M. Fonberg-Broczek

Effects of high pressure treatment on the quality of cooked pork ham prepared with different levels of curing ingredients

The aim of this study was to define the effects of high-pressure treatment (600 MPa, 10 min, 20 °C) on the quality of cooked pork ham prepared with two different levels of curing ingredients in brine. Physical, chemical, microbiological, and sensory tests were performed 24 h after high pressure processing (HPP), as well as after 6 and 8 weeks of storage in refrigerator conditions. The results indicate that HPP causes significant improvement of shelf life of vacuum packed ham, including the samples with reduced level of curing ingredients in brine to 8 weeks in refrigerator conditions (4–6 °C). HPP did not have significant effect on the texture or color of ham. However, it significantly increased the drip loss during storage in the packed samples. This may indicate that HPP has negative effects on water holding capacity of cooked products.

Effects of High Pressure Treatment on the Microbiological Quality, Texture and Colour of Vacuum Packed Pork Meat Products

The aim of the study was to define usefulness of high pressure treatment for inactivation of microorganisms and prolongation of shelf life of two types of cooked pork ham and raw smoked pork loin. The samples of ham and loin in the presentation of standard 200 g pieces were vacuum packed in polylayer polyethylene bags and exposed to high pressure treatment in the range of 300-600 MPa and time of exposure of 10-30 minutes. Results indicate that 300 MPa and 400 MPa pressure applied for 10 minutes was insufficient for prolongation of storage period of ham. Pressure of 500 MPa, applied for 10 minutes caused significant decrease of microbiological parameters studied such as: total bacterial count, psychrophylic bacteria, acidophylic bacteria and enterococci in investigated samples, stored in refrigarator conditions for 4 weeks. Pressure of 600 MPa applied for 10 minutes reduced the number of all investigated microorganisms by 10 5 -10 6 fold. Application of this pressure prolonged storage period of traditionally produced ham to 6-8 weeks. Physico-chemical characteristics of ham, measured 24 h after high pressure treatment and after 4, 6 and 8 weeks of storage, did not change when compared to the initial samples. High pressure treatment caused increase in the colour lightness parameters only in pork smoked loin.

The combined effect of high pressure and nisin or lysozyme on the inactivation of Alicyclobacillus acidoterrestris spores in apple juice

Alicyclobacillus acidoterrestris, a thermoacidophilic and spore-forming bacterium is one of the important target micro-organisms in the quality control of acidic canned foods. High pressure pasteurization (HPP) at 50°C was used for the inactivation of A. acidoterrestris spores in apple juice. Pressure applied both in a continuous and oscillatory mode gave the best results when 200 MPa was used. Increasing the pressure to 500 MPa, as well as lowering its value to 100 MPa, had an adverse effect on the effectiveness of the process. The best results were achieved with the use of a combined treatment, involving oscillatory pressurization at 200 MPa, followed by holding the sample for 60 min at atmospheric pressure and subsequent pressurization at 500 MPa, resulting in a reduction in the spore count of 6.15 log. Nisin significantly enhanced the effect of HPP at 300 MPa. Using pressure of 200 MPa for 45 min with a nisin concentration of 250 IU/mL enabled total spore inactivation (over 6 log). No significant effect of lysozyme at a concentration of 0.05 and 0.1 mg/L at 300 MPa was observed.

New Technique for Kinetic Studies of Pressure-Temperature Induced Changes of Biological Materials

In this paper a high pressure technique for kinetic experiments of biological materials is described. The technique is applicable to a multivessel as well as to a single vessel system. This technique allows the measurement of pressure and temperature to which samples are subjected and to keep homogenous temperature during pressurisation as well as to respond quickly to temperature overshoots caused by adiabatic heating-cooling during pressure build-up and release. Relevant exemplary kinetic data are presented.

Factors influencing the inactivation of Alicyclobacillus acidoterrestris spores exposed to high hydrostatic pressure in apple juice

Alicyclobacillus acidoterrestris, a thermoacidophilic and spore-forming bacterium, survives the typical pasteurization process and can cause the spoilage of juices, producing compounds associated with disinfectant-like odour (guaiacol, 2,6 – dibromophenol, 2,6 – dichlorophenol). Therefore, the use of other more effective techniques such as high hydrostatic pressure (HHP) is considered for preserving juices. The aim of this study was to search for factors affecting the resistance of A. acidoterrestris spores to HHP. The baroprotective effect of increased solute concentration in apple juice on A. acidoterrestris spores during high pressure processing was observed. During the 45 min pressurization (200 MPa, 50°C) of the spores in concentrated apple juice (71.1°Bx), no significant changes were observed in their number. However, in the juices with a soluble solids content of 35.7, 23.6 and 11.2°Bx, the reduction in spores was 1.3–2.4 log, 2.6–3.3 log and 2.8–4.0 log, respectively. No clear effect of age of spores on the survival under high pressure conditions was found. Spores surviving pressurization and subjected to subsequent HHP treatment showed increased resistance to pressure, by even as much as 2.0 log.

