Improvement of pineapple puree quality by deaeration and irradiation treatment | |
| Author | Benjar Chutintrasri |
| Call Number | AIT Diss. no.FB-05-01 |
| Subject(s) | Pineapple industry Irradiated fruit |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. FB-05-01 |
| Abstract | Aseptically packed pineapple puree a high value added product marketed at a premium price is usually better in color, aroma, and flavor than the canned products. However, its quality is lost during storage at ambient temperature due to browning, which limits its shelf life. This study was designed to improve the puree quality for better color and ascorbic acid retention by modifying the existing aseptic processing and exploring alternative non-thermal treatment methods to achieve this goal. A deaerator was introduced after size reduction process since a considerable amount of air was incorporated into the product at this stage. Effects of deaeration on quality of pineapple puree during processing and storage at low temperature (10°C) and ambient temperature (28-34°C) were investigated. It was found that deareation of aseptically packed pineapple puree indicated better color and flavor stability and aided in the retention of ascorbic acid for 6 months of storage. Sensory color scores, Hunter color values, Agtron color values, dissolved O2, headspace O2 and ascorbic acid content were highly con-elated with each other. This showed that color changes were related to O2 consumption and ascorbic acid destruction. Both objective measurements and sensory evaluation showed that quality was preserved when pineapple puree was stored under cold temperature (10°C) whereas deterioration occurred gradually when the puree was stored at ambient temperature. Additional improvement of the aseptic product color could be accomplished by understanding the kinetics of thermal inactivation of polyphenoloxidase (PPO) which was the main cause of enzymatic browning and color degradation during thermal processing. In this study, prevention of browning in pineapple puree after size reduction process by thermal inactivation of PPO was examined at temperatures between 40 and 90°C and a range of exposure time. The results showed that the rate of inactivation varied with temperatures and followed a logarithmic pattern. Kinetic studies showed that the thermal inactivation (40-90°C) of the PPO followed first-order kinetics. The efficient and effective heat treatment process to reduce PPO activity and enzymatic browning in pineapple puree could be derived from any of D, Z, Ea or k values. This information could also be used in non-thermal treatment where PPO enzyme was normally not inactivated and combined heat treatment is needed. The kinetics of color degradation of pineapple puree were also investigated during heat treatment at 70-110°C in order to cover the temperature range used in preheat and sterilization of commercial aseptic pineapple puree. Color changes by heat treatment were evaluated using Hunter colorimeter (L, a, b) and total color difference (TCD) and browning index determination (A420). The changes in Land b values fitted well to the first order kinetic model while TCD, a value and browning index followed the zero order kinetic. TCD and lightness, based on activation energy, were the most sensitive measures of color change in temperature ranges of 70-90°C and 95-110°C, respectively. These results could be utilized to monitor processing effects on color change of pineapple puree. TCD and L parameter might therefore be recommended as on-line quality control parameters during thermal processing of pineapple puree. Non-thermal treatment such as irradiation was the other approach attempted to improve the quality and extend the shelf life of pineapple puree. Effect of irradiation and combined treatment of low dose irradiation and preheat on the survival of microorganisms, PPO inactivation and quality changes of pineapple puree after processing and during storage at 10°C and ambient temperature for up to 6 months were investigated and compared with aseptically packed pineapple puree. The results showed that the use of irradiation alone gave inconsistent activation of PPO with increasing doses (2 to IO kGy) and up to 8 kGy should be used to eliminate all microorganisms. However, with low dose i1rndiation (2 to 4 kGy) combined with preheat treatment (90°C for 5 min), microorganisms were completely eliminated and PPO was inactivated too. The puree with 2 kGy irradiation combined with preheat treatment immediately after processing gave superior quality than that of aseptic sample in preserving the fresh flavor and natural raw fruit color. Its ascorbic acid content was 23.5 mg/I while the commercial aseptic puree retained only 7.3 mg/I and its TCD was significantly lower than that of commercial aseptic puree, i.e. 4.78 versus 5.69, respectively. After 6 months storage, the purees irradiated with 2 kGy and 4 kGy combined with preheat treatment showed no microbial growth. The superior quality was maintained under low temperature storage, the TCD of the sample with 2 kGy irradiated combined with preheat treatment was less than commercial aseptically processed puree and its ascorbic acid content was much greater, i.e. 16.4 mg/I versus 3.3 mg/I, respectively. The results indicated that this sample retained its color and ascorbic acid content better than the commercial aseptic puree after storage for 6 months at 10°C. The sensory evaluation results also confirmed similar trends. However, ambient temperature storage resulted in rapid deterioration including off-flavor, discoloration, and decomposition of ascorbic acid especially in sample with 4 kGy irradiation combined with preheat treatment. Study revealed that improvement of pineapple puree qualities could be achieved by using deaeration and/or utilization of combination of irradiation at low dose with preheat treatment. |
| Year | 2005 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. FB-05-01 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Athapol Noomhorm; |
| Examination Committee(s) | Jindal, V. K. ;Rakshit, S. K. ;Salokhe, V. M. ;Lee, C. Y. ; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2005 |