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Gelation properties of fatty fish processed with or without added sodium chloride, cryoprotectants and antioxidants
Food Research International
27 (1994) 44349
Gelation properties of fatty fish processed with or without added sodium chloride, cryoprotectantb and antioxidants Hussain M. Bakir,* Herbert 0. Hultid & Stephen D. Kelleher Massachusetts
Agricultural Experiment Station, Department of Food Science, University of Massachusetts/Amherst, Marine Foods Laboratory, Marine Station, Gloucester, MA 01930, USA
The effect of 3% (w/w) added salt; an antioxidant mixture consisting of 0.02% (w/w) t-butylhydroquinone (TBHQ) (based on total lipid), 0.2% (w/w) ascorbate and 0.2% (w/w) sodium tripolyphosphate (STPP) added during the grinding and washing steps; and a cryoprotectant mixture of 4% (w/w) sorbitol, 4% (w/w) sucrose, and 0.2% (w/w) STPP added just prior to gel formation were tested for their effects on true strain and stress at breakage and fold test scores of washed bluefish and mackerel mince. The addition of 3% (w/w) NaCl and the cryoprotectant mixture increased true strain values under all conditions; fold test scores followed similar patterns. The antioxidant mixture gave increased strain values in the absence of the added 3% (w/w) NaCl in both bluefish and mackerel prepared with or without cryoprotectants; in the case of mackerel, the antioxidant mixture gave higher true strain values in the presence of salt as well. Stress values were highly variable and no clear trends were observed with bluefish with any of the parameters; seven out of eight samples of mackerel had lower stress values in the presence of the antioxidant mixture. The results may be useful in designing a process for improving the gelation characteristics of fatty fish. Keywords: gelation, antioxidants and fish protein scombrus), bluefish (Pomatomus altatrix).
INTRODUCTION
gelation, mackerel (Scomber
the processing procedure which led to both improved initial odor characteristics and better storage stability. Fujimoto et al. (1988) prepared a dehydrated sardine meat powder with a high osmotic pressure resin followed by de-fatting of the tissue with liquid carbon dioxide. This reduced lipid content by about 50%. In addition to the problems of lipid oxidation, dark-muscled fish species often have poor gelation characteristics (Iwata et al., 1977; Suzuki, 1981; Tsukamasa & Simizu, 1989). The large amount of red muscle in the flesh of fatty fish causes problems due to its low pH, high fat content, and high content of pro-oxidants (Hultin, 1988); removing this tissue before processing into surimi can improve results (Kelleher et al., 1992). We have recently studied the preparation of fish protein gels from washed tissue in the absence of high concentrations of added salt (Hennigar et al.,
Fatty fish are not popular in the United States as fresh fish and their utilization in non-identifiable products, such as those prepared from minced fish or surimi, would be highly desirable. There are, however, several problems in the use of this material for this purpose. One of these is the oxidation of the lipid component which produces rancid, fishy odors and tastes which are undesirable. Techniques to overcome this problem have been reported by various researchers (Nonaka et al., 1989a,b; Kelleher et al., 1992). Kelleher et al. (1992) introduced an antioxidant mixture early in *Present address: Ceimic Inc., Narragansett, RI 02882, USA. tTo whom correspondence should be addressed. Food Research International 0963-9969/94/$07.00 0 1994 Canadian Institute of Food Science and Technology 443
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H. M. Bakir, H. 0. H&in, S. D. Kelleher
1988, 1989; Vareltzis et al., 1989). The ability to form gels without the high concentrations of salt, usually thought to be required, was species-dependent. Dark fleshed fatty species did not have this capacity (Bakir et al., 1994). In addition, it has been observed that a cryoprotectant mixture improves gelation characteristics of red hake muscle prepared in the absence of high concentrations of NaCl (Bakir et al., 1994). The purpose of the experiments reported here was to determine the effect of the antioxidant mixture and cryoprotectants on the ability of minced whole muscle of two fatty species, Atlantic mackerel and bluefish, to form gels in the presence and absence of added NaCl.
Pressure was applied gradually to the bed by a hydraulic hand-operated Carver laboratory press (Fred S. Carver, Inc., Summit, NJ) over a 2-min period until a gauge reading of 10 000 psig was obtained. The material was held at that pressure for 15 min. Antioxidants were added according to the procedure of Kelleher et al. (1992); t-butylhydroquinone at 0.02% (w/w) of total lipid and 0.2% (w/w) of both ascorbate and STPP based on moisture content were added as soon after grinding as possible. The first wash contained 0.2% (w/w) of both ascorbate and STPP while the two subsequent washes contained only the ascorbate. The last wash also contained 0.15% (w/w) NaCl. Preparation of gels
MATERIALS AND METHODS Fish Bluefish (Pomatomus altutrix) and Atlantic mackerel (Scomber scombrus) were purchased from day boats out of Gloucester, MA. The fish were transported on ice to the laboratory where they were held overnight in a 4°C walk-in refrigerator prior to processing. Sodium ascorbate and tripolyphosphate-penta sodium salt (STPP) were obtained from Sigma Chemical Co., St Louis, MO. tertButylhydroquinone (TBHQ) was obtained from Aldrich Chemical Co., Milwaukee, WI. Sucrose (certified) and sorbitol (enzyme grade) were supplied by Fisher Scientific, Inc., Fair Lawn, NJ. Preparation of washed mince Washed mince was prepared with or without antioxidant treatment. The same general procedure was followed for both. The fish were hand-filleted and skinned after which they were passed through a Hobart grinder Model 4822 (Hobart Corp., Troy, OH) with 0.64-cm plate openings. The ground fish was mixed with three volumes of chilled, deionized water (46°C). The mixture was stirred for 2 min by hand and then allowed to settle for a total wash time of 15 min in a room at 6°C. The washed mince was strained through a fiberglass screen (O-28 mm diameter opening) and the process was repeated twice more. The third wash contained 0.15% (w/w) NaCl. The washed mince was placed in the center of a bed of cheesecloth, four layers thick, which was then folded over the top of the mince such that a secure package was formed to prevent loss of mince during subsequent pressure treatment.
