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to Humans, Supplement 7. Lyon: International Agency

for Research on Cancer.

International Programme on Chemical Safety (1998)

Selected Non-heterocyclic Polycyclic Aromatic Hydro-

carbons. Environmental Health Criteria 202. Geneva:

World Health Organization.

Lijinsky W (1991) The formation and occurrence of poly-

nuclear aromatic hydrocarbons associated with food.

Mutation Research 259: 251–261.

Lodovici M, Dolara P, Casalini C, Ciappellano S and Tes-

tolin G (1995) Polycyclic aromatic hydrocarbon con-

tamination in the Italian diet. Food Additives and

Contaminant 12: 703–713.

Phillips DH (1999) Polycyclic aromatic hydrocarbons in the

diet. Mutation Research 443: 139–147.

Thomson B and Muller P (1998) Approaches to the estima-

tion of cancer risk from ingested PAH. Polycyclic

Aromatic Compounds 12: 249–260.

Turrio-Baldassarri L, Di Domenico A, La Rocca C, Iacov-

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hydrocarbons in Italian national and regional diets.

Polycyclic Aromatic Compounds 10: 343–349.

Vaessen HAMG, Schuller PL, Jekel AA and Wilbers

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Polyphenols See Tannins and Polyphenols

Polysaccharides See Carbohydrates: Classification and Properties; Interactions with Other Food

Components; Digestion, Absorption, and Metabolism; Requirements and Dietary Importance; Metabolism of

Sugars; Determination; Sensory Properties

PORK

R W Mandigo, University of Nebraska, Lincoln, NE,

USA

This article is reproduced from Encyclopaedia of Food Science,

Development of the Swine Industry

0001 The earliest known records of swine domestication

are from China and date to 4900 bc. Christopher

Columbus brought the first pigs to the USA via the

Canary Islands in 1493. The early colonists of the

USA brought livestock with them from England

throughout the 1600s. Gradually, as more grain was

grown, larger herds of pigs developed and swine

production became a true industry.

0002 By the early 1800s, swine-slaughtering plants had

emerged at several large population centers in the

USA. The largest of these was at Cincinnati (also

known as Porkopolis at that time) because of its

prime location on the Ohio river. Early slaughtering

plants were located near rivers for four reasons: rivers

provided ice to keep the meat cold, transportation for

products to be shipped, a source of water, and a place

to deposit plant waste materials such as blood.

0003The advent of mechanical refrigeration led to

industry expansion as pork could be processed year-

round and kept fresh longer. Development of rail

systems and the use of refrigerated rail carriages

boosted industry growth as both livestock and meat

could be more widely distributed. In the 1800s, pigs

were often allowed to roam free in pastures and were

fed garbage or what little grain was available. Today,

most pigs are raised in large numbers in environmen-

tally controlled buildings with a very specific diet

designed to maximize growth.

0004The first slaughter operations were separate from

packing operations. By the 1850s, the two had started

to become integrated. Today, many plants have

reverted back to specializing in either slaughter and

fabrication or pork processing. This specialization

has allowed modern-day slaughtering facilities to

process around 1000 head per hour.

PORK 4625

0005 The pigs in the USA today are thought to have

descended from two wild stocks, the European wild

boar (Sus scrofa) and the East Indian pig (Sus vitta-

tus). From these two genetic bases, modern pigs have

been refined into several breeds which each have

distinguishing characteristics. In addition to hair

color and marking differences, breeds have been

developed for specific purposes such as prolificacy,

bacon production, ham production, and others.

0006 In general, pigs have become leaner as the demand

for lard has decreased and the demand for leaner

meats has increased. The modern market pig is

approximately 71.5% carcass while the remaining

28.5% is mostly byproducts used in the medical and

animal feed industries.

Slaughter, Fabrication, and Processing

Procurement

0007 Although pigs of all sizes can be slaughtered, most

swine-slaughtering plants have equipment designed

to handle pigs marketed at about 105 kg. Swine pro-

ducers can sell their pigs to slaughter plants in various

ways. Pigs can be marketed at a central location such

as an auction or a packer buying station or they can

be purchased from the farm by a packer buyer. The

latter method is the most popular today. A new way

to market pigs that has some popularity is contract

producing for a specific packer.

0008 After pigs arrive at the slaughtering plant, they are

slaughtered within 2–3 h of arrival. If a substantial

delay is expected, then they will usually be held in

pens for 12–24 h. It is important to allow pigs time to

become acquainted with their environment as high-

stress conditions can cause undesirable changes in

muscle color and juiciness. In pigs with a certain

genetic make-up, severe stress can cause the meat to

be pale and watery (known as pale, soft, and exuda-

tive, PSE). Long-term stress, on the other hand, can

lead to a condition where the muscle is dark and very

dry-appearing (known as dark, firm, and dry, DFD).

The physiological basis for these conditions is an

abnormal muscle pH change between the time of

death and the completion of rigor mortis. Therefore,

it is necessary to minimize stress by proper handling of

pigs prior to slaughter. Feed is usually kept from the

animals during this period to decrease stomach fill.

