Both liquid and solid wastes from Pacific whiting surimi manufacturing were
characterized and value-added products were recovered. A proteinase in surimi wash
water (SWW) was determined to be cathepsin L with Mr 54,200 on SDS-substrate gel.
Heat treatment and acidification shifted the activity zone to M [subscript r] 39,500. No evidence of
calpain, cathepsin B or H activity was found. Cathepsin L from SWW was recovered
by ohmic heating (55°C for 3 min), ultrafiltration, and freeze-drying with overall yield
of 0.83 g protein/L SWW and 78% recovery of activity. A 5.9 purification fold was
achieved by these processes. The recovered enzyme had an optimum activity at pH 4.0
and showed preferable hydrolytic activity towards casein, acid-denatured hemoglobin and
myofibrils. β-Mercaptoethanol, dithiothreitol and urea enhanced the enzyme
activity. The recovered proteinase showed 18.5% residual activity after
7 wk storage at 4°C.
Proteolytic activity in solid waste and digestive organs from Pacific whiting was
investigated. Pepsin-like proteinase predominated in solid waste, while trypsin-like
proteinase was predominant in viscera. Carboxypeptidase b was found in both viscera
and solid waste.
Protein hydrolysate was produced from Pacific whiting solid waste (PWSW) using
commercial proteinase, Alcalase, under optimum hydrolysis conditions. Enzyme
concentration, reaction time and waste/buffer ratio affected the hydrolysis and nitrogen
recovery (NR). Correlation between the degree of hydrolysis (DH) and NR was high
(R₂=0.978). Freeze-dried hydrolysate contained 79.97% protein and showed similar
amino acid composition to PWSW and Pacific whiting muscle but tryptophan was
reduced. With different DH (20, 30, 40, 50, 60%), surface hydrophobicity, total and
surface sulfhydryl content decreased as the DH increased. The hydrolysate showed a
high solubility over a wide pH range. Fat adsorption and fat binding capacity were
reduced, while foam expansion was enhanced with an increased DH. Hydrolysate with
DH of 30% showed highest emulsifying activity. Low emulsion stability and high foam
stability were obtained in all hydrolysates tested. Hydrolysate showed antioxidant
activity, but no obvious differences in activity were found with varying DH and
hydrolysate concentrations. / Graduation date: 1997
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27453 |
| Date | 17 April 1997 |
| Creators | Benjakul, Soottawat |
| Contributors | Morrissey, Michael T. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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