical, physical, optical, and microstructure characteristics of pea starch-guar gum (PSGG) film was studied. All plasticizers formed homogeneous, transparent, and smooth films, while PEG-400 did not produce film with suitable characteristics. Fourier transform infrared (FTIR) spectroscopy results indicated some interaction between plasticizers and the polymers. Scanning electron microscopy (SEM) observations of the films presented surfaces without cracks, breaks, or openings which were indicator of the miscibility and compatibility of employed plasticizers with PSGG films. The results showed that the films containing plasticizers with higher functional groups had lower equilibrium moisture content at aw <0.4. In general, a reduction in tensile strength and Youngs modulus and an increase in elongation at break were detected when molecular weight of plasticizers and relative humidity increased in all film formulations. Films plasticized with monosaccharide showed similar mechanical properties to those with sorbitol, but lower solubility and water vapour permeability (WVP), higher transparency and moisture content than the sorbitol-plasticized films. The most noticeable plasticization effect was exerted by following order: glycerol > EG > PG > xylitol > fructose > sorbitol > mannitol > galactose > glucose > sucrose > maltitol.

Effect of mineral fortification on textural and oxidative stability of reduced-fat spreads.

The aim of this research was to investigate the effect of mineral fortification on the textural and oxidative stability of reduced-fat spreads produced using κ-carrageenan. Model systems were prepared containing varying amounts of zinc, copper, and iron. The hardness of the spreads stored at 5°C and 25°C was assessed over time using a penetrometer (20° cone), and it was observed that samples were generally weaker compared to the controls. Samples containing the transition minerals iron and copper were very susceptible to oxidation, becoming rancid rapidly. Low levels of zinc addition, between 2–10% of the recommended daily allowance (RDA), led to spreads with acceptable oxidative stability and a textural profile comparable to the controls over the storage period examined.

Optimization of far-infrared vacuum drying conditions for Miang leaves (Camellia sinensis var. assamica) using response surface methodology

Far-infrared (FIR) vacuum is an advanced drying technique that has recently been applied in food processing. Optimal drying conditions for processing tea from Miang leaves using FIR vacuum drying were investigated. Response surface methodology with a central composite design was used to design, analyze, and predict the optimal time and temperature conditions for FIR vacuum drying, taking into account the physicochemical properties of Miang leaves. When the temperature increased from 50 to 65°C and the time from 60 to 120 min, the amount of epicatechin, epicatechin gallate, epigallocatechin gallate, and total catechins significantly (p<0.05) increased while the moisture content and water activity significantly (p<0.05) decreased, compared with controls. The physicochemical properties of dried Miang leaves were significantly (p>0.05) influenced by time and temperature, compared with controls. Drying conditions of 65°C for 120 min are recommended for optimization of drying.