Band 8, Heft 1

Due to the importance of physical ageing in functional properties of the globular protein of β-lactoglobulin as the main protein of whey powder (the by product of cheese manufacturing industry) the possible occurrence of physical ageing in dry powder of β-lactoglobulin with moisture content of 15.9% was studied at different temperatures below and close to the glass transition.Endothermic peaks that corresponded to relaxation enthalpy were observed for a β-lactoglobulin with 4 % moisture. Enthalpy and peak temperature increased on storage of β-lactoglobulin when it was held in the glassy state at different temperatures (20, 40, 60 º C). The general characteristics of the endothermic peaks were similar to those previously reported for synthetic polymers.

Published high pressure carbon dioxide (HPCD) inactivation data of natural microflora in apple juice and Saccharomyces cerevisiae in distilled water were described by the Weibull model. The shape parameter of the Weibull model was assumed to be pressure and temperature independent and could be fixed to reduce the number of parameters of the model from two to one. The rate parameter of the reduced Weibull model can be described in terms of pressure and temperature by use of a second order polynomial function fulfilling a number of constraints. Integrated models (secondary model incorporated into the primary one) produced successful predictions of survival curves for both natural microflora in apple juice and Saccharomyces cerevisiae in distilled water within the interpolation region.

In this research, cow’s milk was pasteurized using microwave (MW) or HTST methods and their effects on some milk components were studied. The results showed no differences between some physico-chemical characteristics like protein, fat, acidity, and solubility percentages due to heat treatments with either MW or HTST and the control samples. The contents of six amino acids (aspartic acid, glycine, glutamic acid, histidine, arginine, and lysine in mg/L) and fatty acids (weight percentage) showed no significant differences using either MW or HTST pasteurization method. There were slight but insignificant differences in trans fatty acid and D-amino acid contents in the milk pasteurized with either MW or HTST method. SDS-PAGE and HPLC analysis of milk proteins did not reveal any differences between the pasteurization methods. It was finally concluded that MW heating is a good alternative to HTST pasteurization.

Ginkgo nuts were used as raw material and peptides were prepared in turn with Neutral protease and Flavourzyme. In single-factor experiments of Neutral protease, conditions of temperature, pH, enzyme concentration and substrate concentration were optimized in term of degree of hydrolysis (DH). Based on the results of single-factor experiments, an orthogonal experiment (L9(3)4) was conducted to optimize the hydrolysis conditions of Neutral protease. The results showed that enzyme concentration, substrate concentration, reaction temperature and initial pH were the main variables that influenced DH. The highest DH was obtained when hydrolysis time, reaction temperature, initial pH, enzyme amount and substrate concentration were 4 h, 45 oC, 7.0, 1.8 mg/mL and 0.02 g/mL, respectively. Subsequently, the resulting solution was further hydrolyzed with Flavourzyme. Initial pH, temperature, time and enzyme concentration were optimized in term of DH. Finally, another orthogonal experiment (L9(3)4) was conducted to get the best enzymatic conditions of Flavourzyme, and enzyme concentration, initial pH, temperature and time were used as factors. The results showed that when Flavourzyme concentration, reaction temperature, initial pH and hydrolysis time were 9.0 mg/mL, 50 oC, 7.0 and 5 h, respectively, DH was the highest. The final degree of hydrolysis was 22.56%.

Sorghum germination resulted in a substantial tannin loss (95.7 %). Proximate composition, titratable acidity, pasting properties, in vitro protein digestibility, and protein solubility were studied post fermentation (Saccharomyces Cerevisiae) of the blended soybean, maize, and germinated sorghum flours. The pH progressively decreased with fermentation time, while titratable acidity increased from 0.029 to 0.118 ml/ml. Crude protein content increased with fermentation (251.7-274.8 mg/g) as a result of a shift in the dry matter composition. In-vitro protein digestibility markedly increased (12 %) as a result of fermentation. Protein solubility curves were above 30% of which highest for both fermented (12 and 24 hours) and unfermented composite flours were at pH 12 (51.77-77.64%) and lowest at pH 4 (30.31-35.98%). SDS-PAGE showed that protein hydrolysis occurred during fermentation over 12 and 24 hours. Unfermented composite flour was potentially stable as food ingredient due to its pasting stability, but the fermented flour low viscosity potential was preferred in this study as more flour will be used during porridge making, hence giving a food with a high nutrient density.

The objective of this study was to improve the quality of fresh spaghetti made from ordinary wheat flour using gluten powder at different levels (0.0, 0.5, 1.5 and 3.0%, w/w, flour basis). The spaghetti dough was evaluated by a Brabender Farinograph. The results indicated that with increasing the gluten level, peak, stability time and consistency of the dough increased. The results of creep test (carried out using a Texture Analyser) showed that with increasing the gluten content, elasticity of the dough increased while its viscosity decreased. Increasing the gluten level reduced the cooking loss and increased the water absorption of the samples cooked in distilled or salted water (2% NaCl). The hardness and the color of the uncooked and cooked spaghettis improved with increasing the gluten content. The sample containing 3% gluten powder cooked in salted water received the highest score for its sensory attributes.

