Browsing by Author "Jayasinghe, M.D."

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    Effect of Guar Gum and Carboxymethyl Cellulose on Heating Behavior of Coconut (Cocos nucifera) Milk
    (Uva Wellassa University of Sri Lanka, 2020) Thennakoon, T.M.N.D.; Madage, S.S.K.; Jayasinghe, M.D.; Medis, W.U.D.; Mudannayake, D.C.
    Thermal processing is used to destroy Clostridium botulinum in low acid canned foods such as coconut milk (CM) and thereby, extend the shelf life. The length of the thermal treatment is established based on the targeted thermal destruction (12D destruction) of C. botulinum. at 121.1°C in the container cold point. Typically, the addition of stabilizers into CM is performed to increase the emulsion stability and to alter the heat transfer behavior. Therefore, the main objective of this study was to investigate how the heating behavior of CM could be changed with the addition of different stabilizers. During the study, heating behavior and heat-sensitive properties of CM were studied at three different temperatures (30, 50 and 80°Ϲ) against the separate addition of Guar Gum (GG) and Carboxymethyl Cellulose (CMC), that were incorporated at levels of 0.05, 0.1 and 0.5%. Extracted fresh CM was standardized for 17% fat and homogenized at 894 g for 5 min. Homogenized samples having different levels of GG and CMC were prepared from standardized CM. Specific gravity and viscosity of prepared samples at 30, 50, and 80°Ϲ were determined using the gravimetric method and viscometer, respectively. Cold point and the length of thermal processing to achieve target thermal death time (F0) of C. botulinum (2.52 min) were determined for prepared CM in aluminum cans. It was found that the specific gravity of samples at 30-80°Ϲ was in the range of 0.9778±0.05- 1.0176±0.01 for GG and 0.9957±0.00-1.0164±0.03 for CMC and that did not significantly differ (p>0.05) and viscosity was in the range of 9.98±3.31-126.70±0.00 for GG and 9.98±3.31- 40.00±3.30 for CMC. The cold point of canned CM was found to be the center of the can which was above 3 cm from the bottom. The addition of stabilizers did not affect the cold point of canned CM. Incorporation of GG and CMC into CM had no significant effect (p>0.05) on the processing time (80.2-88.8 min. for GG and 86.8- 88.8 min. for CMC). In conclusion, the heating behavior of canned CM was not affected by the addition of GG and CMC. Keywords: Coconut Milk, F0, Cold point, Viscosity, Specific gravity
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    Identification of Potential Spoilage and Pathogenic Microorganisms Associated with Production of Thermally Processed King Coconut Water (Cocos nucifera var. aurantiaca) in Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2021) Jayasinghe, M.D.; Jayawardana, T.M.D.N.; Madage, S.S.K.; Hewajulige, I.G.N.; Halmillawewa, A.P.; Divisekera, D.M.W.D.
    Thermally processed king coconut (Cocos nucifera var. aurantiaca) water is one of the fastest growing export commodities in the food and beverage sector in Sri Lanka. Microbial safety of thermally processed king coconut water is demanded by Food and Drug Administration to ensure safe consumption. This study aimed to identify potential spoilage and pathogenic microorganisms associated with king coconut water processed in Sri Lanka. King coconut water samples were collected at pre-identified sampling points; P1-Nut water extraction, P2-Bulk collection, P3- Standardization/Acidification, P4-Pre-heating prior to hot filling and P5; Sterilization/Pasteurization in three processing facilities; F1 (semi-automated), F2 (automated) and F3 (manual), where Pasteurization (100 °C/12.5 min), UHT Sterilization (140 °C/3s) and Pasteurization (100 °C/20 min) were practiced, respectively. Serially diluted king coconut water were plated on Nutrient Agar, Potato Dextrose Agar, Eosin Methylene Blue Agar and Reasoner‟s 2A Agar, incubated at 30 ± 1 °C for 48 h, 25 ± 1 °C for 2 - 5 days, 37 ± 1 °C for 48 h and 37 ± 1° C for 48 h, respectively. Purified bacterial and fungal colonies were morphologically characterized. A total of 29 bacterial isolates and 24 fungal isolates were identified by 16S rRNA and 26S/5.8S rRNA/ITS gene amplification, respectively followed by sequencing using 27F/1492R and ITS-1/ITS-4 primers, respectively. Evolutionary relationships of identified species were predicted using MEGA 7. The study revealed that thermal resistant, facultative-anaerobic, spoilage and pathogenic bacteria (Pantoea dispersa, Bacillus siamensis, Pseudomonas stutzeri, Acinetobacter lactucae) and fungi (Candida carpophila, Pichia kudriavzevii, Debaryomyces nepalensis, Microdochium fisheri, Penicillium citrinum) were survived in the thermally processed finished product. Further, potential risk of Klebsiella pneumoniae, Enterobacter roggenkampii, Enterobacter kobei, Escherichia fergusonii, Bacillus nealsonii, Serratia rubidaea, Trichosporon asahii, Wickerhamomyces anomalus, Saccharomycetales species and Fusarium species were identified at initial processing steps (P1-P3) in studied processing facilities. In conclusion, the study revealed that the existing thermal treatments are not sufficient for the destruction of identified potential spoilage and pathogenic microorganisms associated with studied processes. Thereby, suggesting thermal process validation, while targeting identified potential harmful microorganisms with optimum time-temperature combinations to ensure product safety. Keywords: King coconut water; Spoilage and pathogenic microorganisms; Molecular identification; Thermal processing