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Shellfish (Mussel) Processing and Components
C H A P T E R
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Shellfish (Mussel) Processing and Components Sergio Almonacid*, †, Joselyn Bustamante*, Ricardo Simpson*, †, Marlene Pinto* *Department of Chemical and Environmental Engineering, Universidad Técnica Federico Santa María, Valparaíso, Chile, †Centro Regional para el Estudio de Alimentos Saludables (CREAS), Valparaíso, Chile
CHAPTER POINTS • I ntegrated average harvest of mussels in China, Spain, Chile, and Thailand, was 1,272,131 t, 65% of the total world production. • Raw mussels are a good source of proteins, vitamin B12, Fe, P, and omega-3 fatty acids (DHA + EPA). • Mussels are mainly processed through precooking, freezing, or canning. • The main effect of processing on mussel components is concentration due to water loss. Leaching and reaction have a minor influence. • The consumption of 100 g of canned or frozen mussel meat can satisfy more than 20% of the recommended daily allowance of proteins, vitamin B12, Fe, P, and omega-3 fatty acids (DHA + EPA).
INTRODUCTION Crustaceans and mollusks have increased substan tially in the last 50 years, from 166,975 t in 1950 to approximately 2 million t in 2010. This growth is almost entirely due to the increase in aquaculture production, which was particularly rapid in the 1990s. World produc tion of mussel aquaculture or farming increased from approximately 1 million t in 1990 to nearly 1.8 million t in 2010, which represents a value of US$ 1.5 billion, with an average growth rate of 3.5% annually during this period. It is important to highlight that current world production of mussels relies on farming, representing 95% of the total production in 2010 (FAO, 2007). The
Processing and Impact on Active Components in Food http://dx.doi.org/10.1016/B978-0-12-404699-3.00054-8
mussel farming industry reached a significant produc tion level in the Netherlands with the aquaculture cul tivation of the common mussel, also known as the blue shell mussel (Mytilus edulis). In the 1950s, while countries such as Spain, China, and Italy showed a production of less than 3000 t, the Netherlands harvested annually more than 50,000 t of mussels. The remarkable develop ment of mussel harvesting in the Netherlands achieved a maximum of 120,000 t/year in the 1970s, which has since declined to 40,000–100,000 t/year (FAO, 2012). China is the main producer of mussels, at 700,000 t/ year in 2010, mainly of the species commonly known as sea mussel nei (Mytilus galloprovincialis). The production of mussels in China has grown rapidly in the past 30 years, especially in the 1980s, with an average of 22.1% annual growth rate. In the period between 1980 and 2010, the average annual growth rate was 9.7% (FAO, 2012). Mussel aquaculture is highly concentrated in China, Spain, Chile, and Thailand, whose total average harvest, between 2005 and 2010, accounted for 65% of the total world production, 1,272,131 t/year in 2010. The diversity of cultivated species under the denomi nation of mussels includes 13 species, and according to the world aquaculture production of the Mytilidae, the spe cies Mytilus galloprovincialis is among the most important considering that China and Spain produced 796,698 t of it, on average, between 2005 and 2010. However, in terms of economical implications, the main species is the Chilean mussel (Mytilus chilensis), with a total annual production of US$ 416,561, but the blue mussel (Mytilus edulis) may be the most relevant species given its ratio of US$ per ton of mussel, evaluated at 1.75. This species of mussel reaches its commercial size of two inches after about three years growth. The shells of fresh mussels are hermetically closed or they close when touched (FAO, 2012). Common
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54. MUSSEL PROCESSING
mussels are widely distributed in European waters, extending from the White Sea off of Russia as far south as the Atlantic coast of south France. Mytilus edulis has a very wide distribution, mainly due to its ability to withstand wide fluctuations in salinity, temperature, and oxygen tension. The species is well acclimated to a temperature range of 5–20°C, with an upper limit of thermal tolerance approximately 29°C for adults (FAO, 2004).
HOW COMPOSITION IS ALTERED Nutritional Composition of Mussels Marine-derived foods are a good source of omega-3 fatty acids and have numerous nutrition and health ben efits. Their proteins possess a well-balanced amino acid composition, which may be used directly as a source of amino acids or in preparations such as dispersions or hydrolyzed solutions (Shahidi, 2004). From a nutri tional perspective, mussels represent an excellent sea food choice. They are low in calories and fat and high in protein, as well as rich in many micronutrients, such as vitamins and minerals. Table 54.1 shows the proximal composition of raw mussels, including micronutrients. As with most seafood, mussels are rich in protein, 12% wet base (Table 54.1). They are similar to beef pro tein in quantity and quality, but with less saturated fat, 0.4 as compared with 1.2 g lipid/100 g of product (USDA, 2012). The recommended daily protein intake is 0.75 g/kg body weight (García-Gabarra, 2006). For example, for a person of 70 kg, the daily protein intake should be 52.5 g, which means that with 100 g of mussels, this person would satisfy approximately 23% of his/her requirements. Although mussels are low in lipids, these are of high quality and provide a healthy contribution to the diet, based on their significant concentration of polyunsatu rated and monounsaturated fatty acids (Table 54.1). Today, the amount of fat consumed is considered impor tant, as is its quality. It is desirable that foods include an adequate amount and proportion of essential fatty acids (EFA), omega-6/omega-3, an appropriate amount of monounsaturated fatty acids, a low amount of satu rated fatty acids and, ideally, no fatty acids with transisomers. Mussels are low in total and saturated fat, and more important, this type of mollusk is one of the richest sources of omega-3 fatty acids. Some important traits of omega-3 fatty acids are (Byrd-Bredbenner et al., 2009):
• E ssential for normal development and function of the retina. • Help to regulate nerve transmission.
• R egulate blood pressure, blood clotting, body temperature, inflammation or hypersensitivity reactions, and immune and allergic responses. • Maintain normal kidney function and fluid balance.
