Combination of high pressure with nisin or lysozyme to further process mechanically recovered poultry meat

Abstract

The combined effect of high pressure processing (HPP) and nisin or lysozyme on aerobic mesophile and psychrotrophe populations of mechanically recovered poultry meat (MRPM) was evaluated. Nisin (0, 12.5, 100 and 200ppm) or lysozyme (0 and 150ppm) were added to MRPM, and vacuum-packaged samples were treated at 350 and 450 MPa for 5 and 15min at 20°C. In mesophiles, reductions above 4 log CFU/g were found in some samples. Psychrotrophes proved more sensitive; in MRPM containing 200 ppm of nisin treated at 450 MPa for 15min, no growth was detected (a lethality of more than 8 log units). There was no synergistic effect between HPP and lysozyme. In contrast, combination of HPP and nisin is a promising nonthermal preservation treatment.     

Refrigerated shelf-life evaluation of high pressure processed,raw and sous vide cooked lobster

ABSTRACT

High pressure processing (HPP) and sous vide may increase the shelf-life of high value seafood products without the use of additives. This study investigated the effects of 150MPa or 350MPa for 10min on microbial, sensory, and physicochemical qualities of raw and subsequently sous vide cooked (65°C) lobster tails during 28 days of refrigerated storage. Raw lobster pressurized at 350MPa or sous vide cooked maintained significantly lower microbial counts, total volatile base nitrogen, and biogenic amine levels. Due to off-odors, 90% and 60% of sensory respondents rejected the control and 150MPa raw samples, respectively, by day 7, while 70% rated the 350MPa samples as still acceptable on day 28. For cooked lobster, only 20% of the respondents rejected any samples by day 28. Moderate HPP conditions were effective in extending refrigerated shelf-life of vacuum-packaged raw lobster tails. However, HPP pretreatment did not contribute to additional shelf-life extension for sous vide cooked products.     

High pressure processing and storage of blueberries: effect on fruit hardness

Non-thermal preservation technologies such as high pressure processing (HPP) have low impact in original fruit flavours. The objective of this study was to process the whole blueberries by HPP and investigate the effect on its hardness after processing and during 7 and 28 days storage. Whole blueberry immersed in water was the best packaging option. The blueberries submitted to 200 and 600?MPa for 5–60?min and were stored at 3°C for 1 week. In another experiment, HPP blueberries (200 and 600?MPa for 10?min) were stored for 28 days. No difference in sensorial texture was observed between HPP and fresh unprocessed blueberry, although the instrumental hardness decreased significantly. Hardness was not affected by the processing time and was similar just after HPP and one-week storage. The hardness of HPP-processed blueberries was kept along 28 days storage without considerable weight loss as opposed to fresh fruits which collapsed.     

The application of high pressure–mild temperature processing for prolonging the shelf-life of strawberry purée

The aim of this study was to monitor the shelf-life and quality of strawberry purée preserved using combined high pressure processing (HPP)–mild temperature processing at 300 and 600?MPa for 15 min during cold storage (6°C). Increasing the pressure resulted in a prolonged shelf-life of from 4 to 28 weeks for HPP-preserved purée at 300 and 600?MPa, respectively. The highest inactivation of peroxidases, pectinesterases and polygalacturonases was noted when a higher pressure was used, whereas a lower pressure was more efficient for polyphenoloxidases. The degradation of vitamin C and anthocyanins was 20% and 5% higher at 600?MPa than at 300?MPa, respectively. Significantly fewer changes in the colour coefficient, expressed as ΔE, and the browning index, were observed in purée preserved at 600?MPa. Oxidative and hydrolytic enzymes are highly pressure-resistant, which suggests other inhibitors should be used to increase the shelf-life of good-quality fruit products.     

Effects of high pressure treatment on the quality of chicken patties

The effects of high pressure treatment (500 MPa, 10 min, 20 °C) on the quality of commercial chicken patties (breaded and unbreaded) were evaluated. Physical, chemical and microbiological tests were performed 24 h after high pressure processing (HPP), as well as after 14 and 21 days of storage in refrigerated conditions. It was concluded that the use of high pressures extends the shelf life of vacuum-packaged chicken patties by up to 3 weeks, based on the condition of storage during refrigeration. After this period, the number of mesophilic, psychrotrophic and lactic acid bacteria in the pressure-treated patties was five to six logarithmic cycles lower than that in the control products. HPP did not considerably influence the amount of storage drip loss, texture or colour of the patties; however, it quickened the process of lipid oxidation.     

