JFS
S: Sensory and Nutritive Qualities of Food
Influence of Commercial Diets on Quality Aspects of Cultured Gulf of Mexico Surgeon (Ancipenser oxyrinchus desotoi) A.C.M. OLIVEIRA, S.F ABAN, C.A. SIMS, AND K.M. POR TIER S.F.. O’KEEFE, M. BAL ALABAN ORTIER
ABSTRA CT ultur ed stur geons w er e fed commer cially av ailable diets for mulated for hybr id bass out. ABSTRACT CT:: C Cultur ultured sturgeons wer ere commercially available formulated hybrid bass,, catfish, and tr trout. The impact of these diets in the quality of the edible muscle was investigated through determination of processing yields oximate compositions ofiles y char acter istics tur geon fed the yields,, pr pro compositions,, fatty acid pr profiles ofiles,, muscle color color,, and sensor sensory character acteristics istics.. S Stur turgeon catfish diet were significantly smaller but dressed fillets (percent live weight) were similar for all feeds. Consumer visual acceptability scor es w er e highest for fillets fr om fish fed the catfish diet, and color differ ences w er e deter scores wer ere from differences wer ere deter-mined. Sturgeon fillets from fish fed the trout diet presented a yellowish orange coloration instead of a pale pink coloration. Results show that the diets tested had no detrimental impact in the composition of sturgeon fillets. Keywor ds: fish, stur geon, sensor y, machine vision, fatty acids eywords: sturgeon, sensory
Introduction
G
S: Sensory & Nutritive Qualities of Food
ulf of Mexico sturgeons, also known as Gulf sturgeons, are a subspecies of the Atlantic sturgeon (Ancipenser oxyrhynchus Mitchill) (Vladykov 1955). The 1st Gulf sturgeon fishery started in Tampa Bay, Fla., U.S.A., in 1886 and remained in operation for a short period time (Huff 1975). In 1890, the stock was already depleted, and the fishery was abandoned. A few years later, a gill-net fishery was initiated in Suwannee River, Fla., U.S.A., to sell the meat rather than caviar (Huff 1975). In 1917, drift nets with 6-inch mesh were being used and the fish size was rapidly declining (Huff 1975). The Suwannee River had the healthiest and most viable population ranging from 2250 to 3300 fish averaging about 18 kg (USFWS 1995). The Suwannee River maintained a commercial fishery from 1970 until 1984, when the State of Florida prohibited harvest and possession. Adult sturgeon numbers in the Suwannee were drastically reduced by large commercial catches in 1983 and 1984 (Barkuloo 1988). The U.S. Fish and Wildlife Service (FWS) and Natl. Marine Fisheries Service designated the Gulf sturgeon to be a threatened subspecies, pursuant to the Endangered Species Act of 1973 (USFWS 1995). This listing became official in 1991, and as part of the listing, a special rule was promulgated to allow taking of subspecies for educational purposes, scientific purposes, the enhancement of propagation or survival of the subspecies, zoological exhibition, and other conservation purposes consistent with the ESA (USFWS 1995). The 1st hormone-induced ovulation and spawning of Gulf of Mexico sturgeon took place in 1989 at a hatchery on the Suwannee River (USFWS 1995). The Univ. of Florida in cooperation with the FWS and Caribbean Conservation Corps produced about 60000 fry for fish culture programs in the state (Bardi 1997). In the United
MS 20030627 Submitted 11/4/03, Revised 1/9/04, Accepted 6/14/04. Author Oiveira is with Fishery Industrial Technology Center, Univ. of Alaska Fairbanks, Kodiak, AK 99615. Author O’Keefe is with Dept. of Food Science and Technology, Virginia Tech, Blacksburg, Va. Authors Balaban and Sims are with Food Science and Human Nutrition Dept., Univ. of Florida, Gainesville, Fla. Author Portier is with Dept. of Statistics, IFAS, Univ. of Florida, Gainesville, Fla. Direct inquiries to author Oliveira (E-mail:
[email protected]).