Compared with other sources of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA), blue mussels are a good source of these essential fatty acids, 0.44 g/100 g of fresh produce, contrasted with 0.4 and 0.5 g/100 g for Crustaceans and general Mollusks, respectively (USDA, 2012). In 2009, the European Food Safety Authority (EFSA) published recommendations with regard to PUFAs, advising a dose of 2 g/day of fatty omega-3 alpha-linolenic acid (ALA) and 250 mg/day of the longchain omega-3 fatty acids EPA and DHA (Bresson et al., 2009). The Japan Society for Lipid Nutrition has recom mended a reduction of energy intake of 3–4% for Japanese people, whose average consumption of omega-3 fatty acids of 2.6 g/day, including approximately 1 g/day of EPA + DHA (Hamazaki and Okuyama, 2003). Con sidering that the recommended daily allowance (RDA) of EPA + DHA is 1 g/day, 100 g of fresh mussel provides 44% of the recommended dose. Mussels incorporate important amounts of trace ele ments and minerals necessary to the diet (Do Amaral et al., 1998). Table 54.1 shows information regarding the content of vitamins and minerals provided by 100 g of fresh mussels, compared with the RDA and adequate intake (AI). The per cent contributions to the RDA of mussels’ micronutrients are shown in the same table. The contribution of vitamin B12 is the most significant in proportion to the RDA, whose contribution by 100 g of fresh mussels is 12 μg, or 500% of the RDA (Table 54.1). Vitamin B12 helps the body maintain sheaths around nerve fibers, helps activate another B-vitamin called folic acid, and participates in many cellular processes (Wardlaw et al., 2009). García-Gabarra (2006) reported that the upper-level (UL) or maximum intake of vitamin B12 in adults aged between 19 and 65 years is 1000 μg, a quantity 100-times greater than the content of vitamin B12 in 100 g of fresh Mussel. No toxic or adverse effects have been associated with large intake of vitamin B12, either from food or supplements, in healthy people (Linus Pauling Institute, 2012).
Processing Despite the above considerations, mussels are not consumed raw but are processed in different ways, and their nutritional characteristics may be affected by processing. Mussel processing, regardless of the final product, consists of a first, common stage of precooking, followed by a second stage of processing,
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How Composition is Altered
TABLE 54.1 Proximate and RDA of Nutrients Found in Mussel Nutrient
Unit
100 g raw Mussel RDA man
Water
g
80.58
Energy
kcal
86
Protein
g
11.9
Total lipid (fat)
g
2.24
Carbohydrate
g
3.69
Fiber, total dietary
g
0
Sugar, total
g
0
RDA Woman
100 g raw Mussel
% Contribution Man/Woman
PROXIMATE
MINERALS Calcium, Ca
mg
1000*
1200*
26
2.6/2.2
Iron, Fe
mg
8
18
3,95
49/22
34
8/1
(420a)
(320a)
Magnesium, Mg
mg
400
Phosphorus, P
mg
700
700
197
28/28
Potassium, K
g
4,7*
4,7*
0.32
7/7
Sodium, Na
g
1,5 (1,3/1,2)*
1,5 (1,3/1,2)*
0.29
24/24
Zinc, Zn
mg
11
8
1,6
15/20
Vitamin C, total ascorbic acid
mg
90
75
8
9/11
Thiamin
mg
1,2
1,1
0,16
13/15
Riboflavin
mg
1,3
1,1
0,21
16/19
Niacin
mg
16
14
1,6
10/11
Vitamin B6
mg
1,3/1,7
1,3/1,5
0,05
3/3
Folate, DFE
μg
400
400
42
11/11
Vitamin B12
μg
2,4
2,4
12
500/500
Vitamin A, RAE
μg
900
700
48
5/7
Vitamin A, IU
IU
Vitamin E (alpha-tocopherol)
mg
15
15
0,55
4/4
Vitamin D (D2 + D3)
μg
5 (10/15)
6 (10/15)
0
—
Vitamin D
IU
0
—
Vitamin K (phylloquinone)
μg
0,1
—
310
VITAMINS
160
120
90
LIPIDS Fatty acids, total saturated
g
0.425
Fatty acids, monounsaturated
g
0.507
Fatty acids, polyunsaturated
g
0.606
Cholesterol
g
0.028
Data from USDA, 2012. AI, Adequate Intake.
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54. MUSSEL PROCESSING
FIGURE 54.1 Schematic representation of mussel processing.
which is usually freezing or sterilization (canning) (Figure 54.1). Bello et al. (2012) described these pro cesses in mussels in some detail. They involve the above steps plus some auxiliary operations that result in the production of cooked mussel meat from fresh mussels. Raw, fresh material is collected from hatcheries and
transported to the processing plant. At the plant, they are inspected for quantity and quality, and the selected units continue to the following steps of storage, washing, and conditioning. In the final stage, mussels are either fro zen or commercially sterilized (Figure 54.1). When steril ized, mussel meat that has been cooked and shucked is
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How Composition is Altered
ready for canning. According to Almonacid et al. (2012), this stage is divided into five operations: filling cans with mussels, adding coverage liquid (salted brine), seaming the containers and, finally, heat-processing to commercial sterility (retorting). Once mussel meats are packed into the open cans, hot liquid brine, consisting of an aqueous solution of 1–3% salt and 0.1% citric acid is added to each can at a temperature of 75°C (Almonacid et al., 2012). Thermal sterilization of filled and sealed cans is carried out in saturated steam at temperatures in the range of 110–130°C for the specified time to achieve a final process lethality of Fo = 6 min (or the time speci fied by the process authority). After heating, a final cool ing step is applied with water at ambient temperature (19–21°C). Finally, cans are stored at room temperature and have a shelf-life of at most 4 years under these con ditions (Holdsworth and Simpson, 2007). The mussel-freezing process starts with cooked and shucked meat. It is grouped into blocks of about one inch, which are laid out on trays. The freezing process is usually carried out in blast freezers at −40°C for a long enough time to obtain a temperature of −20°C in the geometrical center of the mussel meat block. The process normally takes approximately 50 min. After that, the unwrapped meat is glazed to mitigate the water loss by evaporation. Finally, glazed and not necessarily packed meats are stored in a cold room at a temperature of −20 °C. Their shelf-life under these conditions should be 8–9 months (Shafiur, 2012). The processing effects on mussel composition are mainly caused by two mechanisms: material exchange between mussel meat and processing media (water, steam, brine, air), and thermal inactivation by high tem perature (molecular lysis or reaction) when mussels are sterilized. Most water loss takes place during the first, common stage of pre-cooking, and the main effect on the proximal composition of mussel meat is by concentra tion. Slabyj (1977) reported a dry weight increase from 18.8% to 25.4% due to water lost during pre-cooking of blue mussels, which means a decrease in water content from 81.2 to 74.7%. Krzynowek and Wigginn (1979) used boiling water for 2 min and observed a change in mois ture from 78.7 to 76.8%. The difference in water loss was due to the pre-cooking method, steaming for 6 min in the first case and cooking in boiling water for 2 min in the second case. Water loss is significantly affected by the pre-cooking method; Bustamante (2009) found that water loss due to pre-cooking ranged from approxi mately 50–60 g/100 g of raw mussel meat, depending on the cooking time (1, 4, or 7 min). The working con ditions depend on the characteristics of each specific load (especially on mussel size) and on the desired final product (Bello et al., 2012). As described by Almonacid et al. (2012), pre-cooking can be performed under differ ent conditions. Casales et al. (1988) used cooking times