Washed mince was made with and without the antioxidant mixture. Each of these minces was then prepared with or without 3% (w/w) added NaCl and with or without a mixture of cryoprotectants. The cryoprotectant mixture consisted of 4% (w/w) sucrose, 4% (w/w) sorbitol, and 0.2% (w/w) STPP. The cryoprotectants were mixed into the washed minces immediately after the last wash for 3 min using a Kitchen Aid (Kitchen Aid, Inc., St Joseph, MI) mixer. Gels were made from 200-g batches of de-watered fish mince using a food processor model Robot-Coupe R301 Ultra (Robot-Coupe USA, Inc., Ridgeland, MS) for chopping. The chilled mince was placed in the bowl of the processor which had been previously chilled at -20°C. It was chopped at high speed for 2 min. When NaCl was used, it was added slowly during the first minute of chopping. The temperature of the fish paste was kept below 15°C at all times. The fish paste was carefully filled by hand into stainless steel tubes to minimize air pockets and immersed in a water bath at 40°C for 30 min and then immediately transferred to a 90°C water bath for 20 min. The tubes were cooled by placing in a mixture of ice and water for 10 min, after which the gels were removed with a plunger. All the above procedures were carried out on the same day. The gels were then held in a refrigerator (0-4”C) in sealed plastic bags for 24-48 h until tested. Strain and stress The refrigerated samples were allowed to reach room temperature (2O-25°C) prior to testing. A torsion technique, applied to dumb bell-shaped segments of the gels, was used to measure true
Gelationproperties of fatty fish
strain and stress at breakage according to the procedure of Wu et al. (1985). Fold test The fold test score was determined using the procedure of Kudo et al. (1973). A score of 5 indicated the sample could be folded twice without cracking, a score of 4 once without cracking, a score of 3 some cracking when folded in half, and a score of 2 indicated the gel broke on folding once. PH Ten grams of sample was blended for 1 min with 90 ml of distilled water. pH was read by placing an electrode into the resultant slurry and allowing the meter to equilibrate for 30 s. Moisture content Moisture was determined using two procedures. One method used a Cenco rapid moisture determination balance (CSC Scientific Co., Inc., Fairfax, VA) equipped with an infrared lamp. The chopped material was spread thinly on a flat aluminum dish and placed under the lamp until a constant weight was obtained. This method was used to determine moisture content of the minced fish before washing for the purpose of adding the exact amount of antioxidants. The moisture content of the gel was determined as weight loss after drying in an oven at 110°C for 18 h. Lipid content Total lipid was extracted and determined according to the method of Bligh and Dyer (1959). Statistical evaluation Ten samples were used in each replicate. Statistical analysis of means was performed using oneway or two-way analyses of variance as described by Ryan et al. (1985). Multiple comparison of means was determined using the procedures described by Steel and Torrie (1960).
RESULTS AND DISCUSSION Three processing variables were examined for each batch of Atlantic mackerel and bluefish. These
445
variables were salt content, treatment with an antioxidant mixture, and the effect of cryoprotectants. In one set of samples the only salt present was the residue from the 0.15% (w/w) added during the final de-watering. A second group of samples had this residual plus an additional 3% (w/w) salt. Samples from each of these two treatments were either treated or not with the antioxidant mixture in the way described in the Materials and Methods section. Finally, each of the four samples treated as described were further separated into those in which gels were made in the presence of the cryoprotectant mixture or in its absence. This gave a total of eight different samples for each batch of fish. No frozen storage was involved in any of the samples. Three complete experiments utilizing bluefish (Table 1) and two complete experiments using Atlantic mackerel (Table 2) are reported. In all cases there was an increase in true strain in samples with salt compared to those without salt. True strain has been suggested as a measure of the quality of the proteins in gels made from fish muscle proteins (Hamann & Lanier, 1987). In general, fatty fish that have been examined in our laboratory showed a greater loss in true strain in the absence of salt compared to that in its presence than did white-fleshed fish (Bakir et al., 1994). In the absence of the added 3% (w/w) NaCl, the antioxidant mixture produced significant (PI 0.05) increases in true strain values of gels prepared from both bluefish and mackerel, regardless of cryoprotectant use. In the case of mackerel, the antioxidant mixture significantly (PI 0.05) improved the true strain values in the presence of salt as well. There appeared to be a trend toward improvement in bluefish gels prepared with salt and treated with antioxidants, but the results were only statistically significant (PIO.05) in one of the three experiments. It is possible that the antioxidants were more effective with mackerel than with bluefish because oxidation is greater in mackerel than in bluefish. The use of cryoprotectants gave gels with significantly (P10.05) higher values of true strain than samples prepared in the absence of cryoprotectants in every experiment, i.e. for both species and all treatments in each experiment. The cryoprotectant mixture was developed to stabilize muscle proteins against denaturation during frozen storage. In these experiments no freezing or frozen storage was involved. Therefore, the cryoprotectants were affecting true strain in some manner other than