This improves percentage of carcass dressing, aids

evisceration during slaughter, helps minimize contam-

ination, and improves color. (See Meat: Slaughter.)

Slaughter

0009 All meat sold interstate in the USA must be inspected

by the US Department of Agriculture, Food Safety

and Inspection Service (USDA-FSIS). Inspection

begins antemortem and continues throughout the

entire slaughter, fabrication, and processing system.

This helps ensure the wholesomeness of meat prod-

ucts offered to the consumer. If the meat will be sold

intrastate only, some states allow inspection by state-

employed inspectors. This inspection, by law, must

be equal to federal inspection. Similar inspection

regimes apply in Europe and other developed regions

of the world.

0010At the time of slaughter, pigs are herded into a

chute where they are stunned to render them uncon-

scious. Stunning can be accomplished by one of

several methods, but is mandatory to comply with

the US Humane Slaughter Act of 1958. If stunning

is not performed correctly, the incidence of poor-

meat-quality problems could increase. An example

of this is a condition referred to as blood splashing.

Blood splashing occurs when small capillaries in

muscle tissue burst during stunning, leaving spots of

blood in the muscle. The most common method of

stunning is accomplished using an electrical current.

Other methods include a blow from a captive bolt to

the head, moving pigs through a carbon dioxide gas

chamber to cause suffocation, or cardiac arrest stun-

ning. The goal of stunning is to render the animals

unconscious while allowing the heart to continue to

beat and pump blood out of the body.

0011After stunning, the pig is immediately shackled,

hoisted by the hind leg, and the jugular vein is severed

with a knife to allow blood to exit the body. Bleeding

will remove around 50% of the blood in the body.

Much of the remaining blood is removed with the

organs during evisceration.

0012Pigs can either be skinned or they can be scalded

and dehaired. To dehair carcasses, the pig is put in a

scalding vat of hot water (60



C) with lye to loosen

the hair follicles. The pig is removed from the scalding

tank and dehaired mechanically and/or by hand using

blades to scrape away the hair. Whole skins from

skinned pigs can be saved and made into pigskin for

use in garments and for gelatin production.

0013After dehairing or skinning, the abdominal and

thoracic cavities are opened and the internal organs

removed. Certain organs are washed, inspected, and

saved as edible byproducts. These include the liver,

heart, tongue, and brain. Other organs may also be

saved as inedible byproducts, and will be discussed

later in this article.

0014The carcass is washed, weighed, and placed in a

cooler for chilling. The cooler temperature is main-

tained at about 2to5



C so that internal areas of

the carcass will be adequately chilled in 24 h. While in

the cooler, most of the remaining stored energy in the

muscle will be depleted and the carcass will undergo

4626 PORK

rigor mortis. Some carcasses are processed before

they go through rigor mortis. This is called hot

boning. Although fabrication is more difficult, the

cuts can be chilled faster than whole carcasses, so

product that has been hot-boned can be moved

through the system faster.

Fabrication

0015 Pig carcasses are fabricated into wholesale cuts, using

knives, saws, and other mechanical equipment. The

wholesale cuts include the ham, loin, Boston shoul-

der, picnic shoulder, belly, and spare ribs. The whole-

sale cuts may be shipped fresh to further processors,

food service operations, or to the retail market. Some

plants will continue to fabricate the wholesale cuts

into retail cuts and trimmings and sell these items.

Many plants that slaughter will carry out further

processing such as curing and smoking bellies and

hams in the same plant. (See Curing.)

Processing

0016 Further processing of pork can involve many different

processes. Processing encompasses many steps, in-

cluding particle size reduction, the addition of non-

meat ingredients, cooking, smoking, and a variety

of packaging procedures. Patties can be made by

grinding pork trimmings, with a specified fat

level, with salt and other seasonings. Restructured

products often have salt and phosphates added

to flaked or chunked meat. These ingredients are

then mixed and formed into steaks, chops, or roasts.

Sausage is another type of further processed

meat. Sausages can be cured, smoked, dried, or

cooked. Some sausages are coarsely ground

while others are finely chopped, forming what is

sometimes called an emulsion or batter. Bratwurst,

frankfurters, and bologna are sausages that typically

contain pork. (See Meat: Sausages and Comminuted

Products.)

0017 The hams and bellies from pork carcasses are

usually cured and smoked. The curing may be done

by packing in a dry cure or, more commonly, by

pumping or injecting a solution containing the

cured ingredients into the meat. The curing solution

may contain any or all of the following ingredients:

water, salt, sugar, phosphate, nitrite, erythorbate, or

spices and seasonings. Water is used to add moisture

to the product as well as acting as the solvent in a

curing solution. Salt solubilizes proteins in meat

so the meat particles bind together better. Salt also

adds flavor and, at high levels, retards microbial

spoilage. Sugar can be used for flavor, to promote

browning, and to act as a food source for desirable

bacteria in some fermented meat products. Phos-

phates are added to help retain water in the product

and to prevent oxidative rancidity from occurring.