451
of 7–10 min in atmospheric steam to open the shells and facilitate removal of mussel meats. Turan et al. (2007) pre-cooked cleaned mussels in boiling water at 100°C for approximately 6 min to open the shells and free the mus sel meat, but they used cooking times of 1, 4, and 7 min at 100°C, and the equipment used for this pre-cooking step was a hot water bath that heated the water up to 100°C by injection of atmospheric steam. At the end of the prescribed pre-cooking time, the mussels are cooled immediately under a spray of potable water for 3 min (Almonacid et al., 2012). In addition to being cooked, mussels also must be opened. Cooked mussels can be discharged in a cooling pool containing treated seawa ter, where they remain until their temperature decreases enough to enable manipulation. This water is at room temperature, but its temperature can increase by 1 or 2°C after receiving a discharge of cooked mussels. The cooked and cooled mussels are transported to two consecutive pools with previously prepared brine. In these pools the viands are separated from the shells (the salty water favors their separation), and because of a density differ ence, the meat flows to a different depth than shells. The brine flowing between the pools favors the separation of the viands and the shells. The remaining shells are man ually removed while the mussels are transported to the next stage (Bello et al., 2012). The amount of water loss is important because it determines the concentrations of mussel meat compounds and their possible leaching into processing media. Table 54.2 shows a general summary of mussel proximate compositions at all stages of pro cessing, comparing many reference sources. Moisture data from Slabyj (1977) are transformed to wet basis for comparison purposes. In general, the moisture content falls from approximately 81% (raw mussel) to 75% (precooked), and then, regardless of the subsequent process ing, the moisture content does not change significantly. As shown in Table 54.2, the protein concentration increases from approximately 11% in raw to 18% in precooked meat (wet basis). However, the original data from Slabyj (1977) show an apparent increase of protein on a dry basis of 63–70% due to decreases in dry-basis carbohy drate and ash concentrations. The author concluded that there is no significant difference in protein content after pre-cooking, that there is no leaching of protein and that the main effect is that of concentration by water loss. Pro tein and fat concentrations in the final product, frozen or canned, are depicted in the same table, where no significant differences from pre-cooked meat can be observed in either frozen or canned meat. For canned mussel, this means that proteins can be denatured by high temperature, but the amino acid concentration is not affected (Casales, 1988). Casales (1988) found no effect on protein or amino acid concentration by different time–temperature conditions (110.5 and 118°C) considering F0 values of 3, 7, and 10 min. No effect on nutritional value or amino acid composition
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TABLE 54.2 Proximal Composition of Mussel Meat from Raw to Processed Raw Meat1
Raw Meat2
Raw Meat3
Raw Meat5
Pre-Cooked3
Pre-Cooked5
Frozen3
Canned3
Canned4
Moisture
80,6
81,5
81,2
78.8
74,6
76.8
76,8
75,7
75,1
Protein
11,9
10
11,8
12.4
17,7
15
16,2
17,2
17
Fat
2,3
2,1
2,9
1.7
4,0
2.8
3,7
4,3
3
3,4
1,5
2.1
1,6
1.7
1,6
1,6
3
Ash CH
3,7
Sum
98,5*
97**
2,7
2,2
1,7
1,2
1,9
100,0
100
100
100
100
1USDA (2012) 2Fuentes
et al. (2009) (1977) 4DTU (2009) 5Krznowek and Wiggin (1979). *Difference should be Ash **Difference should be CH. 3Slabyj
of canned mussels could be found in the literature for canned mussels. It should be noted that no significant dif ferences in amino acid composition have been reported for other seafoods, such as canned urchin (Paracentrotus lividus), albacore tuna, and scallop adductor muscle (de la Cruz-García et al., 2000; Pérez-Martín et al., 1988; Kawashima and Yamanaka, 1996). Frozen storage can have a large effect on the protein and fat concentrations, especially if mussel meat is not properly glazed and/or packed, allowing for moisture lost and affecting organo leptic factors rather than nutritional ones (Gokoglu et al., 2000). Table 54.3 shows that mussels’ fatty acid composition, specifically EPA + DHA, makes an important contribu tion to the human diet. The intake of 100 g of mussel meat can fill 44% of the RDA for these compounds. Otles and Sengor (2005) reported on the fatty acid composition of mussel meat (Mytilus galloprovincialis L.) after various technological processes, including the pre-processing step of steaming for 10 min, polyunsaturated fatty acids represent approximately 38% of fat material in raw mussel, which increases to 57% in pre-cooked mussels, mainly as a consequence of the decrease in monoun saturated and saturated fatty acids. Half of EPA + DHA is retained after pre-cooking, falling from 26.4 to 13.2%. As shown in the proximal analysis of mussel after precooking (Table 54.2), the total fat concentration after precooking changes mainly because of water loss, meaning that the relative change in fatty acid composition is a result of chemical or biochemical reactions due to hightemperature processing, oxidative reactions or longchain fatty acid hydrolysis by lipolytic enzymes. Senturk et al. (2000) showed that fatty acids present in fish shat ter during thermal processing, such as cooking and canning, resulting in relative compositional changes. Importantly, DTU (2009) reported that the concentra tion of EPA + DHA in canned mussel shows the excellent
TABLE 54.3 Most Significant Contributions of Mussel Meat Type of Nutrient
Compound
% RDA
Macronutrients
Protein
23
Micronutrients
Fe
49/22*
P
28
B12
500
DHA + EPA
44
Bioactive *Man/Woman.