The effect of high hydrostatic pressure on the survival of Saccharomyces cerevisiae in model suspensions and beetroot juice

The inactivation of Saccharomyces cerevisiae NCFB 3191 using high hydrostatic pressure of 300 MPa at 20°C with a holding time of 0, 1, 5 and 10 min was investigated with model suspensions in phosphate-buffered saline and in beetroot juice. The reduction in S. cerevisiae NCFB 3191 in model suspensions was about 5 log after 10 min of pressurization, irrespective of the initial level of cell concentration in the samples (5.4–8.7 log cfu/mL). The baroprotective effect of beetroot juice on yeast cells during pressurization was observed; the reduction was lower and was only 3.5 log (the inoculum was 5.4 log cfu/mL). No sublethal injury among the surviving cells of the studied yeast strain was found.

Possibility of Campylobacter jejuni inactivation in smoked salmon by high-pressure treatment

The sterile samples of cold-smoked salmon were placed in polyamide–polyethylene pouches and inoculated with three-strain composite of Campylobacter jejuni (inoculum ca 107 CFU g−1). The inoculated samples were sealed under vacuum and subjected to 200, 300 and 400 MPa of hydrostatic pressure for 0, 5, 10 and 15 min. The number of surviving C. jejuni per gram was determined by the 10-fold dilution method followed by plating on Karmali agar. D 10 values were calculated. This work has shown that for reducing C. jejuni in cold-smoked salmon by 6 log units, the application of 200 MPa for 64.26 min or 300 MPa for 17.10 min or 400 MPa for less than 5 min is needed. Applying such parameters of high-pressure processing should not change significantly the organoleptic properties of the product.

Effect of Ultra High Pressure Under Argon and Temperature on the Volatiles and Piperine Content and Microbiological Quality of Black Pepper (Piper Nigrum L.)

In the search of effective decontamination methods of herbal spices, combined action of high pressure under argon at various temperatures has been applied. Ground black pepper (Piper nigrum L.) samples were exposed to hydrostatic pressure of 1 000 MPa under argon for 30 minutes at elevated temperature (60 °C, 80 °C, 100 °C and 140 °C). Under all experiments conditions vegetative cells of bacteria were totally inactivated. Under conditions of 1 000 MPa and temperature 60 °C 84.3% of moulds spores were killed. The total destruction of vegetative microorganisms was observed at 1 000 MPa in 140 °C. For inactivation of 99.9% of aerobic bacterial spores it was necessary to apply pressure of 1 000 MPa and 140 °C under argon.These results indicate that microorganisms present in ground black pepper, which is the product of low water activity, are very resistant to treatment with pressure and temperature. Changes in the essential oil and piperine content as well as changes in the volatile constituents by means of GC and GC-MS were studied. The essential oil content decreased significantly in all treated samples, the losses increased with temperature. Piperine content significantly (ca. 20%) decreased only in samples pressurised at 100 0C and 140 °C. Volatiles composition changed after all kind of treatment. Decrease of most of the monoterpenes, minor decrease of sesquiterpenes and increase of a-and y-terpinene and 1-terpinen-4-ol were observed.

Inactivation of Staphylococcus aureus and native microflora in human milk by high pressure processing

The storage of unpreserved food, including breast milk, is associated with the growth of microorganisms, including pathogenic bacteria. It is therefore necessary to use suitable processes to eliminate pathogenic microorganisms and reduce the total microbial count in order to ensure product safety for consumers. In the present study, samples of milk obtained from volunteers donating to the human milk bank were artificially contaminated with Staphylococcus aureus ATCC 6538. This bacteria was the model microorganism of choice, being relatively resistant to high pressure as well as posing the most serious risk to infant health. The results obtained show that high pressure processing can reduce the count of S. aureus by about 5 log units at 4°C and about 8 log units at 50°C, and totally eliminate Enterobacteriaceae after 5 min of treatment, and result in a total microbial count reduction after 10 min treatment at 500 MPa at 20°C and 50°C. This suggests the possibility of this technology being applied to ensure the adequate safety and quality of human breast milk in human milk banks.

High Pressure Processed Apple Desserts. Microbiological and Physicochemical Properties

This paper describes studies of the microbiological quality and physicochemical properties of high pressure processed apple desserts. The desserts were produced from fresh apples of excellent quality. After removing useless parts, the fruits were washed, crumbled by cutting and then mixed with pectin acid and sugar or Aspartame at room temperature. Individual portions of dessert were packed in commercial polystyrene packages of 100 or 200 ml and heat sealed with thin aluminium foil cover. Pressure treatment of the desserts was performed at a pressure of 300 MPa, at temperatures 20 °C or 50 °C, in 10 min. Pressurization was conducted using high pressure food processor 1.5 1, 700 MPa developed in the High Pressure Center. Microbiological and physicochemical investigations of the pressure processed desserts were carried out directly after pressurization and after 3 months refrigerator storage. The following parameters were determined: soluble solids, (°Brix at 20 °C), total titrable acidity (g citric acid/100 g f.u.), pH, degradation index (Di) using Fuleki method, Aspartame content and ascorbic acid content. The instrumental colour values L, a, b and dominating wave length were measured with a Minolta Chroma Meter CR200. The appearance, colour, smell, taste and consistency of the desserts were evaluated by a six person trained panel using 5-point quality scores. The products were characterized by good microbiological parameters, slightly gelatinous consistency of fruit jelly, almost natural colour, fresh fruit aroma and a taste better than that of traditional fruit desserts.