Nitrite is the curing agent. Nitrite binds to meat

pigments and causes the meat to develop a stable

pink color. It also lends flavor, acts as an antimicro-

bial agent, and helps to prevent oxidative rancidity.

Erythorbate is used to speed up the curing process,

which is economically important to pork processors.

Spices and seasonings are added to develop flavors

unique to a particular product. (See Smoked Foods:

Principles.)

0018Some sausages are cured and may also contain

acidulants, starter cultures, or extenders. Acidulants

and starter cultures of bacteria can be used to lower

the pH of products in order to develop certain flavors

and protect the product from spoilage. Nonmeat

extenders, such as soya proteins or nonfat dry milk,

may be used as inexpensive protein sources.

0019The US Department of Agriculture (USDA) has

regulations regarding the composition of processed

meat products and the proper use of some ingredients

used in processing. Hams must be labeled according

to the amount of protein they contain on a fat-free

basis. The amount of phosphates, nitrites, erythor-

bate, and nonmeat ingredients added are also limited.

These regulations, and similar ones in other coun-

tries, are designed to provide consumers with high-

quality, safe meat products.

0020Pork is also regulated by the USDA in an attempt to

control the disease trichinosis. Trichinosis is caused

by the organism Trichinella spiralis and can be trans-

mitted from pig to humans by ingestion of infected

muscle tissue. Simply put, the regulation states that

pork for use in products that are not fully cooked in

the home must be certified as ‘trichina-free.’ Pork

may become certified trichina-free by being subjected

to specific heat or freezing to kill the organism. (See

Zoonoses.)

Chemical Composition

0021Fresh pork muscle is 70–75% water, and the protein

content ranges from 18 to 22%. There are three

main types of protein in the pig: myofibrillar (skel-

etal), stromal (connective tissue), and sarcoplasmic

(pigments). Lipid or fat is another major constituent

of fresh pork. It makes up between 5 and 7% of

the muscle tissue. Lipids include phospholipids and

triacylglycerols (also known as triglycerides). The

carbohydrate content of meat is negligible, generally

less than 1%. Vitamin and mineral content of

fresh pork is usually about 1–2%. (See Fats: Classifi-

cation; Meat: Structure; Nutritional Value; Protein:

Chemistry.)

0022Different cuts in the carcass will have different

compositions. This is largely due to the varying fat

PORK 4627

level in different areas of the carcass. Table 1 contains

some example cuts and their typical raw composition.

Nutrient Value and Dietary Significance of

Pork

0023 Pork supplies many nutrients essential for mainten-

ance and growth.

0024 As with other meat, pork is an excellent source of

protein. A single 85-g serving of pork contributes

41% of the daily protein requirement for a normal

adult male. Not only does pork contain a large

amount of protein, this protein is of good quality.

(See Protein: Requirements.)

0025 Pork also contains lipids and fats. About 34%

of pork fatty acids are saturated and 66% are un-

saturated. Cholesterol is another lipid found in

pork. Cholesterol is found in cell membranes in

the animal body and is synthesized in the liver of

humans and animals. Consumption of animal prod-

ucts, therefore, provides a dietary source of choles-

terol which can be used in the body. Cholesterol,

like saturated fats, has been associated with increased

risk of developing heart disease. The relationship is

not well understood, but the American Heart Associ-

ation recommends keeping dietary intake of choles-

terol to less than 300 mg day

1

. One 85-g serving of

pork provides about 79 mg of cholesterol or about

26% of the recommended 300 mg. (See Cholesterol:

Role of Cholesterol in Heart Disease; Fatty Acids:

Properties.)

0026 Pork is an excellent food source for several vita-

mins and minerals. It supplies large amounts of thia-

min, vitamin B

, niacin, riboflavin, and zinc. Pork is

also a good source of vitamin B

, phosphorus, and

iron. Dietary iron can be classified into two types,

heme and nonheme. Heme iron, which is the major

type found in pork, is absorbed more easily and better

utilized by the body. Iron is a component of the

molecule hemoglobin, which is the major carrier of

oxygen in our blood stream. Intake of heme iron is

especially important in warding off anemia, which

may result from a low level of hemoglobin in the

blood. Refer to individual vitamins and minerals.

0027 Pork, when consumed in moderation, is an excel-

lent source of many important dietary nutrients.

Microbiological and Other Hazards

0028Muscle is essentially sterile prior to death. However,

meat destined for human consumption is cross-

contaminated with microorganisms by equipment and

handling at the time of slaughter and processing. Just as

pork is an excellent source of nutrients for our bodies,

muscle or meat is also an excellent growth medium

for microorganisms. Controlling the growth of micro-

organisms on pork by acidifying, curing, salting,

modified-atmosphere packaging, drying, cooking, or

refrigerating is essential. (See Meat: Preservation.)

0029Food poisoning can result from consuming pork

that has been mishandled, allowing certain micro-

organisms to grow. Causative organisms of food

poisoning may include Staphylococcus aureus, Bacil-

lus cereus, Salmonella spp., Listeria monocytogenes,

Yersinia enterocolitica, Clostridium botulinum, C.

perfringens, and Campylobacter fetus ssp. jejuni.