The objective of this work was to study the influence of spray drying conditions on the physicochemical properties of black mulberry (Morus nigra) powder. A lab-scale spray dryer was employed for the spray drying process and maltodextrin DE=9was used as carrier agent.Response surface methodology (RSM) was performed to examine the effects of independent variables on the drying yield, color change, and total anthocyanin content and to determine the optimum processing conditions. Independent variables were: inlet air temperature (110 ºC, 130 ºC, and 150 ºC), compressed air flow rate (400, 600, and 800 l/h), and maltodextrin concentration (8%, 12%, and 16%). For each response, second order polynomial models were developed using multiple linear regression analysis. Analysis of variance was performed to check the adequacy and accuracy of the fitted models. The optimal conditions for drying yield and total anthocyanin content correspond to: temperature= 130 ºC, maltodextrin concentration= 8%, and compressed air flow rate= 800 L/h; these parameters led to the total anthocyanin content, process yield and browning index values of 5.85 (mg/100mL), 75%, 58.57% respectively.

Banana is an agricultural product of great economic importance for various developing countries. The relationship between moisture content and water activity provides useful information for the processing and storage of banana waste. The water activity and moisture content of three banana (Mussa spp. Haploid AAB cv. Nanica) waste items were analyzed to determine the desorption isotherms at six different temperatures (20, 30, 40, 50, 60 and 70°C). The desorption isotherms of the peel, pedicel and pulp of overripe bananas were determined in wide ranges of moisture content (0.001–6.360 kg kg-1 d.b.) and water activity (0.02–0.907). The theoretical GAB model was used for modelling the desorption isotherms. An analytical solution of the Clausius-Clapeyron equation was proposed to compute the isosteric heat of sorption, the differential entropy and Gibbs’ free energy by way of the GAB model when the effect of temperature on the hygroscopic equilibrium was considered.

Button mushroom in the form of whole and slices were dried using convective hot air drying and microwave drying methods. Main objectives were to study the drying behavior and change in colour and textural properties. To get moisture content of 0.08 g/g, hot air drying at 600C took 463 minutes and 350 minutes for whole and sliced mushroom respectively whereas these times were just 9 minutes and 8.5 minutes when the microwave oven was run at 60% of its maximum power (1350 W). The convective hot air drying process can be put into two falling rate periods. The decrease in brightness (indicated by L-value) in dried samples was about 44% as compared to the fresh ones. The variation within the differently dried samples was not much. Hardness was lowest (<2>N) in fresh samples and was highest (>5.5 N) in microwave dried samples with hot air dried samples in between. For most of the samples, the springiness were between 0.4 and 0.6 except for hot air dried sliced samples where it was 0.9. Except in hot air dried samples, the change in cohesiveness was not much. Adhesiveness was found in fresh mushroom only..

In order to design and to adapt equipments for food processing, it is essential to know thermophysical properties. Once temperature and composition affects these properties, models based in such factors are important for further calculation. In this work, density and dynamic viscosity of bovine milk, probably the most processed food fluid in the world, were determined within large ranges of temperature and major constituents (moisture, fat, lactose, protein and minerals), based on typical processing values. Density varied from (962.01 to 1100.45) kg/m3 and dynamic viscosity varied from (0.60 to 63.70) mPa∙s. Temperature and moisture content negatively affected both properties, while lactose, protein and minerals contents positively affected them. An increase in fat content reduced density and increased dynamic viscosity. Experimental density data were fitted to the simplest multiple linear model and dynamic viscosity data were fitted to a multiple type Arrehnius’ model, obtaining good agreement.

This paper describes comparative analysis some of physical and chemical properties of novel Persian walnut cultivars (cv. Urmia and Toyserkan) grown in Iran. The physical properties in terms of linear dimensions, geometric mean diameter, mass, volume, sphericity, surface area, true and bulk densities, porosity, repose angle, shell ratio and static coefficient of friction of nuts and kernels of the walnut cultivars were determined. The highest fat (66.1%), dietary fiber (4.8%), protein (16.33%), potassium (311mg 100g-1) and magnesium (97.5mg 100g-1) contents were obtained in Urmia cultivar (14.92%). Linoleic acid was the major fatty acid, followed by oleic, linolenic and palmitic acids. Amino acid composition analyses indicated that acidic amino acids were the most prominent group with a range from 31.06% (Toyserkan cultivar) to 31.09% (Urmia cultivar).

