RESUMO
Trehalose and sucrose, two sugars that are involved in the protection of living organisms under extreme conditions, and their mixtures with salts were employed to prepare supercooled or freeze-dried glassy systems. The objective of the present work was to explore the effects of different salts on water sorption, glass transition temperature (T(g)), and formation and melting of ice in aqueous sugar systems. In the sugar-salt mixtures, water adsorption was higher than expected on the basis of the water uptake by each pure component. In systems with a reduced mass fraction of water (w less-than-or-equal 0.4), salts delayed water crystallization, probably due to ion-water interactions. In systems where > 0.6, water crystallization could be explained by the known colligative properties of the solutes. The glass transition temperature of the maximally concentrated matrix (T(g)') was decreased by the presence of salts. However, the actual T(g) values of the systems were not modified. Thus, the effect of salts on sorption behavior and formation of ice may reflect dynamic water-salt-sugar interactions which take place at a molecular level and are related to the charge/mass ratio of the cation present without affecting supramolecular or macroscopic properties.
Assuntos
Materiais Biocompatíveis , Criopreservação/métodos , Adsorção , Carboidratos , Crioprotetores , Cristalização , Estabilidade de Medicamentos , Liofilização , Gelo , Sais , Sacarose , Termodinâmica , Trealose , ÁguaRESUMO
The water activity (aw) and pH of acidified (vinegar) bottled vegetables and meat with vegetables--mostly home-canned--was examined in relation to the potential growth of Clostridium botulinum. Most products (vegetables or meat with vegetables) had water activity above the "per se" inhibitory limit (aw < 0.95) for growth of C. botulinum. Regarding pH, 96% of canned vegetables had a pH lower than 4.6, but 81% of the canned meat with vegetables had a pH above 4.6. This was attributed to the well known buffer effect of food proteins, which makes it difficult to lower food pH during acidification with vinegar. It is concluded that most bottled meat with vegetables constitute a potential hazard since these foods are marketed at room temperature, and botulism toxin may be produced if spores are present.
Assuntos
Clostridium botulinum/crescimento & desenvolvimento , Manipulação de Alimentos , Microbiologia de Alimentos , Carne/microbiologia , Verduras/microbiologia , Concentração de Íons de Hidrogênio , ÁguaRESUMO
The water activity (aw) and pH of acidified (vinegar) bottled vegetables and meat with vegetables--mostly home-canned--was examined in relation to the potential growth of Clostridium botulinum. Most products (vegetables or meat with vegetables) had water activity above the "per se" inhibitory limit (aw < 0.95) for growth of C. botulinum. Regarding pH, 96 of canned vegetables had a pH lower than 4.6, but 81 of the canned meat with vegetables had a pH above 4.6. This was attributed to the well known buffer effect of food proteins, which makes it difficult to lower food pH during acidification with vinegar. It is concluded that most bottled meat with vegetables constitute a potential hazard since these foods are marketed at room temperature, and botulism toxin may be produced if spores are present.
Assuntos
Clostridium botulinum , Manipulação de Alimentos , Microbiologia de Alimentos , Carne , Plantas , Concentração de Íons de Hidrogênio , ÁguaRESUMO
The water activity (aw) and pH of acidified (vinegar) bottled vegetables and meat with vegetables--mostly home-canned--was examined in relation to the potential growth of Clostridium botulinum. Most products (vegetables or meat with vegetables) had water activity above the "per se" inhibitory limit (aw < 0.95) for growth of C. botulinum. Regarding pH, 96 of canned vegetables had a pH lower than 4.6, but 81 of the canned meat with vegetables had a pH above 4.6. This was attributed to the well known buffer effect of food proteins, which makes it difficult to lower food pH during acidification with vinegar. It is concluded that most bottled meat with vegetables constitute a potential hazard since these foods are marketed at room temperature, and botulism toxin may be produced if spores are present.(AU)
Assuntos
RESEARCH SUPPORT, NON-U.S. GOVT , Clostridium botulinum/crescimento & desenvolvimento , Manipulação de Alimentos , Microbiologia de Alimentos , Carne/microbiologia , Plantas/microbiologia , Concentração de Íons de Hidrogênio , ÁguaRESUMO
The water activity (aw) and pH of acidified (vinegar) bottled vegetables and meat with vegetables--mostly home-canned--was examined in relation to the potential growth of Clostridium botulinum. Most products (vegetables or meat with vegetables) had water activity above the [quot ]per se[quot ] inhibitory limit (aw < 0.95) for growth of C. botulinum. Regarding pH, 96
of canned vegetables had a pH lower than 4.6, but 81
of the canned meat with vegetables had a pH above 4.6. This was attributed to the well known buffer effect of food proteins, which makes it difficult to lower food pH during acidification with vinegar. It is concluded that most bottled meat with vegetables constitute a potential hazard since these foods are marketed at room temperature, and botulism toxin may be produced if spores are present.
RESUMO
The purpose of this study was to investigate the combined effects of trehalose and cations on the preservation of beta-galactosidase in freeze-dried systems and their relationship to physical properties. Differential scanning calorimetry was employed to measure the glass transition temperature (T(g)) and the endothermal peak area, related to the amount of crystalline trehalose dihydrate present in the samples. In systems in which the trehalose matrix was humidified to conditions which allowed a high proportion of trehalose to crystallize, the enzyme was rapidly inactivated upon heating at 70 degrees C. In these conditions the addition of CsCl, NaCl and particularly KCl or MgCl(2), improved the enzyme stability with respect to that observed in matrices containing only trehalose. For a given moisture content, addition of salts produced very little change on the glass transition temperature; therefore the protective effect could not be attributed to a higher T(g) value. The crystallization of trehalose dihydrate in the humidified samples was delayed in the trehalose/salt systems (principally in the presence of Mg(2+)) and a parallel improvement of enzyme stability was observed.
