Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

Подождите немного. Документ загружается.

relevant compounds, e.g., by using electronic noises

or visual indicators. Future studies are likely to iden-

tify various MCQI for determination of spoilage

cause by microbial activity, autolytic changes, or

chemical reaction in seafood.

Prediction of Shelf-life

001 9 Transportation of seafood and fish raw material is

increasing globally, and this has resulted in needs for

methods to evaluate and predict effects of conditions

of storage and distribution on shelf-life. Quality attri-

butes can be measured in newly processed products,

but unless changes in these attributes can be predicted

as a function of storage conditions, measurements at

the time of processing will be of little value to evalu-

ate products as experienced by consumers/buyers.

Empirical models for relative rates of spoilage, kinetic

models for growth of SSO, and relations between

indices of spoilage and remaining product shelf-life

or time of storage have been suggested for shelf-

life prediction.

Empirical Relative Rates of Spoilage Models

002 0 Temperature is the single most important factor influ-

encing the shelf-life of fresh and lightly preserved

seafood. Despite the complex and dynamic nature of

seafood spoilage, it has been possible to predict the

effect of temperature on the shelf-life of various sea-

foods. The predictions rely on relative rates of spoil-

age (RRS), i.e., the keeping time at a reference

temperature like 0



C divided by the keeping time at



C). The effect of temperature on RRS is similar for

various species of fresh fish, but at the same time,

RRS may differ substantially between fresh and

lightly preserved products. As shown in Figure 2,

the apparent activation energy (E

), for the effect of

temperature on shelf-life, can be only * 20kJ mol

1

( *5 kcal mol

1

) for hot smoked fish and > 100 kJ

mol

1

(>24 kcal mol

1

) for cooked and brined

shrimps stored in modified-atmosphere packaging.

Average RRS values of different fresh seafoods from

cold and temperate waters, including superchilled

and modified-atmosphere-packed products can be

predicted between  3 and þ 15



C by using eqn. 1,

named the square-root spoilage model. For other sea-

foods, the Arrhenius model, which includes the par-

ameter E

to describe the apparent activation energy,

or a simple exponential model, including the slope

parameter, b (eqn. 2), is more appropriate for the

effect of temperature on RRS (Figure 2). RRS models

allow shelf-life to be predicted at different storage

temperatures if only the shelf-life of a product has

been determined at a single known temperature

ref

) (see eqn. 2).

ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ

RRS

ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ

shelf-life at 0



shelf-life at T



¼ 1 þ 0 :1  T ð



CÞð1Þ

shelf-life at T ð



CÞ¼

shelf-life at T

ref



C Þ

exp ½b ðT  T

ref

Þ

ð2Þ

Kinetic Models for Growth of SSO

0021Mathematical models are available to predict the

effect of temperature, atmosphere, water activity,

and other factors on the growth of some SSO

from seafood as well as on the growth of several

pathogenic microorganisms. Nevertheless, only some

models have been validated and confirmed to predict

shelf-life and growth of pathogenic microorganisms

in seafood accurately, i.e., within +25%.

0022Growth of SSO in aerobically stored seafood is

often exponential until the end of the shelf-life is

reached (Figure 1) or includes only a very short lag

phase. This has allowed the shelf-life of different

aerobically stored fishes to be predicted from growth

of the SSO, i.e., Shewanella putrefaciens and psychro-

tolerant Pseudomonas spp. The square-root model

(eqn. 3) is typically used to predict the effect of tem-

perature on maximum specific growth rates (m

max

)of

spoilage and pathogenic microorganisms in seafood.

ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ



max

¼ðT  T

min

Þ:ð3Þ

0023More extensive models, including the effect of

temperature and carbon dioxide concentrations, are

available to predict the growth of P. phosphoreum

0.0

1.0

2.0

3.0

4.0

510152025

Cooked and brined MAP shrimps

Fresh seafood − Cold waters

Fresh seafood − Tropical waters

Hot smoked and packed fish

~ 100

~ 80

~ 20

~ 0.15

~ 0.12

~ 0.025

Temperature (8C)

Ln (relative rates of spoilage)

fig0002Figure 2 Relativeratesofspoilageandcorrespondingtem-

peraturecharacteristics. Apparentactivationenergydetermined

bytheArrheniusequation(E

)andslopeparameterinexponen-

tialspoilagemodel(b). Thesquarerootmodelappropriatefor

freshseafoodfromcoldwatersisshownineqn(1). Modifiedfrom

Dalgaard P (2000) Fresh and lightly preserved seafood. In: Man

CMD and Jones AA (eds.) Shelf Life Evaluation of Foods, 2nd edn,

pp. 110–139. Gaithersburg, MD: Aspen with permission.

2468 FISH/Spoilage of Seafood

tbl0004 Table 4 Seafood associated hazards and their prevention

Hazard Safety concern Preventive measures

Histamine Microbial production of above c. 500 p.p.m. in products Reduce microbial growth and activity by storage of fresh

seafood at <2



C and lightly preserved products at <5



Biotoxins Consumption of warm-water fishes with tetrodo- or cigua-

toxin or filter feeding shellfish with toxins produced by

marine algae

Monitoring and management of fishing areas.