Effect of high hydrostatic pressure processing and squeezing pressure on some quality properties of pomegranate juice against thermal treatment

The aim of this study was to investigate the effect of high hydrostatic pressure (HHP) treatment (200, 300, 400?MPa; 5°C, 15°C and 25°C; 5 and 10 min) on some quality properties of pomegranate juice. Juice samples are obtained under industrial conditions at two different squeezing pressure levels (100 and 150?psi – 0.689 and 1.033?MPa, respectively). Results are compared against conventional thermal treatment (85°C/10 min) and raw sample. For all three processing temperature, HHP combinations at 400?MPa for 10 min were sufficient to decrease the microbial load around 4.0 log cycles for both squeeze levels. All HHP treatments showed no significant decrease at antioxidant activity, total phenolic content and monomeric anthocyanin pigment concentrations, while there was a significant decrease (p?≤?.05) in thermal-treated samples. Being the highest sugar alcohol in pomegranate juice, mannitol content must be considered for determining the authenticity, and mannitol content increased with squeezing pressure and thermal treatment.     

Effect of high hydrostatic pressure on phenolic compounds,ascorbic acid and antioxidant activity in cashew apple juice

The cashew apple is native to Brazil, but there is insufficient information regarding the nutritional properties of this fruit. The objective of this study was to evaluate the impact of high pressure processing (HPP) at room temperature (25 °C) on phenolic compound and ascorbic acid contents and antioxidant capacity of cashew apple juice. This study showed that HPP at 250 or 400 MPa for 3, 5 and 7 min did not change pH, acidity, total soluble solids, ascorbic acid or hydrolysable polyphenol contents. However, juice pressurized for 3 and 5 min showed higher soluble polyphenol contents. Antioxidant capacity, measured by the ferric-reducing antioxidant power method, was not altered by HPP, but when treated at 250 MPa for 3 min, it resulted in an increased value when 2,2-diphenyl-1-picrylhydrazyl was used. These data demonstrate that HPP can be used in the food industry for the generation of products with higher nutritional quality.     

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.     

Quasi-adiabatic compression heating of selected foods

The quasi-adiabatic temperature increase due to compression heating, during high-pressure (HP) processing (HPP), was studied using specially designed equipment. The temperature increase was evaluated as the difference in temperature, during compression, between atmospheric pressure and nominal pressure. The temperature was measured using a thermocouple in the center of a polyoxymethylene cup, which contained the sample. Fresh meat balls, pork meat pate, and tomato purée temperature increases were measured at three initial temperature levels between 40 and 80 °C. Nominal pressure was either 400 or 500 MPa. Results showed that the fat content had a positive effect on temperature increases. Empirical equations were developed to calculate the temperature increase during HPP at different initial temperatures for pressures of 400 and 500 MPa. This thermal effect data can be used for numerical modeling of temperature histories of foods during HP-assisted pasteurization or sterilization processes.     

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.     

The effect of high hydrostatic pressure on the physiological and biochemical properties of pepper (Capsicum annuum L.) seedlings

High hydrostatic pressure is a non-thermal food processing technology, which also has several successful applications in different areas besides food processing. In this study, Capsicum annuum L. (pepper) seeds are subjected to 50, 100, 200 and 300?MPa pressure for 5?min at 25°C and the seedlings of HHP processed seeds are used to compare percentage of seed germination and biochemical properties such as chlorophyll a, b and a/b, proline content, total protein, carotenoid, malondialdehyde, glucose, fructose and phenolic compounds concentrations. As a result of the study, it was observed that there are remarkable changes in terms of biochemical properties especially for seedlings, whose seeds were pressurized at 200 and 300?MPa. More detailed studies are needed to put forward the mechanism behind the changes in biochemical properties.     

High-pressure effects on cooking loss and histological structure of beef muscle

In this study, we investigate the effects of high pressures (up to 600 MPa) applied at room temperature for 10 min on beef cooking loss and structure. The data on cooking loss, pH and protein solubility, as well as the electron microscopy, illustrate the changes in cooking loss and structure with high pressure processing (HPP). There is a significant reduction in cooking loss of beef with HPP. When the beef sample is imposed upon by 300 or 400 MPa, the cooking loss reduction is about 12%. Further, the pH of beef is dramatically increased as the pressure increases, and the pH increases by about 5% when imposed upon by 500 MPa. When a high pressure was applied at room temperature, the structure of the beef tissue apparently changed. Muscle fiber fragments gradually became slender and sarcomeres became lengthened. Our data indicated that high-pressure treatment on beef leads to stretching of the muscle fiber and an increase in the water-holding capacity.     

