Volume 14, Issue 1 -

Silkworm pupae protein (SPP) was pretreated by different processing (heat/alkali/pepsin) and then hydrolyzed by five proteases (trypsin/flavorzyme/papain/protamex/alcalase), respectively. It was found that the combination of heat pretreatment and alkali pretreatment followed by enzymatic hydrolysis with trypsin and flavorzyme could remarkably improve the protein recovery. The hydrolysates obtained from silkworm pupae protein hydrolyzed with trypsin and flavorzyme were stable at the pH range of 4.0–8.0, remaining 95 % of its original reducing power and 90 % of its OH• scavenging activity. However, they were susceptible to alkaline treatments (pH > 10.0) and lost >30 % of their antioxidant activities. Pasteurization (65 °C × 30 min) or autoclaving sterilization (121 °C × 20 min) did not show notable effects on the antioxidant activities. It was concluded that silkworm pupae protein hydrolysates (SPPH) were better to be applied in either neutral or acidic food system rather than in alkaline conditions.

Abstract: Flaxseed gum (FG) was carboxymethylated by reacting it with monochloroacetic acid (MCA). The effects of concentrations of NaOH and MCA, reaction temperature and reaction time, on the degree of substitution (DS) were investigated. Reaction between the FG and MCA at NaOH and MCA concentrations of 0.06 g/mL and 0.08 g/mL, respectively, at 70 °C for 60 min produced carboxymethyl flaxseed gum (CMFG) with a DS of 0.969. Carboxymethylation of FG increased its solubility and light transmittance in water. The nonlinear rheological properties of CMFG solutions were studied using large amplitude oscillatory shear (LAOS) tests, Fourier transform (FT) rheology and Chebyshev stress decomposition methods. The different nonlinear rheological behaviors observed were related to the microstructures of the CMFG solutions as a function of concentration and DS.

Turbot is a valuable commercial species due to its high nutrient content. Moisture is an important indicator of meat spoilage. This study elucidated distinctive water dynamics in turbot flesh in the freezing–thawing process by nondestructive low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques. T 2 relaxation spectra were utilized to describe the mobility and content of different types of water. Principal component analysis (PCA) revealed a clear discrimination of various freezing–thawing cycles. T 1 - and T 2 -weighted MRI provided further visualization of internal information for turbot flesh. Microscopic examination clearly identified protein denaturation and structural shrinkage. Furthermore, NMR parameters and conventional physicochemical parameters of color, shear force and thiobarbituric acid-reactive substances showed good correlations. To sum up, the study revealed that LF-NMR and MRI are promising techniques to portray the relationship between the water dynamics and changes of turbot quality properties during the freezing–thawing process.

Tremella fuciformis is edible and medicinal food since ancient times in China. In this article, the physicochemical and processing properties of Tremella fuciformis powder (TFS) and synergistic interaction with Lotus seed powder (LTS) in aqueous solution were investigated. The elemental compositions of TFS were 1.71 % N, 47.21 % O, 40.35 % C, 6.25 % H and 0.20 % S. Aspartic and Glutamic acids were the major amino acids in TFS for taken about 0.91 % and 1.12 %. TFS dispersion couldn’t form a gel structure at all selected concentrations until the ratio of TFS: LTS was 1:1 at a total concentration of 36 mg/mL. The network strength of TFS/LTS dispersions increased with the total powder concentrations increased during continuous heating from 25°C to 70°C. Gluten, amorphous and crystalline regions, and amorphous starch were observed in mixtures TFS/LTS compared with TFS. TFS/LTS had a more concavo-convex microstructure than TFS due to starch gelatinization in LTS.

In order to study the effect of corn kernel composition and physical structure on moisture distribution and transfer process and obtain the optimal tempering-drying parameters of corn kernel, a physical model was constructed with four different components as follows: seed coat, horny endosperm, farinaceous endosperm and embryo. The drying model was established based on the assumption of different diffusion coefficients and same thermal conductivity for the four components. The software of COMSOL Multiphysics was used to simulate the heat and mass transfer process inside the corn kernel during the thin-layer drying. The results showed that the least total drying time and the best drying quality were achieved under the multistage circulating drying of 10 min hot air drying and 60 min tempering, and the tempering degree was up to 0.9207.