Biotoxins persist cooking and preservation of seafood

Viruses Viral gastoenteritis due to consumption of raw or steamed

molluscan shellfish and ready-to-eat seafoods

Monitoring of harvesting areas, depuration of molluscs,

cooking seafood prior to consumption

Pathogenic bacteria indigenous in aquatic environment

Clostridium botulinum, psychrotolerant Growth and toxin formation in ready-to-eat (hot-smoked and

fermented) products from colder regions

Salting (>3.5% NaCl) and chilled storage (<5



C) prevent

growth and toxin production in seafood

Vibrio parahaemolyticus,V. vulnificus, V. cholerae,

V. a l g i o n l y t i c u s and Plesiomonas shigelloides

Growth to high levels in raw marine seafoods from warmer

waters and in cross-contaminated ready-to-eat products

Avoid consumption of improperly cooked seafood,

particularly molluscan shellfish

Pathogenic bacteria from the animal/human reservoir

and general environment

Salmonnella spp. and Shigella spp. Contamination by even low levels Avoid direct or indirect faecal contamination of products.

Bacteria is inactivated by cooking

Clostridium botulinum proteolytic type A and B Growth and toxin formation in products Inactivate bacteria and their spores by canning (> 2.4 min at

121



C) or prevent growth by chilling (< 10



C), acidification

(pH <4.5) or curing (> 10% NaCl).

Listeria monocytogenes Growth in ready-to-eat seafoods Reduce growth by low storage temperature. Bacteria are

inactivated by cooking

Staphylococcus aureus Growth and toxin formation in products Prevent growth by chilled storage of products

Campylobacter spp. Contaminated molluscan shellfish. Bacteria die in seawater Avoid consumption of raw molluscan shellfish

Parasites Intake of live nematodes, or trematodes in raw and ready-to-

eat seafood

Removal of infected fish or inactivation of parasites by heating

(55



C, 1 min), freezing (20



C, 24 h) or curing

and B. thermosphacta as well as the shelf-life of

fresh modified-atmosphere-packed seafoods. Kinetic

models predict shelf-life from the initial level of SSOs

in products, and further studies are needed to deter-

mine typical distributions of spoilage organisms in

seafoods.

Time–Temperature Integration

002 4 Mathematical shelf-life models can be used to evalu-

ate product temperature profiles as recorded during

distribution of seafoods. Software that includes both

RRS models and kinetic models for growth of SSO is

available to predict product shelf-life under constant

and fluctuating storage conditions. The seafood spoil-

age predictor (SSP) (available from http://www.dfu.-

min.dk/micro/ssp/) is an example of a widely used

program. Time–temperature integration (TTI) tags

that change color in response to a temperature history

are another type of device to evaluate product shelf-

life. Storage temperature influences the shelf-life of

different fresh and lightly preserved seafoods very

differently (Figure 2), and selection of TTI tags with

appropriate temperature kinetics is of utmost import-

ance for successful application of this technology. TTI

tags with apparent activation energies that corres-

pond to those of most seafoods are available. How-

ever, for semi- and lightly preserved seafoods with an

extended shelf-life (Table 1), existing tags relying on

enzymatic, polymerization, or diffusion reactions

may not always be available with appropriate re-

sponse times.

Spoilage and Safety of Seafood

0025 Growth of spoilage microorganisms in seafood re-

duces the risk of pathogenic microorganisms reaching

high levels before products are spoiled and therefore

will not be consumed. Spoilage microorganisms and

reactions can be inhibited by classical processing

and preservation techniques, e.g., salting, drying,

smoking, canning, and freezing (see appropriate art-

icles in the present chapter). In addition, hurdle tech-

nology, minimal processing, and targeted inhibition

of SSO can be used as mild preservation procedures to

extend the shelf-life of seafood. Clearly, inhibition of

spoilage reactions should be linked with a carefully

evaluated product safety.

0026 The major hazards responsible for seafoodborne

diseases are histamine, biotoxins, viruses, bacteria

and parasites (Table 4). Seafood is estimated to

cause up to 10% of all outbreaks and approximately

3% of all cases of foodborne disease. The safety of

seafood products varies considerable and is influ-

enced by a number of factors, including the origin of

the fish or shellfish (marine or freshwater; cold or

tropical regions; clean or polluted waters), microbio-

logical ecology of the product, handling and process-

ing practices, and preparation before consumption

(Table 4).

0027Histamine fish poisoning is the single most fre-

quent seafoodborne disease (* 30% of all cases).

Fortunately, symptoms including facial flushing,

vomiting, diarrhea, and headache are relatively mild

and of short duration. Molluscan shellfish is the type

of seafood most frequently causing seafoodborne dis-

eases (> 50% of all cases). These shellfish are filter-

feeders and concentrate algae, bacteria, viruses, and

chemicals from the surrounding water. Despite this

situation, molluscan shellfish (with intestines) are

often consumed raw and then may cause viral gastro-

enteritidis (Norwalk-like and hepatitis A), infections

by Vibrio spp. and various shellfish toxic syndromes

resulting from toxins produced by different marine

algae (dinoflaggelates). In regions of Asia, raw fresh-

water fishes are used in various dishes, and as a result

of this, a high percentage of the population can be

infected with parasites (trematodes). Several other

aspects of seafood safety are less closely linked to

consumer behavior (Table 4). Because of the increas-

ing international trade with fish raw material and

seafoods, the safety of these products is of global

importance. Continued efforts to apply hazard analy-

sis critical control point systems in all steps of the

seafood chain are essential to improve the safety

record of these products at an international level.

See also: Chilled Storage: Microbiological

Considerations; Clostridium: Botulism; Fish: Tuna and

Tuna-like Fish of Tropical Climates; Food Poisoning:

Classification; Histamine; Listeria: Listeriosis;

Minimally Processed Foods; Preservation of Food;

Sensory Evaluation: Sensory Characteristics of Human

Foods; Shellfish: Contamination and Spoilage of

Molluscs and Crustaceans; Spoilage: Chemical and

Enzymatic Spoilage; Bacterial Spoilage; Storage

Stability: Mechanisms of Degradation; Parameters

Affecting Storage Stability; Shelf-life Testing

Further Reading

Ashie INA, Smith JP and Simpson BK (1996) Spoilage and

shelf life extension of fresh fish and shellfish. Critical

Reviews in Food Science and Nutrition 36: 87–121.

