| Summary: | In this study, the effectiveness of
whey protein isolate (WPI) and WPI enriched thyme essential oil coating to
improve the quality of horse mackerel during frozen storage at -18 oC±2
were evaluated for nine month. Whey protein isolate without thyme essential oil
(WPI0) and three different proportion thyme essential oil (3, 5 and 7 %, v/v)
in whey protein isolate (WPI3, WPI5 and WPI7) coating solutions were applied to
horse mackerel. As a control, non-coated and distillated water coating (DW) horse
mackerel were used. The results showed
that the lowest peroxide value (PV) (meq of peroxide oxygen kg−1) and
thiobarbutiric acid value (TBA) (mg malonaldehyde/kg muscle) were determined in
WPI coatings enriched with 3% thyme essential oil treated group (p<0.05)
while the highest PV and TBA values were determined in WPI coatings enriched
with 5% and 7% thyme essential oil treated groups (p<0.05). Among the treatment, DW and the WPI coatings
enriched with 7% thyme oil gave significantly higher protein solubility than
other treatments during frozen storage (p<0.05). Electrophoretic studies in
the presence and absence of β-mercaptoethanol showed that high molecular weight
polymers via non-disulfide and disulfide cross-linking occurred in the horse
mackerel proteins extracted in 5% NaCl in all groups during frozen storage.
Sensory assessment showed that the horse mackerel coated WPI enriched with 5
and 7% thyme essential oil could not be stored for more than 9 months.
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