Food poisoning is quite common and, in its mildest

forms, is often mistaken for influenza because the

symptoms are very similar. Generally, foodborne ill-

nesses are relatively short-lived and more uncomfort-

able than harmful. However, food poisoning can be a

very serious matter. It can be debilitating or even fatal

for those with poor immunological defenses such as

infants or the elderly. Like other microorganisms,

pathogens which cause food poisoning are well con-

trolled by heat, refrigeration, chemicals, or other

means mentioned earlier. However, undercooking,

improper cooling, or recontamination of cooked

food by raw food are common ways that pathogens

appear in the food supply. (See Bacillus: Food

Poisoning; Campylobacter: Properties and Occur-

rence Clostridium: Food Poisoning by Clostridium

perfringens; Botulism; Listeria: Properties and Occur-

rence; Staphylococcus: Food Poisoning.)

0030Of particular concern in pork is the parasitic nema-

tode T. spiralis. This organism forms a cyst in porcine

muscle. The organism can be transmitted to humans

who consume the contaminated pork, but is readily

destroyed by heating the muscle to 62



C. Processing

plants that sell pork which is not likely to be cooked

again are required to heat or freeze the meat to certify

that it is trichina-free.

0031Pork-slaughtering and processing plants have rigid

sanitation programs that allow production of safe

food. Good sanitation at the plant and proper hand-

ling throughout the food chain help keep microbial

growth under control. Plants producing pork must

keep processing temperatures below 10



C or stop

production and sanitize the equipment every 8 h.

Most plants keep their working temperature low

enough to require cleaning and sanitizing only once

every 24 h. Cleaning and sanitizing are not the same

tbl0001 Table 1 Composition of various raw pork cuts (g kg

1

raw

meat)

MoistureFat ProteinAsh

Ham slice 730 55 205 10

Bacon 370 530 95 5

Loin chop 710 70 210 10

Spare ribs 575 245 170 10

4628 PORK

thing, but they are most effective when carried out

together. Generally speaking, a plant is cleaned with

soap and water to remove residual meat particles.

Then the soap is rinsed off and sanitizer is applied

to kill microorganisms that survived the cleaning.

Common sanitizers used can be chlorine, ammonia,

or iodine-based. (See Sanitization.)

0032 A great deal of effort is spent to clean and sanitize

the plant thoroughly, as well as educate employees

about the importance of good hygiene in reducing

food contamination. Microbiological status of the

processing area is monitored daily. In addition, the

plant must pass a sanitation inspection by a USDA

inspector before the day’s production can begin.

0033 Despite all the in-plant efforts to control micro-

organisms, pork can still be contaminated or growth

of microorganisms already present can occur as a

result of product abuse in the warehouse, on the

delivery truck, in the retail outlet, or in the home.

Perishable foods should always be frozen or refriger-

ated at temperatures below 4



C. Once cooked, pork

should be kept above 60



C or quickly cooled to

under 4



C. Many microorganisms grow rapidly in

the temperature range 4–60



C. Two very common

mishandling problems that occur in the home are

failing to refrigerate leftovers promptly and reconta-

minating cooked product by using the same utensils

used with the raw product.

0034 To minimize microbiological hazards and maxi-

mize eating quality, the recommendations in Table 2

have been devised as maximum limits for storage

of pork. Molds and yeasts are of little concern in

fresh pork because the high water activity allows

bacteria to dominate. In dried pork items such as

pepperoni, molds may grow on the surface. However,

mold growth is retarded by a potassium sorbate dip

applied by the manufacturer or by vacuum pack-

aging. (See Spoilage: Bacterial Spoilage; Molds in

Spoilage; Yeasts in Spoilage; Water Activity: Effect

on Food Stability.)

0035 Very few other hazards exist with the consumption

of pork. Muscle from pigs is regularly monitored for

drug and pesticide residues by the USDA. Incidences

of contaminated meat have been isolated and total far

less than 1% of the pork supply.

Food Uses and Products

0036Pork is a very versatile food that can be prepared in

many ways. Popular entre

e items include pork roast,

ham steaks, barbecued spare ribs, and grilled pork

chops. Pork is also a common component of many

foods such as bacon on pizza or ham dices in a chef’s

salad.

0037Pork trimmings can be ground and made into pat-

ties or sausages of all types, including frankfurters,

pepperoni, and Italian sausage.

Waste or Byproduct Utilization

0038People in the swine industry say that no part of the pig

is wasted. This statement is not far from the truth.

The major waste product from the live pig is manure,

which is a good nitrogenous fertilizer.

0039Waste products from swine slaughter and process-

ing are perhaps better referred to as byproducts

because they are seldom wasted. Blood, bones, and

inedible viscera from pig slaughter are usually dried

and ground for use in animal feeds. Gelatin is made

from collagenous proteins found in pig skin. Indus-

trial lubricants, plastics, and rubber are made from

fat trimmed off pig carcasses. Pig skin fabric can be

produced from cured pork skins. Even the pig’s hair is

sometimes used for brushes or insulation.