Colby J-W, Enriquez-Ibarra LG and Flick GJ (1993) Shelf

life of fish and shellfish. In: Charalambous G (ed.)

Shelf Life Studies of Foods and Beverages, pp. 85–143.

Amsterdam: Elsevier.

Dalgaard P (2000) Fresh and lightly preserved seafood. In:

Man CMD and Jones AA (eds) Shelf Life Evaluation of

Foods, 2nd edn. pp. 110–139. Gaithersburg, MD: Aspen.

Feldhusen F (2000) The role of seafood in bacterial food-

borne diseases. Microbes and Infection 2: 1651–1660.

2470 FISH/Spoilage of Seafood

Gram L and Huss HH (2000) Fresh and processed fish and

shellfish. In: Lund BM, Baird-Parker AC and Gould GW

(eds) The Microbiological Safety and Quality of Foods,

pp. 472–506. Gaithersburg, MD: Aspen.

Huss HH (1995) Quality and Quality Changes in Fresh

Fish. FAO Fisheries Technical Paper. No. 348.

Huss HH, Ababouch L and Gram L (2003) Assessment and

Management of Seafood Safety and Other Quality

Aspects. FAO Fisheries Technical Paper.

Leisner JJ and Gram L (2000) Spoilage of fish. In: Robinson

RK, Batt CA and Patel PA (eds) Encyclopedia of Food

Microbiology, pp. 813–820. San Diego: CA.

Olafsdo

ttir G, Luten J, Dalgaard P et al. (1998) Methods

to Determine the Freshness of Fish in Research and

Industry. Paris: International Institute of Refrigeration.

Dietary Importance of Fish and

Shellfish

A Arin

o, J A Beltra

n and P Roncale

s, University of

Zaragoza, Zaragoza, Spain

Background

0001 During the 1990s, the world’s population consumed

ever larger quantities of fish. In discussing food uses

of fish, the term ‘fish’ refers to edible species of

finfish, molluscs, and crustaceans coming from the

marine or freshwater bodies of the world, either by

capture fisheries or by aquaculture. In 1990, direct

human consumption of fish amounted to 71.7 million

tonnes (live weight equivalent), rising to 93.8 million

tonnes in 1997, an increase of almost a third over a

period of only seven years. The average availability

per capita was 15.9 kg per year during 1996, and fish

provided (per day) 28 kcal, 4.4 g of protein, and 1.0 g

of fat. There are wide differences among countries in

fish consumption, as measured by the average yearly

intake per person, ranging from countries with less

than 1.0 kg per person to countries with over 100 kg.

In recent years, the volume of fishery products

marketed fresh has increased; in 1997, about a third

of all fish was marketed fresh, compared with only a

fifth in 1987.

0002 Edible fish muscle contains 18% protein and 1–2%

ash; the percentage of lipids varies from less than 1%

to more than 20% in high-fat finfish. While fish has a

prominent role as a source of valuable animal pro-

teins in many communities, it seldom has a dietary

significance as a source of kilocalories. Overall, fish

provides about 16% of the animal proteins in the

world and is a source of vitamins, minerals, and

essential fatty acids. Food and nutritional profession-

als and consumers have known for years that fish is a

high-protein food that is low in energy, total fat, and

saturated fat when compared with other protein-rich

animal foods. In addition, a large proportion of the

fat in fish is polyunsaturated, the o-3 (n-3) fatty acids.

0003Because of increased evidence for the cardio-

vascular benefits of fish (particularly fatty fish), con-

sumption of at least two fish servings per week is

recommended to maintain health. The predominant

beneficial effects include a reduction in sudden

death, decreased risk of arrhythmia, lower plasma

triacylglycerol levels, and a reduced blood-clotting

tendency.

0004As fish have become more popular, there have been

increasing reports of foodborne diseases attributed to

these foods. Foodborne diseases following exposure

to fish can result from the food itself (toxic species,

allergies), but also bacterial or viral contamination of

the fish, naturally occurring seafood toxins, or the

presence of additives and chemical residues due to

environmental contamination.

General Characteristics of Food Finfish

0005A very large number of species of finfish are used for

food by the world’s population as a whole. The dress-

ing percentage of finfish (60–70%) is similar to that

of beef, pork, or poultry. The percentage of edible

tissue in dressed carcasses of finfish (without head,

skin, and viscera) is higher than that of other food

animals, because fish contains less bone, adipose

tissue, and connective tissue. There are three main

categories of finfish widely used as foods. The bony

fishes, the Teleosts, provide two compositional

groups: white fish (or lean fish) such as cod, haddock,

most flat fishes and whiting, and fatty fish, such as

herring, sardines, salmon, mackerel, and tuna. The

third category includes the cartilaginous Elasmo-

branch fish, such as dogfish, shark, and skate.

White Fish

0006The flesh of these fish is very low in fat and consists

primarily of muscle and thin layers of connective

tissue. The concentrations of most of the B vitamins

are similar to those in mammalian lean meats, though

fish may contain higher amounts of vitamin B

and

. The mineral levels are also similar, although the

very fine bones that are eaten with the fish flesh can

raise the calcium content; fish is also a significant

source of iodine. These fish accumulate oils in their

livers, which are a rich source of vitamin A (retinol),

vitamin D and long-chain polyunsaturated fatty acids

(PUFA) in their triacylglycerols (TAGs).

FISH/Dietary Importance of Fish and Shellfish 2471

Fatty Fish

0007 These fish have fat in their flesh, which is usually

much darker than that of white fish, with similar

blocks of muscle and connective tissue. The amount

of fat is related to the breeding cycle of the fish, and

after breeding, the fat content falls considerably.