446
H. A4. Bakir, H. 0. Hultin, S, D. Kelleher Table 1. Effects of salt, cryoprotectants (cryo), and antioxidants (AO) on physical properties of blue&b gels Washed mince Experiment 1 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0 Without salt With cryo With A0 Without A0 Without cryo With A0 Without A0 2 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0 Without salt With cryo With A0 Without A0 Without cryo With A0 Without A0 3 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0 Without salt With cryo With A0 Without 0 Without cryo With A0 Without A0
Gels
Water (%)
PH
True strain
Stress
80.1 f 0.1 76.8 f 0.1
6.6 6.4
1.81 f 0.08” 1.59 f 0.16’
22.0 f 3.3* 25.3 f 4.5d
76.7 f 0.9 73.7 + 0.6
6.4 6.0
1.48 f O.llb 1.17 f 0.07”
55.9 f 6.9” 47.5 f 6.3’
78.4 zk0.6 78.1 + 1.5
7.0 6.8
1.53 f O.llb 1.24 + 0.17’
17.4 f 1.P 19.0 f 2.oeJ
79.6 + 4.7 77.7 zk0.2
6.4 5.9
1.05 f 0.07d 0.71 f 0.05’
44.5 Ik 4.76 40.1 * 4.1’
72.2 f 0.5 68.7 f 0.2
6.4 6.3
1.91 f 0.13” 1.85 rt 0.11”
62.4 f 7.1bc 88.9 f 6.5”
74.6 f 0.4 77.6 f 0.3
6.2 6.1
1.49 f 0.056 1.41 * 0.036
64.1 f 5.9b 50.0 * 2.2’
72.6 f 0.0 68.8 rf:0.4
6.7 6.7
1.30 f 0.07’ 1.15 * 0.12d
37.5 f 1.9/ 55.4 f 4. l’d
77.6 f 0.3 79.8 f 0.3
6.6 6.5
0.92 f 0.02’ 0.73 f o.od
50.2 f 4.5” 41.0 * 7.6
60.9 f 1.1 72.0 f 1.6
8.1 6.7
1.87 f 0.11” 1.77 * 0.15”b
78.1 f 10.5” 59.5 f 6.9’
75.6 f 0.3 66.3 f 0.1
6.4 6.3
1.38 + 0.12d 1.31 f 0.14d
35.3 f 4.4d 64.3 f 5.8’
64.8 f 0.0 72.6 f 0.3
8.4 7.0
1.75 f 0.1 lb 144 + 0.05d
77.2 f 8.5” 33.6 f 2.4d
76.2 _+0.3 62.1 f 1.8
7.1 6.8
0.99 + 0.12’ 0.51 f 0,06g
31.9 f 5.4d 27.3 f 4.1d
-
Fold test
Values of true strain and stress in the same column (for each experiment) with different superscripts (u-g) are significantly different PI 0.05). A0 mixture: 0.02% (w/w) t-butylhydroquinone (lipid basis), 0.2% (w/w) ascorbate, 0.2% (w/w) sodium tripolyphosphate (STPP); cryo mixture: 4% (w/w) sorbitol, 4% (w/w) sucrose, 0.2% (w/w) STPP. Strain and stress: n = S-10; moisture: n = 2.
protection against freeze denaturation. Sugars and phosphates can protect proteins from denaturation during heat treatment (Findlay & Barbut, 1992; Konno, 1992) which may account for the
observed data. Although some denaturation is thought to be necessary before gelation of fish muscle proteins can occur, excessive denaturation may lead to poor gel structure. Thus, protection
447
Gelationproperties of fatty jish Table 2. Effects of salt, cryoprotectants (cryo), and antioxidants (AO) on physical properties of mackerel gels Washed mince
-
Stress
Fold test
1.74 + 0.08” 1.57 * o.09bc
67.5 f 2.4’ 95.6 + 6.3”
5 5
6.6 6.6
1.48 f 0.08’ 1.22 k 0.13d
45.9 + 5.5’ 78.9 f 4.5”
5 3
68.0 Y!Z 1.3 69.4 f 0.7
6.9 7.2
1.62 f O.lOb 1.48 f 0.14’
51.2 f 6.2” 84.0 f 14.2”
5 5
80.0 f 0.2 76.4 f 1.4
7.2 7.1
1.16 zk0.11“ 0.86 * 0.03’
52.9 rt 59“ 77.0 f 4.3”
3 2
69.3 + 3.1 62.1 f 1.7
6.8 6.5
1.91 + 0.09” 1.67 f O.llb
46.9 + 5@ 89.2 f 5.3”
5 5
77.4 * 0.7 73.3 + 0.3
6.5 6.4
1.59 + 0.08” 1.40 zkO.lld
54.4 f 5.9’d 75.8 f 5.5b
5 5
70.7 + 0.5 63.4 f 1.6
7.2 7.1
1.49 f O.lO’d 1.24 f 0.05’
43.7 * 4.1’ 56.2 + 4.3’
5 4
78.1 + 0.2 72.6 f 0.1
7.1 6.9
1.12 f 0.04 0.67 f 0.05g
51.4 + 3.9cd 53.6 zk 1.8cd
3 2
Experiment
Water (%)
PH
True strain
1 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0
70.0 f 1.4 65.4 + 0.1
6.9 6.8
79.1 f 1.1 75.9 f 1.4
Without salt With cryo With A0 Without A0 Without cryo With A0 Without A0 2 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0 Without salt With cryo With A0 Without A0 Without cryo With A0 Without A0
Gels
-
Values of true strain and stress in the same column (for each experiment) with different superscripts (u-g) are significantly different PI 0.05). See Table 1 for A0 and cryo compositions. Strain and stress: n = 8-10; moisture: n = 2.
afforded the proteins by the cryoprotectants during heating could have produced gels with higher values of true strain than those without the cryoprotectant mixture. Values of pH in the gels prepared with cryoprotectants generally were somewhat higher than samples prepared in their absence. In many cases, this difference was relatively small, between 0.1 and 0.2 pH units. Nevertheless, this difference in pH could have contributed to the improvement in true strain when the cryoprotectant mixture was used. Trevino et al. (1990) showed that cohesiveness in sardine gels was sensitive to pH. Any increase in pH would probably be due to the STPP of the cryoprotectant mixture. All samples prepared with 3% (w/w) added salt gave fold test scores of 5, except for one of the gel samples prepared from bluefish without antioxi-
dants and cryoprotectants that had a score of 4. All samples prepared without salt but in the presence of both cryoprotectants and antioxidants also gave fold test scores of 5. Samples prepared without salt or antioxidants but with the cryoprotectant mixture gave variable results. The three sets of bluefish gels scored 5, 4, and 3 and the two sets of mackerel gels had fold test scores of 5 and 4. Those samples that were prepared without 3% (w/w) added salt and without the cryoprotectant mixture gave the poorest fold test scores. Nevertheless, samples of this group (without salt, without cryoprotectants) that contained the antioxidant mixture produced higher fold test scores than did samples in the absence of the antioxidants. Results obtained by measuring stress at failure were variable. The only trend that seemed consistent was seen in gels prepared from mackerel.