S278 JOURNAL OF FOOD SCIENCE—Vol. 69, Nr. 7, 2004 Published on Web 8/24/2004
States, commercial aquaculture of white sturgeon (Ancipenser transmontanus) is a high-profit business (Mims and others 2002). White sturgeon eggs are high-priced (about $113/lb to $531/lb), and sturgeon meat is premium-priced (about $11.0/kg to $13.2/kg) (Mims and others 2002). There is great potential for commercialization of Gulf of Mexico sturgeon meat and caviar in domestic and international markets. However, there are no commercially available diets specifically formulated for Gulf sturgeon, and very little information can be found in the literature regarding the chemical composition of its edible muscle. One of the few studies in this area was conducted by Chen and others (1995). The researchers compared the fatty acid profiles of 13 wild Gulf sturgeons to the fatty acid profile of cultured Gulf sturgeons fed a salmonid diet. The authors showed that fatty acids signature can be used to differentiate between wild and cultured stocks. The 1st objective of this study was to evaluate the impact of 3 different commercially available diets on headed and gutted (H&G) and dressed fillet yields of Gulf sturgeon. The 2nd objective was to investigate dietary effects on quality parameters of Gulf sturgeon edible muscle such as color, proximate composition, fatty acid profile, and sensory aspects of Gulf sturgeon. This research was conducted at a time when the State of Florida was promoting and encouraging aquaculture of Gulf of Mexico sturgeon. Since that time, issues of fish status have negatively impacted interest in this fish for aquaculture. However, the species is identical in most ways to the Atlantic sturgeon (Vladykov 1955), and results are applicable to Atlantic sturgeon, which is cultured in Canada and elsewhere.
Materials and Methods
A
ll Gulf sturgeons used in this study were artificially spawned at the Univ. of Florida during 1998. Fish were kept in circular tanks under recommended conditions, as recently reported by Mims and others (2002). Note that water temperature is critical for optimal sturgeon growth, which occurs at 68 °F to 79 °F. Water temperatures above 82 °F cause fish to slow or stop feeding and growth (Mims and others 2002). Therefore, during the feeding trial, close control of water temperature was critical. Water quality was strictly controlled © 2004 Institute of Food Technologists Further reproduction without permission is prohibited
Quality of sturgeon fed different commercial diets . . .
Cooking procedure Two hundred milliliters of distilled water were added to each of the 3 large pans, labeled for each diet, and a steamer basket was placed into each pan. Water was brought to a boil. Three fillets from each treatment were steamed at a time, in baskets, for 3 min. Fillets were then turned over and steamed for an additional 4 min, cooled, and cut into 2 cm2 pieces before serving to sensory panelists while warm. Cooking water was discarded, and pans were rinsed for every batch.
er end of the scale equivalent to “dislike extremely,” and a score of 9 (maximum score) to “like extremely.” A total of 67 panelists participated in the study, and every panelist evaluated each sample twice.
Tr iangle test for differ ence difference Cooked fillets from sturgeon fed the 3 diets were compared in 3 separate triangle tests. The procedures described by Botta (1995) were used. Samples were coded with 3-digit random numbers, and randomized for presentation order and placement on the tray. Each panelist received a tray with 3 small, coded plastic cups containing 2 to 3 pieces of cooked sturgeon fillets. A plastic fork, an unsalted cracker, and a cup of water were also provided. Panelists were asked to taste the cooked sturgeon samples in the order presented. They were presented 3 trays and asked to take a 5- to 10min break between evaluations. Fish were steamed just before serving and there were no measured temperature differences between samples. A total of 35 panelists participated in this test.