The flesh of the fatty fish is generally richer in the

B vitamins than that of white fish, and there are

significant amounts of vitamins A and D present.

The mineral concentrations are not very different,

but fatty fish is a better source of iron. The fat of

these fish, or more correctly the oil, is particularly

rich in very-long-chain PUFA, especially those of the

o-3 (n-3) series such as eicosapentaenoic (EPA) and

docosahexaenoic (DHA) acids. These fish accumulate

oils in their muscles, belly flap, and skin (subdermal

fat).

Cartilaginous Fish

0008 These fish include the sharks and rays, whose flesh is

rich in connective tissue and relatively low in fat,

although they do accumulate oils in their livers. Com-

positionally, the concentrations of the vitamins and

minerals are very similar to those in white fish. These

fish are remarkable in that they have a high urea

content, and so protein values based on total nitrogen

are overestimated.

General Characteristics of Food Shellfish

0009 The term ‘shellfish’ includes any aquatic invertebrate,

such as a mollusc or crustacean that has a shell or

shell-like exoskeleton. Owing to the presence of

tough exoskeletons, the edible portion in shellfish

(around 40%) is less than in finfish, with the excep-

tion of cephalopods, whose dressing percentage is 70–

75%. In many communities, these foods are very

highly valued gastronomically.

Molluscs

0010 A wide range of molluscs are eaten by man, including

bivalves such as mussels, oysters, and scallops, gas-

tropods such as winkles and whelks, and cephalopods

such as squids and octopuses. The flesh is muscular

with low levels of fat, although the fat is more satur-

ated and richer in cholesterol than that of finfish. The

mineral levels in shelfish are usually somewhat higher

than in finfish, and the vitamin concentrations are

low. The bivalves and gastropods are often eaten

whole after boiling and sometimes raw; usually,

only the muscular mantles of cephalopods are eaten,

after cooking. In some cultures, only selected parts

are eaten, for example only the white adductor muscle

of the scallop is eaten in North America.

Crustacea

0011These include a range of species both fresh water such

as crayfish, and marine such as crabs, shrimps,

prawns, and lobsters. These animals have a segmented

body, a chitinous exoskeleton, and paired, jointed

limbs. The portions eaten are the muscular parts of

the abdomen and the muscles of claws of crabs and

lobsters. The flesh is characteristically low in fat and

high in minerals, with vitamin levels similar to those

found in finfish.

Nutritional Role of Fish and Shellfish

0012Interest in the health benefits of fish and shellfish

began decades ago when researchers noted that cer-

tain groups of people – including the Inuit and the

Japanese, who rely on fish as a dietary mainstay –

have a low rate of ischemic diseases (i.e., heart attack

or stroke). Part of the cardiovascular health benefits

of fish oils and their n-3 fatty acids can be explained

by the ability of both EPA and DHA present in fish to

reduce serum TAGs and very-low-density lipo-

proteins (VLDL-cholesterol). A growing body of evi-

dence indicates that foods rich in o-3 PUFAs confer

cardioprotective effects beyond those that can be

ascribed to improvements in blood lipoprotein pro-

files. As a result, current recommendations point out

the benefits of eating fish at least twice a week,

though even relatively small amounts of fish may

decrease the overall risk of death from heart disease.

Most experts do not advise routine use of fish oil

supplements, and they favor eating fish and shellfish

regularly in the context of a healthy diet and a regular

pattern of physical activity.

0013The caloric value of fish is related to fat content

and varies with species, size, diet, and season. Fish is

generally considered to be a low-calorie food when

compared with meats and poultry. Most lean or lower

fat species of fish such as cod, hake, flounder, and sole

contain less than 100 kcal per 100-g portion, and

even fatty fish like mackerel, herring, and salmon

contain approximately 250 kcal or less in a 100-g

serving. Most crustaceans contain less than 1% fat

in the tail muscle because depot fat is stored in the

hepatopancreas, which is in the head region. With

fish, each consumer can ingest fewer calories to

meet their daily protein needs, which makes fish a

good choice for diets designed to help you lose or

maintain a desirable weight.

Fish Lipids, v-3 PUFA Content, and Health

0014In fish, the depot fat is liquid at room temperature

(oil) and is seldom even visible to the consumer;

an exception is in the belly flaps of salmon steaks.

2472 FISH/Dietary Importance of Fish and Shellfish

Many species of finfish and almost all shellfish

contain less than 2.5% total fat, and less than 20%

of the total number of calories comes from fat.

Almost all fish have less than 10% total fat, and

even the fattiest fish such as herring, mackerel, and

salmon have no more than 20% fat (see Table 1).

To obtain a good general idea of the fat content of

most finfish species, the color of the flesh should be

considered. The leanest species such as cod and floun-

der have a white or lighter color, and the fattier fish

such as salmon, herring, and mackerel have a much

darker color.

0015 The triacylglycerol depot fat in edible fish muscle is

subject to seasonal variations in all marine and fresh-

water fish from all over the world. Fat levels tend to

be higher during times of the year when fish are

feeding heavily (usually during the warmer months)

and in older and healthier individual fish. Fat levels

tend to be lower during spawning or reproduction.

When comparing fat contents between farmed and

wild-caught food fish, it should be considered that

farmed species have a tendency to show a higher

proportion of muscle fats than their wild counter-

parts. Also, the fatty acid composition in the lipids

of farmed fish is dependent on the type of dietary

fat used for raising the fish. Cholesterol is independ-

ent of fat content and similar in wild and cultivated

fishes.

