Description:
The aim of this study was to investigate the factors affecting the survival and growth of four food-borne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus) in sweet and fermenting brewery wort. The Gram-negative pathogens (E. coli and Salm. Typhimurium) were capable of growth during the initial stages of fermentation in hopped wort, although they were quickly inactivated when added during the later stages of fermentation. When the wort was left unpitched, the two Gram-negative pathogens grew unabated. Pathogen growth and survival was enhanced as the pH was increased, and as both the ethanol and original gravity were decreased. Although having no effect on the Gram-negative pathogens, low levels of hop iso-
Description:
Changes in chemical composition, physical and sensory characteristics were followed in two pecan cultivars Wichita and Western Schley harvested from a commercial orchard at Gatton in Queensland seven times during 1996. Testa colour of both pecan cultivars darkened and opalescence decreased as the nuts matured. Bitterness of Western Schley pecans decreased with maturity. Colour of shuck, shell and kernel of both cultivars developed as the nuts matured. Wichita pecans were larger than Western Schley at all harvest times. Both nut-in-shell and kernel moisture decreased with maturity, whereas oil and sucrose contents increased. Both pecan cultivars had reached advanced maturation by the first harvest on March 18.
Description:
Traditional methods of naturally black olive production employ a series of static washings prior to fermentation. This work investigates the static washings and the effects they have on the subsequent spontaneous fermentation of Kalamata olives. Significant quantities of organic carbonaceous material, including phenolic compounds, were removed during the static washings. The rate of removal peaked after four static washings, and then declined. Bacteria (including lactic acid bacteria) and yeast were found to be present in high numbers throughout the static washings. An increase in the number of static washings resulted in the removal of inhibitory phenolic compounds. This led to a reduction in the lag phase and an increase in the specific growth rate for both the yeast and lactic acid bacteria during the subsequent spontaneous fermentations. However, an increased incidence of spoilage moulds was observed in the fermentations when the olives underwent thirteen static washings.
Description:
Traditional methods of naturally black olive production employ a series of static washings prior to fermentation. This work investigates the static washings and the effects they have on the subsequent spontaneous fermentation of Kalamata olives. Significant quantities of organic carbonaceous material, including phenolic compounds, were removed during the static washings. The rate of removal peaked after four static washings, and then declined. Bacteria (including lactic acid bacteria) and yeast were found to be present in high numbers throughout the static washings. An increase in the number of static washings resulted in the removal of inhibitory phenolic compounds. This led to a reduction in the lag phase and an increase in the specific growth rate for both the yeast and lactic acid bacteria during the subsequent spontaneous fermentations. However, an increased incidence of spoilage moulds was observed in the fermentations when the olives underwent thirteen static washings.
Description:
Opalescence is an unattractive browning of the interior of the pecan kernel compared to the white interior of normal kernels. The discoloration is due to the presence of free oil, resulting from decompartmentalization in the endosperm of opalescent pecans. Using a subjective scoring system, approximately 70% of Australian-grown pecan kernels tested were found to exhibit opalescence to some degree. Evaluation of kernels for opalescence during the harvesting-processing chain showed that opalescence first becomes evident in kernels after mechanical cracking. Opalescent kernels were found to have lower levels of calcium and higher amounts of oil compared to nonopalescent kernels. Differential scanning calorimetry showed that kernels do not freeze at -18°C.
Description:
The ultrastructure of pecans was investigated using light microscopy, environmental scanning electron microscopy, scanning electron microscopy, and transmission electron microscopy. Specific methodology for the sample preparation of pecans for electron microscopy investigations was developed. Electron microscopy of the ultrastructure of opalescent (discoloration of the interior) and nonopalescent kernels revealed that cellular damage was occurring in opalescent kernels. The damage was due to cell wall and membrane rupture, which accounted for the release of oil throughout the kernel. This rupture is due to the lower level of calcium in the cell membranes of opalescent pecans, as shown by energy dispersive X-ray spectrometry, making them more susceptible to damage.
Description:
The flow properties of ketchup were assessed upon addition of commonly used food thickeners: guar, xanthan and CMC gum at three different concentrations (0.5%, 0.75% and 1%) and four temperatures (25, 35, 45 and 55 °C). The ketchup without supplementation served as a control. All ketchup formulations exhibited non-Newtonian, pseudoplastic behaviour at all temperatures and hydrocolloid levels. The Power-law and Herschel-Buckley model were successfully applied to fit the shear stress versus shear rate data. The flow behaviour indices, n and n′, varied in the range of 0.189–0.228 and 0.216–0.263, respectively. The consistency coefficients, k and k′, were in the range of 8.42–27.22 and 6.56–20.10 Pa s n, respectively. The addition of hydrocolloids increased the yield point (τ0) and apparent viscosity of the ketchup in comparison to that of the control. The Arrhenius equation was successfully used to describe the effects of temperature on the apparent viscosity of the prepared formulations. The E a value appeared in the range between 5492.6 and 21475.8 J mol−1. [ABSTRACT FROM AUTHOR]
Description:
Water uptake behavior of three cultivars of lentils (Boomer, French-green and Nugget) was studied at three different hydration temperature regimes (room temperature, 50 °C and 85 °C). Boomer had the highest amount of water uptake capacity (74.60 g water/100 g of seeds) at room temperature (20 °C) which can be linked with its pore properties. French-green lentils imbibed the largest amount of water at elevated soaking temperatures (50 °C and 85 °C) and can be attributed to its higher seed surface area to volume ratio, high protein content and relatively thinner seed coat. Water uptake at elevated temperatures (50 °C and 85 °C) were predicted by a two parameter Mitscherlich model (R2 > 0.99,
Description:
Okara-maize flour blends were extruded in a co-rotating twin-screw extruder in order to assess their suitability as snack foods. Response surface methodology (RSM) using a central composite design was used to evaluate the effects of process variables (extrusion temperature (120-180 degrees C), screw speed (100-180 rpm) and feed composition (20-40 percent ww) and moisture content (14-22 percent ww)). Multiple regression equations were developed to describe the effects of each variable on product responses. The product characteristics such as bulk density, expansion index, appearance (colour, porosity), flavor (aroma, grittiness and off-odor), texture (hardness, crispness and brittleness) and overall acceptability were determined through experiments and sensory analyses. Through superimposed RSM contour map, it was found that the feed composition with 30 percent okara content, 14.5-19.3 percent moisture content and the extrusion temperature 120.0-171.2 degrees C and screw speed of 140 rpm, respectively to be the optimum extrusion conditions. The sensory tests showed that the products extruded at the optimized condition had the best appearance, taste, texture and overall acceptability. These results show that the okara-maize blends can be extruded into acceptable snack foods.
