Edward R. Richter

Microbial safety and shelf-life of apple juice and cider processed by bench and pilot scale PEF systems

Abstract The effect of pulsed electric field (PEF) treatment on the inactivation of E. coli O157:H7 (bench scale) and shelf-life evaluation of aseptically packaged apple juice and cider (pilot plant scale) were investigated. Apple juice samples inoculated with E. coli O157:H7 were processed through a bench scale PEF system with electric field strengths of 34, 31, 28, 25, and 22 kV/cm and a mean total treatment time of 166 μs. Through a pilot-plant scale PEF system, fresh apple cider and reconstituted apple juice were processed using a 35-kV/cm electric field strength and 94 μs mean total treatment time, aseptically packed into 213-g (6 oz) plastic cup containers and stored at 4, 22, and 37°C for 70 days. PEF and heating (60°C for 30 s) were combined to process fresh apple cider. The inactivation of E. coli O157:H7 by the bench scale PEF system resulted in a 4.5 log reduction ( P P

Inactivation of Escherichia coli O157:H7 and Escherichia coli 8739 in apple juice by pulsed electric fields.

The effect of high voltage pulsed electric field (PEF) treatment on Escherichia coli O157:H7 and generic E. coli 8739 in apple juice was investigated. Fresh apple juice samples inoculated with E. coli O157:H7 and E. coli 8739 were treated by PEF with selected parameters including electric field strength, treatment time, and treatment temperature. Samples were exposed to bipolar pulses with electric field strengths of 30, 26, 22, and 18 kV/cm and total treatment times of 172, 144, 115, and 86 micros. A 5-log reduction in both cultures was determined by a standard nonselective medium spread plate laboratory procedure. Treatment temperature was kept below 35 degrees C. Results showed no difference in the sensitivities of E. coli O157:H7 and E. coli 8739 against PEF treatment. PEF is a promising technology for the inactivation of E. coli O157:H7 and E. coli 8739 in apple juice.

Antimicrobial activity of banana puree

An unidentified substance extracted from concentrated banana puree has been shown to inhibit Clostridium sporogenes and other Gram-positive sporeforming bacteria. Water and methanol extracts of concentrated banana puree produced zones of inhibition when tested by well plate biological assay. Organic acids at concentrations normally present in banana puree were found not to be solely responsible for the observed inhibition. The unknown substance demonstrated inhibitory effects at pH values as high as 7.5. Heat stability studies showed that the compound(s) are stable to normal retort temperatures.

Concurrent Detection of Foodborne Pathogens: Past Efforts and Recent Trends

Rapid and specific identification of foodborne pathogens is important for not only for food producers but also consumers as well as food safety authorities. Foods can harbor pathogen bacteria of different species, thus it is also important to be able to detect different pathogens simultaneously from the food samples even though they are in very low number. Detection of bacteria depends on different factors such as the initial number, food matrix, sensitivity of the method, competitor microflora and physical state of the bacteria whether they are injured or not. Simultaneous detection of different bacteria yet adds another hurdle for the level of detection, and thus, different approaches have developed and tested so far to optimize the maximum recovery.