0016 Most protein-rich foods including red meat and

poultry as well as fish contain cholesterol. Almost

all types of fish and shellfish contain well under

100 mg of cholesterol per 100 g, and many of the

leaner types of fish have typically 40–60 mg for

100 g of edible muscle. It is known that most shellfish

also contain less than 100 mg of cholesterol per 100-g

serving. Shrimp contain somewhat higher amounts of

cholesterol, over 150 mg per 100 g, and the squids are

the only fish product with a significantly elevated

cholesterol content, which averages from 300 mg

per 100-g portion. Fish roe, caviar, the internal organs

of fish (such as livers), the tomalley of lobsters and the

hepatopancreas of crabs can contain high amounts of

cholesterol.

v-3 PUFA in Fish and Shellfish

0017The polyunsaturated fatty acids of many fish lipids

are dominated by two members of the o-3 family

(n-3), C20:5 n-3 (EPA) and C22:6 n-3 (DHA). They

are so named because the first of the several double

bonds occur three carbon atoms away from the

terminal end of the carbon chain.

0018All fish and shellfish contain some o-3 but the

amount can vary, as the relative concentrations of

PUFAs are species-specific (see Table 2). Generally,

the fattier fish contain more o-3 fatty acids than the

leaner fish. The amount of o-3 fatty acids in farm-

raised products can also vary greatly, depending on

the diet of the fish or shellfish. Many companies now

recognize this fact, and provide a source of o-3 fatty

acids in their fish diets. o-3 fatty acids can be des-

troyed by heat, air, and light, so the less processing,

heat, air exposure, and storage time, the better the

o-3 can be preserved in fish. Freezing and normal

cooking cause minimal o-3 losses, whereas deep

frying and conditions leading to oxidation (rancidity)

can destroy some o-3 fatty acids.

0019The beneficial effects of eating fish for human

health have been well documented. Research has

shown that EPA and DHA are useful in (1) treatment

or prophylaxis of thromboembolic conditions, (2) re-

ducing cardiovascular mortalities and increased sur-

vival of patients, (3) decreasing stroke incidence, and

(4) preventing fatal heart arrhythmia. DHA could also

play an important role for full brain and eye tissue

development and functions (learning ability and visual

tbl0001 Table 1 Fat levels in fish and shellfish commonly found in the

marketplace

Low (<2.5% fat),

less than 20% of

total calories from fat

Medium (2.5 ^ 5% fat),

between 20 and 35%

of total calories from

fat

High (> 5% fat)

between 35 and

50% total calories

from fat

Cod, haddock, pollock Anchovy Catfish (farmed)

Grouper, Snapper Bluefish Eel

Most flatfishes Bream Herring

Pike Carp Mackerel

Shark, skate Swordfish Salmon

Tilapia Trout Sardine

Whiting, hake Tuna (bluefin)

Most molluscs Whitefish

Most crustaceans

More than 10% fat.

tbl0002Table 2 Selected fish and shellfish grouped by their o-3 fatty

acid content

Low-level

group

(<0.5 g per 10 0 g)

Medium-level

group

(0.5 ^ 1g/100 g)

High-level

group

(> 1gper100g)

Carp Bass Anchovy

Catfish Bluefish Herring

Cod, haddock, pollock Halibut Mackerel (most species)

Grouper Pike Sablefish

Most flatfishes Red Snapper Salmon (most species)

Perch Swordfish Tuna (bluefin)

Snapper Trout Whitefish

Tilapia Whiting

Most molluscs Clams

Most crustaceans Oysters

FISH/Dietary Importance of Fish and Shellfish 2473

acuity) in late pregnancy or in preterm infants. Pos-

sible relationships between o-3 fatty acids and other

disorders such as digestive tract cancers, rheumatoid

arthritis, inflammatory reactions, and asthma are also

currently being studied (see Table 3).

Fish proteins

0020 Both finfish and shellfish are a highly valuable source

of proteins in human nutrition. The protein content

of fish flesh, in contrast to that of fat, is highly con-

stant, independent of seasonal variations related to

the feeding and reproductive cycles, and shows only

small differences among species. Table 4 summarizes

the approximate protein content of the various finfish

and shellfish groups. Fatty finfish and crustacea have

slightly higher than average protein concentrations.

Bivalves have the lowest values if the whole body

mass is considered, since most of them are usually

eaten whole, whereas values are roughly average if

specific muscular parts alone are consumed; the latter

is the case with the scallop, in which mostly only the

adductor muscle is eaten.

0021 The essential amino acid composition is given in

Table 5. Fish proteins, with only slight differences

among groups, possess a high nutritive value, similar

to that of meat proteins and slightly lower than that

of egg. It is worth pointing out the elevated supply,

relative to meat, of essential amino acids such as

lysine, methionine, and threonine. In addition, due

in part to the low collagen content, fish proteins are

easily digestible, giving rise to a digestibility coeffi-

cient of nearly 100.

0022 The recommended dietary allowances (RDA) or

dietary reference intakes (DRI) of protein for human

male or female adults are within the range of 45–65 g

per day. In accordance with this, an intake of 100 g of

fish would contribute 15–25% to the total daily pro-

tein requirement of healthy adults and some 70% to

that of children. A look towards the dietary import-

ance of Mediterranean diet is convenient; one of its

characteristics is the high consumption of all kinds of

fish, chiefly fat fish. In many Mediterranean coun-

tries, fish intake averages over 50 g per day (edible

flesh); thus, fish protein contributes over 10% to the

total daily protein requirements steadily over the

whole year in those countries.

0023Less known is the fact that the consumption of fish

protein, independently of the effect exerted by fish

fat, has been related to a decrease in the risk of

atherogenic vascular diseases. In fact, it has been

demonstrated that diets in which fish is the only

source of protein increase the blood levels of HDL

in comparative studies with milk or soya proteins.

