Identification Of The Pressure-resistant Bacteria And Study On Combined Mild Temperature And Ultrahigh Pressure On Coconut Puree

Coconut, called the solid endosperm, is the main component of coconut. Fresh coconut is rich in fat, protein, and a variety of vitamins, trace elements and minerals. Coconut is perishable for the inevitably infection by microorganisms in product processing. Therefore, to develop more efficient and effective new sterilization technology is of great significance. This topic is Hainan province natural science fund project (20153078).This research based on fresh coconut, and identification was conducted on the barotolerant microbes remained after ultrahigh pressure processing. A combined mild temperature and ultrahigh pressure sterilization process for the coconut puree was investigated in the forms of intermittent pressure. In order to prolong the shelf life of coconut puree, the effect of different Sterilization was also studied. The results of the experiments were drawn as following:1. Two strains of barotolerant microbes in coconut puree were screened out and identified as Leuconstoc mesenteroides subsp mesenteroides and Leuconstoc mesenteroides subsp dextranicum by morphological features, physiology and molecular biology (16SrDNA) method.2. Lethal effect of intermittent preesure treatments on strains is superior to contant pressure treatment under the same condition, when comparing with constant and intermiteent pressure treatments. Treatment with intermittent pressure of300-600MPa can greatly improve the lethal effect of compression strain.The fatality rate on Leuconstoc mesenteroides subsp mesenteroides and Leuconstoc mesenteroides subsp dextranicum were92.6%and89.5%. Lethality goes up significantly along with the temperature increasing and when the temperature is above55℃, the lethality increases smoothly. At65, lethality of L. mesenteroides subsp mesenteroides and L. mesenteroides subsp dextranicum were98.9%and98.2%.3. A combined mild temperature and ultrahigh pressure sterilization process for the coconut puree was investigated. The effect of different pressure combinations, sterilizing time and processing temperatures on the colony count, non-enzymatic browning degree, soluble solid, peroxide value and color aberration of coconut puree were studied. The sterilization conditions were optimized by orthogonal test. The technical parameters for optimization were started with a lower pressure (200MPa at35℃) treatment for5min, followed by a higher pressure (500MPa at35℃) for another5min. The colony count was decreased to63CFU/g by99.9%under these optimum conditions. Combined mild temperature and ultrahigh pressure treatment effectively killed microorganisms in the coconut puree, and had little effect on the sensory quality indexes, such as flavor, color, nutrition, etc.4. The preservation effect of coconut puree by mild temperature and ultrahigh pressure was superior to constant ultrahigh pressure and pasteurized processing. When the coconut puree was treated with different sterilization methods, the result showed that non-enzymatic browning degree, peroxide value and color aberration increased gradually, pH value, soluble solids and protein content showed a decreasing trend during storage. After75days, the phenomenon of bulge bag was found in pasteurized processing, and the microorganisms multiply quickly. When coconut puree were stored at the same temperature, the intermittent ultrahigh pressure revealed the best effect on maintaining fat and protein content, delaying the non-enzymatic browing degree, inactivating the microorganisms. Therefore, the intermittent ultrahigh pressure treatment could extend the shelf life of coconut puree up to110days, which was35days longer than pasteurized processing and20days longer than our preliminary research.