SPME method optimized by box-behnken design for impact odorants in reduced alcohol wines

The important sampling parameters of a headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) procedure such as the extraction temperature, extraction time, and sample volume were optimized to quantify 23 important impact odorants in reduced alcohol red and white wines. A three-factor design of Box-Behnken experiments was used to determine the optimized sampling conditions for each analyte, and a global optimized condition at every ethanol concentration of interest determined using a desirability function that accounts for a low signal response for compounds. Shiraz and Chardonnay wines were dealcoholized from 13.7 and 12.2% v/v ethanol respectively, to 8 and 5% v/v, using a commercially available membrane-based technology. A sample set of the reduced alcohol wines were also reconstituted to their natural ethanol level to evaluate the effect of the ethanol content reduction on volatile composition. The three-factor Box-Behnken experiment ensured an accurate determination of the headspace concentration of each compound at each ethanol concentration, allowing comparisons between wines at varying ethanol levels to be made. Overall, the results showed that the main effect of extraction temperature was considered the most critical factor when studying the equilibrium of reduced alcohol wine impact odorants. The impact of ethanol reduction upon the concentration of volatile compounds clearly resulted in losses of impact odorants from the wines. The concentration of most analytes decreased with dealcoholization compared to that of the natural samples. Significant differences were also found between the reconstituted volatile composition and 5% v/v reduced alcohol wines, revealing that the dealcoholization effect is the result of a combination between the type of dealcoholization treatment and reduction in wine ethanol content

Parboiled rice: Understanding from a materials science approach

The material properties like glass transition temperature, diffusion, microstructures of rice kernels and gelatinisation and retrogradation of the rice starch are reviewed to understand the nature and quality of the parboiled rice. Details of the diffusion related material properties of rice kernels such as the rate of diffusion, different models of diffusion, diffusion in glassy and rubbery state and diffusion in the gelatinised starch are discussed. The influences of hydrothermal treatment on the properties of the rice kernel are also highlighted to understand the overall quality of parboiled rice

Colour change in rice during hydration: Effect of hull and bran layers

The colour change (yellowing or reddening) that occurs during parboiling affects the consumer acceptance of parboiled rice. In order to understand the factors controlling colour change in rice during hydration, trials were performed that examined the effect of variety (four commercial varieties: Kyeema, Langi, ReiziqP and SherpaP), milling properties (SherpaP High Head Rice Yield and SherpaP Low Head Rice Yield), degree of processing before hydration (paddy, brown rice, milled rice) and hydration temperature (below and above gelatinisation temperature: 60 C and 90 C respectively). The total colour difference (DE00) was calculated and four different models (zero order, first order, fractional and Page) were evaluated in order to predict the DE00. The Page model was found to be the best model for predicting DE00. There was no difference in DE00 between the breakage resistant and breakage prone grains however the varietal effect was observed. The degree of processing of rice before hydration affected the total colour change where the brown rice had the highest DE00 followed by paddy and milled rice

Whey protein peptides as components of nanoemulsions: A review of emulsifying and biological functionalities

Milk proteins are used to make emulsions, and may be used to make nanoemulsions. Nanoemulsions are a nanotechnology with food applications, and possess superior physicochemical and sensorial properties compared to macro- and microemulsions. They are also able to deliver bioactive compounds when consumed. In this review, three aspects of food nanoemulsions will be examined: (1) the production and properties of food nanoemulsions, (2) emulsifiers/surfactant (ionic, non-ionic, phospholipid, polysaccharide, and protein) used in nanoemulsions production. The suitability of proteins and protein hydrolysates as nanoemulsifiers is discussed, with a particular focus on whey protein, (3) the potential of whey protein derived peptides as both emulsifiers and bioactive compounds in nanoemulsion delivery systems. Lastly, the potential delivery of bioactive peptides and other bioactive compounds within nanoemulsion systems is also discussed

The diffusion of moisture in paddy during hydration and dehydration processes

Hydration and dehydration behavior and the effective diffusivity of paddy during the process of parboiling were studied. Hydration of three different paddy samples (Sherpa low and high head rice yield and Reiziq) were performed below (60°C) and above (90°C) the gelatinization temperature. The hydration period ranged from 5 to 300 minutes at 60°C and 5 to 90 minutes at 90°C. All of the paddy samples showed different hydration behavior below and above the gelatinization temperature, discerned with two different stages at 60°C and three stages at 90°C. Dehydration was carried out at 40°C just after hydration (without tempering the kernel), which mostly took place at the falling rate period. The hydration and dehydration pattern was not different between the high HRY and low HRY paddy, indicating a limited contribution of microfissures to the diffusion rate in the paddy. Five commonly used semi-empirical models were used to predict the hydration and dehydration behavior of paddy and, among them, the Page model was found to be the most suitable. The effective diffusivity during hydration was dependent on the temperature of hydration, which was 1.83 × 10-11 to 2.11 × 10-11 m2/s at 60°C and 6.68 × 10-11 to 7.94 × 10-11 m2/s at 90°C. The effective diffusivity during dehydration depended on the soaking temperature and period of soaking; it was lower for high-temperature-hydrated samples than low-temperature-hydrated samples. The study concluded that the mass water diffusivity was not affected by the microfissures within the paddy kernel, and the hydration pattern was strongly dependent on whether the temperature was above or below the gelatinization temperature

Food texture is only partly rheology

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Screening of whey protein isolate hydrolysates for their dual functionality: Influence of heat pre-treatment and enzyme specificity

Heat pre-treated and non heat pre-treated whey protein isolate (WPI) were hydrolysed using α-chymotrypsin (chymotrypsin), pepsin and trypsin. The in vitro antioxidant activity, ACE-inhibition activity and surface hydrophobicities of the hydrolysates were measured in order to determine if peptides with dual functionalities were present. Dual functional peptides have both biological (e.g. antioxidant, ACE-inhibition, opioid activities) and technological (e.g. nanoemulsification abilities) functions in food systems. Heat pre-treatment marginally enhanced the hydrolysis of WPI by pepsin and trypsin but had no effect on WPI hydrolysis with chymotrypsin. With the exception of the hydrolysis by trypsin, heat pre-treatment did not affect the peptide profile of the hydrolysates as analysed using size exclusion chromatography, or the antioxidant activity (P > 0.05). Heat pre-treatment significantly affected the ACE-inhibition activities and the surface hydrophobicities of the hydrolysates (P < 0.05), which was a function of the specificity of the hydrolysing enzyme. Extended hydrolysis (up to 24 h) had no significant effect on the DH and the molecular weight profiles (P > 0.05) but in some instances caused a reduction in the antioxidant activity of WPI hydrolysates. The chymotrypsin hydrolysate showed a broad MW size range, and was followed by pepsin and then trypsin. The bioactivities of the hydrolysates generally decreased in the order; chymotrypsin > trypsin > pepsin. This study showed that by manipulating protein conformation with pre-hydrolysis heat treatment, combined with careful enzyme selection, peptides with dual functionalities can be produced from WPI for use as functional ingredients in the manufacture of functional foods