value of 1 g/100 g of mussel meat, which would satisfy 100% of the RDA. It should be noted that a mussel can has approximately 180 g of drained weight. Another mollusk, the sea urchin, has been analyzed for fatty acid composition after canning (de la Cruz-García et al., 2000). Canning in water did not significantly affect the amount of each fatty acid, and the retention of EPD + DHA after canning was 83.1% in a process without pre-cooking, which means that the retention of this important bioac tive compound differs between shellfish. The effects of processing on micronutrients, miner als, and vitamins have been studied by Slabyj (1977) for the pre-cooking, freezing, and canning of mussel meat. Table 54.3 shows the most significant micronutrients provided by mussels, vitamin B12, Fe, and P. In general, some elements leach out during pre-cooking, such as I, K, and Na, and the rest of elements are not significantly affected by pre-cooking. Further processing results in leaching of Mg and K, mainly during canning, but also as a consequence of freezing. The elements Fe and P show no significant losses through all the processing steps: Fe changes from 29 to 35 and 42 ppm dry weight in frozen and canned processing, respectively. The increase is due to concentration by water loss. Similarly, P increases from 10,500 (raw mussel) to 12,000 and 11,300 ppm for
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References
frozen and canned, respectively. With regard to vitamin B12, the only available data are for canned mussel, which shows a value of 10 μm/100 g of drained meat, compared with 12 μm/100 g in raw mussel (DTU, 2009). From these data, it is possible to conclude that processed mussels are still a good source of the components shown in Table 54.3 and most of the components of the raw mussel as well.
by Voegborlo et al. (1999) and 1.5 mg per week for Pb by WHO/FAO (1999). Perez-Lopez (2003) concluded that one would need to consume 20 cans of this mollusk per week to reach the upper level for Cd and 30 cans in the same period for Pb. From these data, it can be concluded that mussels grown in properly controlled areas do not constitute a danger to human health from heavy metals.
OTHER WAYS IN WHICH COMPOSITION IS ALTERED
ANALYTICAL TECHNIQUES
Due to the biological characteristics of mussels (they have a high capacity to carry out bioconcentration phe nomena from the marine environment in which they grow), health problems may occur if toxic compounds are present in the environment. Under these conditions, suitable checks of the water quality and implementa tion of purification processes for mollusks intended for human consumption must be considered (Parejo,1989). One of the most abundant types of pollutants in marine environments, which are linked to human activity, are metals. These compounds can generate toxicological problems with significant health impacts (Pérez-López, 2003). In this sense, it is important to make a clear distinction between the elements that have essential functions for life, as it is the case of copper and zinc (Copa-Rodriguez and Basadre-Pampín, 1994), and those whose intake at low doses triggers to toxicity, such as lead and cadmium (Voegborlo et al., 1999). The tolerable daily intakes of zinc and copper are 40 and 10 mg/adult, respectively (García-Gabarra, 2006). Perez-Lopez et al. (2003) carried out a study to determine the contents of heavy metals in canned mussels and found the following average concentrations (expressed in wet weight):
Zinc: 311.8 ppm Copper: 6.335 ppm Cadmium: 0.333 ppm Lead: 0.714 ppm.
The recommended dietary intake of zinc is 11 mg for an adult (Table 54.1). Considering a mussel can of 100 g drained weight, it is possible to estimate the metal intake from the consumption of one can. The estimated Zn intake is 31.3 mg so one would cover the RDA and would not exceed the upper limit of 40 mg. The estimated cop per intake is 0.634 mg, clearly under the limit of tolerance of 10 mg/person per day (or 15 cans/day). On the other hand, if the needs of copper are estimated at 3.2 mg/ person per day (Copa-Rodriguez and Basadre-Pampín, 1994), one would need to eat five mussel cans per day to meet this requirement. With regard to the other two metals, a level of tolerable intake of 400–500 μg per week, for Cd has been reported
Proximate analyses are determined according to stan dard methods from AOAC, and other important compo nents such as fatty acid composition, amino acid profile and micronutrients utilize gas chromatography, HPLC, and Atomic Absorption Spectrophotometry, respec tively, as shown by Fuentes et al. (2009).
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FAO, 2007. Estado actual del cultivo y manejo de moluscos bivalvos y su proyección futura. Factores que afectan su sustentabilidad en América Latina. ISSN 2071–1026. FAO, 2012. FishStatJ version 2.0.0. Software for fishery statistical time series, between 1950 and 1980. Available at: www.fao.org/fishery/ statistics/software/fishstatj/en. Fuentes, A., Fernández-Segovia, I., Escriche, J.A., Serra, J.A., 2009. Comparison of physico-chemical parameters and composition of mussels (Mytilus galloprovincialis Lmk.) from different Spanish ori gins. Food Chem. 112, 295–302. García-Gabarra, A., 2006. Ingesta de Nutrientes: Conceptos y Reco mendaciones Internacionales (2a Parte). Nutrición Hospitalaria 21, 437–447 (N°4). Gokoglu, N., Erkan, N., Ozden, O., 2000. The effect of frozen storage on proximate composition and quality of mussels (Mitylus galloprovincialis). J. Aquatic Food Product Technol. 9 (2), 83–88. Hamazaki., T., Okuyama, H., 2003. The Japan Society for Lipid Nutri tion recommends to reduce the intake of linoleic acid. A review and critique of the scientific evidence. World Rev. Nutr. Diet. 92, 109–132. Holdsworth, D., Simpson, R., 2007. Canning Operations. In: Thermal Processing of Packaged Foods, second ed. Springer, New York. Kawashima, K., Yamanaka, H., 1996. Free amino acids responsible for browning of cooked scallop adductor muscle. Fisheries Sci 62, 293–296. Krzynowek, J., Wiggin, K., 1979. Seasonal variation and frozen storage stability of blue mussels (Myths edulis). J. Food Sci. 44, 1644–1645. Linus Pauling Institute, 1012. Available from: http://lpi.oregonstate. edu/infocenter/vitamins/vitaminB12/ (accessed November 2012.). Otles, S., Sengor, G., 2005. Effect of Various Technological Processes on the Fatty Acid Composition of Mussel (Mytilus galloprovincialis, L.). Int. J. Food Eng. 1 (3), ISSN (Online), 1556–3758. Parejo, C.B., 1989. In: Mundi-Prensa, (Ed.), Moluscos: Tecnología de Cultivo: Madrid, p. 167–173.
