ESTIMATION OF pH OF SUGAR CANE JUICES A . T HIGH TEMPERATURE
A Philips digital pH-meter (PW9422) equipped with a Philips high temperature pH-electrode (CH 85D-SD) and platinum 100 thermometer was used in the autocalibrate mode to standardise itself using 2 NBS-buffers (phthalate and borax solutions). The instrument automatically identifies each buffer and uses the current temperature to select the exact buffer value from its look-up table. Temperature compensation for electrode slope changes due to temperature changes was also automatic.
Evaluation of sucrose loss in evaporators for different processing configurations
The chemical compositions were determined for juice and condensate samples collected at various locations in the Robert evaporator sets at two Australian sugar factories. The purpose of the investigations was primarily to determine the magnitude of sucrose degradation and the consequences of those degradation reactions, such as reduced pH of condensate. Robert evaporators are used almost exclusively in Australian sugar factories. One of the factories involved in the trials incorporates a cogeneration facility and undertakes extensive vapour bleeding from large vessels at the first and second effects. The second factory undertakes no bleeding of vapour and the residence time for juice in the front end of the evaporators is much shorter than in the evaporator set at the cogeneration factory. Boiling temperatures are also lower at the front end of the set. The sucrose degradation results have been compared with the predictions using the Vukov expression (as a function of juice pH, juice brix, temperature and residence time). Average sucrose losses of 0.85% and < 0.05% were measured for the cogeneration factory and for the second factory, respectively. Predicted losses for the conditions at the cogeneration factory were ~1.16% and for the second factory < 0.05%. A sucrose loss of 1% across the evaporators would likely cause a 1.6% reduction in sugar production compared with a factory operating with a 0.1% sucrose loss at the evaporators. Subsequent modelling was undertaken to predict the sucrose losses that would be expected if Kestner or falling film tube evaporators (both providing shorter residence times than Robert evaporators) were used as replacements for Robert evaporators at the first effect. The expected changes in sucrose losses from supplying juice at higher pH to the evaporators and using process steam at lower saturation temperature were also considered.
Synergistic Effect of High Temperature and High pH on the Destruction of Salmonella enteritidis and Escherichia co1i O157:H7.
This study was undertaken to determine if high temperature and high pH interact synergistically to enhance the rate of destruction of two important gram-negative foodborne pathogens, Escherichia coli O157:H7 and Salmonella enteritidis . The rates of destruction in NaHCO3-NaOH buffers at pH 7.0, 10.0, and 11.0 were determined at 35, 40, 45, 50, 55, 60, and 65°C. Use of an improved heating protocol eliminated a "tailing effect" at longer exposure times. The present study demonstrated that the combination of high pH and high temperature resulted in a highly significant synergistic interaction (P > F = 0.0001), which caused rapid death of both E. coli O157:H7 and S. enteritidis . This "alka-therm" technology might be used commercially to destroy gram-negative foodborne pathogens on various raw agricultural commodities.