448
H. AL Bakir, H. 0. H&in, S. D. Kelleher Table 3. Ratio of true strain values in the absence aad presence of antioxidants With salt With cryoprotectant
With salt Without cryoprotectant
Without salt With cryoprotectant
Without salt Without cryoprotectant
Bluefish 1 2 3 Average
0.88 0.97 1.06 0.97
0.79 1.01 0.95 0.92
0.81 0.88 0.82 0.84
0.68 0.79 0.52 0.66
Mackerel 1 2 Average
0.87 1.03 0.95
0.88 0.79 0.84
0.71 0.85 0.78
0.60 0.81 0.71
See Table 1 for antioxidant
and cryoprotectant
compositions.
Table 4. Ratio of true strain vaks in tbe absence and presence of cyoprotectants With salt With AO”
With salt Without A0
Without salt With A0
Without salt Without A0
Bluefish 1 2 3 Average
0.82 0.78 0.74 0.78
0.73 0.76 0.74 0.74
0.69 0.71 0.57 0.66
0.57 0.63 0.35 0.52
Mackerel 1 2 Average
0.85 0.83 0.84
0.77 0.84 0.81
0.72 0.75 0.74
0.58 0.54 0.56
“AO, antioxidant. See Table 1 for A0 and cryoprotectant
compositions.
Seven out of the eight samples that were comparable, except for the presence or absence of the antioxidants, had lower values of stress in the presence of the antioxidants. This was not true of bluefish, where both the presence of salt and cryoprotectants influenced the response of the gels to the presence of the antioxidants. There appeared to be no simple relationship of stress values to the moisture content of the gel. A summary of the effect of treatment with the antioxidant mixture in the presence and absence of 3% (w/w) added salt and the cryoprotectant mixture on the ratio of the true strain values in the absence and presence of the antioxidants is given in Table 3. A ratio close to unity indicates that the antioxidant had little effect on the strain values of that particular sample. As the effect of treatment with the antioxidants increases, the ratio should decrease. The average values for the three experiments with bluefish show a decrease in the ratio in samples prepared with salt/with cryoprotectants > with
salt/without cryoprotectants > without salt/with cryoprotectants > without salt/without cryoprotectants. Results with gels prepared from mackerel showed the same trend as bluefish. The results are suggestive of an increasing effect of the addition of the antioxidant mixture as other factors which produce high strain values, such as salt and the cryoprotectant mixture, are left out. Establishing these trends as fact will take further experimentation. A similar evaluation of the presence of cryoprotectants in the presence or absence of NaCl and the antioxidant mixture is shown in Table 4. The same trend for both species was observed here as was observed for the effect of the antioxidants. The generally lower ratios observed for the gels prepared from both species without the addition of cryoprotectants as opposed to those prepared in their presence, compared to the same samples with and without antioxidants, indicates that the cryoprotectant mixture had a greater role in achieving high true strain values than did the antioxidant mixture in these experiments.
Gelation
properties
ACKNOWLEDGEMENTS This work was supported in part by the Massachusetts Agricultural Experiment Station, by contract No. 2-5618-16 from the National Coastal Resources Research and Development Institute, and by NOAA contract No. 88-NER-205 of the Saltonstall-Kennedy program.
REFERENCES Bakir, H. M., Hultin, H. 0. dc Kelleher, S. D. (1994). Some properties of fish gels made from several Northwest Atlantic species in the presence of high and low salt. J. Food Process. Preset-v. 18, 103-17. Bligh, E. G. & Dyer, W. J. (1959). A rapid method of total lipid extraction and purification. Can. J. Biochem. Physiol., 37, 91 l-7. Findlay, C. J. & Barbut, S. (1992). A response surface investigation of the effects of sodium chloride and tripolyphosphate on the thermal properties of beef muscle. Meat Sci., 31, 155564. Fujimoto, K., Endo, Y., Cho, S.-Y., Watabe, R., Suzuki, Y., Konno, M., Shoji, K., Arai, K. & Saito, S. (1988). A new method for producing Kamaboko from sardine meat powder by dehydration with a high osmotic pressure resin and defatting with liquified carbon dioxide. Nippon Suisan Gakkaishi, 54, 1071.
Hamann, D. D. & Lanier, T. C. (1987). Instrumental methods for predicting seafood sensory texture quality. In Seafood Quality Determination, ed. D. E. Kramer & J. Liston. Elsevier Press, New York, pp. 123-36. Hennigar, C. J., Buck, E. M., Hultin, H. O., Peleg, M. & Vareltzis, K. (1988). The effect of washing and sodium chloride on mechanical properties of fish muscle gels. J. Food Sci., 53, 963-4.
Hennigar, C. J., Buck, E. M., Hultin, H. O., Peleg, M. & Vareltzis, K. (1989). Mechanical properties of fish and beef gels prepared with and without washing and sodium chloride. J. Food Qual., 12, 155-66. Hultin, H. 0. (1988). Potential lipid oxidation problems in fatty fish processing. In Fatty Fish Utilization: Upgrading from Feed to Food, ed. N. Davis. UNC Sea Grant College Program, Raleigh, NC, pp. 185-223.
of fatty Jish
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Iwata, K., Kanna, K. & Okada, M. (1977). Kamaboko formation of mackerel and red sea bream myosins. Bull. Jap. Sot. Sci. Fish., 43, 237.
Kelleher, S. D., Silva, L. A., Hultin, H. 0. & Wilhelm, K. A. (1992). Inhibition of lipid oxidation during processing of washed, minced Atlantic mackerel. J. Food Sci., 57, 1103-8, 1119.
