ABSTRACT
In this study, thermal inactivation parameters (D- and z-values) of Alicyclobacillus acidoterrestris spores in McIlvaine buffers at different pH, apple juice and apple nectar produced with and without ascorbic acid addition were determined. The effects of pH, temperature and ascorbic acid concentration on D-values of A. acidoterrestris spores were also investigated using response surface methodology. A second order polynomial equation was used to describe the relationship between pH, temperature, ascorbic acid concentration and the D-values of A. acidoterrestris spores. Temperature was the most important factor on D-values, and its effect was three times higher than those of pH. Although the statistically significant, heat resistance of A. acidoterrestris spores was not so influenced from the ascorbic acid within the concentration studied. D-values in apple juice and apple nectars were higher than those in buffers as heating medium at similar pH. The D-values ranged from 11.1 (90 degrees C) to 0.7 min (100 degrees C) in apple juice, 14.1 (90 degrees C) to 1.0 min (100 degrees C) in apple nectar produced with ascorbic acid addition, and 14.4 (90 degrees C) to 1.2 min (100 degrees C) in apple nectar produced without ascorbic acid addition. However, no significant difference in z-values was observed among spores in the juices and buffers at different pH, and it was between 8.2 and 9.2 degrees C. The results indicated that the spores of A. acidoterrestris may survive in fruit juices and nectars after pasteurization treatment commonly applied in the food industry.
Subject(s)
Ascorbic Acid/pharmacology , Beverages/microbiology , Food Handling/methods , Gram-Positive Endospore-Forming Rods/physiology , Hot Temperature , Malus/microbiology , Colony Count, Microbial , Consumer Product Safety , Dose-Response Relationship, Drug , Food Microbiology , Gram-Positive Endospore-Forming Rods/drug effects , Gram-Positive Endospore-Forming Rods/growth & development , Humans , Hydrogen-Ion Concentration , Models, Biological , Spores, Bacterial/growth & development , TemperatureABSTRACT
A simple and rapid method using liquid chromatography coupled to diode array detection (LC-DAD) was developed for the determination of acrylamide in potato-based foods at low levels. The method entails extraction of acrylamide with methanol, purification with Carrez I and II solutions, evaporation and solvent change to water, and cleanup with a Oasis HLB solid-phase extraction (SPE) cartridge. The final extract was analyzed by LC-DAD for quantification and by liquid chromatography coupled to mass spectrometry (LC-MS) for confirmation. The chromatographic separations were performed on a hydrophilic and a hydrophobic interaction columns having good retention of acrylamide under 100% aqueous flow conditions (k' 3.67 and 2.54, respectively). The limit of quantitation was estimated to be 4.0 microg/kg based on the signal-to-noise ratio of 3 recorded at 226 nm. Recoveries of acrylamide from potato chips samples spiked at levels of 250, 500 and 1000 (n = 4 for each level) microg/kg ranged between 92.8 and 96.2% with relative standard deviations of less than 5%. The results of this study revealed that a conventional LC instrument coupled to DAD can also be used accurately and precisely, as an alternative to tandem LC-MS methods for the determination of acrylamide in potato-based foods.
Subject(s)
Acrylamide/analysis , Chromatography, High Pressure Liquid/methods , Solanum tuberosum/chemistry , Atmospheric Pressure , Mass Spectrometry , Reference Standards , Sensitivity and SpecificityABSTRACT
Phenolic compounds of fruit juices are responsible for haze and sediment formation as well as for color, bitterness and astringency. The influence of ultrafiltration (UF) and laccase-UF combination was investigated on phenolic contents of pomegranate juices and on filtration output. Laccase-treated and then ultrafiltered pomegranate juices have shown a rapid increase in their color, when compared to only ultrafiltered (control) samples. Kinetic parameters of laccase were also determined. During the oxidation period, the changes occurring in pomegranate juices were estimated from phenolic contents, color and anthocyanin measurements. Results have shown that laccase oxidation produced a significant decrease in phenolic content of pomegranate juices while juice color the increased. However, in recent literatures, the possibility to remove polyphenols in apple juices was reported. We decided in this study that laccase treatment can not be applied due to the loss of natural red color and unwanted dark brownish color formation in pomegranate juice.
