Nola Caffin

Application of the Williams–Landel–Ferry model to the viscosity–temperature relationship of Australian honeys

The rheological behaviour of nine unprocessed Australian honeys was investigated for the applicability of the Williams-Landel-Ferry (WLF) model. The viscosity of the honeys was obtained over a range of shear rates (0.01-40 s(-1)) from 2degrees to 40 degreesC, and all the honeys exhibited Newtonian behaviour with viscosity reducing as the temperature was increased. The honeys with high moisture were of lower viscosity, The glass transition temperatures of the honeys, as measured with a differential scanning calorimeter (DSC), ranged from -40degrees to -46 degreesC, and four models (WLF. Arrhenius, Vogel-Tammann-Fulcher (VTF), and power-law) were investigated to describe the temperature dependence of the viscosity. The WLF was the most suitable and the correlation coefficient averaged 0.999 +/- 0.0013 as against 0.996 +/- 0.0042 for the Arrhenius model while the mean relative deviation modulus was 0-12% for the WLF model and 10-40% for the Arrhenius one. With the universal values for the WLF constants, the temperature dependence of the viscosity was badly predicted. From non-linear regression analysis, the constants of the WLF models for the honeys were obtained (C-1 = 13.7-21.1: C-2 = 55.9-118.7) and are different from the universal values. These WLF constants will be valuable for adequate modeling of the rheology of the honeys, and they can be used to assess the temperature sensitivity of the honeys

Optimization of the microencapsulation of lemon myrtle oil using response surface methodology

Response surface methodology (RSM) was applied to study the effects of types of wall materials (modified starch + maltodextrin and whey protein concentrate + maltodextrin), feed concentration, oil concentration, and outlet air temperature on oil retention and surface oil content of the encapsulated powder. The results revealed that the oil retention was significantly (P < 0.05) affected by the constant term of types of wall materials and the linear term of feed concentration but seemed to be almost independent (P > 0.05) of experimental range of oil concentration and outlet air temperature. The types of wall materials, oil load, and outlet air temperature showed a significant (P < 0.05) influence on surface oil content. The types of wall materials (Hi-Cap and WPC) also influenced significantly the oil retention and surface oil content. Based on the limited range of experimental conditions used in this work, it was not possible to choose the wall materials that can give both high oil retention and low surface oil content. Disregarding the effect of wall material, an optimum response was obtained at 40% of feed concentration (w/w), 18% of oil concentration, and 65°C of outlet air temperature.

Phenolic Contents and Antioxidant Activities of Major Australian Red Wines throughout the Winemaking Process

Three Australian red wine types (Shiraz, Cabernet Sauvignon, and Merlot) were analyzed for antioxidant activity and a range of phenolic component contents using various spectral methods. More than half of the total phenolic compounds were tannins, whereas monomeric anthocyanins and flavonols were present in much lesser amounts (<10%). The evolution of phenolic contents and the respective antioxidant activities in wine samples from all stages of winemaking showed progressive changes toward those of commercial wines. The antioxidant activity of the wines in DPPH and ABTS assays was positively correlated with total phenolic contents and tannins. Comparisons of the three wine varieties based on their individual phenolic component groups and antioxidant activities showed limited differences between the different varieties. However, when all of the variables were combined in a principal component analysis, variety differentiation was observed. The three varieties of red wines all contained similar and high concentrations of antioxidants despite differences in grape variety/maturity and winemaking process, suggesting that related health benefits would accrue from all of the red wines studied.

Drying of Lemon Myrtle (Backhousia citriodora) Leaves: Retention of Volatiles and Color

Lemon myrtle plant (Backhousia citriodora) leaves were dried at three different drying temperature conditions (30, 40, and 50°C) in a fluidized bed dryer. The retention of the principal volatile compound, citral, was analyzed in dried products obtained at these three drying conditions. The changes in the color parameters L*, a*, b* of leaves were also analyzed. More than 90% of citral was retained at 50°C drying temperature, whereas the retention at 30 and 40°C was 81 and 85%, respectively, suggesting that higher temperature is beneficial to achieve higher retention of volatiles. However, in terms of the color, all the color parameters were changed maximum at 50°C drying temperature unfavorably, suggesting that the higher temperature drying causes more degradation of the pigment. Blanching of the leaves in hot water at 80°C for 1 min prior to drying did not result in any improvement in volatile retention or color.