Konno, K. (1992). Suppression of thermal denaturation of myosin subfragment- 1 of Alaska pollock (Theragra chalcogramma) by sorbitol and accelerated inactivation by pyrophosphate. J. Food Sci., 57, 2614. Kudo, G., Okada, M. & Miyauchi, D. (1973). Gel-forming capacity of washed and unwashed flesh of some Pacific coast species of fish. Mar. Fish. Rev., 32(12), 10-15. Nonaka, M., Hirata, F., Saeki, H., Nakamura, M. & Sasamoto, Y. (1989a). Gel forming ability of highly nutritional fish meat for food stuff from sardine. Nippon Suisan Gakkaishi, 55, 2 157-62.
Nonaka, M., Hirata, F., Saeki, H. & Sasamoto, Y. (1989b). Manufacture of highly nutritional fish meat for food stuff from sardines. Nippon Suisan Gakkaishi, 55, 1575-81. Ryan, B. F., Joiner, B. L. & Ryan, T. A. (1985). Minitab Handbook, 2nd edn. P.W.S.-Kent Publishing Co., Boston, MA. Steel, R. & Torrie, J. H. (1960). Principles and Procedures of Statistics. McGraw-Hill, New York, p. 101. Suzuki, T. (1981). Fish and Krill Protein: Processing Technology. Applied Science Publishers, London. Trevino, B., Moreno, V. & Morrissey, M. (1990). Functional properties of sardine surimi related to pH, ionic strength and temperature. In Advances in Fish Technology and Biotechnology for Increased Projitability, ed. M. N. Voigt & J. R. Botta. Technomic Publishing Company, Lancaster, PA, pp. 413-22. Tsukamasa, Y. & Simizu, Y. (1989). The gel-forming properties of the dorsal muscle from Clupezformes and Salmonoidei. Nippon Suisan Gakkaishi, 56, 529-34.
Vareltzis, K., Buck, E. M., Hultin, (1989). Fish gel formation without ment via mixed species. .I. Food 107-21. Wu, M. C., Hamann, D. D. & Lanier, ical and calorimetric investigations systems during thermal processing.
H. 0. & Laus, M. J. added salt: improveProcess. Preserv.. 13, T. C. (1985). Rheologof starch-fish protein J. Texture Studies, 16,
53-74.
(Received 28 July 1993; accepted 1993)
29 November
27 (1994) 44349
Gelation properties of fatty fish processed with or without added sodium chloride, cryoprotectantb and antioxidants Hussain M. Bakir,* Herbert 0. Hultid & Stephen D. Kelleher Massachusetts
Agricultural Experiment Station, Department of Food Science, University of Massachusetts/Amherst, Marine Foods Laboratory, Marine Station, Gloucester, MA 01930, USA
The effect of 3% (w/w) added salt; an antioxidant mixture consisting of 0.02% (w/w) t-butylhydroquinone (TBHQ) (based on total lipid), 0.2% (w/w) ascorbate and 0.2% (w/w) sodium tripolyphosphate (STPP) added during the grinding and washing steps; and a cryoprotectant mixture of 4% (w/w) sorbitol, 4% (w/w) sucrose, and 0.2% (w/w) STPP added just prior to gel formation were tested for their effects on true strain and stress at breakage and fold test scores of washed bluefish and mackerel mince. The addition of 3% (w/w) NaCl and the cryoprotectant mixture increased true strain values under all conditions; fold test scores followed similar patterns. The antioxidant mixture gave increased strain values in the absence of the added 3% (w/w) NaCl in both bluefish and mackerel prepared with or without cryoprotectants; in the case of mackerel, the antioxidant mixture gave higher true strain values in the presence of salt as well. Stress values were highly variable and no clear trends were observed with bluefish with any of the parameters; seven out of eight samples of mackerel had lower stress values in the presence of the antioxidant mixture. The results may be useful in designing a process for improving the gelation characteristics of fatty fish. Keywords: gelation, antioxidants and fish protein scombrus), bluefish (Pomatomus altatrix).
INTRODUCTION
gelation, mackerel (Scomber
the processing procedure which led to both improved initial odor characteristics and better storage stability. Fujimoto et al. (1988) prepared a dehydrated sardine meat powder with a high osmotic pressure resin followed by de-fatting of the tissue with liquid carbon dioxide. This reduced lipid content by about 50%. In addition to the problems of lipid oxidation, dark-muscled fish species often have poor gelation characteristics (Iwata et al., 1977; Suzuki, 1981; Tsukamasa & Simizu, 1989). The large amount of red muscle in the flesh of fatty fish causes problems due to its low pH, high fat content, and high content of pro-oxidants (Hultin, 1988); removing this tissue before processing into surimi can improve results (Kelleher et al., 1992). We have recently studied the preparation of fish protein gels from washed tissue in the absence of high concentrations of added salt (Hennigar et al.,
Fatty fish are not popular in the United States as fresh fish and their utilization in non-identifiable products, such as those prepared from minced fish or surimi, would be highly desirable. There are, however, several problems in the use of this material for this purpose. One of these is the oxidation of the lipid component which produces rancid, fishy odors and tastes which are undesirable. Techniques to overcome this problem have been reported by various researchers (Nonaka et al., 1989a,b; Kelleher et al., 1992). Kelleher et al. (1992) introduced an antioxidant mixture early in *Present address: Ceimic Inc., Narragansett, RI 02882, USA. tTo whom correspondence should be addressed. Food Research International 0963-9969/94/$07.00 0 1994 Canadian Institute of Food Science and Technology 443
444
H. M. Bakir, H. 0. H&in, S. D. Kelleher
1988, 1989; Vareltzis et al., 1989). The ability to form gels without the high concentrations of salt, usually thought to be required, was species-dependent. Dark fleshed fatty species did not have this capacity (Bakir et al., 1994). In addition, it has been observed that a cryoprotectant mixture improves gelation characteristics of red hake muscle prepared in the absence of high concentrations of NaCl (Bakir et al., 1994). The purpose of the experiments reported here was to determine the effect of the antioxidant mixture and cryoprotectants on the ability of minced whole muscle of two fatty species, Atlantic mackerel and bluefish, to form gels in the presence and absence of added NaCl.
