Static ultra-high pressure (200, 270, and 340 MPa) and sinusoidal and step-pressure (0-270 MPa) pulses were compared by determining their effects on bacteria and yeast survival counts. Samples were commercial pineapple chunks used as is and fresh cut pineapple and pineapple juice inoculated with Saccharomyces cerevisiae 2407-1a. Surviving bacteria and yeast counts were determined using plate count agar (PCA), acidified potato dextrose agar (PDA) and yeast extract dextrose agar (YEPD). Commercially acceptable reduction of microflora for pineapple (greater than 2.5 log cycles) were observed at static pressure of 340 MPa for 15 min at three temperatures (~4, 21, and 38°C). Longer process times (40 and 60 min) at this pressure did not result in further significant count reductions. Lower pressure treatments, 270 and 200 MPa for 15 min, at these temperatures reduced the microbial population of pineapple by 1-2 log and less than one log, respectively. Static pressures treatments of 270 and 340 MPa at 21°C were found to reduce bacterial and yeast counts by 5-log cycles on inoculated fresh cut pineapple. Total bacteria and yeast counts remained <25CFU/plate after a 1/10 sample dilution during 60 days of storage at 4°C. Sinusoidal and step-pressure pulses were compared with static pressure treatments for the inactivation of S. cerevisiae 2407-1 a in pineapple juice. No inactivation was observed after 40-4,000 fast sinusoidal pulses (10 cycles/s) at 4-400 s in the 235-270 MPa range. Static 270 MPa treatments at 40 and 400 s resulted in 0.7 and 5.1 decimal reductions, respectively. Slower 0-270 MPa step pulses at 0.1 (10 pulses), 1 (100 pulses) and 2 (200 pulses) cycles/s with 100 s total on-pressure time resulted in 3.3, 3.5, and 3.3 decimal reductions, respectively. A comparable static pressure treatment resulted in 2.5 decimal reductions. Changing the on-pressure/off-pressure time ratio showed that treatments with longer on-pressure time were more effective. Step pressure pulses (0-270 MPa) on inoculated pineapple chunks for 100s at 0.1 (10 pulses, T3) and 2 (200 pulses, T5) cycles/s were more effective than a 100 s static 270 MPa (T1). After 30 days of refrigerated storage T1 samples showed >10³CFU/g in bacteria and yeast counts, while T3 and T5 had < 10CFU/plate after a 1/10 sample dilution. Both 5 and 10 min step pulsed 0-270 MPa treatments were as effective as 15 min static 270 and 340 MPa. Treatments T3 and T5 for 5 min yielded 0-4 CFU/plate after a 1/10 sample dilution during 30 days of refrigerated storage and recovery of pressure-injured cells was not observed. Static 15 min pressure at 270 MPa and 340 MPa resulted in 0-10 and 0-8 CFU/plate after a 1/10 sample dilution during the same 30 days of refrigerated storage. Step pressure treatment seems to be more effective than static pressure for inactivating bacteria and yeast in pineapple; recovery of pressure-injured cells was not observed under refrigerated storage conditions. / Graduation date: 1997

Thesis (Ph. D.)--University of Hawaii at Manoa, 1996. / Includes bibliographical references (leaves 125-138). / Microfiche. / vi, 138 leaves, bound ill. 29 cm

No description available.

Pineapple juice of low acid content was prepared by removal of acids by using weakly basic anion exchange resin, IRA-93. The changes in the contents of titratable acid, pH and total soluble solids of model solutions that contained the principal constituents of pineapple juice (citric acid, citrate salt and sucrose) were investigated. The adsorption of individual acids and changes in composition of juice after a de-acidification process were explored. The adsorbed acids were recovered as solutions by some eluants, and studies on colour development in the recovered solutions carried out. The solutions of adsorbed acids recovered by NaOH from the resin, which had been treated by model solutions, were brown in colour. The brown colour was also found immediately when NaOH was added to the resin treated with pineapple juice but it was not found in the treated juice during acid removal treatment when its pH rose to 10. A greater amount of the dark colour was observed in the desorbed solution from the resin that had been treated with pineapple juice. The use of sulphuric acid, sodium chloride, sodium sulphate, sodium bicarbonate and phosphate buffer solution to desorb the acids from pineapple juice-treated resins reduced the intensity of the colour, measured at pH 3.5, of desorbed acid solutions. The colours of the desorbed solutions were pH dependent. Either solution of sulphuric acid or sodium chloride has a comparable desorbing power to a solution of sodium hydroxide whereas the rest has a lower desorbing power / Master of Science (Hons) (Food Science)

Graduation date: 1992

Typescript. Thesis (Ph. D.)--University of Hawaii, 1958. Bibliography: leaves [75]-79.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliography.

Drying of agricultural products using solar energy is a method for preservation that has been used for centuries all over the world. This method has been effective especially in tropical and subtropical climates, due to the great availability to solar energy. The village Edumafa in Ghana has great cultivation of pineapples but has no post harvest process. A post harvest process as drying of pineapples can increase cultivation and introduce a new product to be sold at the market. This thesis is investigating the possibility of drying pineapples in coastal Ghanaian climate including both experimental method and simulation. A well functioning solar dryer is constructed based on literature study, which after the dryer is studied in simulated environment. Modifications on the model based on the actual dryer are simulated focusing on the temperature and air velocity distribution. The experimental study results in drying pineapple slices corresponding to eight pineapples in two days. Simulation of the solar collector shows that increased temperature at the end of the solar collector can be achieved when decreasing inclination and decreasing the size of the energy storage layer. Simulation of the drying chamber results in improved distribution of temperature and air velocity inside the drying chamber, providing improved drying conditions with increased inlet size and added flow disturbance. Further studies based on this thesis would be a study of adjustable thickness of the energy storage, and transient simulation. Adjustable thickness of the energy storage and air duct on a experimental dryer could improve the drying in undesirable weather conditions, why a study of defining the optimal adjustment thicknesses for different weather conditions could be of interest. Transient simulation of the drying process accounting for the weather change could improve the drying, since the geometry changes could be made and the drying process studied directly in the simulation tool before building the actual dryer. Transient study of the drying process could even study the effect of different thicknesses of the pineapple slices during drying.

Thesis (Ph. D.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references. Also available online.

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1963. / Bibliography: l. [69]-73. / v, 73, [1] leaves mount. ill., diagrs., tables (part fold.)