Volume 14, Issue 7-8 -

A newly self-developed electronic nose (E-nose) system for the detection of “Hongyan” strawberry freshness at different storage periods was studied. The system consisted of six metal oxide semiconductor sensors connected to a data acquisition system and a computer with pattern recognition software. The aroma emitted by “Hongyan” strawberry samples was detected during post-harvesting storage, and stable E-nose response values were used to develop cluster analysis and classification models. The successive projections algorithm was employed to optimize the sensors array, and the results obtained by gas chromatography–mass spectrometry analysis proved that the optimized sensor array was feasible to differentiate decayed strawberries from fresh ones. Partial least squares discriminant analysis and support vector machine (SVM) models were built. Accuracy of 94.9 % on the testing set was obtained based on the optimized sensor array, and this result was satisfactory compared to that of commercial PEN3 E-nose.

Crank’s analytical approximations for Fick’s diffusion equation were used to investigate the effect of moisture dependent sample thickness and diffusivity on the behavior of yam ( Dioscoreaceae rotundata ) cubicles during drying processes. Drying and shrinkage experiments were separately conducted at temperatures of 30, 40 and 50 °C in a cabinet drier. The comparative study of moisture dependent shrinkage and moisture dependent diffusivity justifies the interdependence of diffusivity and shrinkage due to water loss during drying. The behavior for yam is best explained by a combination of fractal moisture dependent shrinkage and moisture dependent diffusion, describing both the drying and rate curves better with good prediction of the high moisture regions. This assertion was reached as a result of low mean square error, standard error, percentage relative deviation, Akaike’s Information Criterion and high coefficient of determination. The results may indicate a varying mobility of water in food matrix of different moisture content in the multilayer and monolayer regimes.

Wheat bran is modified thermochemically through reaction with citric acid, as carboxyl groups bearing agent, according to a dry condition method at the elevated temperature. In this study, the main objectives are optimization the factors affecting on the pendant carboxylic acid groups of wheat bran–citrate, including concentration of citric acid solution (0–1.8 M), volume of citric acid solution (5.4–16.2 g), curing temperature (0–170 °C), curing time (0–90 min.), mixing method (solution mixing vs kneading) of reactants, and the catalyst effect (0–5, sodium phosphate dibasic dodecahydrate/citric acid molar ratio). The amount of pendant carboxylic acid groups is determined by simple acid-base titration. The obtained methylene blue adsorption data is well matched with the amount of pendant carboxylic acid groups in wheat bran–citrate and this amount increase with an increase in pendant carboxylic acid groups.

Effects of ozone treatment on the storage quality of post-harvest tomato were investigated. The tomatoes packed in microporous film were treated with 4.29 mg·(m 3 ) −1 , 8.57 mg·(m 3 ) −1 , 12.86 mg·(m 3 ) −1 and 17.14 mg·(m 3 ) −1 ozone gas for 1 h at 0℃. The firmness, ethylene, vitamin C (VC), malonaldehyde (MDA), ascorbate peroxidase (APX), peroxidase (POD) and aromatic compounds were tested to determine the proper ozone concentrations. Compared with other treatments, 17.14 mg·(m 3 ) −1 ozone could maintain the firmness of tomato, depress ethylene, keep the content of VC and aromatic compounds, and inhibit the accumulation of MDA and activity of POD and APX, which had a good fresh-keeping effect on tomato.

The effects of instant controlled pressure drop (DIC) drying, and blanching-assisted DIC (B + DIC) on texture, volume ratio (VR), colour, microstructures of different tissues, and cell-morphology of fruit and vegetable chips was examined. Results revealed that B + DIC had a significant effect on fruits and vegetable chips as compared with DIC treated. The DIC dried mango chips were observed to have low hardness (26.12 N) and maximum crispness (10.43) that were also observed in mango chips under B + DIC treated (14.66), exhibiting a puffy structure and crispy texture. Well expanded structure which reflected by VR was found in the mango (0.46 mL) and king oyster mushroom (KOM) (0.36 mL) chips under both treatments. The maximum total colour changes (∆E) were also obtained in the mango (30.40) and carrot (42.87) chips under B + DIC. The microstructures of the apple, carrot, KOM and potato chips products, which corresponded to its well expanded appearances, showed a honeycomb-like pores structure, observed for DIC treated apple, fresh potato, B + DIC dried KOM as well as in sweet potato. In addition, the B + DIC-treated carrot chips, pores size, increased the cell wall and expanded. Moreover, the mushroom chips mostly were shrunken after hot water blanching.

In the present work, water soluble chitosan (WSC) was prepared and growth curves of Lactobacillus delbrueckii and Escherichia coli were examined in vitro. In vivo , mice were randomly divided into three groups (10 mice in each group), treated with water, 1 g/kg WSC and 0.25 g/kg of WSC respectively for 24 days. Subsequently, levofloxacin (65 mg/kg) was given for 6 days. The dynamic changes of bacterial communities were evaluated by denaturing gradient gel electrophoresis periodically. L. delbrueckii and E. coli have been inhibited by WSC in vitro . The bacteria from the genera of Bacteroides, Lactobacillus, Enterococcus and Devosia were dominant gut flora in the intestinal tract of mice. The growth of Lactobacillus has been dramatically stimulated, whereas Enterococcus faecium and Parabacteroides distasonis which were opportunistic bacterial pathogens have been inhibited. So WSC can be considered as a new food supplement to protect the intestinal microflora and regulate imbalance.

Pullulan particles were prepared to improve water solubility. The pullulan droplet with the concentration of 5%, 10%, 15% or 20% (w/w) was injected and frozen in the cryogenic media of liquid nitrogen at −196 °C or cold air at −15 °C, then freeze dried. The results show that most of dried pullulan particles pre-processed in either liquid nitrogen or cold air can be completely dissolved in water within 60 s. The water solubility of as-prepared particles in liquid nitrogen is better than that in cold air. The particles frozen at −196 °C have smaller and more uniform pore structures together with a larger specific surface area than those frozen at −15 °C. It is found that the particles from 10% pullulan solution with liquid nitrogen have largest water solubility and also highest specific surface area (11.78 m 2 /g).

Ammonium bicarbonate microcapsules (AMBCMC) were prepared by phase separation method using palm stearin/carnauba wax (CNW) as wall materials. The morphology of AMBCMC showed that the microcapsules were mainly spherical shapes. DSC analysis results suggested that the microcapsule shells began melting at the temperature 47.9 °C, while the shells were thoroughly destructed at the temperature above 78.1 °C. The particle sizes of AMBCMC were chiefly distributed in the range of 30 ~ 300 μm. Ammonium bicarbonate (AMBC) in microcapsules was highly stable under different relative humidity, and AMBCMC was hardly damaged even at 95% relative humidity. The thermal stability of AMBC increased, while AMBC encapsulated in microcapsules still could decompose and release gas at 70 °C as well as free AMBC. Furthermore, AMBC encapsulated in microcapsules showed strong survivability in the presence of citric acid. The results indicated that the stability and compatibility of AMBC were effectively increased after microencapsulation.