Pérez-López, M., Bellón, E., Alonso, J., Melgar, M.J., 2003. Contenido en metales pesados (Zn, Cd, Pb y Cu) en conservas de mejillón (Mytilus sp). ALIMENTARIA (349), 73–80. Perez-Martin, R.I., Franco, J.M., Aubourg, S., Gallardo, J.M., 1988. Changes in free amino acid content in albacore (Thunnus alalunga) muscle during thermal processing. Z Lebensm Untersuch Forsch 187, 432–435. Senturk, A., Baygar, T., Gokoglu, N., Kaplan, M., Sentruk, I., 2000. Determination of the changes with some chemical and microbio logical quality of Yellowfin Tuna (Thunnus albacores, L. 1758) during canning process. Ministry of agriculture and rural affairs of Turkey. The control of directorship of Dardanlles Province. Project number: TAGEM/GY/98/07/01/015. Slabyj, B.M., 1977. Processing effect on proximate composition and mineral content of meats of blue mussel (Mytilus edulis). J. Food Sci. 42 (5), 1153–1155. Shafiur, M., 2012. Chilling, Freezing and Thawing Process Design. In: Ahmed, J., Shafiur, M. (Eds.), Handbook of food Process Design, vol. 1. Wiley–Blackwell, Oxford, pp. 430–455. Shahidi, F., 2004. Functional seafood products. ACS Symposium Series 702, 29–49. Turan, H., Sönmez, G., Yesim, C., elikM, Yalc¸in Kaya, Y., 2007. Effects of different salting process on the storage quality of Mediterra nean mussel (Mytilus galloprovincialis L. 1819). J. Muscle Foods 18, 380–390. USDA, 2012. The U.S. Department of Agriculture. National Nutrient Database for Standard Reference, Release 25. Home Page, http:// www.ars.usda.gov/ba/bhnrc/ndl. Food list available at: http:// ndb.nal.usda.gov/ndb/search/list. Voegborlo, R.B., El-Methnani, A.M., Abedin, M.Z., 1999. Mercury, cadmium and lead content of canned tuna fish. Food Chem. 67, 341–345. WHO/FAO, 1999. Summary of the 53rd meeting of the joint FAO/ WHO expert committee on food additives (JECFA), agenda item 4a.
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Shellfish (Mussel) Processing and Components Sergio Almonacid*, †, Joselyn Bustamante*, Ricardo Simpson*, †, Marlene Pinto* *Department of Chemical and Environmental Engineering, Universidad Técnica Federico Santa María, Valparaíso, Chile, †Centro Regional para el Estudio de Alimentos Saludables (CREAS), Valparaíso, Chile
CHAPTER POINTS • I ntegrated average harvest of mussels in China, Spain, Chile, and Thailand, was 1,272,131 t, 65% of the total world production. • Raw mussels are a good source of proteins, vitamin B12, Fe, P, and omega-3 fatty acids (DHA + EPA). • Mussels are mainly processed through precooking, freezing, or canning. • The main effect of processing on mussel components is concentration due to water loss. Leaching and reaction have a minor influence. • The consumption of 100 g of canned or frozen mussel meat can satisfy more than 20% of the recommended daily allowance of proteins, vitamin B12, Fe, P, and omega-3 fatty acids (DHA + EPA).
INTRODUCTION Crustaceans and mollusks have increased substan tially in the last 50 years, from 166,975 t in 1950 to approximately 2 million t in 2010. This growth is almost entirely due to the increase in aquaculture production, which was particularly rapid in the 1990s. World produc tion of mussel aquaculture or farming increased from approximately 1 million t in 1990 to nearly 1.8 million t in 2010, which represents a value of US$ 1.5 billion, with an average growth rate of 3.5% annually during this period. It is important to highlight that current world production of mussels relies on farming, representing 95% of the total production in 2010 (FAO, 2007). The
Processing and Impact on Active Components in Food http://dx.doi.org/10.1016/B978-0-12-404699-3.00054-8
mussel farming industry reached a significant produc tion level in the Netherlands with the aquaculture cul tivation of the common mussel, also known as the blue shell mussel (Mytilus edulis). In the 1950s, while countries such as Spain, China, and Italy showed a production of less than 3000 t, the Netherlands harvested annually more than 50,000 t of mussels. The remarkable develop ment of mussel harvesting in the Netherlands achieved a maximum of 120,000 t/year in the 1970s, which has since declined to 40,000–100,000 t/year (FAO, 2012). China is the main producer of mussels, at 700,000 t/ year in 2010, mainly of the species commonly known as sea mussel nei (Mytilus galloprovincialis). The production of mussels in China has grown rapidly in the past 30 years, especially in the 1980s, with an average of 22.1% annual growth rate. In the period between 1980 and 2010, the average annual growth rate was 9.7% (FAO, 2012). Mussel aquaculture is highly concentrated in China, Spain, Chile, and Thailand, whose total average harvest, between 2005 and 2010, accounted for 65% of the total world production, 1,272,131 t/year in 2010. The diversity of cultivated species under the denomi nation of mussels includes 13 species, and according to the world aquaculture production of the Mytilidae, the spe cies Mytilus galloprovincialis is among the most important considering that China and Spain produced 796,698 t of it, on average, between 2005 and 2010. However, in terms of economical implications, the main species is the Chilean mussel (Mytilus chilensis), with a total annual production of US$ 416,561, but the blue mussel (Mytilus edulis) may be the most relevant species given its ratio of US$ per ton of mussel, evaluated at 1.75. This species of mussel reaches its commercial size of two inches after about three years growth. The shells of fresh mussels are hermetically closed or they close when touched (FAO, 2012). Common
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448
54. MUSSEL PROCESSING
mussels are widely distributed in European waters, extending from the White Sea off of Russia as far south as the Atlantic coast of south France. Mytilus edulis has a very wide distribution, mainly due to its ability to withstand wide fluctuations in salinity, temperature, and oxygen tension. The species is well acclimated to a temperature range of 5–20°C, with an upper limit of thermal tolerance approximately 29°C for adults (FAO, 2004).
