Long-Term Storage of Vegetable Juices Treated by High Hydrostatic Pressure: Assurance of the Microbial Safety.

Food business operators search for new, mild technologies, which extend the shelf life of product without changing the sensory and nutritional properties. High hydrostatic pressure (HHP) meets these requirements; however it also triggers sublethal injury of bacterial cells. Sublethal injuries could spoil the product during storage and potentially pose major public health concerns. This study aims to examine the changes of sublethally injured pathogens cells in two vegetable juices: carrot juice (pH 6.0-6.7) and beetroot juice (pH 4.0-4.2) that are induced by HHP (300-500 MPa). The possibilities of recovery of bacterial cells during 28 days of juices storage at two different temperatures (5°C and 25°C) were determined using plate count methods. During the entire period of storage of carrot juice at refrigerated temperature, the propagation and regeneration of L. innocua strains were observed. Storage at 25°C showed that the number of these bacteria drastically decreased between 14 and 21 days. The above phenomenon was not detected in E. coli case. There was no cells recovery during long-term refrigerated storage for all strains in beetroot juice. However, in some cases spoiling of this product intermittently occurred at 25°C storage temperature. This work demonstrates that carrot juice supports growth and regeneration of HHP-sublethally injured L. innocua, while beetroot juice can be classified as a safe product.

Dielectric Spectroscopy of Pressurized Saccharomyces cerevisiae.

Results of broadband dielectric spectroscopy (BDS) in Saccharomyces cerevisiae (baker's yeast), in situ as the function of pressure are presented. They show a clear evidence of a threshold to the new pattern of the pressure evolution of the static dielectric permittivity and DC electric conductivity already for Pt ≈ 200MPa at T = 5 oC and Pt ≈ 300MPa at T = 25 oC. BDS monitoring versus pressure tests up to P = 400MPa revealed particularly notable changes of properties after 30 minutes of compressing. Finally, the correlation between the amount of the spectrophotometric maximum absorbance and the DC electric conductivity was found. All these indicate significance of BDS as the tool for testing of pressure properties of cells assemblies, model foods etc., in situ under high pressures.

Germination and Inactivation of Alicyclobacillus acidoterrestris Spores Induced by Moderate Hydrostatic Pressure.

Given the importance of spoilage caused by Alicyclobacillus acidoterrestris for the fruit juice industry, the objective of this work was to study the germination and inactivation of A. acidoterrestris spores induced by moderate hydrostatic pressure. Hydrostatic pressure treatment can induce the germination and inactivation of A. acidoterrestris spores. At low pH, spore germination of up to 3.59-3.75 log and inactivation of 1.85-2.04 log was observed in a low pressure window (200-300 MPa) applied at 50 degrees C for 20 min. Neutral pH suppressed inactivation, the number of spores inactivated at pH 7.0 was only 0.24-1.06 log. The pressurization temperature significantly affected spore germination and inactivation. The degree of germination in apple juice after pressurization for 30 min with 200 MPa at 20 degrees C was 2.04 log, with only 0.61 log of spores being inactivated, while at 70 degrees C spore germination was 5.94 log and inactivation 4.72 log. This temperature strongly stimulated germination and inactivation under higher (500 MPa) than lower (200 MPa) pressure. When the oscillatory mode was used, the degree of germination and inactivation was slightly higher than at continuous mode. The degree of germination and inactivation was inversely proportional to the soluble solids content and was lowest in concentrated apple juice.

[Occurrence of biogenic amines in ripening cheeses taken from the Warsaw market]. / Wystepowanie amin biogennych w serach dojrzewajacych pochodzacych z rynku warszawskiego.

Biogenic amines occurring in foods, particularly fish products and cheeses, may pose a risk to consumer health, monitoring their levels in foods is still valid. The aim of this study was determination of biogenic amines in ripening cheeses available at retail on the Warsaw market and validation of two methods for the determination of amines: high performance liquid chromatography in reverse phase system (RP-HPLC) and spectrofluorimetric method in 1995 year The parameters validated RP-HPLC method for histamine, tyramine, putrescine and kadaweryne ranged: limit of detection (LOD) of 0.7 mg/ kg to 1.3 mg/kg, the limit of quantification (LOQ) of 1.4 mg/kg to 2.6 mg/kg, the recovery of 92-111% and spectrofluorimetric method validation parameters of two amines: histamine and tyramine in the range: LOD of 2.4 mg/kg to 3.18 mg/kg, LOQ 4.8 mg/kg to 6.38 mg/kg, recovery 94-106.5%. The results indicate that the main amines occurring in the group studied ripened cheeses were tyramine and putrescine. The sum of all identified amines in the sample did not exceed 264.4 mg/kg.

[High pressure processing of spices in atmosphere of helium for decrease of microbiological contamination]. / Zastosowanie wysokiego cisnienia w atmosferze helu do obnizenia zanieczyszczenia mikrobiologicznego przypraw ziolowych.

The aim of the study was to investigate the microbiological decontamination of coriander and caraway when HPP technology was applied in elevated temperature in helium atmosphere. The HPP and heat treatment was conducted for 30 minutes at 800 and 1 000 MPa and temperature range was 60 - 121 degrees C. Contamination with aerobic mesophilic bacteria was decreased by about 2 logarithmic cycles. Total elimination of coliform and yeast and moulds was observed. The efficacy of HPP treatment under helium atmosphere depended on the content of the water in tested samples. It can be concluded that high pressure treatment under atmosphere of helium, combination of proper high pressure and time improved the microbiological quality of spices.

High pressure processing for food safety.

Food preservation using high pressure is a promising technique in food industry as it offers numerous opportunities for developing new foods with extended shelf-life, high nutritional value and excellent organoleptic characteristics. High pressure is an alternative to thermal processing. The resistance of microorganisms to pressure varies considerably depending on the pressure range applied, temperature and treatment duration, and type of microorganism. Generally, Gram-positive bacteria are more resistant to pressure than Gram-negative bacteria, moulds and yeasts; the most resistant are bacterial spores. The nature of the food is also important, as it may contain substances which protect the microorganism from high pressure. This article presents results of our studies involving the effect of high pressure on survival of some pathogenic bacteria -- Listeria monocytogenes, Aeromonas hydrophila and Enterococcus hirae -- in artificially contaminated cooked ham, ripening hard cheese and fruit juices. The results indicate that in samples of investigated foods the number of these microorganisms decreased proportionally to the pressure used and the duration of treatment, and the effect of these two factors was statistically significant (level of probability, P

[The content of histamine and tyramine dependent of microbiological quality of salted herring stored at different temperatures]. / Zawartosc histaminy i tyraminy w zaleznosci od jakosci mikrobiologicznej sledzi solonych, przechowywanych w róznych temperaturach.

Twenty six samples of salted herring from Warsaw food market were analyzed. Herrings in high-salted brine (with 26% content of salt) were stored for 21 days at temperature of 4 degrees C and 22 degrees C; low-salted (16% content of salt in brine) herring were stored for 42 days at temperature of 4 degrees C and 22 degrees C. Microbiological contamination level was assessed by standard methods for fish products, and biogenic amines--histamine and tyramine content by spectrofluorometric methods. There was no level change of both amines in high-salted herrings. Significant increase of tyramine content was observed in low-salted samples, depending on the time of storage. The highest level of tyramine up to 318 mg/kg--was observed after 6 weeks of storage. Histamine content increased in low-salted sampled up to 35 mg/kg during the period of storage. Aerobic microflora in the amount up to 10(6)/g was detected during storage of low-salted samples. Such level changes were not observed in high-salted herring samples.