Quality assessment of commercially harvested weathervane scallops
(Patinopecten caurinus) from Alaska
Kathryn
1
Brenner* ,
1
Oliveira ,
2
Rosenkranz ,
2
Burt ,
Alexandra
Gregg
Ryan
Marsha
3
1,4,
4
Bechtel , Charles Crapo
and Raymond RaLonde
2
Spafard ,
Peter J.
1Fishery
Industrial Technology Center, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Kodiak, AK 99615-7401,
USA.
2Alaska Department of Fish and Game, Division of Commercial Fisheries, Kodiak, AK 99615-7401, USA
3USDA-ARS, Subarctic Research Unit, Fishery Industrial Technology Center, Kodiak AK, 99615-7401, USA.
4Marine Advisory Program, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Anchorage, AK 99501.USA
Introduction
Alaska’s commercial weathervane scallop fishery is primarily prosecuted by catcher-processor vessels that shuck, wash, grade, and freeze scallop muscles
onboard. The 2006-2008 average for weathervane scallop harvest was about 204,545 Kg with an ex-vessel value of $3.36 million dollars. From 1994-2002 the
eastern Gulf of Alaska region (GOA; Yakutat) accounted for 31% of statewide scallop landings. Fishermen have reported that scallops caught in some GOA
areas are of lower value due to poor quality; characterized by weak muscle strength, stringy and spongier texture, and off-white to grayish muscle color. The
objective of this research was to quantify variability in meat quality of commercially harvested weathervane scallop using physical and biochemical
analyses.
KAMSS 2011
Kodiak , Alaska
Results
Materials and methods
In summer of 2009, two groups of 40 whole scallops, Weak (WS) and Not Weak (NWS), were sampled from
Yakutat. Kodiak scallop meats (KS1, KS2), known for their high quality and market value were procured locally
in April and August 2009. Physical characteristics studied included shell and muscle dimensions and weights
(WS and NWS), texture analysis of edible muscle, and determination of animal age. Proximate composition
was determined using standard AOAC methods. Lipid classes, fatty acids, amino acid, minerals and pH were
determined as previously described by Bechtel and Oliveira (2006).
Figure 1 shows that WS had significantly higher moisture (81.6%) than NWS (78.1%), KS1 (76.4%) and KS2 (76.8%), while protein content was significantly
lower in WS (15.4) than in NWS (17.5), KS1 (19.3%) and KS2 (19.2%). WS were significantly older (14.8 annuli) than NWS (5.4 annuli) as shown in Figure 2. A
condition index (CI) of edible meat to body ratios was calculated using Formula 1 and was significantly lower in WS (23.6) when compared to NWS (33.7) (Table
1). Figure 3 shows that pH in all three samples was significantly different, and that WS had the highest pH (6.8), however, all pH values were below 7. Lipid
class analysis (Figure 4) showed high levels of phospholipids (PL) and low levels of triglycerides (TG) overall, with WS having significantly lower PL than
NWS, KS1 and KS2. WS had lower FA levels overall compared to NWS, KS1 and KS2 (Table 2), and ω3 FA levels were significantly lower in WS (112.2mg/g)
than in NWS (179.9 mg/g), KS1 (138.9 mg/g) and KS2 (171.5 mg/g).