Determination of Viscosity of Some Australian Honeys Based on Composition

Abstract Rheological properties of four unprocessed unifloral Australian honeys (heath, tea tree, yapunya, and yellow box) and an artificial honey were analysed at 20°C. A model previously used to describe viscosity data of various sugar and sugar mixtures was used to describe the concentration dependence of the viscosity of honey samples with varying moisture contents. The model successfully described the sugar concentration dependence of the unadulterated and medium moisture (70–85% solids) range honey samples.

Effect of antimicrobial spice and herb extract combinations on listeria monocytogenes, staphylococcus aureus, and spoilage microflora growth on cooked ready-to-eat vacuum-packaged shrimp

Two spice and herb extract combinations from galangal (Alpinia galanga), rosemary (Rosmarinus officinalis), and lemon iron bark (Eucalyptus staigerana) were evaluated for their ability to inhibit the growth of inoculated Listeria monocytogenes and Staphylococcus aureus and naturally present spoilage microflora on cooked ready-to-eat shrimp stored for 16 days at 4 or 8 °C. A combination of galangal, rosemary, and lemon iron bark significantly reduced (P < 0.05) levels of aerobic bacteria and lactic acid bacteria at 4 °C on day 12 by 1.6 and 1.59 log CFU/g, respectively. By day 16, levels of these bacteria were equivalent to those of controls. The shrimp treated with this spice and herb extract combination had significantly lower (P < 0.05) lipid oxidation from day 4 to day 16. Similarly, a combination of galangal and rosemary extract significantly reduced (P < 0.05) levels of aerobic bacteria and lactic acid bacteria at 8 °C on day 8 by 2.82 and 2.61 log CFU/g, respectively. By days 12 and 16, levels of these bacteria were equivalent to those of controls. The shrimp treated with this spice and herb combination had significantly lower (P < 0.05) lipid oxidation on days 4 and 16. None of the spice and herb extract combinations had an effect on levels of L. monocytogenes or S. aureus or changed the color or pH of the shrimp during storage. The results of this study indicate that combinations of galangal, rosemary, and lemon iron bark extracts can be used to control the growth of spoilage microflora on ready-to-eat shrimp.

Small food service establishments still on amber light for adopting Australian HACCP‐based food safety code

The increasing incidence of food‐borne diseases emphasises the importance of improving and maintaining a high standard of food safety in food service establishments. Currently, a proposal to develop an Australian national food hygiene standard based on the hazard analysis and critical control point (HACCP), principles, is being discussed by major stakeholders with a view to improving the standard of food safety. Notes that food service representatives are naturally supportive of high standards of food safety, but feel the costs associated with HACCP‐based food safety are prohibitive for small businesses, and they advocate that the costs of staff training in food safety be borne by the entry level employee. Reports on the diverse standards of hygiene found in a cross‐section of food service establishments in south‐east Queensland, Australia. Hygiene standards were found to be satisfactory in only ten of the 19 sites surveyed. Small restaurants and hotel/clubs compared unfavourably with larger food service providers, (which included cafeterias, hospitals, resorts and a contract airline caterer). As the food service industry is still dominated by small operations, these findings suggest that there are major challenges ahead in devising a national food hygiene standard which will be accepted and be implemented by this sector.

Friction Factors and Rheological Behavior of Australian Honey in a Straight Pipe

Abstract The pumping characteristics of four Australian honey samples were investigated in a straight pipe. Six flow rates (100–500 kg h−1) were studied at three temperatures (35–50°C). The pressure loss increased with an increase in the length of the pipe, as the flow rate was increased and as the temperature was reduced. In the 25.4 mm-pipe, the Reynolds number ranged from 0.2–32.0 and are substantially less than the critical value (2040–2180) for laminar condition in the system. The relationship between the wall shear stress and shear rate approximated power-law behaviour, and the power-law index was not significantly (p > 0.05) different from 1.0. The honey samples exhibited Newtonian behaviour at all the temperatures and this was confirmed by rheometric studies using Couette geometry. A friction chart was generated independent of temperature and the type of honey. An equation was developed to predict the pressure loss of the honey in a typical pipeline at any temperature once the viscosity–temperature relationship had been established.

Small establishments present challenge for Australian food safety code

The increasing incidence of food‐borne diseases emphasises the importance of improving and maintaining a high standard of food safety in food service establishments. Currently, a proposal to develop an Australian national food hygiene standard based on the HACCP principles, is being discussed by major stakeholders with a view to improving the standard of food safety. This article reports on the diverse standards of hygiene found in a cross‐section of food service establishments in south‐east Queensland, Australia. Hygiene standards were found to be satisfactory in only ten of the 19 sites surveyed. It is important for the success of the national food safety strategy that any legal framework, codes of conduct and auditing of standards, complement the existing workplace practices and culture of food service establishments.