Effect of high pressure on growth and bacteriocin production of Pediococcus acidilactici HA-6111-2

This study was aimed to investigate the effect of high pressure processing (HPP, 200–600?MPa) on the (i) survival of Listeria innocua and Pediococcus acidilactici HA-6111-2; (ii) production of bacteriocin bacHA-6111-2 and (iii) activity of bacteriocin against untreated and pressure-treated L. innocua cells. Inactivation of P. acidilactici was observed for pressures of >300?MPa. However, at this pressure level, L. innocua was more sensitive. Bacteriocin crude extract was pressure stable, with a decrease for pressures of ≥400 MPa. Pressures of ≤200?MPa did not affect bacteriocin production when compared with non-pressure-treated cells, whereas higher pressures caused a 2- to 4-fold decrease on the maximum level of bacteriocin production. Growth curves of P. acidilactici were fitted with the modified Gompertz model. The lag phase period depended on the magnitude of the pressure applied: there was a delay in the exponential phase as pressure increased and, as a consequence, in the beginning of bacteriocin production. Since P. acidilactici HA-6111-2 and its bacteriocin have shown resistance to pressures up to 300–400 MPa, they could be used in combination with HPP in order to improve food safety.     

Fourier transform infrared spectroscopy to detect thermal degradation of vegetable and chrome-tanned leather

Abstract

The present experimental study determined the thermal degradation stages for vegetable and chrome-tanned leathers (goat and sheep) at 90, 100, and 130?°C by using Fourier transform infrared spectroscopy (FTIR) and differential thermal analysis. Infrared spectra revealed that a temperature of 90?°C affected the adsorbed water band at 3400?cm^?1. Moreover, this temperature slightly reduced the vibrations of amide II and amid III (1340?cm^?1) confirming the preliminary decomposition of protein folds, but it is worth noting that the aliphatic side chains remained stable at this stage of aging. At 100?°C, there was a sharp rupturing in the phenolic-OH bond and side-by-side N–H vibrations decreased dramatically. The peak decomposition occurred at 130?°C, where the amide I and amide III intensities significantly increased, which can be considered indicative of protein unfolding. Those changes are substantiation of protein denaturation. Thermal analysis demonstrated that thermal aging significantly reduced the required temperature for the process of oxidation. The oxidation occurred at 217?°C in goat sample aged at 90?°C. Nevertheless, the reference sample suffered from oxidation at about 220?°C, while with increasing aging temperatures (at 100 and 130?°C), endothermic reactions were observed. Such reactions are usually associated with protein denaturation.     

Moderate hydrostatic pressure–temperature combinations for inactivation of Bacillus subtilis spores

We report the effect of using moderate hydrostatic pressure, 40–140?MPa, at moderate temperature (38–58°C) to inactivate Bacillus subtilis spores in McIlvaine's citric phosphate buffer at pH 6. We have investigated several parameters: pressure applied, holding time, pressure cycling, and temperature. The kinetics of spore inactivation is reported. The results show that spore inactivation is exponentially proportional to the time the sample is exposed to pressure. Spore germination and inactivation occur at the hydrostatic pressures/temperature combinations we explored. Cycling the pressure while keeping the total time at high pressure constant does not significantly increase spore inactivation. We show that temperature increases spore inactivation at two different rates; a slow rate below 33°C, and at a more rapid rate at higher temperatures. Increasing pressure leads to an increase in spore inactivation below 95?MPa; however, further increases in pressure give a similar rate kill. The time dependence of the effect of pressure is consistent with the first-order model (R²?>?0.9). The thermal resistance values (Z_T) of B. subtilis spores are 30°C, 37°C, and 40°C at 60, 80, 100?MPa. The increase in Z_T value at higher pressures indicates lower temperature sensitivity. The pressure resistance values (Z_P) are 125, 125 and 143?MPa at 38°C, 48°C, and 58°C. These Z_P values are lower than those reported for B. subtilis spores in the literature, which indicates higher sensitivity at pressures less than about 140?MPa. We show that at temperatures <60°C, B. subtilis spores are inactivated at pressures below 100?MPa. This finding could have implications for the design of the sterilization equipment.     