Pressure was applied gradually to the bed by a hydraulic hand-operated Carver laboratory press (Fred S. Carver, Inc., Summit, NJ) over a 2-min period until a gauge reading of 10 000 psig was obtained. The material was held at that pressure for 15 min. Antioxidants were added according to the procedure of Kelleher et al. (1992); t-butylhydroquinone at 0.02% (w/w) of total lipid and 0.2% (w/w) of both ascorbate and STPP based on moisture content were added as soon after grinding as possible. The first wash contained 0.2% (w/w) of both ascorbate and STPP while the two subsequent washes contained only the ascorbate. The last wash also contained 0.15% (w/w) NaCl. Preparation of gels
MATERIALS AND METHODS Fish Bluefish (Pomatomus altutrix) and Atlantic mackerel (Scomber scombrus) were purchased from day boats out of Gloucester, MA. The fish were transported on ice to the laboratory where they were held overnight in a 4°C walk-in refrigerator prior to processing. Sodium ascorbate and tripolyphosphate-penta sodium salt (STPP) were obtained from Sigma Chemical Co., St Louis, MO. tertButylhydroquinone (TBHQ) was obtained from Aldrich Chemical Co., Milwaukee, WI. Sucrose (certified) and sorbitol (enzyme grade) were supplied by Fisher Scientific, Inc., Fair Lawn, NJ. Preparation of washed mince Washed mince was prepared with or without antioxidant treatment. The same general procedure was followed for both. The fish were hand-filleted and skinned after which they were passed through a Hobart grinder Model 4822 (Hobart Corp., Troy, OH) with 0.64-cm plate openings. The ground fish was mixed with three volumes of chilled, deionized water (46°C). The mixture was stirred for 2 min by hand and then allowed to settle for a total wash time of 15 min in a room at 6°C. The washed mince was strained through a fiberglass screen (O-28 mm diameter opening) and the process was repeated twice more. The third wash contained 0.15% (w/w) NaCl. The washed mince was placed in the center of a bed of cheesecloth, four layers thick, which was then folded over the top of the mince such that a secure package was formed to prevent loss of mince during subsequent pressure treatment.
Washed mince was made with and without the antioxidant mixture. Each of these minces was then prepared with or without 3% (w/w) added NaCl and with or without a mixture of cryoprotectants. The cryoprotectant mixture consisted of 4% (w/w) sucrose, 4% (w/w) sorbitol, and 0.2% (w/w) STPP. The cryoprotectants were mixed into the washed minces immediately after the last wash for 3 min using a Kitchen Aid (Kitchen Aid, Inc., St Joseph, MI) mixer. Gels were made from 200-g batches of de-watered fish mince using a food processor model Robot-Coupe R301 Ultra (Robot-Coupe USA, Inc., Ridgeland, MS) for chopping. The chilled mince was placed in the bowl of the processor which had been previously chilled at -20°C. It was chopped at high speed for 2 min. When NaCl was used, it was added slowly during the first minute of chopping. The temperature of the fish paste was kept below 15°C at all times. The fish paste was carefully filled by hand into stainless steel tubes to minimize air pockets and immersed in a water bath at 40°C for 30 min and then immediately transferred to a 90°C water bath for 20 min. The tubes were cooled by placing in a mixture of ice and water for 10 min, after which the gels were removed with a plunger. All the above procedures were carried out on the same day. The gels were then held in a refrigerator (0-4”C) in sealed plastic bags for 24-48 h until tested. Strain and stress The refrigerated samples were allowed to reach room temperature (2O-25°C) prior to testing. A torsion technique, applied to dumb bell-shaped segments of the gels, was used to measure true
Gelationproperties of fatty fish
strain and stress at breakage according to the procedure of Wu et al. (1985). Fold test The fold test score was determined using the procedure of Kudo et al. (1973). A score of 5 indicated the sample could be folded twice without cracking, a score of 4 once without cracking, a score of 3 some cracking when folded in half, and a score of 2 indicated the gel broke on folding once. PH Ten grams of sample was blended for 1 min with 90 ml of distilled water. pH was read by placing an electrode into the resultant slurry and allowing the meter to equilibrate for 30 s. Moisture content Moisture was determined using two procedures. One method used a Cenco rapid moisture determination balance (CSC Scientific Co., Inc., Fairfax, VA) equipped with an infrared lamp. The chopped material was spread thinly on a flat aluminum dish and placed under the lamp until a constant weight was obtained. This method was used to determine moisture content of the minced fish before washing for the purpose of adding the exact amount of antioxidants. The moisture content of the gel was determined as weight loss after drying in an oven at 110°C for 18 h. Lipid content Total lipid was extracted and determined according to the method of Bligh and Dyer (1959). Statistical evaluation Ten samples were used in each replicate. Statistical analysis of means was performed using oneway or two-way analyses of variance as described by Ryan et al. (1985). Multiple comparison of means was determined using the procedures described by Steel and Torrie (1960).
