Combination Of High Hydrostatic Pressure Research Articles

Production of heterotetramers as a strategy to prevent familial amyloidotic polyneuropathy, a fatal amyloidogenic disease

Transthyretin (TTR) is a 127-residue homotetrameric β-sheet-rich protein that transports thyroxine in the blood and cerebral spinal fluid. Familial amyloidotic polyneuropathy is a hereditary form of amyloidosis associated with one over 80 different point mutations in TTR, being V30M the most frequent and L55P the most aggressive in the symptoms evoked. Conversely, the variant T119M is very stable and non-amyloidogenic. Thus, this mutation seems to be suitable to prevent tetramer aggregation. At pH5.0, the combination of high hydrostatic pressure, 4M urea and 1°C, the tetramers of T119M were irreversible dissociated into unfolded monomers. Upon urea dilution at pH7.0, these monomers initially refold back into folded monomers and then slowly (hours) reassemble into native tetramers. Since at pH 7.0 the monomers of T119M last for a period of time, we thought to produce heterotetramers by mixing the monomers of T119M with L55P and V30M. Heterotetramers composed of T119M and L55P subunits were observed and these tetramers displayed a decreased yield of fibril formation, suggesting that the presence of T119M subunits within the tetramer is an interesting strategy to prevent aggregation of TTR. Interestingly, when incubated at pH4.0, the “non-amyloidogenic” T119M monomer undergoes aggregation forming amyloid fibrils as observed with other variants of TTR. These data will be presented in combination with all the dissociation-unfolding profile of T119M tetramers and monomers. Financial support: CNPq.

Inactivation of peroxidase and lipoxygenase in carrots, green beans, and green peas by combination of high hydrostatic pressure and mild heat treatment

The efficiency of high hydrostatic pressure (HHP) with the combination of mild heat treatment on peroxidase (POD) and lipoxygenase (LOX) inactivation in carrots, green beans, and green peas was investigated. In the first part of the study, the samples were pressurized under 250-450 MPa at 20-50 ◦ C for 15-60 min. In the second part, two steps treatments were performed as water blanching at 40-70 ◦ C for 15 and 30 min after pressuriza- tion at 250 MPa and 20 ◦ C for 15-60 min. Carrot POD was decreased to 16% residual activity within the first 30 min at a treatment condition of 350 MPa and 20 ◦ C and then it decreased to 9% at 60 min. When the carrots were wa- ter blanched at 50 ◦ C for 30 min after HHP treatment of 250 MPa at 20 ◦ C for 15 min, 13% residual POD activity was obtained. For green beans, the most effective results were obtained by two steps treatment and approximately 25% residual POD activity was obtained by water blanch- ing at 50 ◦ C for 15 min after pressurization at 250 MPa and 20 ◦ C for 60 min. An effective inactivation of POD in green peas was not obtained. For carrots, LOX activity could not be measured due to very low LOX activity or the presence of strong antioxidants such as carotenoids. After pressurization at 250 MPa and 20 ◦ C for 15 or 30 min, wa- ter blanching at 60 ◦ C for 30 min provided 2-3% residual LOX activity in green beans. The treatment of 250 MPa for 30 min and then water blanching at 50 ◦ C for 30 min

Recovery of Escherichia Coli O157:H7 and Salmonella in Milk and Cream of Chicken Soup from High Hydrostatic Pressure (HHP) and Bacteriocin Applications Upon Storage

By the application of HHP; more than 8 log cycle reduction was achieved for E. coli O157:H7 933 and Salmonella FDA in milk and cream of chicken soup in 5 min. Storage of HHP treated milk samples showed absence of both bacteria for 24 h at 4 °C and for 48 h at 37 °C. The population of the strains in cream of chicken soup exceeded their initial value after 5 days of storage at 25 °C. BP 1 was combined with HHP and used for inhibition of surviving bacterial species in cream of chicken soup. There was at least 7 log cycle reduction in E. coli O157:H7 933 and Salmonella FDA after 5 and 7 days of storage at 25 °C respectively, when compared to HHP alone. Combination of HHP with BP 1 extended the shelf life of cream of chicken soup for both bacterial species an additional 2 days at 25 °C when compared with HHP treatment alone.

Inactivación de formas esporuladas de Bacillus subtilis mediante campos eléctricos pulsantes de alta intensidad en combinacion con otras tecnicas de conservacion de alimentos/Inactivation of Bacillus subtilis spores using high intensity pulsed electric fields in combination with other food conservation technologies

The inactivation of Bacillus subtilis spores using high intensity pulsed electric fields (HIPEF) was investigated. Spores were not inactivated when HIPEF treatment (60 kV/cm, 75 pulses) was used alone. The combination of-HIPEF and moderate temperatures around 60°C, and/or the activation of spore suspension prior to HIPEF treatment, and/or the use of up to 5000 IU/ml lysozyme, did not inactivate spores. High hydrostatic pressure (1500 atm, 30 min, 40°C) resulted in the initiation of germination of more than five log cycles in the number of spores, making them sensitive to subsequent pasteurization heat treatment, whereas they were not sensitive to subsequent HIPEF treatment at temperatures less than 40 °C. An intermediate step is needed which allows the outgrowth of spores to vegetative cells. Thus, the combination of high hydrostatic pressure and HIPEF treatment offers an attractive alternative to the stabilization of food products by heat to inactivate spores.

Use of High Hydrostatic Pressure and Irradiation To Eliminate Clostridium sporogenes Spores in Chicken Breast

High pressure has been studied for its usefulness in reducing microbial contaminants in foods. We sought to determine whether this technology could be used in combination with irradiation to develop shelf-stable products. We first determined the optimal pressure, temperature, and time conditions that would result in maximum reduction of Clostridium sporogenes spores in fresh chicken. At ambient temperature, a pressure of 6,800 atm for up to 60 min resulted in a 5-log-unit reduction. Heating the samples during pressurization at 80°C for 20 min resulted in the lowest number of survivors compared to samples that were heated and pressurized for only 1 and 10 min. Further, irradiation at a medium dose (3.0 kGy) before and after pressurization at 6,800 atm and 80°C for 1, 10, and 20 min revealed no significant differences in spore counts between samples that were pressurized and then irradiated or vice-versa. We then examined the effect of high pressure in lowering the irradiation dose necessary to eliminate all spores. The irradiation D value of C. sporogenes spores was calculated to be 4.1 kGy. Samples were then irradiated at various doses followed by pressurization at 6,800 atm at 80°C for 20 min. The irradiation D value was lowered to approximately 2 kGy, indicating that a combination of high hydrostatic pressure and irradiation can be used to produce chicken with an extended shelf life without the use of high irradiation doses.