Consumer attribute analysis test A group of 7 people with fair experience in sensory evaluation of aquatic food products define the attributes used during this test in preliminary sensory evaluations of cooked sturgeon fillets. The attributes selected were tenderness, moistness, fishiness, rubberiness, and acceptability. This test was basically a consumer acceptability test in which untrained panelists rated a few attributes in addition to acceptability. Each panelist received a tray with 3 small, coded plastic cups containing 2 to 3 pieces of cooked sturgeon fillets. A plastic fork, an unsalted cracker, and a cup of water were also provided. Panelists were asked to taste samples in the order presented. A total of 66 panelists took part. Unstructured scales (15 cm) with verbal anchors at both ends were used (Botta 1995). Panelists were trained to use unstructured scales with anchors before the evaluation.
Proximate analysis
All samples were tasted in the sensory evaluation laboratory in the Food Science and Human Nutrition Dept. (FSHN) at the Univ. of Florida. Panelists included in all sensory evaluations were faculty, staff, and student at FSHN ranging in age from 18 to 70y. Panelists participating in all sensory evaluations were randomly selected and untrained. All panelists included in the sensory evaluations claimed to consumed fish or fish products at least twice a month. The ratio of females to males varied from 60:40 to 40:60 for all sensory evaluations. Ethnicity of participants was not recorded.
Six sturgeon fillets were used from each diet treatment. Each fillet was comminuted to a paste using a standard food processor. A portion of 100 g of each of the commercial diets was pulverized using a mortar and pestle. Moisture and ash were determined according to AOAC method 938.08 (Helrich 1990). Protein was determined by Micro-Kjeldahl, and 2 blanks were conducted for every batch of 6 samples (Woyewoda and others 1986). Lipid content was determined using a modified Bligh and Dyer method (Christie 1982). Oils were stored in a screw-cap tube flushed with nitrogen and stored at –80 °C until preparation of methyl esters for gas chromatography (GC) analysis. All analyzes were duplicated.
Consumer visual acceptability test
Fatty acid pr ofile and gas chr omatogr aphy analysis profile chromatogr omatography
Six trays (70 × 35 × 20-cm height) containing a layer of approximately 15 cm of crushed ice were used to present sturgeon dressed fillets. Four fillets of the same treatment were placed in each tray, for a total of 2 trays for every treatment. Each tray was coded with 3-digit distinct random numbers, and covered with a transparent plastic film to mimic presentation at a seafood counter. Trays were placed on 2 separate tables with each table having 3 trays, 1 for every group of sturgeon dressed fillets. Therefore, results from each panelist were replicated. Panelists did not know that the test was duplicated and received 2 separate ballots to fill out for inspection of samples on each table. Ballots consisted of one 9-point hedonic scale for acceptability for each sample and a question about whether the participant would be willing to buy the product based on its appearance. A score of 1 (minimum score) was assigned for the low-
Fatty acid methyl esters were prepared from lipid extracts according to Maxwell and Marmer (1983). Fatty acid methyl esters were placed in a 2-mL GC auto-sampler snap-cap amber vials with Teflon-lined septa, and stored under nitrogen at –30 °C until analysis. A GC model 14A (Shimadzu, Norcross, Ga., U.S.A.) fitted with a DB225 (30 m × 0.25-mm inner dia; 0.25-m film) capillary column (J&W, Folsom, Calif., U.S.A.) was used for fatty acid analysis. Hydrogen was used as carrier gas at a linear-flow velocity of 40 cm/s. Injector and detector temperatures were 275 °C, and the oven was programmed from 140 °C to 240 °C at 4 °C/min. Total run time was 25 min. The oven was held at 240 °C for 10 min after the run to ensure elution of high boiling compounds. A Shimadzu CR5A reporting integrator was used for data collection and peak area determinations. Standards used to identify peaks were Supleco 37 (Supleco,
Sensory evaluations
URLs and E-mail addresses are active links at www.ift.org
Vol. 69, Nr. 7, 2004—JOURNAL OF FOOD SCIENCE
S279
S: Sensory & Nutritive Qualities of Food
throughout the feeding trial to meet the recommended concentrations of dissolved oxygen (>5.0 mg/L), alkalinity, hardness (50 to 400 mg/L as CaCO3), pH (6.5 to 8.5), salinity (0 to 3 ppt), nitrite (