0040Perhaps the most important byproducts of swine

slaughter and processing are those used in medicine.

Hormones such as pig insulin or heparin can be pre-

pared for human use. Heart valves from pigs have

been used to replace damaged or diseased human

heart valves and are often used in heart disease re-

search. Skin grafts from pig skin have been success-

fully used on human burn victims. These are only a

few examples of many medicinal uses of byproducts

from the swine industry.

Acknowledgments

0041Appreciation is expressed to Doreen Blackmer for

research and editorial assistance.

See also: Bacillus: Food Poisoning; Campylobacter:

Properties and Occurrence; Cholesterol: Role of

Cholesterol in Heart Disease; Clostridium: Food

Poisoning by Clostridium perfringens; Botulism; Curing;

Fats: Classification; Listeria: Properties and Occurrence;

Meat: Structure; Slaughter; Preservation; Sausages and

Comminuted Products; Nutritional Value;

Staphylococcus: Food Poisoning; Zoonoses

Further Reading

Mandigo R (1989) Pork Operations in the Meat Industry.

Washington, DC: American Meat Institute.

tbl0002 Table 2 Pork storage recommendations

Refrigerator (2^4



C) Freezer (18



Fresh pork 4 days

3–6 months

Cured pork 7 days 2 months

Packaging and handling prior to the consumer will greatly impact shelf-

life of pork.

Ground meat, 2 days.

Ground meat, 1–2 months.

PORK 4629

National Academy of Sciences, National Research Council,

Food and Nutrition Board (1986) Recommended Daily

Dietary Allowances, 10th edn. Washington, DC:

National Academy of Sciences.

National Live Stock and Meat Board (1973) Hog is Man’s

Best Friend. Chicago: National Live Stock and Meat

Board.

National Live Stock and Meat Board (1977) Lessons on

Meat. Chicago: National Live Stock and Meat Board.

National Live Stock and Meat Board (1987) Exploring Diet

and Health. Chicago: National Live Stock and Meat

Board.

Troller J (1983) Sanitation in Food Processing. Orlando:

Academic Press.

US Department of Agriculture (1983) Composition of

Foods; pork products, raw, processed, prepared. USDA

Handbook, nos. 8–10. Washington, DC: Human Nutri-

tion Information Service.

PORT

Contents

The Product and its Manufacture

Composition and Analysis

The Product and its

Manufacture

E Cristovam, University of Adelaide, Adelaide,

Australia

A Paterson, University of Strathclyde, Glasgow, UK

Background

0001 Ports are fortified wines based upon a long tradition

with expert blending employed for style, create

defined characters and produce the quality factor

that makes port highly prized. Production methods

differ from table wines primarily in that the fermen-

tation – in some case still from spontaneous endoge-

neous microfloora of the must – takes place only

during the 2–3 days of maceration. During this

period, there is extraction of soluble compounds re-

sponsible for characteristic color and flavor charac-

ters of ports. Addition of brandy terminates the

fermentation, leaving a young wine with high

amounts of residual sugars. Such fortified wines

have been produced in Portugal since the seventeenth

century. Originally exported to Britain, since the

1960s France has been the largest importer. Many

port houses are still British-owned and blenders

follow house styles, believed to yield wines suited to

British markets. Port is also used in elegant cocktails

and receptions (‘Porto de honra’). Three major prod-

uct styles are recognized – Portuguese, English, and

French – based on house cultures. Ports have many

myths and traditions associated with Christmas,

gout, the British upper classes, and formal dinner

parties. Consumer rituals abound, Port should be

passed to the left from the host, and ladies should

not touch a Port bottle. These wines are established

products with an image of luxury, with seasonal

peaks in demand dominated by that from the older

generation and males. Port wine is a key product for a

national economy of Portugal and a symbolic asset

representing the country world-wide: unfortunately,

demand is decreasing, probably as a result of social

and lifestyle changes. However, port is now drunk on

formal occasions, and such changes may enhance the

demand for higher-quality wines.

History and Origin

0002The designation ‘port’ in wines appeared during

the second half of the seventeenth century when

this fortified product increased in popularity in

Britain, replacing Bordeaux wines in English trade.

This was enhanced by the Methuen Treaty between

England and Portugal in 1703, guaranteeing pre-

ferential customs tariffs for port wines to balance

similar tariffs for imports of British textiles by

Portugal.

0003At that time such wines, from the Douro in North-

ern Portugal, were red, dry, and coarse, with an alco-

hol content of 12–13%. Subsequently, brandy was

added to stabilize wines, to reduce spoilage during

the long sea journey around Western Europe. How-

ever, this fortification practice became central to

the production process – removing excess acidity,

4630 PORT/The Product and its Manufacture

rounding the flavor character and creating a charac-

teristic set of attributes that became unique to port

wine. In 1756, the Marquis of Pombal set legal

boundaries for the Douro Valley vineyards, annual

production quotas, and strict rules for cultivation,

transportation, and prices. Even a tasting was re-

quired before wine was sold. The aim was to safe-

guard port wine’s authenticity, and effectively, a new

product was created. In 1921, a further addition was

made to the definition of port wines in that these must

be lodged in the country for a given period before

being deemed fit for export.