RESULTS AND DISCUSSION Three processing variables were examined for each batch of Atlantic mackerel and bluefish. These
445
variables were salt content, treatment with an antioxidant mixture, and the effect of cryoprotectants. In one set of samples the only salt present was the residue from the 0.15% (w/w) added during the final de-watering. A second group of samples had this residual plus an additional 3% (w/w) salt. Samples from each of these two treatments were either treated or not with the antioxidant mixture in the way described in the Materials and Methods section. Finally, each of the four samples treated as described were further separated into those in which gels were made in the presence of the cryoprotectant mixture or in its absence. This gave a total of eight different samples for each batch of fish. No frozen storage was involved in any of the samples. Three complete experiments utilizing bluefish (Table 1) and two complete experiments using Atlantic mackerel (Table 2) are reported. In all cases there was an increase in true strain in samples with salt compared to those without salt. True strain has been suggested as a measure of the quality of the proteins in gels made from fish muscle proteins (Hamann & Lanier, 1987). In general, fatty fish that have been examined in our laboratory showed a greater loss in true strain in the absence of salt compared to that in its presence than did white-fleshed fish (Bakir et al., 1994). In the absence of the added 3% (w/w) NaCl, the antioxidant mixture produced significant (PI 0.05) increases in true strain values of gels prepared from both bluefish and mackerel, regardless of cryoprotectant use. In the case of mackerel, the antioxidant mixture significantly (PI 0.05) improved the true strain values in the presence of salt as well. There appeared to be a trend toward improvement in bluefish gels prepared with salt and treated with antioxidants, but the results were only statistically significant (PIO.05) in one of the three experiments. It is possible that the antioxidants were more effective with mackerel than with bluefish because oxidation is greater in mackerel than in bluefish. The use of cryoprotectants gave gels with significantly (P10.05) higher values of true strain than samples prepared in the absence of cryoprotectants in every experiment, i.e. for both species and all treatments in each experiment. The cryoprotectant mixture was developed to stabilize muscle proteins against denaturation during frozen storage. In these experiments no freezing or frozen storage was involved. Therefore, the cryoprotectants were affecting true strain in some manner other than
446
H. A4. Bakir, H. 0. Hultin, S, D. Kelleher Table 1. Effects of salt, cryoprotectants (cryo), and antioxidants (AO) on physical properties of blue&b gels Washed mince Experiment 1 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0 Without salt With cryo With A0 Without A0 Without cryo With A0 Without A0 2 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0 Without salt With cryo With A0 Without A0 Without cryo With A0 Without A0 3 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0 Without salt With cryo With A0 Without 0 Without cryo With A0 Without A0
Gels
Water (%)
PH
True strain
Stress
80.1 f 0.1 76.8 f 0.1
6.6 6.4
1.81 f 0.08” 1.59 f 0.16’
22.0 f 3.3* 25.3 f 4.5d
76.7 f 0.9 73.7 + 0.6
6.4 6.0
1.48 f O.llb 1.17 f 0.07”
55.9 f 6.9” 47.5 f 6.3’
78.4 zk0.6 78.1 + 1.5
7.0 6.8
1.53 f O.llb 1.24 + 0.17’
17.4 f 1.P 19.0 f 2.oeJ
79.6 + 4.7 77.7 zk0.2
6.4 5.9
1.05 f 0.07d 0.71 f 0.05’
44.5 Ik 4.76 40.1 * 4.1’
72.2 f 0.5 68.7 f 0.2
6.4 6.3
1.91 f 0.13” 1.85 rt 0.11”
62.4 f 7.1bc 88.9 f 6.5”
74.6 f 0.4 77.6 f 0.3
6.2 6.1
1.49 f 0.056 1.41 * 0.036
64.1 f 5.9b 50.0 * 2.2’
72.6 f 0.0 68.8 rf:0.4
6.7 6.7
1.30 f 0.07’ 1.15 * 0.12d
37.5 f 1.9/ 55.4 f 4. l’d
77.6 f 0.3 79.8 f 0.3
6.6 6.5
0.92 f 0.02’ 0.73 f o.od
50.2 f 4.5” 41.0 * 7.6
60.9 f 1.1 72.0 f 1.6
8.1 6.7
1.87 f 0.11” 1.77 * 0.15”b
78.1 f 10.5” 59.5 f 6.9’
75.6 f 0.3 66.3 f 0.1
6.4 6.3
1.38 + 0.12d 1.31 f 0.14d
35.3 f 4.4d 64.3 f 5.8’
64.8 f 0.0 72.6 f 0.3
8.4 7.0
1.75 f 0.1 lb 144 + 0.05d
77.2 f 8.5” 33.6 f 2.4d
76.2 _+0.3 62.1 f 1.8
7.1 6.8
0.99 + 0.12’ 0.51 f 0,06g
31.9 f 5.4d 27.3 f 4.1d
-
Fold test
Values of true strain and stress in the same column (for each experiment) with different superscripts (u-g) are significantly different PI 0.05). A0 mixture: 0.02% (w/w) t-butylhydroquinone (lipid basis), 0.2% (w/w) ascorbate, 0.2% (w/w) sodium tripolyphosphate (STPP); cryo mixture: 4% (w/w) sorbitol, 4% (w/w) sucrose, 0.2% (w/w) STPP. Strain and stress: n = S-10; moisture: n = 2.
protection against freeze denaturation. Sugars and phosphates can protect proteins from denaturation during heat treatment (Findlay & Barbut, 1992; Konno, 1992) which may account for the
observed data. Although some denaturation is thought to be necessary before gelation of fish muscle proteins can occur, excessive denaturation may lead to poor gel structure. Thus, protection
447
Gelationproperties of fatty jish Table 2. Effects of salt, cryoprotectants (cryo), and antioxidants (AO) on physical properties of mackerel gels Washed mince
-
Stress
Fold test
1.74 + 0.08” 1.57 * o.09bc
67.5 f 2.4’ 95.6 + 6.3”
5 5
6.6 6.6
1.48 f 0.08’ 1.22 k 0.13d
45.9 + 5.5’ 78.9 f 4.5”
5 3
68.0 Y!Z 1.3 69.4 f 0.7
6.9 7.2
1.62 f O.lOb 1.48 f 0.14’
51.2 f 6.2” 84.0 f 14.2”
5 5
80.0 f 0.2 76.4 f 1.4
7.2 7.1
1.16 zk0.11“ 0.86 * 0.03’
52.9 rt 59“ 77.0 f 4.3”
3 2
69.3 + 3.1 62.1 f 1.7
6.8 6.5
1.91 + 0.09” 1.67 f O.llb
46.9 + 5@ 89.2 f 5.3”
5 5
77.4 * 0.7 73.3 + 0.3
6.5 6.4
1.59 + 0.08” 1.40 zkO.lld
54.4 f 5.9’d 75.8 f 5.5b
5 5
70.7 + 0.5 63.4 f 1.6
7.2 7.1
1.49 f O.lO’d 1.24 f 0.05’
43.7 * 4.1’ 56.2 + 4.3’
5 4
78.1 + 0.2 72.6 f 0.1
7.1 6.9
1.12 f 0.04 0.67 f 0.05g
51.4 + 3.9cd 53.6 zk 1.8cd
3 2
Experiment
Water (%)
PH
True strain
1 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0
70.0 f 1.4 65.4 + 0.1
6.9 6.8
79.1 f 1.1 75.9 f 1.4
Without salt With cryo With A0 Without A0 Without cryo With A0 Without A0 2 With salt With cryo With A0 Without A0 Without cryo With A0 Without A0 Without salt With cryo With A0 Without A0 Without cryo With A0 Without A0
Gels
-
Values of true strain and stress in the same column (for each experiment) with different superscripts (u-g) are significantly different PI 0.05). See Table 1 for A0 and cryo compositions. Strain and stress: n = 8-10; moisture: n = 2.
