Band 13, Heft 2 -

Wheat flour, whole wheat flour, 25 and 50 % rye flour substituted wheat flour blends, 15 and 30 % wheat bran substituted wheat flour blends were supplemented with amyloglucosidase (at 0.000875 and 0.001 %), glucose oxidase (at 0.0003 and 0.001 %) and hemicellulase (at 0.001 and 0.005 %). The effects of enzymes on the extensographic properties of dough and quality characteristics of bread (specific volume, baking loss percentage and final moisture content) were studied. The interaction between type of flour/blend, type of enzyme and dosage of enzyme affected resistance to extension, extensibility and ratio of resistance to extensibility of doughs significantly. The interactions between type of flour/blend, type of enzyme and dosage of enzyme affected specific volume, baking loss percentage and final moisture content of breads significantly. The findings in this study indicated that enzymes can exhibit unexpected effects on dough and bread properties depending on type of flour and dosage of enzyme.

The development of jujube brandy is restricted severely by excessive methanol production. Three methods to reduce methanol production were compared: fermentation material, boil and storage container. Boil treatment showed the best result, reducing methanol from 1.77 to 0.21 g/L, which was chosen for further analysis for comparing aroma compounds. Boil treatment increased ester, acids, and hydrocarbons; decreased alcohols, aldoketones, and terpenoids. The largest changes were seen in esters, hydrocarbons, and terpenoids. A pilot test of Boil treatment was performed. Results from the pilot test were consistent with laboratory results, with a significant decrease in methanol from 7.69 to 0.54 g/L. During the pilot test, methanol levels were measured in each fermentation layer and no significant difference was seen. Methanol levels were also measured in different distillation times. The foreshot had the highest concentration of methanol and the feint had the lowest concentration of methanol. Therefore, boil treatment combined with appropriate distillation will effectively solve the problem of excessive methanol production.

Mathematical model to predict tea infusion kinetics which accounts for swelling kinetics of tea granules is presented. Swelling kinetics of tea granules has never been taken into account for models developed so far. Differential equations (DEs) for concentration of tea constituents inside tea granule with respect to radius and time were derived. Solution methodology for these DEs is developed based on Crank-Nicholson scheme. Tea infusion profile is obtained using this model by knowing the swelling kinetics, partition constant and initial contents in tea granules. Diffusivity and product of interfacial area ( A s ) and backward rate constant ( k −1 ) are the fitting parameters. Model prediction is fitted to the experimental data published previously ( R 2 = 0.90–0.98). The fitted diffusivity (3.33 × 10 −10  m 2 /s) and A s k −1 (2 m 3 /(kg.s)) predicted the infusion profile of other sized tea granules very well. This model predicts the infusion during initial stage very accurately without any empirical parameter.

Abstract: In this research, effect of Refractance Window (RW) drying on the quality properties of the kiwifruit samples was investigated. Drying temperatures of 80–100 °C, slice thickness of 0.8–2.4 mm and Mylar thickness of 100–300 µm were the independent variables and different qualitative attributes including drying duration, textural hardness, colour, rehydration ratio and organoleptic properties were responses monitored in each situation. Drying temperature was the most important factor contributed to quality features of RW dried kiwifruits with significant effects on all properties. Similarly, slice thickness influenced nearly all quality traits except textural hardness and some colour indices. However, Mylar membrane thickness failed to affect about every qualitative property of kiwifruit samples significantly. The majority of organoleptic properties of RW dried kiwifruits, including flavour, colour, texture, shrinkage and overall acceptance, were judged to be in the range of medium to good quality (scores of 3–4) by panellists.

The present study investigated the potential of several indigenous fungal strains to produce industrially important exo-polygalacturonase (exo-PG) utilizing locally available agro-industrial wastes in solid-state fermentation (SSF). Amongst various substrates employed, wheat bran supported the highest biosynthesis of exo-PG. Different process variables such as, fermentation duration, moisture level, pH and temperature were optimized using one-variable-at-a-time (OVAT) statistical approach. Results revealed that an initial medium pH of 3.0 at 35 °C together with MnSO 4 , glycine and pectin have progressive influence on exo-PG synthesis by P. notatum , while C. versicolor displayed utmost enzyme activity at pH 5.0, temperature 30 °C, moisture 50 % using CaCO 3 , (NH 4 ) 2 SO 4 , and lactose as nutritional sources. The enzymatic cocktail treatment achieved a significantly improved clarity by reducing the turbidities, viscosities and absorbance’s of three fruit juices. Scaling up of various fermentation parameters might have potential to produce enhanced activities of exo-PG for different industrial sectors, particularly in food industry.

