Preliminary study on the role of ionic calcium in gelation and proteolysis of UHT milk

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dc.contributor.authorChove, Lucy Mlipano
dc.contributor.authorLewis, Michael
dc.date.accessioned2023-03-06T14:57:25Z
dc.date.available2023-03-06T14:57:25Z
dc.date.issued2017-12-28
dc.descriptionJournal articleen_US
dc.description.abstractA study was conducted to determine the influence of ionic calcium on gelation and proteolysis in milk. Raw milk was heated to 142 °C for 2s followed by cooling to 5 °C to make UHT milk. Two sequestering agents, Trisodium citrate (TSC) and Sodium hexametaphosphate (SHMP) were added at 0.04 - 0.08% (w/v) to the processed UHT milk to reduce the ionic calcium levels. Proteolysis and gelation were induced by addition of trypsin (248 BAEE units), 0.03% (v/v) chymosin and 10 6 cfu/mL Pseudomonas fluorescens NCIMB 702085 (Ps. fl. 416) to UHT milk. Samples were stored at 25 °C for 21⁄2 weeks to monitor gelation and Ca 2+ and some were incubated at 37 °C for 2h to monitor proteolysis. SHMP reduced more Ca 2+ than TSC. Ca 2+ reduction was accompanied by an increase in pH, most evident with TSC at 25 °C. Gelation was not observed in samples inoculated with Ps. fl. 416 (with sequestering agents) even after 9 days of storage, suggesting the importance of calcium in gelation. Chymosin treated samples gelled on day 0, whereas other samples gelled after 4 days. Trypsin increased Ca 2+ to levels higher than originally present in control UHT skim milk. Although in the current study, proteolysis was higher in samples inoculated with Pseudomonas fluorescens 416, no clear relationship was established between proteolysis and gelation in UHT milk. This observation implies that proteolytic activity is not influenced by Ca 2+ . However, longer time study using sodium azide to prevent bacterial contamination would be required to confirm these findings.en_US
dc.identifier.issn2166-1073
dc.identifier.urihttp://www.suaire.sua.ac.tz/handle/123456789/4986
dc.language.isoenen_US
dc.publisherMacrothink Instituteen_US
dc.subjectChymosinen_US
dc.subjectGelationen_US
dc.subjectIonic calciumen_US
dc.subjectProteolysisen_US
dc.subjectPseudomonas fluorescensen_US
dc.subjectSodium hexametaphosphate (SHMP)en_US
dc.subjectTrypsinen_US
dc.subjectTrisodium citrate (TSC)en_US
dc.titlePreliminary study on the role of ionic calcium in gelation and proteolysis of UHT milken_US
dc.typeArticleen_US
dc.urlhttps://doi.org/10.5296/jfs.v7i1.12081en_US

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