afforded the proteins by the cryoprotectants during heating could have produced gels with higher values of true strain than those without the cryoprotectant mixture. Values of pH in the gels prepared with cryoprotectants generally were somewhat higher than samples prepared in their absence. In many cases, this difference was relatively small, between 0.1 and 0.2 pH units. Nevertheless, this difference in pH could have contributed to the improvement in true strain when the cryoprotectant mixture was used. Trevino et al. (1990) showed that cohesiveness in sardine gels was sensitive to pH. Any increase in pH would probably be due to the STPP of the cryoprotectant mixture. All samples prepared with 3% (w/w) added salt gave fold test scores of 5, except for one of the gel samples prepared from bluefish without antioxi-
dants and cryoprotectants that had a score of 4. All samples prepared without salt but in the presence of both cryoprotectants and antioxidants also gave fold test scores of 5. Samples prepared without salt or antioxidants but with the cryoprotectant mixture gave variable results. The three sets of bluefish gels scored 5, 4, and 3 and the two sets of mackerel gels had fold test scores of 5 and 4. Those samples that were prepared without 3% (w/w) added salt and without the cryoprotectant mixture gave the poorest fold test scores. Nevertheless, samples of this group (without salt, without cryoprotectants) that contained the antioxidant mixture produced higher fold test scores than did samples in the absence of the antioxidants. Results obtained by measuring stress at failure were variable. The only trend that seemed consistent was seen in gels prepared from mackerel.
448
H. AL Bakir, H. 0. H&in, S. D. Kelleher Table 3. Ratio of true strain values in the absence aad presence of antioxidants With salt With cryoprotectant
With salt Without cryoprotectant
Without salt With cryoprotectant
Without salt Without cryoprotectant
Bluefish 1 2 3 Average
0.88 0.97 1.06 0.97
0.79 1.01 0.95 0.92
0.81 0.88 0.82 0.84
0.68 0.79 0.52 0.66
Mackerel 1 2 Average
0.87 1.03 0.95
0.88 0.79 0.84
0.71 0.85 0.78
0.60 0.81 0.71
See Table 1 for antioxidant
and cryoprotectant
compositions.
Table 4. Ratio of true strain vaks in tbe absence and presence of cyoprotectants With salt With AO”
With salt Without A0
Without salt With A0
Without salt Without A0
Bluefish 1 2 3 Average
0.82 0.78 0.74 0.78
0.73 0.76 0.74 0.74
0.69 0.71 0.57 0.66
0.57 0.63 0.35 0.52
Mackerel 1 2 Average
0.85 0.83 0.84
0.77 0.84 0.81
0.72 0.75 0.74
0.58 0.54 0.56
“AO, antioxidant. See Table 1 for A0 and cryoprotectant
compositions.
Seven out of the eight samples that were comparable, except for the presence or absence of the antioxidants, had lower values of stress in the presence of the antioxidants. This was not true of bluefish, where both the presence of salt and cryoprotectants influenced the response of the gels to the presence of the antioxidants. There appeared to be no simple relationship of stress values to the moisture content of the gel. A summary of the effect of treatment with the antioxidant mixture in the presence and absence of 3% (w/w) added salt and the cryoprotectant mixture on the ratio of the true strain values in the absence and presence of the antioxidants is given in Table 3. A ratio close to unity indicates that the antioxidant had little effect on the strain values of that particular sample. As the effect of treatment with the antioxidants increases, the ratio should decrease. The average values for the three experiments with bluefish show a decrease in the ratio in samples prepared with salt/with cryoprotectants > with
salt/without cryoprotectants > without salt/with cryoprotectants > without salt/without cryoprotectants. Results with gels prepared from mackerel showed the same trend as bluefish. The results are suggestive of an increasing effect of the addition of the antioxidant mixture as other factors which produce high strain values, such as salt and the cryoprotectant mixture, are left out. Establishing these trends as fact will take further experimentation. A similar evaluation of the presence of cryoprotectants in the presence or absence of NaCl and the antioxidant mixture is shown in Table 4. The same trend for both species was observed here as was observed for the effect of the antioxidants. The generally lower ratios observed for the gels prepared from both species without the addition of cryoprotectants as opposed to those prepared in their presence, compared to the same samples with and without antioxidants, indicates that the cryoprotectant mixture had a greater role in achieving high true strain values than did the antioxidant mixture in these experiments.
Gelation
properties
ACKNOWLEDGEMENTS This work was supported in part by the Massachusetts Agricultural Experiment Station, by contract No. 2-5618-16 from the National Coastal Resources Research and Development Institute, and by NOAA contract No. 88-NER-205 of the Saltonstall-Kennedy program.
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(Received 28 July 1993; accepted 1993)
29 November