0004 In the 1860s, phylloxera destroyed most vineyards

in the demarcated region. This forced a restructuring

of viticulture and winemaking techniques. At the

same time, imitations of port started to appear from

France and Spain. At the beginning of the twentieth

century, in order to counteract such fraud and main-

tain quality, regulations were imposed for the produc-

tion, sale, and export of Ports. Denomination of

origin was reserved for fortified wines from the

Douro region, in Northeast Portugal, with a min-

imum of 16.5% alcohol. Distillation of Douro wines

was prohibited, and fortifying spirit had to be

obtained from other regions.

0005 In 1926, a bonded area was created in Gaia – Vila

Nova de Gaia – a city opposing Porto on the Douro

river mouth (Figure 1). Gaia became part of the demar-

cated region, and here, port trade companies were

forced to build lodges to age wines. Now, shipments

can be made from both Gaia and the demarcated

Douro region. Lodges maturing in the Douro produce

wines with characteristic baked flavor notes through

the high temperatures experienced upriver.

0006By the 1930s, exports were at a peak, but prices

soon fell as quality was neglected, and production

exceeded market demands. To counter this, legisla-

tion was introduced to control the two facets of the

port industry – production and trade. In 1932, wine-

growers were organized into guilds, now Casa do

Douro (CD), responsible for monitoring vineyards,

wine quality, and grape brandy production. A year

later, a guild of port wine shippers was established,

and the Instituto do Vinho do Porto (IVP) was formed

to coordinate activities. The IVP regulates the de-

scription of ports with respect to dates and indication

of age, controls the seal of guarantee, and still coord-

inates Casa do Douro activities.

0007Prior to entering or leaving Gaia, all ports are

submitted to a chamber of tasters, constituted by

experienced specialists. This is overseen by a con-

sultative committee of tasters from individual port

firms, chosen on the basis of reputation and expertise,

but confirmed and formally appointed by the Minis-

try of Economy. This gives expert tasting opinions

and has the final decision.

0008In theory, any must produced within the Douro

demarcated region can be used for port. However,

the IVP sets limits to annual quantities of wine to be

‘beneficiado’ (improved or benefited). Growers must

apply to the CD for the right to produce within this

allowance. Applications must list the name of the

fig0001 Figure 1 (see color plate 122) Vila Nova de Gaia; bonded area in Portugal.

PORT/The Product and its Manufacture 4631

petitioner, the municipality and parish of each

property, property names, number of vines over 4

years old, estimated production, and amount of

wine to be used for port. Applications are checked

against a register that makes reference to a classifica-

tion system. Class A vineyards are, on average,

granted a benefit of 600 l per thousand vines and

Class E 400 l per thousand vines. Production is quan-

tified in pipes – the volume of a traditional 550-l oak

cask. Allowances are varied according to vineyard

classification, total allowance for the year, and pro-

spects for wine production in that year.

0009 Today, port is a product that requires careful qual-

ity management strategies. To protect the industry,

there is an upper limit on the number of vintages

that can be declared and maxima to the fractions of

wine in houses that can be traded in any year.

Production Area

0010 The boundaries of the demarcated Douro region – the

oldest in the world – have remained largely un-

changed since 1756 (although revised in 1907, with

minor alterations in 1921). This region consists of

four districts: Vila Real, Braganc¸a, Viseu, and Guarda

covering c. 250 000 acres, with three subregions:

Baixo Corgo, Alto Corgo, and Douro Superior

(Figure 2), each with individual characters. Vines

cover approximately 15% of the region, with the

Baixo Corgo dominating. Small vineyards can be

found throughout the region, with the larger vine-

yards mostly located in the Douro Superior. Before

planting on the steep mountainous slopes, terraces

must be formed. This was done in the past with

hammers and dynamite but is now done with bull-

dozers when possible. Grape production is difficult

because of the nature of the soil, schistose with gran-

ite in certain areas, and narrow terraces. The climate

is harsh with frosty winters, hot (> 37



C) dry

summers, and in certain areas wet springs.

Grape Varieties

0011 Only approximately 10 500 hectares (26 000 acres)

are authorized for vineyards that can be used for port

production. Most vine varieties are regional, grafted

on to rootstock types chosen for grape variety and soil

compatibility. The rootstocks used are Rupestris du

Lot, Berlandier hybrids, either Riparia strains (420-A,

SO4, 161/49) or the Rupestris varieties (R.99 and

R.110).

0012The varied microclimates in the Douro region

have resulted in 48 grape varieties being used in port

production. However, there has been a rationali-

zation to increase quality and optimize vine planting

and grape production. Currently, an official EC rec-

ommendation quotes 29 varieties for port: 15 red and

14 white. Desirable red grape varieties produce

tannic, intensely colored wines. Until recently, one

of the most popular was Tinta Francisca, derived

from Pinot Noir. Other important varieties are Tour-

iga Nacional, Tinta Roriz (Tempranillo in Spain),

Touriga Francesa, Tinta Barroca, and Tinto Ca

The dominant white grape varieties are Malvasia

Fina, Viosinho, Donzelinho, and Gouveio.

