Ž tion affected sensory properties of the flesh. A total of 12 tasters eight male, four
. Ž
. female assessed three samples one from each dietary treatment using a standard rating
Ž .
procedure AS2542.2.3, SAA, 1988 at each of three sessions. All fish from any
treatment were from one pond. All samples presented to each taster were matched for position within the fish, and were from fish of the same weight rank. Temperature of the
samples served was 758C. Order of tasting the treatments was balanced across the panel. Samples were served to tasters in individual booths illuminated with white light
Ž
. daylight equivalent . Purified water was freely available for palate cleansing prior and
during tasting. Tasters identified and rated the colour of internal flesh, and odour, flavour and texture characteristics on structured graphic line scales. Overall acceptability
of the flesh was also rated, and tasters were given the opportunity to record additional descriptors and add any general comments about the samples.
2.5. Biochemical analyses All chemical analyses were done in duplicate. Fish samples were analysed for dry
Ž .
Ž .
matter, ash, crude fat and energy bomb calorimetry by the AOAC 1990 procedures. Ž
. Ž Nitrogen was determined by the method of Havilah et al. 1977
crude protein s N = .
Ž .
6.25 . Amino acids were determined by the method of Cohen et al. 1989 and analysed following acid hydrolysis using high pressure liquid chromatography and Waters
Ž .
Pico-Tag Waters, Lane Cove, NSW, Australia . Sulphur amino acids were determined separately following performic acid digestion, and tryptophan, which is lost during acid
Ž .
hydrolysis, was not analysed Cohen et al., 1989 . 2.6. Statistical analysis
All experiments were designed for analysis using single-factor ANOVA. Homogene- ity of variance was assessed using Cochrans’ Test, and multiple comparison among
means using Student Newman–Keuls procedure. Mean values were considered signifi- cant at P - 0.05.
For each of the sensory variables measured, scores for each diet were compared using a randomised block analysis of variance with sessions and panellists as blocking terms.
Ž .
Where a significant P - 0.05 F ratio was found then pairwise comparisons of the
mean scores were made using the least significant difference procedure.
3. Results
3.1. SurÕiÕal, growth, FCR and production Ž
. Results for survival, growth performance, feed conversion ratio FCR and fish
production rates are presented in Table 3. Survival was above 96.8 in all ponds and there were no significant differences in survival between treatments. Proximate composi-
tion of whole fish fed different diets is presented in Table 4. There were no significant Ž
. differences
P 0.05 in dry matter, nitrogen, ash, energy or fat, in the whole body
Table 4 Proximate body composition of whole silver perch at completion of the nutrition experiment
Fish Dry matter
Nitrogen Ash
Energy Fat
Ž . Ž
. Ž
. Ž
. Ž
. sample
dry basis dyr basis
MJrkg dry basis dry basis
SP35 41.230.34
6.180.11 7.880.05
29.720.17 50.920.45
95LC1 43.140.05
5.390.08 6.870.20
30.550.13 55.040.51
95LC2 42.921.78
5.680.05 7.650.67
30.120.34 54.402.05
Ž .
Values are meansS.E.M. for fish sampled from 3 replicate ponds fish sampled from 2 ponds for SP35 diet . Ž
. No significant difference was observed in these data P 0.05; ANOVA .
composition of fish fed different diets. The mean weights at harvest and the mean Ž
. weight increments were significantly higher
P - 0.05 for fish fed the 95LC1 and Ž
. 95LC2 compared with those fed SP35 Table 3 . FCRs for fish fed LC diets were
Ž .
significantly lower than for those fed SP35 Table 3 . 3.2. Water quality
Ž .
Diet did not have a significant effect ANOVA; P 0.05 on water quality. The ranges of the monthly means for each variable were: water temperature 19.7 to 27.68C;
dissolved oxygen 4.9 to 7.7 mg l
y1
; pH 6.7 to 9.0; and total ammonia nitrogen ranged from 0.3 to 2.2 mg l
y1
. Unionised ammonia exceeded 0.1 mg l
y1
in most ponds during
Fig. 1. Silver perch diet comparison-mean taste panel scores: Odour profile.
Fig. 2. Silver perch diet comparison-mean taste panel scores: Texture profile.
Fig. 3. Silver perch diet comparison-mean taste panel scores: Flavour profile.
the December–February period, and concentrations as high as 0.4 mg l
y1
were recorded in some ponds during January. On such occasions feeding rates were reduced and the
ponds were flushed. 3.3. Sensory eÕaluation
The results from sensory evaluation for odour, texture and flavour of silver perch are presented in Figs. 1–3. Sensory evaluation results showed that fish from all dietary
treatments were highly acceptable. Analysis of flesh appearance indicated fish fed Ž
. 95LC2 were significantly whiter less yellow than fish fed the other diets. There were
Ž .
no significant differences P 0.05 in odour or flavour characteristics of the flesh
Ž .
Figs. 1 and 3, respectively , although a slightly stronger weedyrherbaceous flavour was detected in fish fed diet 95LC1. This diet also produced flesh which was rated
Ž .
Ž .
significantly P - 0.05
more flaky in texture Fig. 2 . None of these differences
significantly altered overall liking scores.
4. Discussion
