Basic HTML Version
International Journal of Aquaculture, 2014, Vol.4, No.21 123
-
130
http://ija.biopublisher.ca
128
4.6 Determination of peroxide value (PV)
The PV was determined in duplicate using titrimetric
method as described by AOAC, (2005). 30 ml glacial
acetic acid-chloroform solution (3:2 v/v) was added to
5g of extracted fat and swirled. Potassium iodide
(0.5ml of KI solution) was added to react with the
peroxides and iodine was liberated. After 1 min., 30
ml of water was added. Then the solution was titrated
with 0.1 N sodium thiosulfate (Na
2
S
2
O
3
) using 0.5ml
of 1% starch as indicator, until the blue colour
disappeared. The peroxide value was calculated by
multiplying ml of Na
2
S
2
O
3
by normality and by 1000
then divided by grams of catfish sample.
4.7 Determination of thiobarbituric acid level (TBA)
Oxidative stability of smoked catfish was measured by
Thiobarbituric acid reactive substance (TBA-RS)
following the procedure Cd19-90 (AOCS, 1996).
Results were expressed as mg malonaldehyde /Kg dry
weight. A 5g sample of fat from the belly flap of the
fish was combined with distilled water and thoroughly
mixed. After addition of 2.5 ml of 4 N HCl, Dow
antifoam A, and boiling beads, the sample was
distilled and the first 50 ml collected. An aliquot of the
distillate (5 ml) was combined with 5 ml of TBA
reagent and heated in a boiling water bath for 35 min.
Absorbance of the solution was determined at 530 nm,
using a slope of TEP (1,1,3,3-tetraethoxypropene,
Sigma Chem. Co., St. Louis, MO) standard curve,
which was derived to correlate with the expected
range of values. Absorbance readings were calculated
as µ
milligrams of malonaldehyde (or TBARS) per
kilogram of sample. The TBARS was calculated by
the following formula:
TBARS = (T*V1*1000) / (V2*W)
T = µ moles malonaldehyde (TEP) equivalent to
absorbance of sample as determined from the standard
curve; V1= volume (ml) of distillate collected, usually
50ml;
V2= volume (ml) of distillate aliquot withdrawn for
analysis, usually 5ml;
W= weight of fish added to distil, usually 5g.
4.8 Organoleptic assessment
Sensory evaluation was carried out according to the
method of Clucas and Ward, (1996). Evaluation was
done at 24 hours after smoking, 6, 12 and 18 weeks on
taste, flavour, texture, appearance and overall
acceptability. The mean overall acceptability was
calculated and recorded.
4.9 Analytical methods
Proximate composition of the smoked
C.
gariepinus
was analyzed 24 hours after smoking and 18 weeks.
One fish from each treatment were taken 24 hours
after smoking and 18 weeks and analyzed for their
proximate composition according to the methods of
Association of Official Analytical Chemists {A.O.A.C,
(2005)}
4.10 Statistical analysis
Proximate composition, organoleptic assessment,
microbial loads and biochemical parameters that
resulted from the experiment were subjected to one-
way analysis of variance (ANOVA) using SPSS
(Statistical Package for Social Science 2006 version
15.0). Duncan multiple range test was used to
compared differences among individual means.
Authors’ contributions
This work was carried out by three authors; AOI, SEO and
OAO. Author AOI conceived the idea; AOI, SEO and OAO
designed the study and wrote the protocol, author OAO
supervised the study. Author AOI performed the experiment
and author SEO performed the statistical analysis as well as
managed the literature searches. Also, Author SEO wrote the
first draft of the manuscript. All authors read and approved the
final manuscript.
References
American Oil Chemists’ Society (AOCS), 1996,
Official Methods and
Recommended Practices, Physical and Chemical Characteristics of
Oils, Fat and Waxes, Section I
, American Oil Chemists’ Society,
Champaign, IL.
Antonia da Silva L.V., 2002, Hazard analysis critical control point (HACCP),
microbial safety, and shelf life of smoked blue catfish
(Ictalurus
furcatus
). M. Sc. dissertation of Louisiana State University and
Agricultural and Mechanical College, ix + 109pp
Antonia da Silva L.V, Prinyawiwatkul W, King J.M., No H.K, Bankston (Jr),
J.D and Ge B., 2008
,
Effect of preservatives on microbial safety and
quality of smoked blue catfish
(
Ictalurus furcatus
) steaks during
room-temperature storage. Food Microbiology 25: 958-963
Association of Official Analytical Chemists (AOAC), 2005, Official
Methods of Analysis, 18
th
edition. Washington DC
Clucas I.J and Ward A.R., 1996
,
Post-Harvest Fisheries Development: A
guide to Handling, Preservation, Processing and Quality. Chathman
Maritime, Kent ME44TB, United Kingdom.
Conway E.J., 1968, In micro diffusion analysis and volumetric error.
Lockwood and sons Limited, London. 465pp
Deni B., 1996, The Royal Horticultural Society Encyclopedia of Herbs and
Their Uses. Dorling Kindersley Book: 424
Eyo A.A., 2001, Fish processing technology in the tropics. University of