0013Of the Douro red grapes, Touriga Nacional is con-

sidered to produce the finest and most complex wine,

although the yield is low. It is also a vigorous and

adaptable variety, growing in a wide range of condi-

tions. Wines from Touriga Nacional have an aroma

character suggesting red fruit, often with floral notes,

notably of violets. Flavors are complex, elegant, bal-

anced, and rich in nonaggressive tannins, and finishes

are long and smooth.

0014Another red grape, Tinta Roriz, grows best on

fertile soils, producing large, tight clusters of thick-

skinned grapes of a high quality. Wines, less colored

than those from Touriga Nacional, also have rich

aroma characters dominated by red berries, with

strong herbal overtones. Flavor characters are strong

and astringent from harsh tannins, and lengthy fruity

finishes contribute structure in blending.

0015The most fragrant wines are from Touriga Fran-

cesa. This variety is adaptable but requires a warm

growing season to completely ripen grapes. Strong

floral characters, notably of rose, dominate the

aroma notes. Flavor, with fruity and floral attributes

and earthy overtones, is thought to be well balanced

with a long, concentrated finish. These wines contrib-

ute aroma and structure to products in blending.

0016Tinta Barroca is a high-yielding variety with large,

loose clusters of thin-skinned, oversized berries.

Wines are soft, fragrant, and delicate with a lingering

red fruit aftertaste, but are often lacking in complex-

ity and light in color. These wines contribute little to

blend structure. Tinto Ca

o produces a smaller grape

than other varieties.

0017A central problem in the Douro is finding a balance

between the desirable character attributes in varietal

grapes and production yield. The overall must color

Baixo

Corgo

Portugal

Spain

Alto

Corgo

Douro

Superior

Atlantic Ocean

fig0002 Figure 2 Regia

o Demarcada do Douro.

4632 PORT/The Product and its Manufacture

in young port wines, central to production, is influ-

enced more by cultivar than by season.

Production Method

0018 Harvesting of port grapes is difficult. Grapes are

picked entirely by hand, between 15 September and

15 October depending on the weather and region, in

vineyards that slope at an average of 45



. After grape

destemming, traditionally grape treading was carried

out to extract must in a ‘lagar’ (a large open, shallow

stone tank). However, this quaint procedure has gen-

erally been replaced by more readily controlled and

standardized practices. Currently, most port is pro-

duced in closed fermentation tanks often equipped to

turn over the wine automatically. Alternatives in-

clude open tanks, in which must is pumped around,

and concrete or stainless steel tanks, fitted with

mechanical stirrers. Grapes are generally broken in

centrifugal crushers with pumps. In certain produc-

tion sites, for total or partial removal of skins,

crushed grapes fall into a blender that shreds skins

completely. The fermenting must is run off when

most sugars have been converted into alcohol after

2–3 days of fermentation. After separation from

solids, fermentation is inhibited by aguardente

(grape brandy) addition. Wine officially becomes

port at 19–20% (abv).

0019 Brandy fortification, in addition to quenching the

spontaneous fermentation, contributes specific sens-

ory attributes to wine, improves chemical stability,

and controls the final sweetness intensity. The sweet-

ness in ports comes only from unfermented sugars.

Fermentation must therefore be terminated when the

residual wine sugars contribute to the desired sweet-

ness. The quality of brandy added to the fermenting

must is also a key factor in determining the chemical

composition and final flavor character potential of

quality ports.

0020 The nascent port wines are stored in tanks, vats, or

casks. It is not clear whether container capacity influ-

ences final wine character, but container material cer-

tainly does. More important seems to be the storage

site, i.e. whether upriver at Douro or by the sea at Gaia

– concrete tanks with a tartaric acid coating or stainless

steel are often used. Once transported to Gaia, wines

must be submitted to the IVP tasters for classification.

Group 1 wines are considered ‘of immaculate quality,

carrying special privileges’. Group 2 wines have slight

imperfections but are fit for usage. The final Group, 3,

is for wines rejected either by tasters or by analysts.

Traditional Vintage

0021 The traditional process, predominant until 1960,

consisted of handpicking of grapes by groups of

workers with transport in large baskets either on

the shoulders or by cart. At the winery, workers

crushed grapes barefoot in the lagar, marching

back and forth in a line, until the juice floated on

top of a pulpy residue. This initiated the fermenta-

tion with must darkening as the color was extracted

from skins. To maintain the fermentation, paddles

stirred the must, and when sufficient sugar was

converted to alcohol, the liquid was run off into

wooden vats and 110 l of Aguardente added for

each 440 l of wine.

0022The nascent port was held in ‘toneis’ and tasted

regularly until it was ready to be transported by expert

boatmen down the river Douro in ‘barcos rabelos,’ in

the spring following the harvest, or vintage. Gaia was

originally chosen as the bonded area because port

pipes could be easily off-loaded from riverboats to

lodges and transferred to seagoing vessels.

