THE EFFECT OF DIFFERENT COOLING TECHNIQUES ON THE ...

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SemwangaFigure 8: Principle component analysis (PCA) relating microbial and chemical data of thesample treatments (NC, SIC, SIC-CBC, CBC, SF-SIC) with storage time (d1 to d13). PC1 vsPC2 (X-expl: 71% and 22%). Bi-plot of scores (samples in blue) and loadings (chemical andmicrobial parameters in red).UNU-Fisheries Training Programme24
Semwanga5DISCUSSI<strong>ON</strong>The study describes the microbial quality, chemical and sensory characteristics of redfishskinless or skin-on fillets processed three days post catch as influenced by different inprocesscooling techniques. It further shows the behaviour of specific spoilage organisms(SSO) during slow and fast superchilling of the skinless and skin-on fillets, respectively, overthe storage period simulating distribution and storage. The cooling techniques implied the useof slurry ice as a fillet pre-cooling medium and/or CBC technique to superchill the filletsbefore packaging. However, mechanical problems with the deskinning machine at the CBCprocessing site did not allow for production of superchilled skinless fillets as intended.Instead, two groups of superchilled skin-on fillets (CBC+/-SIC treatments) were compared toskinless fillets prepared as three groups; untreated (no in-process cooling) or cooled by slurryice and then stored in closed EPS boxes or sea freight boxes with drainage holes. Table 5summarises the main findings for the differently treated redfish fillets at their sensoryrejection point.Table 5: Microbial and chemical indicators of spoilage for differently treated redfish fillets atthe end of shelf life according to the Torry schemeTreatment NC SIC SIC-CBC CBCSensory shelf life 11-12 11-12 10 8-9(days)Product Temp (°C)* -0.4±0.7 -0.4±0.7 -1.1±0.3 -0.9±0.2TVC (log CFU/g) 6.4 6.9 7.8 6.3H 2 S-prod. bacteria 6.0 6.6 6.7 5.8Pseudomonads 5.4 5.1 5.2 4.9P. phosphoreum 4.9 >5.5 4.8 3.6TVB-N (mgN/100g) 12.3 14.7 14.2 13.5TMA (mgN/100g) 2.3 5.6 1.3 1.7P-ratio 0.187 0.381 0.091 0.126pH (units) 6.8 6.8 6.8 6.8*Mean product temperature of redfish fillets over the maximum shelf life period indicatedThe results indicate that H 2 S-producing bacteria were the most dominant spoilage organismsin all treatments. P. phosphoreum and H 2 S-producing bacteria counts were observed to behigher in slurry ice cooled fillets (SIC, SIC-CBC) than in NC and CBC treated fillets,respectively at the end of sensory shelf life. This further demonstrates the effect salt uptakehad on SSO growth. By lowering the muscle freezing point, salt uptake in SIC and SIC-CBCtreatments may have provided some protection for SSO in superchilled fillets and allowedthem to grow faster than at a similar temperature with a lower salt level as in NC and CBCproducts. Similar findings were reported by Reynisson et al., (2010) and Lauzon et al.,(2009). In addition to that, salt uptake may have shielded the SIC-CBC fillets fromdeteriorative changes caused by freezing damages to some extent, in comparison to CBCfillets as demonstrated by the shorter shelf life of CBC fillets. H 2 S-producing bacteria wereobserved to be more tolerant to superchilling conditions than P. phosphoreum. This agreeswith what Olafsdottir et al., (2006) reported during aerobic storage of cod fillets.Pseudomonads were apparently the least affected by the treatments applied among the SSOevaluated.UNU-Fisheries Training Programme25
Page 1 and 2: P.O. Box 1390, Skulagata 4120 Reykj
Page 3 and 4: SemwangaLIST OF FIGURESFigure 1: Te
Page 5 and 6: Semwangaactive spoiler Photobacteri
Page 7 and 8: Semwanga2STATE OF ART2.1 Fish spoil
Page 9 and 10: Semwangacompounds and abundance of
Page 11 and 12: Semwanga2.4 In-process coolingCombi
Page 14 and 15: Semwangaboric acid solution, then t
Page 17 and 18: Semwanga4.2 Shelf life of redfish f
Page 19 and 20: Semwanga5% of the sensory variation
Page 21 and 22: Log cfu /gLog cfu/gLog cfu/gLog cfu
Page 23: pH (units)NaCl %Semwanga4.5 pH and
Page 27 and 28: Semwangaof microbial origin. Indeed
Page 29 and 30: SemwangaACKNOWLEDGEMENTSI extend my
Page 31 and 32: SemwangaEtienne M. (2005). SEAFOODp
Page 33 and 34: SemwangaMausse, E. C.J., 2000. Shel
Page 35 and 36: SemwangaAPPENDIX 1 - Torry scheme a
Page 37 and 38: SemwangaAPPENDIX 2 - Mean data with
Page 39 and 40: SemwangaDay 10 Day 13Sensory attrib

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