Figure 3: pH of scallop adductor muscle
Figure 1: Proximate composition of scallop
adductor muscle
Table 2: Fatty acid (FA) profiles of scallop
adductor muscle showing most abundant FAs
(>10mg/g oil)
% of total proximate composition
a
80
a,b
b b
a
70
60
Weak
Not weak
Kodiak 1
Kodiak 2
C16:0
29.29b ± 5.47
48.35a ± 4.63
39.91a,b ± 8.32
45.76a ± 5.31
C18:0
11.40b ± 2.49
15.66a ± 1.70
12.64a,b ± 2.55
13.80a,b ± 1.59
C20:5ω3
35.63b ± 8.36
56.75a ± 6.58
44.48a,b ± 9.74
67.89a ± 7.60
C22:6ω3
66.94b ± 16.03 113.32a ± 10.64 89.26a,b ± 16.26 92.09a,b ± 10.65
Σ ALL FA
199.76b ± 40.06 305.13a ± 30.12 246.58a,b ± 52.04 300.50a ± 37.43
Weak
50
Not Weak
b
40
c
Kodiak 1
30
20
b
a,b
Kodiak 2
a a
10
a
a a
a a,b c b,c
a a a a
0
Different superscript letters indicate statistical
difference between groups at P<0.05
Different superscript letters within a variable indicate
statistical difference at P<0.05
Figure 2: Mean annuli (growth rings) of
scallop shell
Σ SAT
47.72b ± 8.88
73.32a ± 7.06
61.38a,b ± 12.54
68.73a ± 7.79
Σ MUFA
21.84b ± 3.00
31.89a,b ± 4.09
33.86a,b ± 8.56
41.54a ± 5.15
Σ PUFA
P/S
Figure 4: Lipid class analysis of scallop adductor
muscle
ω3
ω6
127.29b ± 28.47 194.40a ± 18.89 147.74a,b ± 30.58 184.10a ± 23.78
2.67a ± 0.20
2.65a ± 0.06
2.41a ± 0.08
2.67a ± 0.07
112.18b ± 23.39 179.91a ±17.40 138.88a,b ± 27.82 171.49a ± 22.35
15.11a ± 6.09
14.20a ± 1.54
8.86a ± 4.06
12.20a ± 2.09
8.16b ± 2.43
12.69a,b ± 0.58
17.13a ± 4.55
14.21a ± 1.59
100
90
a,b a,b
ω3/ω6
a
b
EPA + DHA 102.58b ± 24.24 170.07a ± 17.10 133.74a,b ± 25.92 159.99a ± 18.24
a
% of Total lipid
80
70
Weak
60
Different superscript letters within rows
indicate statistical difference at P<0.05
Not Weak
50
40
Kodiak 1
30
Kodiak 2
20
a
10
0
b
TG
Different superscript letters indicate statistical
difference between groups at P<0.05
Formula 1. Condition Index (CI) of edible meat to
body
S Meat Wt.
X 100 (%)
CI=
S Body Wt.
Table 1: Mean weights and CI of scallop
body and adductor muscle
Body Wt.
Meat Wt.
a
Weak
Not Weak
89.7a
53.5b
21.2a
18.0b
a a,b
a,b
FFA
a,b a,b
b
b
ST
PL
Different superscript letters within a variable indicate
statistical difference at P<0.05
TG Triacylglycerols; FFA Free Fatty Acids; ST Sterol; PL
Phospholipid
Discussion
Proximate composition of NWS, Kodiak 1 and Kodiak 2 are consistent with published data (Krzynowek and
Murphy, 1987), while WS are higher in moisture and lower in protein and carbohydrate than expected.
Conversions of fatty acids into fatty acid methyl ester for analysis was very low due to the high PL content of
the scallop muscle; however, the FA profile is consistent with specimens having high PL levels (Richoux et al,
2005). FA analysis indicated lower levels of key FA in WS than in NWS, Kodiak 1 and Kodiak 2. In general,
analysis quantified that there are significant physical and biochemical differences between WS and NWS, and
not surprisingly, that there are also differences between eastern GOA (Yakutat) and western GOA (Kodiak).
Further research would perhaps shed light on the reasons behind these physical and biochemical differences.
References
AOAC. Helrich K, editor. 1990. Official methods of analysis of the Association of Official Analytical Chemists. 5th ed. Arlington, VA: Official Analytical Chemists, Inc
Bechtel PJ and Oliveira ACM. 2006. Chemical characterization of liver lipid and protein from cold water fish species. J. Food Sci. 71(6):S480-485.
CI
23.6b
33.7a
Different superscript letters within
rows indicate statistical difference at
P<0.05
Krzynowek J, Murphy J. 1987. Proximate composition, energy, fatty acid, sodium, and cholesterol content of finfish, shellfish, and their products. NOAA Technical
Report NMFS 55. U.S. Department of Commerce. NOAA. NMFS. Gloucester, MA. Pp1-52.
Richoux NB, Deibel D, Thompson RJ, Parrish CC. 2005. Seasonal and developmental variation in the fatty acid composition of Mysis mixta (Mysidaxea) and
Acanthostepheia malmgreni (Amphipoda) from the hyperbenthos of a cold-ocean environment (Conception Bay, Newfoundland). J. Plankton Research. Volume 27,
number 8, pp719-733.