The sorption equilibrium of water for cape gooseberry at different temperatures (25, 35, 50 and 60°C) over a range of relative humidity levels, from 0.10 to 0.90, were determined using a gravimetric static method. The isosteric heat and Gibbs free energy were calculated from the sorption equilibrium. GAB, BET, SMITH, modified de Halsey, modified de Chung-Pfost, modified Oswin and modified Henderson models were tested to fit the experimental data. The GAB model was found to be the most suitable for describing the sorption curves. The monolayer moisture content values for the sorption at different temperatures were calculated using the BET model. The sorption curves show a Type III behavior. The isosteric heat decreased with increases in moisture content, while the Gibbs free energy increased.

Maize starch-water suspensions (8.0%) were submitted to the pulsed electric fields (PEF) with different electric field strength and treatment time up to 50 kV/cm and 1272 μs. Samples were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR). GPC analysis showed that molecular weights (Mw and Mn) were decreased with increasing electric field strength and treatment time. DSC studies showed a decrease in gelatinization temperatures (To and Tp) and the enthalpy of gelatinization (ΔHgel) with increasing electric field strength and treatment time. It was explored that electric field strength played a dominant role in the PEF treatments. On the other hand, it was demonstrated from NMR and TGA analysis that no significant difference among the native and PEF-treated maize starches was obtained, which indicated that PEF treatments did not affect the chemical structure of maize starch.

Fractional separation of gluten using the fast protein liquid chromatography (FPLC) and a numerical method for determination of Mark-Houwink-Sakurada (MHS) equation were studied. With 1% SDS buffer as solvent, the gluten was disassembled into two components: SDS soluble (SDS-S-G) and SDS insoluble gluten proteins (SDS-IS-G). The average molecular weight (Mn, Mw and Mz) and intrinsic viscosity [η] were measured by the multi-angle laser light scattering (MALLS) in conjunction with a size-exclusion chromatography (SEC) and viscosimetry. MHS equations for SDS soluble gluten and SDS insoluble gluten proteins were established as: (SDS-S-G) [η]=1.7459×10-2Mv0.6933=1.7459×10-2qMHSMw0.6933=1.6677×10-2Mw0.6933 (SDS-IS-G) [η]=7.5682×10-3Mv0.7323=7.5682×10-3qMHSMw0.7323=7.2079×10-3Mw0.7323 where qMHS was the polydispersity correction factor.

Physical (geometric, volumetric and colour) and mechanical properties of apple (cv. Fuji) as affected by Methyl Jasmonate treatments were analyzed. Geometric mean diameter, fruit mass, sphericity and surface area ranged from 71.36 to 69.97 mm, 196.53 to 194.83 g, 1.126 to 1.129, and 161.32 to 158.11 cm2 with MeJA doses, respectively. The bulk and fruit densities varied from 383.65 to 364.22 kg/m3 and from 967.96 to 954.63 kg/m3, with MeJA treatments. L*, a*, b* value of skin apple changed from 50.76 to 46.89, from 28.06 to 30.35, and from 24.58 to 22.43, respectively with MeJA doses. The skin and flesh firmnesses varied from 101.49 to 112.60 N and 74.18 to 72.71 N, respectively. The sphericity and projected area increased with MeJA doses used. As the MeJA doses increased, the bulk and fruit densities decreased, whereas volume increased. L*, b* and hue angle characteristics of skin apple were found to decrease, whereas a* was found to increase with MeJA doses. The fruit-removal-force was decreased linearly with increasing MeJA doses. The rubber surface offered the maximum friction followed by plywood and galvanized metal for MeJA doses.

This paper focuses on the drying kinetics at different temperatures of air in the chamber (lab scale dryer). A theoretical drying model was suggested. A number of experiments were carried out to study the drying characteristics of the fresh pepper berries in a lab scale dryer at six different temperatures which ranged from 30o C to 55o C at 5oC interval. In accordance with the experiments and the proposed model of drying of pepper fruits, the main parameters that contribute to accelerate the process can be distinguished. The parameters include the temperature of drying, the air humidity of the fruits surrounding and velocity of saturated water vapour transfer between the fruits and the surrounding. From the experiments, it was noticed that the change in size over time depends on the drying temperature. The drying process was accompanied by a number of processes that may be taken into account in refining the theoretical model. Characteristic drying time, according to the developed model exponentially depends on temperature, is proportional to the volume of pepper fruit, and inversely proportional to the coefficient of mass transfer. Mass transfer coefficient can be changed by changing of the air flow surrounding the berries in the drying chamber. This will work effectively in case when the drying is limited by high humidity in the surrounding.

