Band 14, Heft 11-12 -

In this study, Lactobacillus plantarum (LP), alone or in combination with Streptococcus thermophilus , was used to ferment yam juice. Changes in the composition (phenols, organic acids, reducing sugars and volatile substances) and functional characteristics (antioxidative activity and ability to regulate the intestinal flora) of yam juice during fermentation were investigated. The results showed that the total phenolic (TP) content increased from 201.27 to 281.27 and 285.77 μg/mL for LP- and L. plantarum and S. thermophilus (LPST)-fermented yam juice, respectively. The antioxidative activity of yam juice improved significantly after fermentation, highly correlating with its TP content. In addition, LP- or LPST-fermented yam juice had positive effects on members of the human intestinal flora, improving the activity of Bifidobacterium and inhibiting the growth of Escherichia coli . Sensory analysis showed that LPST-fermented yam juice had a highest score. The results of this study showed that fermented yam juice can serve as a healthy beverage for consumers with low immunity or an imbalance of the intestinal flora.

In order to evaluate the applicability of nanofiltration (NF) polyphenols determined by total phenolic compounds content with application of Folin method in grape seed extract, response surface analysis methodology was used to analyze the concentration process with the indices of membrane fouling and antioxidant activity. In addition to the influencing factors of molecular weight cut-off (MWCO) of NF membrane, procyanidin concentration and pH value, the evaluation index of procyanidin rejection was taken into account for the process optimization by Box-Behnken response surface method on the basis of single factor test. According to Box-Behnken central composite experiment design, the optimal conditions were obtained as follows: NF MWCO of 400 Da, 27.66 μg/mL procyanidins, and pH 5.20. The predicted rejection of procyanidins under the optimum conditions was 97.17% and the experimental value was 96.36 ± 0.87%, which was in accordance with the predicted value. The experimental value of total polyphenolic content (TPC) was 91.09 ± 0.46%. The antioxidant activity was increased about 2.24 times and the antioxidant activity was correlated with the procyanidin content. Moreover, it was easy to clean membrane fouling. The NF was an effective method for concentrating polyphenolic compounds from grape seed extracts without the loss of polyphenolic compounds. The agricultural product utilization was improved greatly and the power consumption was decreased by the NF technology.

Production of hazelnut milk powder (HMP) was investigated using maltodextrin (MD) as supporting material. Spray-drying and freeze-drying techniques were used to obtain the powder material. MD was added at concentrations of 5%, 10% and 15% (w/w) prior to drying. The powder properties were evaluated by determining flowing properties (Hausner ratio and angle of repose), thermal behaviour using DSC, molecular properties using FTIR, solubility and zeta potential. Hausner Ratio for both spray dried (SDHMP) and freze-dried (FDHMP) samples varied from 1.30 to 1.64 corresponding to very poor flow. The FDHM powder samples exhibited slightly lower Hausner Ratio values than SDHM powders. FTIR spectras showed that both SDHM and FDHM exhibited similar absorbance characteristics with slight differences. Lower endothermic transition temperatures were recorded from FDHMP when compared to SDHMP. The solubility in water for both powder samples ranged from 20 to 65 % depending on the drying method and MD content. Based on the residual moisture content, water activity, solubility and flowability, spray drying process was found to produce better quality powders compared to freeze drying process.

Three treatments, namely germination-parboiling (PG), freeze-thaw cycle (FTC) and high pressure processing (HPP) were compared for phytochemical content and antioxidant activity of brown rice (BR). These were determined in raw (uncooked), cooked, and in-vitro digested BR and compared with those from untreated BR and white rice (WR). PG showed the highest retention of phytochemicals after cooking (87–100%) while it dropped to 59–72% with FTC and 64–76% with HPP. After in-vitro digestion, the highest amount of phenolics was found in PG-24 h and flavonoids in FTC for two cycles. The antioxidant activity, as determined by oxygen radical absorbance capacity and ABTS methods, showed the highest value to be associated with in-vitro digested sample of PG-24 h, and lowest in WR. The results of this study show that these three treatments could improve or retain the phenolic content and antioxidant activity in cooked BR after in-vitro digestion.

For the purpose to study the effect of ultrasound treatment on heat pump drying, the experiments were conducted on pea seeds at drying temperature of 30, 35 and 40 °C , ultrasound power of 0, 60 and 100 W and frequency of 0, 28 and 40 kHz. The influence of ultrasound and temperature on the drying process was studied by analyzing the drying characteristics of pea seeds. The results demonstrated that increasing the ultrasound power, frequency and drying temperature can improve the drying rate and the Midilli model can describe the drying kinetics of pea seeds well. The effective moisture diffusion coefficient increased with the increase of ultrasound power, frequency and drying temperature, while there was no obvious trend for the change of seed activation energy under different conditions. The seed viability was promoted with the raise of ultrasound power and fell when increasing drying temperature.