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

Food texture is only partly rheology

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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

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

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