The efficacy of three sanitizers (10 mL/L peracetic acid, 10 mL/L hydrogen peroxide and 20 mL/L commercial GRAS disinfectant) for inactivating Salmonella spp. inoculated onto the surface of whole tomatoes stored up to 8 days was investigated when they were used alone or in combination with pulsed ultraviolet light (PUV). Ten mL/L peracetic acid alone resulted in an average 3 log10 reductions throughout the 8-day storage. Ten mL/L hydrogen peroxide and 20 mL/L commercial biodegradable GRAS sanitizer alone yielded 1.41 and 1.29 log10 reductions, respectively, on day 0, but from day 2 to day 8 of storage, their disinfecting effect dwindled, with no significant difference detected from control (water rinse) on day 8 (p ≤ 0.05). The 60s PUV treatments alone achieved less than 2 log10 reductions, but when it was combined with 10 mL/L hydrogen peroxide, the bacterial reduction significantly increased to over 4 log10 during the 8-day storage (p ≤ 0.05). Similarly, PUV also enabled 20 mL/L commercial GRAS sanitizer to have unchanged bactericidal effect throughout the 8-day storage period. Results from this study showed that sanitizers combined with PUV radiation could generate a significant and lasting inactivation of Salmonella spp. on the surface of tomatoes.

The purpose of the present work was to study the effect of guava pomace and pulse powder incorporation in to rice based extrudates on physical characteristics. Guava pomace collected after juice extraction was dried and milled. It was then added with pulse powder-rice flour blend at different combinations based on Central Composite Rotatable Design (CCRD). The independent variables were moisture content (17 – 21%), temperature (115 – 135°C), screw speed (230 – 270rpm), and varying proportion of rice, pulse and guava pomace. Higher feed moisture content resulted in extrudates with a higher density, lower expansion, higher water absorption index, lower water soluble index, and higher hardness. Higher barrel temperature resulted in reduced density, increased expansion, and water solubility index. Addition of guava pomace resulted in increase in water absorption index, hardness and decreased bulk density, expansion and water solubility index. The study suggested the guava pomace may be utilized up to the level of 10% to in Ready to Eat Snacks.

A methodology for making thermostable konjac glucomannan (KGM) gels was examined with a view to eventual use with fish mince to make restructured products. A gelation method was developed with 3 and 6 % (w/v) aqueous dispersions of glucomannan (ADG) by adding alkali v/v (NaOH or KOH) up to pH 11.8- 12 and then allowing it to set (1 hr at 30ºC and 4 hrs at 5ºC). Both 3 and 6 % are suitable concentrations and KOH and NaOH (at 0.6 and 1M) are the most suitable alkalis for deacetylation of the glucomannan at pH 11.8- 12.0.

A low-cost charcoal evaporative cooler was designed and tested for the storage of camel milk in an arid pastoral area of northern Kenya. The cooler, 0.75 m3 in capacity, was made of galvanised iron frame reinforced with wire mesh inside and out, leaving a 10 cm-wide cavity which was filled with charcoal. A water reservoir linked to the cooler at the top through a perforated pipe kept the charcoal continuously wet through drip system. A wind driven fan on the roof enhanced air movement through the charcoal walls by sucking out the air in the cooler. The cooler was evaluated for temperature and product response. The inside temperature was 1-11°C lower than outside temperature and inside humidity was 0-49% higher than outside. During the hottest time of the day (14.00 hrs) when cooling was most needed, the cooler consistently maintained an average temperature drop of 10.5±0.4°C below ambient temperature, which varied from 29-32°C. This reduction in temperature was 35.6% and statistically significant (p≤0.05). During this time, cooling efficiency varied between 74.2 to 86.7%. Temperature of camel milk inside the cooler did not significantly increase (p>0.05) between morning time and evening time. However, temperature of control milk at ambient conditions significantly (p≤0.05) changed over the same period, from 22.6±0.08°C to 28.1±0.08°C. Milk inside the cooler was also significantly cooler (p≤0.05) than control milk in the evening, with a net temperature reduction of 27.0%. Total bacterial count changed from 31.4±2.1 x 104 cfu/ml to 43.1±1.9 x 104 and 1638±81 x 104 cfu/ml for test and control milk, respectively, after storage for 10 hours. As an inexpensive alternative to mechanical refrigeration, evaporative cooling technology is promising and suitable for rural application in arid pastoral areas without grid electricity, to minimise risk of milk spoilage at collection points and retail level, and thereby encourage organised women groups to get involved in milk marketing as a source of income.

Green and roasted coffee oil was extracted using supercritical CO2 at temperatures of (333, 343, 353 and 363) K and pressures from (235 to 380) bar, providing a CO2 densities range from (680 to 880) kg.m-3. The mathematical models of Del Valle-Aguilera and Chrastil were applied to predict the oil solubility. The Del Valle-Aguilera led to elevated deviations between the predict solubility values and those observed experimentally. The Chrastil model provided better results, with better fitting being observed. With this procedure, the mean percentage deviation was 0.16 and 0.19, respectively, for green and roasted coffee oil, showing a good correlation between the observed and predicted values.