HOW COMPOSITION IS ALTERED Nutritional Composition of Mussels Marine-derived foods are a good source of omega-3 fatty acids and have numerous nutrition and health ben efits. Their proteins possess a well-balanced amino acid composition, which may be used directly as a source of amino acids or in preparations such as dispersions or hydrolyzed solutions (Shahidi, 2004). From a nutri tional perspective, mussels represent an excellent sea food choice. They are low in calories and fat and high in protein, as well as rich in many micronutrients, such as vitamins and minerals. Table 54.1 shows the proximal composition of raw mussels, including micronutrients. As with most seafood, mussels are rich in protein, 12% wet base (Table 54.1). They are similar to beef pro tein in quantity and quality, but with less saturated fat, 0.4 as compared with 1.2 g lipid/100 g of product (USDA, 2012). The recommended daily protein intake is 0.75 g/kg body weight (García-Gabarra, 2006). For example, for a person of 70 kg, the daily protein intake should be 52.5 g, which means that with 100 g of mussels, this person would satisfy approximately 23% of his/her requirements. Although mussels are low in lipids, these are of high quality and provide a healthy contribution to the diet, based on their significant concentration of polyunsatu rated and monounsaturated fatty acids (Table 54.1). Today, the amount of fat consumed is considered impor tant, as is its quality. It is desirable that foods include an adequate amount and proportion of essential fatty acids (EFA), omega-6/omega-3, an appropriate amount of monounsaturated fatty acids, a low amount of satu rated fatty acids and, ideally, no fatty acids with transisomers. Mussels are low in total and saturated fat, and more important, this type of mollusk is one of the richest sources of omega-3 fatty acids. Some important traits of omega-3 fatty acids are (Byrd-Bredbenner et al., 2009):
• E ssential for normal development and function of the retina. • Help to regulate nerve transmission.
• R egulate blood pressure, blood clotting, body temperature, inflammation or hypersensitivity reactions, and immune and allergic responses. • Maintain normal kidney function and fluid balance.
Compared with other sources of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA), blue mussels are a good source of these essential fatty acids, 0.44 g/100 g of fresh produce, contrasted with 0.4 and 0.5 g/100 g for Crustaceans and general Mollusks, respectively (USDA, 2012). In 2009, the European Food Safety Authority (EFSA) published recommendations with regard to PUFAs, advising a dose of 2 g/day of fatty omega-3 alpha-linolenic acid (ALA) and 250 mg/day of the longchain omega-3 fatty acids EPA and DHA (Bresson et al., 2009). The Japan Society for Lipid Nutrition has recom mended a reduction of energy intake of 3–4% for Japanese people, whose average consumption of omega-3 fatty acids of 2.6 g/day, including approximately 1 g/day of EPA + DHA (Hamazaki and Okuyama, 2003). Con sidering that the recommended daily allowance (RDA) of EPA + DHA is 1 g/day, 100 g of fresh mussel provides 44% of the recommended dose. Mussels incorporate important amounts of trace ele ments and minerals necessary to the diet (Do Amaral et al., 1998). Table 54.1 shows information regarding the content of vitamins and minerals provided by 100 g of fresh mussels, compared with the RDA and adequate intake (AI). The per cent contributions to the RDA of mussels’ micronutrients are shown in the same table. The contribution of vitamin B12 is the most significant in proportion to the RDA, whose contribution by 100 g of fresh mussels is 12 μg, or 500% of the RDA (Table 54.1). Vitamin B12 helps the body maintain sheaths around nerve fibers, helps activate another B-vitamin called folic acid, and participates in many cellular processes (Wardlaw et al., 2009). García-Gabarra (2006) reported that the upper-level (UL) or maximum intake of vitamin B12 in adults aged between 19 and 65 years is 1000 μg, a quantity 100-times greater than the content of vitamin B12 in 100 g of fresh Mussel. No toxic or adverse effects have been associated with large intake of vitamin B12, either from food or supplements, in healthy people (Linus Pauling Institute, 2012).
Processing Despite the above considerations, mussels are not consumed raw but are processed in different ways, and their nutritional characteristics may be affected by processing. Mussel processing, regardless of the final product, consists of a first, common stage of precooking, followed by a second stage of processing,
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449
How Composition is Altered
TABLE 54.1 Proximate and RDA of Nutrients Found in Mussel Nutrient
Unit
100 g raw Mussel RDA man
Water
g
80.58
Energy
kcal
86
Protein
g
11.9
Total lipid (fat)
g
2.24
Carbohydrate
g
3.69
Fiber, total dietary
g
0
Sugar, total
g
0
RDA Woman
100 g raw Mussel
% Contribution Man/Woman
PROXIMATE
MINERALS Calcium, Ca
mg
1000*
1200*
26
2.6/2.2
Iron, Fe
mg
8
18
3,95
49/22
34
8/1
(420a)
(320a)
Magnesium, Mg
mg
400
Phosphorus, P
mg
700
700
197
28/28
Potassium, K
g
4,7*
4,7*
0.32
7/7
Sodium, Na
g
1,5 (1,3/1,2)*
1,5 (1,3/1,2)*
0.29
24/24
Zinc, Zn
mg
11
8
1,6
15/20
Vitamin C, total ascorbic acid
mg
90
75
8
9/11
Thiamin
mg
1,2
1,1
0,16
13/15
Riboflavin
mg
1,3
1,1
0,21
16/19
Niacin
mg
16
14
1,6
10/11
Vitamin B6
mg
1,3/1,7
1,3/1,5
0,05
3/3
Folate, DFE
μg
400
400
42
11/11
Vitamin B12
μg
2,4
2,4
12
500/500
Vitamin A, RAE
μg
900
700
48
5/7
Vitamin A, IU
IU
Vitamin E (alpha-tocopherol)
mg
15
15
0,55
4/4
Vitamin D (D2 + D3)
μg
5 (10/15)
6 (10/15)
0
—
Vitamin D
IU
0
—
Vitamin K (phylloquinone)
μg
0,1
—
310
VITAMINS
160
120
90
LIPIDS Fatty acids, total saturated
g
0.425
Fatty acids, monounsaturated
g
0.507
Fatty acids, polyunsaturated
g
0.606
Cholesterol
g
0.028
Data from USDA, 2012. AI, Adequate Intake.
