Effect of high hydrostatic pressure on seeds Carica papaya
The breaking of seed dormancy induced by stress [1] is extremely important with regard to the acceleration of germination process [1,2]. Abiotic stress processes, just like high hydrostatic pressure (HHP), are applied in several biotechnological studies, mainly because HHP induces changes in physiological and biochemical processes [3]. Pretreatment with a stress induction tool can be lethal or induce the synthesis of protective factors. When the stress does not kill the organism, it is called sublethal stress, and it can even increase the resistance to other stresses. High hydrostatic pressure is an important model in stress response study, for it has the ability to change the plasma membrane fluidity so as to keep the organism alive, which allows studies on the metabolic changes. Water is used as the medium of fluid pressure transmission since it has lower compressibility and greater compatibility, resulting in less risk of contamination. In our experiment, Carica Papaya seeds were put into a polyethylene tube containing water, the system is then closed in a capsule of high resistance steel, and suffers pressures between 10 and 400 MPa. The seeds were set to germinate in vitro, while the pressure transfer fluid present in the capsule was used to analyze abscisic acid per HPLC. The HHP generated positive effects due the seed hydration, which reflected in the percentage and speed of germination [4]. The begin of the seeds germination subjected to HHP was anticipated to 70 hours due to greater water retention, characterized by the increasing of weight (about 2.8 times greater when compared to dry weight), followed by germination values between 70-90%, while the seeds subjected to ambient pressure (control group) showed hydration of about 2.4 times and germination around 55-65%. The ambient pressure (0.1 MPa) showed lower water retention, resulting in lower mean percentage and germination speed when compared to HHP treatments. The abscisic acid (ABA) is closely related to tolerance to stress conditions (HHP) and its relation to gibberellin (GA) is crucial in the process of germination. The pressure transfer fluid has proven useful for the detection of abscisic acid, characterized by the presence of chromatograph peak with retention time equals to analyses of samples fortified with industrial ABA. The analyses of the HPLC chromatograms demonstrate changes in the composition of the water used as medium of pressure transfer. The seeds undergoing HHP pressure showed through gas chromatogram, differences between the concentrations of protein, peptides and phenol, when compared to the seeds subjected to hydrostatic control group. The balance between the concentrations of abscisic acid and gibberelin is related to germination. The presence of ABA in fluid of pressure transfer indicates a factor of germination capacity of seeds subjected to HHP stress. HHP stress is an effective biotechnological tool in the search for new mechanisms of stimulation of Carica Papaya seeds in order to provide improved germination and breaking of dormancy. Some data obtained in this experiment were omitted because due to patent submission.
Application of High Hydrostatic Pressure in Modifying Functional Properties of Starches: A Review
: Starch, after cellulose is the second abundant compound in nature. Natural structure of starches generally restricts their functions in industry and particularly in food industry. Various chemical, physical and enzymatic methods have been used for starch modification. In this paper, the characteristics of starch and its changes during high hydrostatic pressure (HHP) processing are discussed. In general, HHP restricts the swelling power of starch granules, so their viscosity is lower in comparison with the samples processed by heating. On the other hand, it provides the possibility of starch gelatinization at room temperature or even below 0°C. A number of starches when pressurized at concentrations higher than 15% produce paste with creamy texture which can be used in dietary foods instead of oil. Furthermore, HHP treatment prevents the harmful effect of starches in some tissues due to reduced size of starch granules. In addition, HHP treatment produces resistant starches, which are valuable in the treatment of diabetes and some cancers. In all, since the degree of similarity of changes is achievable in different situation, that it has great importance in food industry, because of the optimum pressure condition is determined, based on the main objectives alike deactivation of microorganisms and enzymes, transferring, mixing, pumping, maintaining quality, aroma, texture, etc.
Concentration of amino acids in wine after the end of fermentation by Saccharomyces cerevisiae strains
Both quantitative and qualitative differences in the utilization and release of assimilable nitrogen by two wine strains of Saccharomyces cerevisiae (cerevisiae and capensis) under different conditions of oxygen were observed. These differences were influenced by the presence of oxygen at the beginning of the fermentation, and by the strain of S cerevisiae. The release of some amino acids post-fermentation may be the result of reoxidation of NAD(P)H in order to maintain a normal redox balance. Copyright © 2003 Society of Chemical Industry