Nonprotein Nitrogen (NPN) Compounds in

Fish

0024NPN compounds are mostly in the fiber sarcoplasm

and include free amino acids, peptides, amines, amine

oxides, guanidine compounds, quaternary ammonium

molecules, nucleotides, and urea (Table 6). This frac-

tion accounts for a relatively high percentage of total

nitrogen in the muscle of some aquatic animals, 10–

20% in teleosts, about 20% in crustacea and

molluscs, 30–40% – and in special cases up to 50%

– in elasmobranchs. In contrast, NPN in land animals

usually represents no more than 10% of total

nitrogen.

0025Most marine fish contain trimethylamine oxide

(TMAO); this colorless, odorless, and flavorless

compound is degraded to trimethylamine (TMA),

tbl0003 Table 3 Summary of beneficial effects of eating fish for the cardiovascular condition and other diseases

Cardiovascular disease (CVD) Other diseases

Protects again heart disease Protects against age-related maculopathy

Prolongs lives of people after a heart attack Alleviates rheumatoid arthritis

Protects against sudden cardiac arrest caused by arrhythmia Protects against certain types of digestive tract cancers

Protects against stroke (thrombosis) Mitigates inflammation reactions and asthma

Lowers blood lipids such as triacylglycerols and VLDL-cholesterol

Lowers blood pressure

tbl0004 Table 4 Protein content of different groups of fish and shellfish

Fishgroup gper100 g

White finfish 16–19

Fatty finfish 18–21

Crustacea 18–22

Bivalves 10–12

Cephalopods 16–18

tbl0005Table 5 Proximate content of essential amino acids in fish and

shellfish (g per 100 g of protein)

Fish group Ile Leu Lys Met Phe Thr Trp Val

Finfish 5.3 8.5 9.8 2.9 4.2 4.8 1.1 5.8

Crustacea 4.6 8.6 7.8 2.9 4.0 4.6 1.1 4.8

Molluscs 4.8 7.7 8.0 2.7 4.2 4.6 1.3 6.2

2474 FISH/Dietary Importance of Fish and Shellfish

which gives a ‘fishy’ odor and causes consumer rejec-

tion. This compound is not present in land animals

and freshwater species (except Nile perch and tilapia

from Lake Victoria). TMAO reductase catalyzes the

reaction and is found in several fish species (red

muscle of scombroid fish, white and red muscle of

gadoids) and in certain microorganisms (Enterobac-

teriaceae).

0026 Creatine is quantitatively the main component of

the NPN fraction. This molecule plays an important

role in fish muscle metabolism through its phosphor-

ylated form; it is absent in crustacea and molluscs.

0027 Endogenous and microbial proteases yield some

free amino acids; taurine (Tau), alanine (Ala), glycine

(Gly) and imidazole-containing amino acids seem to

be the most frequent. Gly and Tau contribute to the

sweet flavor of some crustaceans. Migratory marine

species such as tuna, characterized by a high propor-

tion of red muscle, have a high content (about 1%) of

free histidine (His). A noticeable amount of this

amino acid has also been reported in freshwater

carp (Cyprinus carpio). The presence of free His is

relevant in several fish species because it can be

microbiologically decarboxylated to histamine (see

Scombroid Fish (Histamine) Poisoning below).

0028 Nucleotides and related compounds generally play

an important role as coenzymes. They participate

actively in muscle metabolism and supply energy to

physiological processes. They have a noticeable par-

ticipation in flavor; moreover, some of them may be

used as freshness indices. Adenosine triphosphate

(ATP) is degraded to adenosine diphosphate (ADP),

adenosine monophosphate (AMP), inosine mono-

phosphate (IMP), inosine (Ino), and hypoxantine

(Hx). This pattern of degradation takes place in fin-

fish, whereas AMP is degraded to adenosine and

thereafter to Ino in shellfish. The degradation chain

is very fast to IMP or AMP in finfish and shellfish,

respectively. IMP degradation to Ino is generally slow,

except in scombroids and flat fish. Ino degradation to

Hx is slower. IMP is a flavor potentiator, whereas Hx

imparts a sour taste, and high levels are toxic. ATP,

ADP and AMP decompose quickly to form a build-up

of Ino and Hx. As this corresponds well with a decline

in freshness, the ratio of the quality of inosine and

hypoxanthine to the total quantity of ATP and related

substances is called the K-value and used as an index

representing freshness of fish meat.

0029Guanosine is an insoluble compound that gives the

characteristic brightness of fish eye and skin. It is

degraded to guanine, which does not have this

property; therefore, brightness decreases until it

completely disappears.

0030The NPN fraction contains other interesting com-

pounds, such as small peptides. Most of them contrib-

ute to flavor; besides this, they have a powerful

antioxidant activity. Betaines constitute a special

group of compounds that contribute to the specific

flavor of different aquatic organisms: homarine in

lobster, glycine-betaine and butiro-betaine in crust-

acea, and arsenic-betaine in crustacea. Arsenic-

betaine has the property of fixing arsenic into the

structure, giving a useful method for studying water

contamination with this element.

Fish Vitamins

0031The vitamin content of fish and shellfish is rich and

varied, although somewhat variable. In fact, signifi-

cant differences are neatly evident among groups,

especially regarding fat-soluble vitamins. Further-

more, vitamin content is highly variable within

groups, also showing large differences among species

as a function of feeding regimes.