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54. MUSSEL PROCESSING
FIGURE 54.1 Schematic representation of mussel processing.
which is usually freezing or sterilization (canning) (Figure 54.1). Bello et al. (2012) described these pro cesses in mussels in some detail. They involve the above steps plus some auxiliary operations that result in the production of cooked mussel meat from fresh mussels. Raw, fresh material is collected from hatcheries and
transported to the processing plant. At the plant, they are inspected for quantity and quality, and the selected units continue to the following steps of storage, washing, and conditioning. In the final stage, mussels are either fro zen or commercially sterilized (Figure 54.1). When steril ized, mussel meat that has been cooked and shucked is
7. MARINE FOODS
How Composition is Altered
ready for canning. According to Almonacid et al. (2012), this stage is divided into five operations: filling cans with mussels, adding coverage liquid (salted brine), seaming the containers and, finally, heat-processing to commercial sterility (retorting). Once mussel meats are packed into the open cans, hot liquid brine, consisting of an aqueous solution of 1–3% salt and 0.1% citric acid is added to each can at a temperature of 75°C (Almonacid et al., 2012). Thermal sterilization of filled and sealed cans is carried out in saturated steam at temperatures in the range of 110–130°C for the specified time to achieve a final process lethality of Fo = 6 min (or the time speci fied by the process authority). After heating, a final cool ing step is applied with water at ambient temperature (19–21°C). Finally, cans are stored at room temperature and have a shelf-life of at most 4 years under these con ditions (Holdsworth and Simpson, 2007). The mussel-freezing process starts with cooked and shucked meat. It is grouped into blocks of about one inch, which are laid out on trays. The freezing process is usually carried out in blast freezers at −40°C for a long enough time to obtain a temperature of −20°C in the geometrical center of the mussel meat block. The process normally takes approximately 50 min. After that, the unwrapped meat is glazed to mitigate the water loss by evaporation. Finally, glazed and not necessarily packed meats are stored in a cold room at a temperature of −20 °C. Their shelf-life under these conditions should be 8–9 months (Shafiur, 2012). The processing effects on mussel composition are mainly caused by two mechanisms: material exchange between mussel meat and processing media (water, steam, brine, air), and thermal inactivation by high tem perature (molecular lysis or reaction) when mussels are sterilized. Most water loss takes place during the first, common stage of pre-cooking, and the main effect on the proximal composition of mussel meat is by concentra tion. Slabyj (1977) reported a dry weight increase from 18.8% to 25.4% due to water lost during pre-cooking of blue mussels, which means a decrease in water content from 81.2 to 74.7%. Krzynowek and Wigginn (1979) used boiling water for 2 min and observed a change in mois ture from 78.7 to 76.8%. The difference in water loss was due to the pre-cooking method, steaming for 6 min in the first case and cooking in boiling water for 2 min in the second case. Water loss is significantly affected by the pre-cooking method; Bustamante (2009) found that water loss due to pre-cooking ranged from approxi mately 50–60 g/100 g of raw mussel meat, depending on the cooking time (1, 4, or 7 min). The working con ditions depend on the characteristics of each specific load (especially on mussel size) and on the desired final product (Bello et al., 2012). As described by Almonacid et al. (2012), pre-cooking can be performed under differ ent conditions. Casales et al. (1988) used cooking times
451
of 7–10 min in atmospheric steam to open the shells and facilitate removal of mussel meats. Turan et al. (2007) pre-cooked cleaned mussels in boiling water at 100°C for approximately 6 min to open the shells and free the mus sel meat, but they used cooking times of 1, 4, and 7 min at 100°C, and the equipment used for this pre-cooking step was a hot water bath that heated the water up to 100°C by injection of atmospheric steam. At the end of the prescribed pre-cooking time, the mussels are cooled immediately under a spray of potable water for 3 min (Almonacid et al., 2012). In addition to being cooked, mussels also must be opened. Cooked mussels can be discharged in a cooling pool containing treated seawa ter, where they remain until their temperature decreases enough to enable manipulation. This water is at room temperature, but its temperature can increase by 1 or 2°C after receiving a discharge of cooked mussels. The cooked and cooled mussels are transported to two consecutive pools with previously prepared brine. In these pools the viands are separated from the shells (the salty water favors their separation), and because of a density differ ence, the meat flows to a different depth than shells. The brine flowing between the pools favors the separation of the viands and the shells. The remaining shells are man ually removed while the mussels are transported to the next stage (Bello et al., 2012). The amount of water loss is important because it determines the concentrations of mussel meat compounds and their possible leaching into processing media. Table 54.2 shows a general summary of mussel proximate compositions at all stages of pro cessing, comparing many reference sources. Moisture data from Slabyj (1977) are transformed to wet basis for comparison purposes. In general, the moisture content falls from approximately 81% (raw mussel) to 75% (precooked), and then, regardless of the subsequent process ing, the moisture content does not change significantly. As shown in Table 54.2, the protein concentration increases from approximately 11% in raw to 18% in precooked meat (wet basis). However, the original data from Slabyj (1977) show an apparent increase of protein on a dry basis of 63–70% due to decreases in dry-basis carbohy drate and ash concentrations. The author concluded that there is no significant difference in protein content after pre-cooking, that there is no leaching of protein and that the main effect is that of concentration by water loss. Pro tein and fat concentrations in the final product, frozen or canned, are depicted in the same table, where no significant differences from pre-cooked meat can be observed in either frozen or canned meat. For canned mussel, this means that proteins can be denatured by high temperature, but the amino acid concentration is not affected (Casales, 1988). Casales (1988) found no effect on protein or amino acid concentration by different time–temperature conditions (110.5 and 118°C) considering F0 values of 3, 7, and 10 min. No effect on nutritional value or amino acid composition
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54. MUSSEL PROCESSING
TABLE 54.2 Proximal Composition of Mussel Meat from Raw to Processed Raw Meat1
Raw Meat2
Raw Meat3
Raw Meat5
Pre-Cooked3
Pre-Cooked5
Frozen3
Canned3
Canned4
Moisture
80,6
81,5
81,2
78.8
74,6
