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Acta Alimentaria
Authors:
B. Csehi
,
B. Salamon
,
T. Csurka
,
E. Szerdahelyi
,
L. Friedrich
, and
K. Pásztor-Huszár

it is used as a food ingredient ( Toldrà et al., 2004 , 2008 ). High hydrostatic pressure treatment (HHP) can be suitable for this. HHP is a gentle food preservation process, during treatments the microorganisms in food are partially or completely

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Laboratory batches of fresh tomato juices were treated in several experimental trials by high hydrostatic pressure alone or in combination with various concentrations of oregano, thyme or dill seed oils. Lactic acid bacteria formed the dominating component of the spoilage microbiota during post-processing storage at 15 °C causing spoilage of the untreated samples within 4 days. One tenth of a percent oregano or thyme oils at least doubled the microbiological shelf life, while their respective concentrations of 0.5% alone, or 400 MPa 5-20 min high hydrostatic pressure treatment alone resulted in microbial stability for at least two weeks. Two hundred MPa for 10 min resulted only in an approx. 3 days delay of spoilage, whereas 0.1% thyme oil increased the efficiency of this moderate UHP-treatment, resulting in a microbiologically stable product for at least 3 weeks at the storage temperature applied.

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The effect of high hydrostatic pressure (HHP) and nisin was studied on micro-organisms in minced chicken and beef meat. Pressure in the range of 0-800 MPa and nisin (670 IU g-1) were applied for vacuum packed minced meat. In chicken meat the total viable cell count decreased by 3 log cycles as an effect of HHP at 300 MPa and by 5 log cycles in combination with nisin. The D value is 35-39 MPa for pseudomonads in minced chicken meat. In case of inoculation with L. monocytogenes, the cell count in beef meat was reduced only by pressure higher than 200 MPa (“shoulder”) with a characteristic value of D=37-38 MPa. B. cereus spores, both dormant and heat activated, were very resistant (D=800 MPa) in beef. However, the survival of pressurised spores after chilled storage (for two weeks at 4 °C) was smaller for non-heat activated spores than for heat activated spores. Efficiency of HHP combined with nisin needs further research work.

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602 Cao , X., Bi , X., Huang , W., Wu , J., Hu , X. & Liao , X. (2012): Changes of quality of high hydrostatic pressure processed cloudy and clear strawberry juices during

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, I. , and Balla , Cs. ( 2014 ). Effect of high hydrostatic pressure treatment on volatiles of berry purées . Acta Alimentaria , 43 : 51 – 57 . 10.1556/AAlim.43.2014.Suppl.8 Gao , G. , Ren , P. , Cao , X. , Yan , B. , Liao , X. , Sun

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A recombinant Bacillus subtilis strain containing a plasmid encoding a luxAB fusion, which gave bioluminescence upon addition of an exogenous long-chain aldehyde as substrate for the endogenous luciferase enzyme, was used as test organism. Its populations were treated with 300 MPa for 20 min, or 600 MPa for 20 min at around room temperature, and this treatment is foreseen as a quality-friendly, non-thermal pasteurisation of foods. Besides the estimation of viable cell counts, the extent of pressure-induced germination and post-process development were investigated by phase-contrast microscopy, turbidimetry and luminometry. Increased heat sensitivity of pressurized spore populations was observed both by viable cell counting during a linearly programmed elevation of temperature and a simultaneous differential scanning calorimetry. This was related to pressure-induced germination of spores, although a small fraction remained ungerminated. The luciferase pool built into the spores during their formation seemed to have withstood pressurization. Spore germination was accompanied by the emergence of bioluminescence which also indicated sensitively the characteristic changes of metabolic activity running parallel with the development of untreated cell populations and that of the survivors of the hydrostatic pressure treatments when the cells were incubated in a nutrient broth.

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Progress in Agricultural Engineering Sciences
Authors:
István Dalmadi
,
Dávid Kántor
,
Kai Wolz
,
Katalin Polyák-Fehér
,
Klára Pásztor-Huszár
,
József Farkas
, and
András Fekete

High hydrostatic pressure (HHP) processing technology offers the possibility to preserve quality attributes. Objective test methods describing quality in a complex form have an important role in the development of new products and in the quality assurance of different technologies. Therefore, research was performed to compare the effects of HHP treatment and heat pasteurization on visual appearance, volatile composition, taste and texture properties of strawberry purees measured by sensorial and objective methods. Sensory evaluation did not show significant differences between samples. Similar result was obtained from the color measurements. Viscosity of purees changed only slightly as a result of the treatments. Electronic nose and electronic tongue were found to be promising tools for discrimination of strawberry purees treated by different levels of high hydrostatic pressure or thermal treatment. Canonical discriminant analysis showed that control and “600 MPa for 5 minutes” samples were quite similar. Samples treated by 600 MPa for 15 minutes were distinguished from the above mentioned ones. The heat treated samples (80°C for 5 and 15 minutes) were definitely separated from the control samples. Fusion of the data from the electronic nose and tongue showed the same trend and improved the classification of the treated puree samples.

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Abstract  

High hydrostatic pressure (HHP) has been investigated as an alternative to thermal processing for food preservation. HHP has been known to affect high molecular weight polymers causing phase change. Starch is gelatinized at a pressure on the order of 600–700 MPa, at 25 °C. Gelatinized starch recrystallizes during storage affecting the texture and shelf life of food products. The effect of HHP processing on the crystallization of starches from different botanical origins during storage at 4 and 23 °C was investigated. Crystallization kinetics of HHP treated wheat and corn starch gels were compared using DSC. The effect of crystallization on structure was evaluated in terms of storage modulus. The rate of retrogradation depended on the storage temperature (23 °C and 4 °C) and the botanical origin of the starch. The least crystallization was observed in HHP treated wheat starch stored at 23 °C. The storage modulus increased with crystallization of starch.

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The aim of the present study was to evaluate the effect of high hydrostatic pressure (HHP) processing (at 450 or 600 MPa for 300 s) on microbial quality as well as on organoleptic properties of fish salad with mayonnaise during 26 days of storage at 5 and 10 °C. The salad contained diced smoked trout fish, mayonnaise, and different kinds of spices. These freshly made salads usually have only a couple of days of shelf life. The HHP treatment basically did not affect the physical and organoleptic characteristics of the fish salad with mayonnaise. At both storage temperatures, the HHP treated samples showed enhanced safety and increased shelf-life up to 3 weeks.

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Acta Alimentaria
Authors:
Á. Koncz
,
L. Mészáros
,
J. Farkas
,
K. Pásztor-Huszár
,
R. Helt
, and
N. Lechner

Thermal and HHP treatments were compared. We established that the applied HHP treatments reduced the total cell count more significantly than thermal treatments. For example, the 10 min 600 MPa/10 min HHP treatment was equivalent to about 10 min thermal treatment at 70 °C. This combination of temperature and time is not used in the pasteurisation practice of the dairy industry. The various thermal treatments reduce the phosphatase enzyme activity to between one-third and one-hundredth of the original activity. The HHP treatments yielded similar results. Six hundred MPa pressure caused 10 to 70% decrease in the enzyme activity, while 700 MPa pressure led to a decrease of one log cycle.In the second year we tried to investigate the kinetics of the effect of HHP treatment. The 5, 10, 20, 40 min holding times were systematically applied in the range of 400 to 700 MPa. According to the results, 600 and 700 MPa HHP treatments effectively assured a decrease in the total cell count and the alkaline phosphatase enzyme activity. No organoleptic changes occurred.

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