0032The approximate vitamin concentration ranges

of the various finfish and shellfish groups are

tbl0006 Table 6 Nonprotein nitrogen compounds in several commercially important fish species and mammalian muscle (mg per 100 g wet

weight)

Compounds Cod Herring Shark species Lobster Mammal

To t a l N P N 1200 1200 3000 5500 3500

Total free amino acids: 75 300 100 3000 350

Arginine <10 <10 <10 750 <10

Glycine 20 20 20 100–1000 <10

Glutamic acid <10 <10 <10 270 36

Histidine <1.0 86 <1.0 <10

Proline <1.0 <1.0 <1.0 750 <1.0

Creatine 400 400 300 0 550

Betaine 0 0 150 100

Tr i m e t h y l a m i n e o x i d e 350 250 500–1000 100 0

Anserine 150 0 0 0 150

Carnosine 0 0 0 0 200

Urea 0 0 2000 35

FISH/Dietary Importance of Fish and Shellfish 2475

summarized in Table 7. The RDA or DRI for male or

female adults is also given, as well as the percentage

supplied by 100 g of fish. Regarding fat-soluble vita-

mins, vitamin E (tocopherol) is distributed most

equally, showing relatively high concentrations in all

fish groups, higher than those of meat. However, only

a part of the vitamin E content is available as active

tocopherol on consumption of fish, since it is oxidized

as it protects fatty acids from oxidation. The presence

of vitamins A (retinol) and D is closely related to the

fat content, and so they are almost absent in most

low-fat groups. Appreciable but low concentrations

of vitamin A exist in fatty finfish and bivalve mol-

luscs, whereas vitamin D is very abundant in fatty

fish. In fact, 100 g of most fatty species supply over

100% of the RDA of this vitamin.

0033 Water-soluble vitamins are well represented in all

kinds of fish, with the sole exception of vitamin C

(ascorbic acid), which is almost absent in all of them.

The concentrations of the rest are highly variable;

however, with few exceptions, they constitute a

medium-to-good source of such vitamins, compar-

able with, or even better than, meat. The contents of

vitamins B

(riboflavin), B

(piridoxin), niacin, biotin

and B

(cobalamin) are relatively high. Indeed, 100 g

of fish can contribute up to 38, 60, 50, 33, and 100%,

respectively, to total daily requirements of those

vitamins. Fatty fish also provide a higher supply of

many of the water-soluble vitamins than white fish

and shellfish, namely piridoxin, niacin, pantothenic

acid, and cobalamin. Crustacea also possess a rela-

tively higher content of pantothenic acid, whereas

bivalve molluscs have a much higher concentration

of folate and cobalamin.

0034A Mediterranean diet, rich in fish – and especially

in fatty finfish – contributes steadily over the year to

an overall balanced vitamin supply. The last row of

Table 7 illustrates this; the supply of vitamins D, B

, and niacin of this particular diet is more than

15% of the daily requirements, whereas all other

vitamins, except ascorbic acid, contribute to a lesser,

but significant, extent.

Fish Minerals

0035The approximated composition of fish in selected

minerals is given in Table 8. The first point to note

is the fact that all kinds of finfish and shellfish present

a well-balanced content of most minerals, either

macro- or oligoelements, with only a few exceptions.

Sodium content is low, similar to other muscle and

animal origin foods. However, it must be taken into

account that sodium is usually added to fish in most

cooking practices in the form of common salt; also,

tbl0007 Table 7 Vitamin content of the different groups of fish and shellfish (mg or mg per 100 g)

A(mg) D (mg) E (mg) B

(mg) B

(mg) Niacin

(mg)

Biotin (mg) Pantothenic

acid (mg)

Folate

(mg)

(mg) C

(mg)

White finfish Tr Tr 0.3–1.0 0.02–0.2 0.05–0.5 0.15–0.5 1.0–5.0 1.0–10 0.1–0.5 5.0–15 1.0–5.0 Tr

Fatty finfish 20–60 5–20 0.2–3.0 0.01–0.1 0.1–0.5 0.2–0.8 3.0–8.0 1.0–10 0.4–1.0 5.0–15 5.0–20 Tr

Crustacea Tr Tr 0.5–2.0 0.01–0.1 0.02–0.3 0.1–0.3 0.5–3.0 1.0–10 0.5–1.0 1.0–10 1.0–10 Tr

Molluscs 10–100 Tr 0.5–1.0 0.03–0.1 0.05–0.3 0.05–0.2 0.2–2.0 1.0–10 0.1–0.5 20–50 2.0–30 Tr

Cephalopods Tr Tr 0.2–1.0 0.02–0.1 0.05–0.5 0.3–0.1 1.0–5.0 1.0–10 0.5–1.0 10–20 1.0–5.0 Tr

RDA/DRI 1000 5 10 1.2 1.3 1.3 16 30 5.0 400 2.4 60

%RDA per 100 g 0–10 0–100 2–30 1–20 2–38 5–60 1–50 3–33 2–20 0.3–12 40–100 0

% RDA/M.d.

25075 1525185 8 21000

Mediterranean diet.

tbl0008 Table 8 Selected mineral content of the different groups of fish and shellfish (mg per 100 g)

Na K Ca Mg P Fe Zn Mn Cu Se Cr Mo I

White finfish 50–150 200–500 10–50 15–30 100–300 0.2–0.6 0.2–1.0 0.01–0.05 0.01–0.05 0.02–0.1 0.005–0.02 0.005–0.02 0.01–0.5

Fatty finfish 50–200 200–500 10–200 20–50 200–500 1.0–5.0 0.2–1.0 0.01–0.05 0.01–0.05 0.02–0.1 0.005–0.02 0.005–0.02 0.01–0.5

Crustacea 100–500 100–500 20–200 20–200 100–700 0.2–2.0 1.0–5.0 0.02–0.2 0.1–2.0 0.05–0.1 0.005–0.02 0.01–0.05 0.01–0.2

Molluscs 50–300 100–500 50–200 20–200 100–300 0.5–10 2.0–10 0.02–0.2 0.02–10 0.05–0.1 0.005–0.02 0.01–0.2 0.05–0.5

Cephalopods 100–200 200–300 10–100 20–100 100–300 0.2–1.0 1.0–5.0 0.01–0.1 0.02–0.1 0.02–0.1 0.005–0.02 0.01–0.2 0.01–0.1

RDA/DRI 1000 420 700 10 15 1.5 0.07 0.15

%RDA per

100 g

1–20 4–50 15–100 2–50 1–30 1–100 25–100 8–100

% RDA/M.d.