76.8
76,8
75,7
75,1
Protein
11,9
10
11,8
12.4
17,7
15
16,2
17,2
17
Fat
2,3
2,1
2,9
1.7
4,0
2.8
3,7
4,3
3
3,4
1,5
2.1
1,6
1.7
1,6
1,6
3
Ash CH
3,7
Sum
98,5*
97**
2,7
2,2
1,7
1,2
1,9
100,0
100
100
100
100
1USDA (2012) 2Fuentes
et al. (2009) (1977) 4DTU (2009) 5Krznowek and Wiggin (1979). *Difference should be Ash **Difference should be CH. 3Slabyj
of canned mussels could be found in the literature for canned mussels. It should be noted that no significant dif ferences in amino acid composition have been reported for other seafoods, such as canned urchin (Paracentrotus lividus), albacore tuna, and scallop adductor muscle (de la Cruz-García et al., 2000; Pérez-Martín et al., 1988; Kawashima and Yamanaka, 1996). Frozen storage can have a large effect on the protein and fat concentrations, especially if mussel meat is not properly glazed and/or packed, allowing for moisture lost and affecting organo leptic factors rather than nutritional ones (Gokoglu et al., 2000). Table 54.3 shows that mussels’ fatty acid composition, specifically EPA + DHA, makes an important contribu tion to the human diet. The intake of 100 g of mussel meat can fill 44% of the RDA for these compounds. Otles and Sengor (2005) reported on the fatty acid composition of mussel meat (Mytilus galloprovincialis L.) after various technological processes, including the pre-processing step of steaming for 10 min, polyunsaturated fatty acids represent approximately 38% of fat material in raw mussel, which increases to 57% in pre-cooked mussels, mainly as a consequence of the decrease in monoun saturated and saturated fatty acids. Half of EPA + DHA is retained after pre-cooking, falling from 26.4 to 13.2%. As shown in the proximal analysis of mussel after precooking (Table 54.2), the total fat concentration after precooking changes mainly because of water loss, meaning that the relative change in fatty acid composition is a result of chemical or biochemical reactions due to hightemperature processing, oxidative reactions or longchain fatty acid hydrolysis by lipolytic enzymes. Senturk et al. (2000) showed that fatty acids present in fish shat ter during thermal processing, such as cooking and canning, resulting in relative compositional changes. Importantly, DTU (2009) reported that the concentra tion of EPA + DHA in canned mussel shows the excellent
TABLE 54.3 Most Significant Contributions of Mussel Meat Type of Nutrient
Compound
% RDA
Macronutrients
Protein
23
Micronutrients
Fe
49/22*
P
28
B12
500
DHA + EPA
44
Bioactive *Man/Woman.
value of 1 g/100 g of mussel meat, which would satisfy 100% of the RDA. It should be noted that a mussel can has approximately 180 g of drained weight. Another mollusk, the sea urchin, has been analyzed for fatty acid composition after canning (de la Cruz-García et al., 2000). Canning in water did not significantly affect the amount of each fatty acid, and the retention of EPD + DHA after canning was 83.1% in a process without pre-cooking, which means that the retention of this important bioac tive compound differs between shellfish. The effects of processing on micronutrients, miner als, and vitamins have been studied by Slabyj (1977) for the pre-cooking, freezing, and canning of mussel meat. Table 54.3 shows the most significant micronutrients provided by mussels, vitamin B12, Fe, and P. In general, some elements leach out during pre-cooking, such as I, K, and Na, and the rest of elements are not significantly affected by pre-cooking. Further processing results in leaching of Mg and K, mainly during canning, but also as a consequence of freezing. The elements Fe and P show no significant losses through all the processing steps: Fe changes from 29 to 35 and 42 ppm dry weight in frozen and canned processing, respectively. The increase is due to concentration by water loss. Similarly, P increases from 10,500 (raw mussel) to 12,000 and 11,300 ppm for
7. MARINE FOODS
453
References
frozen and canned, respectively. With regard to vitamin B12, the only available data are for canned mussel, which shows a value of 10 μm/100 g of drained meat, compared with 12 μm/100 g in raw mussel (DTU, 2009). From these data, it is possible to conclude that processed mussels are still a good source of the components shown in Table 54.3 and most of the components of the raw mussel as well.
by Voegborlo et al. (1999) and 1.5 mg per week for Pb by WHO/FAO (1999). Perez-Lopez (2003) concluded that one would need to consume 20 cans of this mollusk per week to reach the upper level for Cd and 30 cans in the same period for Pb. From these data, it can be concluded that mussels grown in properly controlled areas do not constitute a danger to human health from heavy metals.
OTHER WAYS IN WHICH COMPOSITION IS ALTERED
ANALYTICAL TECHNIQUES
Due to the biological characteristics of mussels (they have a high capacity to carry out bioconcentration phe nomena from the marine environment in which they grow), health problems may occur if toxic compounds are present in the environment. Under these conditions, suitable checks of the water quality and implementa tion of purification processes for mollusks intended for human consumption must be considered (Parejo,1989). One of the most abundant types of pollutants in marine environments, which are linked to human activity, are metals. These compounds can generate toxicological problems with significant health impacts (Pérez-López, 2003). In this sense, it is important to make a clear distinction between the elements that have essential functions for life, as it is the case of copper and zinc (Copa-Rodriguez and Basadre-Pampín, 1994), and those whose intake at low doses triggers to toxicity, such as lead and cadmium (Voegborlo et al., 1999). The tolerable daily intakes of zinc and copper are 40 and 10 mg/adult, respectively (García-Gabarra, 2006). Perez-Lopez et al. (2003) carried out a study to determine the contents of heavy metals in canned mussels and found the following average concentrations (expressed in wet weight):
Zinc: 311.8 ppm Copper: 6.335 ppm Cadmium: 0.333 ppm Lead: 0.714 ppm.
The recommended dietary intake of zinc is 11 mg for an adult (Table 54.1). Considering a mussel can of 100 g drained weight, it is possible to estimate the metal intake from the consumption of one can. The estimated Zn intake is 31.3 mg so one would cover the RDA and would not exceed the upper limit of 40 mg. The estimated cop per intake is 0.634 mg, clearly under the limit of tolerance of 10 mg/person per day (or 15 cans/day). On the other hand, if the needs of copper are estimated at 3.2 mg/ person per day (Copa-Rodriguez and Basadre-Pampín, 1994), one would need to eat five mussel cans per day to meet this requirement. With regard to the other two metals, a level of tolerable intake of 400–500 μg per week, for Cd has been reported
Proximate analyses are determined according to stan dard methods from AOAC, and other important compo nents such as fatty acid composition, amino acid profile and micronutrients utilize gas chromatography, HPLC, and Atomic Absorption Spectrophotometry, respec tively, as shown by Fuentes et al. (2009).
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