Modern Vintage

0023With decreased manpower through migration, major

changes have been, and are, taking place in port

production. The vinification process, blending pol-

icies, maturation practices, and transport to lodges

in Vila Nova de Gaia have changed considerably.

0024The widespread introduction of electricity in the

early 1960s led to the replacement of human contri-

butions with the autovinification process. Such mech-

anization led to establishment of wine centers at

larger quintas. The result was that farmers sold more

grapes, and wine production was centralized to facili-

tate improved quality control. Closed autovinifica-

tion plants and open tanks came into use, but

certain producers still believe that open-tank fermen-

tations with automatic paddles optimize the color

extractions from must.

0025Since the 1970s, production has moved from indi-

vidual quintas to wineries with a greater plant cap-

acity: currently, both fermentation and storage tanks

are considerably larger. By the 1980s, over 80% of

port was produced in wineries, with cooperatives

producing approximately 40%.

0026Grapes arrive by lorry in open steel containers and

are weighed, tipped into reception tanks, and imme-

diately carried by screw feeders into a crushing and

stemming machine. This is typically an upright cylin-

der, approximately 1 m in diameter, which centrifu-

gally removes stalks to an extent depending on the

tannin requirement. The must is pumped into square

concrete or triangular stainless steel tanks, autovini-

fication vats, an autovinificator cylinder is clamped

on, and a water escape valve is filled. Provided that

the temperature is c.16



C, the must starts fermenting

almost immediately. Fermentations last 2–3 days,

with sugar contents assessed continuously from

PORT/The Product and its Manufacture 4633

specific gravity. The total sweetness of the port is

derived from the original grape sugars.

0027 Young ports stay in wooden vats or cement holding

tanks in the Douro until they are ready for transport

to Gaia in the spring by the road tankers. The narrow

and winding roads of the Douro retain some of the

hazards of bygone eras.

0028 White port production uses white grapes, often

with limited maceration, and wines are aged under

oxidizing conditions. Grape skins acquire a golden-

brown hue at harvest, and in order to produce a light

gold, rather than a yellow–white, port, it is necessary

to minimize skin contact during fermentation. Con-

sequently grape skins are removed after crushing,

and the maceration time is also kept to a minimum.

Oxidation is not encouraged if complex floral aroma

notes and pale yellow color are desired in the final

wine.

Maturation and Blending

0029 Young ports are stored in vats or casks made of oak

or mahogany in the Douro. During the first

winter, wine is racked (pumped off) from the lees

into fresh casks. The first tasting in November

uses a classification based on sensory attributes. The

finest wines, produced in an exceptional grape

quality year, are usually set aside with a view to

declaring a vintage; most are used for blending.

Vintages represent highpoints in port wine quality.

During the initial 2 years, wines are racked frequently

with aeration as often and vigorously as required for

the attributes considered desirable after aging, as

determined by the winemaker. Winter conditions

help precipitate colored matter together with yeast

and potassium salts of tartaric acid. Young ports are

then observed to ‘close up’ or show a color intensifi-

cation. Ports are transported to Gaia for classification

in early spring.

0030 Port was traditionally stored in lodges or cellars in

Gaia but can now be retained in the Douro. Ruby

wines, matured in the Douro, are subjected to its

climatic extremes and are considered to lose vigor

and freshness. A common view is that older tawny

ports should mature in the Douro, and younger ruby

ports in Gaia, where temperature and humidity are

less variable.

0031 On arrival at Gaia, casks are stored by vineyard

and vintage in the cellars of individual port houses.

Large cylindrical stainless steel vats and lined con-

crete are often used for the temporary storage of

wines on arrival, but maturation, for at least 2 and

usually for 3–40 years or longer, is in wood. Cellar-

masters decide between the 550-l ‘pipas’ (pipes or oak

casks), and larger casks (25 000–35 000 l) or vats

(550 000 to 750 000 l) (Figure 3).

0032On arrival in Gaia, a second tasting takes place:

wines are classified, and the first lotas (blends) are

married in large vats fitted with stirrers or pumping.

This is on the basis of decisions on the potential of

each wine and amalgamating similar wines. There is

then separation of the top-quality wines i.e. those to

be used when declaring a vintage. Such wines are kept

separate for two winters and a summer, and if they do

not develop to predefined standards, a vintage will

not be declared that year, and the wines will be used

for blending.

0033The purpose of blending is to obtain specific final

sets of sensory attributes, port types, and styles. Con-

sequently, young port is always stored in well-

seasoned vats or pipes to retain the fresh aroma

characters and deep red color with purple hues. As

production is based on traditions, wooded ports are

created to ensure continuity of style; new blends con-

tain a percentage of previous wines. Previously, indi-

vidual pipes were blended, but currently, concrete or

large wood vats are filled from maturation casks.

0034Ports are blended from wines varying in age and

character. Cellar-masters choose young wines on the

basis of fruit flavor notes and color, and older wines

for body and ‘smoothness.’ The objective is a charac-

ter and quality typical of the style of that port house.

fig0003Figure 3 Wooden casks and vats used for wine maturation.

4634 PORT/The Product and its Manufacture