6 5 30 18 2 2 100 100

Mediterranean diet.

2476 FISH/Dietary Importance of Fish and Shellfish

surimi-based and other manufactured foods contain

high amounts of added sodium. Potassium and cal-

cium levels are relatively low, too, though the latter are

higher in fish than in meat; in addition, small fish

bones are frequently eaten with fish flesh, thus increas-

ing calcium intake. Fish is a good source of magnesium

and phosphorus, at least as good as meat. These elem-

ents are particularly abundant in crustacea, fatty fin-

fish show elevated levels of phosphorus, and bivalve

molluscs have high amounts of magnesium.

0036 Fish is a highly valuable source of most oligoele-

ments. Fatty fish provides a notable contribution to

iron supply, similar to that of meat, whereas shellfish

have higher concentrations of most dietary metals. In

particular, crustacea and bivalve molluscs supply zinc,

manganese, and copper concentrations well above

those of finfish. Worth mentioning is the extraordin-

ary dietary supply of iodine in all kinds of finfish and

shellfish; however, this depends on the concentration

present in feed, particularly in plankton organisms.

0037 In summary, 100 g of fish afford low levels of sodium

and medium-to-high levels of all the remaining dietary

minerals. In fact, they cancontribute up to 50–100% of

total daily requirements of magnesium, phosphorus,

iron, copper, selenium, and iodine. A Mediterranean

diet, rich in fatty fish and all kinds of shellfish, can lead

to an overall balanced mineral supply, which may well

reach over 20% of the daily requirements of phos-

phorus, iron, selenium, and iodine.

Sanitary Aspects of Fish Consumption

0038 Fish and shellfish consumption, besides its nutritional

role as a nutrient source, may also cause syndromes

and diseases due to infection or intoxication. Table 9

summarizes the most frequent sources of fish food

diseases. Some of the etiologic agents are common to

other food products (parasites, bacterial pathogens,

viruses, and chemicals), either from the environment

or from processing. Fish and shellfish contain other

morespecifictoxiccompoundslikeendogenoustoxins,

toxins from trophic chains, and bacterial toxins.

Endogenous Toxins

0039 Puffer Fish Poisoning is characterized by a very

potent toxin called ‘tetrodotoxin’ (TTX), which is

produced by some members of the family Tetraodon-

tidae (pufferfish). The toxin is mainly found in the

liver, ovaries, and intestines, whereas muscle tissue is

normally free of this. The symptoms are somewhat

similar to those described for paralytic shellfish

poisoning (PSP), i.e., initial tingling and numbness

of lips, tongue, and fingers, leading to paralysis of

the extremities and the respiratory system, which

may lead to death. The origin of TTX is not clear; it

has been linked to certain common marine vibrios

(part of the microflora of pufferfish) that produce a

form of the toxin. Low concentrations of the toxin

(1–4 mg) may constitute a lethal dose for humans; it

must be taken into account that internal organs of

pufferfish usually contain 40 mgg

1

in intestines to

400 mgg

1

in ovaries.

Toxins from Trophic Chains

0040Ciguatera Poisoning results from the consumption of

fish that have been fed with toxic dinoflagellates,

Gambierdiscus toxicus and Prorocentrum concavum,

being the most common. This poisoning is associated

to tropical and subtropical areas and it affects

specially large fishes from bottom and reef zones

(grouper, barracuda, red snapper and sea basses).

The symptoms are both gastrointestinal and neuro-

logical, the onset time is usually within a few hours

and the prognosis for recovery is good if the patient

survives the first 24 h; however, the recovery period

can be rather prolonged in some cases.

0041PSP results from the ingestion of bivalve molluscs

that have consumed toxinogenic dinoflagellates

(microscopic marine plancktonic algae) of the genera

Alexandrium, Gymnodinium, and Pyrodinium. The

ultimate cause of PSP is a complex of at least 12 toxins

– saxitoxins – with neurological effects. The symp-

toms appear within 0.5–2 h of eating toxic shellfish

and can cause death by respiratory paralysis, usually

within 12–24 h; patients surviving this period recover

completely. The lethal dose for humans is 1–4 mg, and

the Food and Drug Administration (FDA) limit is

80 mg per 100 g of shellfish tissue. A single raw mussel

can contain up to 24 mg, and cooked mussel, 4 mg.

tbl0009Table 9 Fish and shellfish toxicity

1. Endogenous

Puffer fish poisoning

Other less important endogenous toxic molecules: blood

toxins, certain fish roe

2. Toxins from trophic chains

Biological origin

Ciguatera poisoning

Paralytic shellfish poisoning

Diarrhetic shellfish poisoning

Neurotoxic shellfish poisoning

Amnesic shellfish poisoning

Environmental contamination: chemicals, heavy metals,

radioactivity, etc.

3. Microbial activity

Bacterial pathogens

Virus

Scombroid fish (histamine) poisoning

4.Parasites

5. Toxic compounds from fish processing

FISH/Dietary Importance of Fish and Shellfish 2477