This paper presents the application of feed forward and cascade forward neural networks to model the non-linear behavior of pistachio nut, squash and cantaloupe seeds during drying process. The performance of the feed forward and cascade forward ANNs was compared with those of nonlinear and linear regression models using statistical indices, namely mean square error (MSE$MSE$), mean absolute error (MAE$MAE$), standard deviation of mean absolute error ( SD MAE ) and the correlation coefficient (R2${R^2}$). The best neural network feed forward back-propagation topology for the prediction of effective moisture diffusivity and energy consumption were 3-3-4-2 with the training algorithm of Levenberg-Marquardt (LM). This structure is capable to predict effective moisture diffusivity and specific energy consumption with R2${R^2}$= 0.9677 and 0.9716, respectively and mean-square error (MSE$MSE$) of 0.00014. Also the highest R2${R^2}$ values to predict the drying rate and moisture ratio were 0.9872 and 0.9944 respectively.

Abstract: Chinese alkaline noodle (CAN) is one of popular staple foods in Asia. Whole wheat flour (WWF) is healthier than refined wheat flour (WF). This study investigated the effect of substitution level of WWF on physicochemical and sensory properties of CAN. Results showed that increasing WWF amount significantly reduced tensile strength (TS) and extensibility (E) of cooked CAN, but increased TS/E ratio from 6.05 to 13.22 mN/mm. High WWF substitution (>60 %) significantly increased cooking loss and decreased the elasticity of CAN. CAN prepared with WWF had darker, redder and yellower color than control. However, free and bound phenolics and DPPH radical scavenging capacity of CAN obviously increased with the amount of WWF. CAN with 0–40 % WWF had similar sensory scores in color, flavor, texture and overall preferences. The study suggests that healthy whole grain CAN with higher phytochemicals and acceptable eating quality can be produced by using 20–40 % WWF.

This work investigated the agglomeration of native cornstarch and production of microcapsules by dripping of sodium alginate suspensions into calcium chloride solution. The crosslinking reaction formed a calcium alginate that worked as an encapsulation matrix and coated the cornstarch granules. The spherical beads produced were rigid and compact, and resistant to mechanical handling. The differential scanning calorimetry (DSC) computed the thermal resistance of the cornstarch-alginate beads. Particles containing 50 % w/w calcium alginate showed an increased gelatinization peak compared to particles with a higher starch content. The increase in alginate fraction resulted in beads with a higher particle density. Scanning electron micrographs showed the coating of cornstarch by the calcium alginate matrix. The beads were compact and with no superficial pores. DSC thermograms of native cornstarch showed a gelatinization temperature of 70.0 °C, and the gelatinization range was 64.6–80.4 °C, while beads containing 50 % alginate had an increased peak at 79.5 °C and the gelatinization interval was 71.0–90.2 °C. When compared with the native cornstarch, cornstarch-alginate beads had a lower water absorption, and the gelatinization occurred at a higher temperature and over a wider temperature range.

The effects of the mixture of pig skin (PS) and coconut powder (CP) on the gelling and rheological properties of composite gel prepared with squid myofibrillar protein (MP) and lard were studied. The addition of PS and CP gel had significantly improved the water-holding capacity (WHC) and gelling properties of MP-Lard composite gel. Besides, composite gels with an adequate amount of PS and CP gel had a better texture and higher whiteness. The SDS-PAGE results showed that the presence of PS and CP gel did not affect the coagulated proteins in composite gels. The three-dimensional network structures of composite gels containing PS and CP gel were more compact and homogeneous. In general, the mixture of PS and CP could enhance the gel quality of MP-Lard composite gel and it could be used as a fat substitute in surimi products.

Abstract: Hibiscus calyces extract was microencapsulated by freeze drying and spray drying using partially hydrolyzed guar gum (PHGG), polydextrose (PD) or gum Arabic (GA) at 10 % as encapsulating agents. The retention of anthocyanins ranged from 59.8 to 64.6 % and from 66.4 to 74.3 %, and for antioxidant activity from 66.54 to 71.71 and 69.90 to 73.26 %, for spray-dried and for freeze-dried powders, respectively. The best result obtained, for the anthocyanins content, reducing capacity and ABTS, was for the powder produced by freeze drying using GA. Regarding physical powder properties, samples produced by spray drying using GA, followed by PHGG had the best results, with values of 95.80 and 95.20 %, 31.33 and 28.87 %, 17.43 and 10.96°C for solubility, hygroscopicity and Tg, respectively. Microscopy analysis also indicated that powders produced by spray drying using GA and PHGG had the best structures, showing particles of spherical shape and without agglomeration.