Interactive effect of pressure and temperature on the preservation of rat primary-cultured astrocytes and human glioblastoma cell line A172

Environmental factors such as temperature and pressure are important determinants of cell survival. Although the effect of temperature on cell preservation has been previously reported, the effects of pressure, an equally important thermodynamic parameter, have not been sufficiently investigated. In this study, we investigated the effect of temperature and pressure on cellular viability, morphology, adhesiveness, cell death, cell cycle and glucose metabolism in rat primary-cultured astrocytes and A172 human glioblastoma cell line subjected to 4-day preservation. It was revealed that under favorable preservation conditions (temperature: 15°C–20°C, pressure: 0.1–30?MPa) (1) cell morphology and adhesiveness of preserved cells were maintained similar to freshly isolated cells; (2) cell cycle was arrested; (3) glucose uptake and intra/extra-cellular pH decrease were suppressed. These results suggest that lowering temperature to 15°C–20°C or increasing pressure up to 30?MPa at temperatures of 20°C–25°C can reduce cellular metabolism and maintain cell-membrane fluidity, thus resulting in higher viability.     

Comparison of physical and chemical properties of high pressure- and heat-treated Lychee (Litchi chinensis Sonn.) in syrup

Lychee usually has white flesh, but its flesh is very sensitive to thermal and enzymatic impairment and ultimately changes in color. This investigation was intended to study the magnitude of color change in lychee by high pressure and thermal processing. The lychee was packed in syrup prior to being processed. Pressurized lychee was performed at 600 MPa at 30°C or 50°C for 20 min, while the pasteurized sample was heated at 90°C for 3 min. It was found that pressurization induced lower color L*, a* and b* values, including low anthocyanin content. For enzymatic activities, high pressure could reduce the activity of polyphenoloxidase by 33–51%, whereas pasteurization markedly reduced that activity by 90%.     

Hydrostatic high pressure applied to food sterilization III: Application to spices and spice mixtures

Abstract

The response of suspensions of spices and spice mixtures in water to high pressure treatment was investigated. Inactivation of the microbial load–mainly aerobic and unaerobic spore formers–was strongly dependent on water activity and temperature. Samples were completely decontaminated after three pressure cycles (30 min at 80 MPa followed by 30 min at 350 MPa) at 70 °C at a minimum water activity of 0.91. Pressure treated samples were examined for sensory and chemical changes. No significant changes in odour and appearance were recognized by a trained sensory panel, nor were changes in the volatile compounds of the samples detected by static headspace gaschromatography.     

The variability of times to detect growth from individual Clostridium botulinum type E endospores is differentially affected by high pressure treatments

High pressure thermal (HPT) processing is a candidate technology for the production of safe and stable food. However, little is known about the effect of HPT or high hydrostatic pressure (HHP) treatments at ambient temperature on the variability of times to detect growth from individual spores. We investigated this effect by treating Clostridium botulinum type E spores with HHP (200–600?MPa, 20°C) and HPT (600?MPa, 80°C and 800?MPa, 60°C). Our results indicate that the mean detection times increase and the frequency distribution shifts toward longer times when HHP treatment intensity is increased. HPT treatments result in a highly scattered distribution. In contrast, pressure levels ≤300?MPa decrease detection times and heterogeneity of their distribution, which could lead to an increase in the potential risk originating from C. botulinum type E spores. Data provided here could help to refine risk assessment regarding this important food intoxicator.     

Variable-Temperature and High-Pressure Micro-Raman Spectra of Inorganic Artists' Pigments: Crystalline Wulfenite,Lead(II) Molybdate(VI), PbMoO4

Variable-temperature (?150°C to 600°C) and high-pressure (up to ～5 GPa) micro-Raman spectra have been obtained for the mineral wulfenite [lead(II) molybdate(VI), PbMoO₄], a main constituent of the artists' pigment, orange molybdate. The spectra were quite similar in both the temperature and the pressure studies, except for broadening and shifting of some peaks. No phase changes were detected, although there is possibly some amorphization beginning at ～600°C. The photoacoustic IR spectrum in the 1950–450 cm^?1 region is reported for characterization purposes. The long-term stability of PbMoO₄ with respect to extreme changes in both temperature and pressure illustrates the importance of orange molybdate in artwork and protective coatings.