Description:
The change in textural attributes (hardness, chewiness and rate of softening) of three potato cultivars (Russet Burbank, Desiree and Sebago) was investigated. Uniform cylindrical samples (35-mm diameter and 3-mm thick) were prepared and exposed to different thermal processing regimes including; heating at 85°C, 95°C in water and steaming (100.2°C). The effect of salt on these textural attributes was also investigated using different salt concentrations (1.5%, 3% and 6% (w/w) NaCl). After thermal treatments the samples were subjected to texture profile analysis. The instrumental textural attributes were greatly affected by the cultivars and the thermal processing regimes. The change in textural attributes upon steaming was only marginally different compared to that at 95°C in water. Low concentrations of salt (1-3%) were found to accelerate the softening of the texture in these cultivars especially at lower temperatures. The textural attributes were modelled using a two-parameter reaction kinetics model. There was reasonable agreement by the model findings on the textural attributes prepared from all the thermal processing regimes and in presence and absence of (within average absolute error of 1.9-7%). Further, the model indicated that the order of reaction varied from 1.15-2.18 indicating that the changes in textural attributes in these thermal processing regimes followed higher reaction orders. [ABSTRACT FROM AUTHOR]
Description:
Hurdle technology employs the intelligent combination of different preservation factors to achieve mild but reliable preservation effects. Fresh coconut gratings treated with different combinations of hurdles such as acidulants, humectants, preservatives, antioxidants, a mild heat treatment and packaging were evaluated for changes in physico-chemical and sensory properties. It is possible to preserve the grating for four weeks in laminated polythene packages at 5°C in combination with 3% sodium chloride, 0.3% citric acid, 0.009% sodium citrate, 0.02% butvlated hydroxvanisole.
Description:
In this study, we investigated the effects and mechanisms involved in high pressure argon and xenon (HP Ar + Xe) mixed treatment on wound healing in fresh-cut apples and pineapples. Fresh-cut apples and pineapples treated by HP (1.8 MPa absolute) Ar and Xe (Ar:Xe = 2:9 partial pressure) were stored at 4 degrees C for 96 h. H2O2 production, the activities of related enzyme, the accumulation of phenolics and lignin were compared amongst those untreated and treated by HP air, normal atmosphere pressure (NAP Ar + Xe). The apple and pineapple samples subjected to the above treatments were inoculated with Escherichia coli and Saccharomyces cerevisiae, respectively, and incubated at 10 degrees C for one week. The growth of E. coli or S. cerevisiae was monitored to evaluate the wound-induced response to defense or the resistance against infection. Results showed that the HP (Ar + Xe) mixed treatment promoted the wound-healing response and enhanced resistance against the infection of E. coli or S. cerevisiae in fresh-cut apples and pineapples. The enhanced wound healing ability in fruit pieces subjected to HP (Ar + Xe) mixed treatment is found to be associated with the increase in H2O2 production and the accumulation of phenolics and lignin during storage after treatment. (C) 2012 Elsevier Ltd. All rights reserved.
Description:
High amylose starch–glycerol (HAG) films were produced incorporating beeswax, candelilla wax and carnauba wax in the presence and absence of Tween-80 in order to determine the distribution of wax in the films during the film formation process. The distribution of these waxes within the film was studied using Synchrotron based Fourier Transform Infrared Spectroscopy (S-FTIR) which provided 2D mapping along the thickness of the film. The incorporation of 5% and 10% wax in HAG films produced randomly distributed wax or wax-rich domains, respectively, within these films. Consequently, the addition of these waxes to HAG increased the surface roughness and hydrophobicity of these films. The addition of Tween-80 caused variations in wax-rich bands within the films. The HAG + carnauba wax + Tween-80 films exhibited domed wax-rich domains displayed with high integrated CH2 absorption value at the interior of the films, rougher surface and higher contact angle values than the other films. The S-FTIR 2D images indicated that the distribution of wax in starch–wax films correlated with the roughness and hydrophobicity of the starch–wax films.