Abstract: Hydrogen peroxide has been studied as an alternative for sulfur in the white sugar industry. Sulfur has been associated to allergic diseases, mainly asthma. In this study, artificial neural network (ANN) models are proposed to predict the effects of different variables (peroxidation time, temperature, pH, H 2 O 2 dosage, and initial °Brix) on sugarcane juice color removal and sucrose content. Experimental results and the ANN models revealed that temperature showed the greatest influence on the decrease of juice color; nevertheless, the effect of temperature depended on pH: at pH<;5.0 a decrease in juice absorbance was observed at temperatures close to 38 °C, whereas in the pH range of 5.0–6.3, absorbance decreased only at about 50–62 °C, regardless of the amount of hydrogen peroxide used. On the other hand, the remaining sucrose content after peroxidation was influenced by the initial °Brix and by pH.

Abstract: Stress-relaxation behavior of single rice kernel was studied using a dynamic mechanical analyzer (DMA) in compression mode. The relaxation modulus was measured in a moisture content range of 12–30 % on dry basis (d.b.) and a temperature range of 25–80°C. A constant stain value of 1 % (within the linear viscoelastic range) was selected during the stress-relaxation tests. The relaxation modulus was found to decrease as the temperature and moisture increased. A master curve of relaxation modulus as a function of temperature and moisture content was generated using the time–moisture–temperature superposition principle. Results showed that the generalized Maxwell model satisfactorily fitted the experimental data of the stress-relaxation behavior and the master curve of relaxation modulus ( R 2 > 0.997). By shifting the temperature curves horizontally, the activation energy of the stress relaxation was obtained which significantly decreased with increase in the moisture content.

Effects of two combination drying methods as well as two single drying methods on the quality of papaya chips were studied. The longest drying time was found in freeze drying (FD), while the shortest drying time was found in hot-air-explosion puffing drying (HA-EPD). The papaya chips dried by FD exhibited the lowest shrinkage, while the highest shrinkage was found in the hot-air drying (HAD) dried sample. The lowest and highest total color differences (△E) were found in the FD and FD-EPD. The FD dehydrated papaya chips showed the highest retention of ascorbic acid and total carotenoids. The fastest rehydration rate was also observed in samples dried by FD. The worst rehydration capacity was found in FD-EPD, which related to the collapsed porous microstructure. Papaya chips prepared by FD-EPD showed crispier texture, which were in line with their expanded porous microstructures. In conclusion, the application of combining with EPD may improve the retention of nutrition of papaya.

Astragalus mongholicus is a famous traditional Chinese medicinal herb because of its human health benefits and bioactive compounds. Pulverization process directly affects quality and dissolution of bioactive compounds of A . mongholicus . In the present study, liquid nitrogen was introduced to pulverization process of A . mongholicus . The pulverization with addition of liquid nitrogen (LNP) effectively retained powder color, crushed tissue fiber, and reduced hardness of A . mongholicus . Furthermore, LNP significantly improved elasticity and solubility of the powder, as well as soluble solid contents. In addition, extraction yield of polysaccharides, characteristic bioactive compounds in A . mongholicus , was increased by 10.5 % by combination of LNP and Tween-80 enzyme extraction. These results suggest that LNP can be a promising technology for preparation of A . mongholicus powder. The information will also contribute to improvement of manufacturing technology of Chinese medicinal herb.

This study aimed to evaluate fatty acid composition and physicochemical properties of Iranian milkweed seed oil (IMSO) and olive cultivar Roghani oil (OCRO). The extraction yield and unsaturated fatty acids content of IMSO were 21.9 % (dry basis) and 65 %, respectively. The monounsaturated fatty acids/polyunsaturated fatty acids ratio, calculated oxidizability, peroxide value, unsaponifiable matter, total tocopherol content, total phenolic content, total sterol, wax content, carbonyl value, conjugated diene value and oxidative stability index of IMSO and OCRO were measured. The results indicated that oxidation stability (OS) of IMSO (6.46 h) was significantly higher than OS of OCRO (5.53 h). In addition, application of IMSO to OCRO resulted in higher OS that was the greatest after 10 % addition of IMSO.