Band 12, Heft 8 -

In this work, a methodology to measure torque during dough mixing in large scale was developed and the baking performance of bread dough formulated with resistant starch (RS) and enzymes was evaluated. Dough was formulated with 12.5 g/100 g of RS and 4 mg/100 g of a mixture of enzymes, glucose-oxidase (Gox), tranglutaminase (TG) and xylanase (HE) in proportions according to a three-component mixture design of experiments. Dough was mixed in a large-scale dynamic rheometer measuring instant torque and speed in real time through a personal computer (PC) interface. Maximum torque during mixing and parameters of the dough development curves obtained from rheofermentometer were fit to mathematical models within 95 % of confidence. Gox and TG showed positive effects on the maximum height of dough, while HE showed a negative one. Also, it was found that Gox and TG in the presence of HE could be important for reducing dough weakening.

Fresh-cut yacon slices were first heat treated (60–80 °C, 5–25 min) and then exposed to air at room temperature for up to 10 min. Color parameters of internal surface were measured and two kinetic models were evaluated: 1) Color degradation during thermal treatment, and 2) Color stability during subsequent air exposure. More severe treatments led to lower color quality but higher stability. The relative white index was the best color parameter and the color changes followed a zero-order kinetics. The temperature dependence of rate constants were evaluated using the Arrhenius model. The activation energy for color degradation was 14.7 kJ/mol, and for color stability it was 47.9 kJ/mol indicating color stability parameters to be more sensitive to temperatures than color degradation. The color parameter models developed were comparable to polyphenoloxidase inactivation model and provided a rapid physical method for evaluating color degradation and subsequent color stability of yacon slices.

Spouted pouches are being increasingly used in the beverage sector. However, aseptic packaging technology used for spouted pouches requires a highly complex sterilisation and rinsing process for the packaging materials before filling. This paper deals with the pouch packaging sterilisation process used in aseptic technology. A mixture composed of vaporised hydrogen peroxide and hot sterile air is injected into the package through a sterilisation nozzle. A CFD multicomponent model in ANSYS CFX (version 14.5) has been created and validated in order to simulate the real process. Based on this model, the paper aims to minimise hydrogen peroxide consumption and optimise the sterilisation treatment of the packaging. This issue has been approached using multi-objective optimisation software applied to CFD multicomponent simulations. The most suitable nozzle position inside the pouch has been established, as well as the optimal treatment time, concentration and flow rate of the sterilising mixture.

Sea cucumbers are popular traditional tonic foods in Asia and the Middle East and are often dried for storage or sale. Rehydration of dried sea cucumber is a necessary step before further processing. The kinetics for ultrasound-assisted rehydration were mathematically described using mechanistic (Fick’s diffusion) and empirical (Peleg’s equation, Weibull model) models. The effective diffusivities of water transport with ultrasound were in the range of 0.182 mm 2 min –1 –0.197 mm 2 min –1 , which was greater than the value of the control, at 0.179 mm 2 min –1 , considering Fick’s diffusion. Peleg’s equation was concluded to be the best model to predict the ultrasound-assisted rehydration of dried sea cucumber. Its rehydration efficiency was increased 16-fold by ultrasound and rehydration time was reduced up to 45 h, the sea cucumbers did not show any negative effects on their texture properties after rehydration.

In this study, 1 wt% lecithin (–), chitosan (+), and λ-carrageenan (–) were prepared to manufacture multiple-layered liposomes with optimal formulations developed in a previous study by using layer-by-layer electrostatic deposition. We observed their particle size, ζ-potential, sedimentation behavior, and microstructure for 6 weeks. Multiple-layered liposomes were quenched with calcein to evaluate stability in terms of factors such as encapsulation efficiency and released amount of calcein. The particle size of multi-layered liposomes increased with storage periods and the ζ-potential of multiple-layered liposomes gained a neutral charge. Interestingly, negatively charged layered liposomes were smaller than positively charged layered liposomes and showed a lower polydispersity index. Moreover, the ζ-potential did not apparently change compared to positively charged layered liposomes. For the calcein release study, multiple-layered liposomes significantly sustained quenched calcein more than that observed using non-layered liposomes. This study showed that it was possible to increase the thickness of the liposome surface and to manipulate its charge using chitosan and λ-carrageenan through electrostatic deposition. Results showed that manufacturing negatively charged multiple-layer (over 4-layer) liposomes with charged biopolymer improved the physicochemical stability of liposomes.

The effect of gallic acid treatment on mechanical and water barrier properties in zein and zein–corn starch composite films was investigated. Four concentrations of corn starch (5 %, 10 %, 15 %, 20 %) were used in composite films making a final solid concentration of 6 % (w/v) in the film forming solution. One composite film containing 10 % corn starch was also prepared in absence of gallic acid for comparison purpose. Gallic acid treatment improved tensile strength (TS) and water vapor permeability (WVP) while solubility was increased in control zein films. On the other hand, gallic acid treatment significantly ( p  < 0.05) reduced TS and increased WVP in zein–corn starch composite films. Interestingly, mechanical and water barrier properties of composite films prepared in absence of gallic acid were comparatively better than gallic acid treated composite films. These findings provided useful insights in how each individual hydrocolloid in the composite film was differently affected by gallic acid treatment.

The drying kinetics and mathematical modeling of hot-air drying of yam slices were investigated under two-stage relative humidity (RH) control strategy with 60 °C and 1.5 m/s as its constant drying temperature and air velocity, respectively. Results indicate high RH in the initial stage results in high sample’s temperature that enhances water diffusion in the falling rate drying period. Within the scope of current work, change in RH in the later drying period has insignificant influence on sample’s temperature rise while low RH can accelerate the drying rate. Compared to drying at constant 20 % RH at the same drying air temperature, the drying strategy of using 40 % RH over the first 15 min and then lowing to 20 % RH for the remainder time yields a shorter drying time. Weibull model adequately described the moisture content variation with time for all experiments with the scale parameter ranging from 105.02 to 122.38 min and the values of shape parameters from 0.988 to 1.183. The effective moisture diffusivity determined from the Weibull model varied from 2.032 to 2.610×10 −8  m 2 /s. The rehydration ratio increased as the overall drying time was reduced. Microstructure examination shows that higher RH in the initial drying stage can lead to a more porous microstructure which enhances drying, while fast drying rate in the initial drying period generates a crust layer which hinders drying.

The objective of this study was to determine suitable conditions for yoghurt spray drying in a pilot-scale equipment with a rotary atomizer using drying auxiliary agents to reduce wall deposition in the drying chamber. First, the effects of the main process variables (disk rotation speed: 25,000–30,000 rpm; inlet air temperature: 160–180 °C; feed flow rate: 5.2–8.7 kg/h) were studied with a 2 3 central composite experimental design. Following, six different drying agents (maltodextrins 5 dextrose equivalent [DE] and 10 DE, EmCap ® , acacia gum, skimmed milk and fumed silica) were tested to identify the most promising additive to improve process yield. Excellent results on wall deposition, product recovery, product color and particle size distribution span were achieved with fumed silica Aerosil ® at 3 %, 26,000-rpm atomizer speed, 160 °C inlet air temperature and 8.7 kg/h yoghurt feed flow rate. The action of the fumed silica on particle agglomerates produced a free-flowing powder with good homogeneity.