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

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glass or plastic. There are several types of cells

available from commercial sources: a microcell for

small volumes of solutions, a stoppered cell for

volatile solutions, and a flow cell for measuring

the absorbance of flowing solutions. The most

common detectors are photomultiplier tubes or

phototubes. Photodiode arrays, which are solid-state

detectors, are also used in newer spectrophotometers.

The electrical current produced in these detectors is

amplified and plotted on a recorder or displayed

on the spectrophotometer as either absorbance or

percentage transmittance.

0020 Measurements are made by inserting a cell contain-

ing a sample into the light path of the spectropho-

tometer. The concentration of a substance can be

determined either from a calibration curve or from a

calculation based on the Beer–Lambert law through

the use of an instrumental readout.

0021 Commerical spectrophotometers are classified into

two broad categories, single- and double-beam

systems, depending on their optics. The individual

components of the system have the same function.

0022 A basic spectrophotometer is a single-beam instru-

ment, which has only one light path for radiation

(Figure 2a). This instrument is simple and inexpen-

sive, but is somewhat troublesome to measure with

because a sample and a reference (or a reagent blank)

must be placed alternatively in the light path, and

for measurement at different wavelengths, set-up pro-

cedures are required at each wavelength. It is well

suited for quantitative measurements at a single

wavelength.

0023The double-beam system provides two equivalent

paths, both originating with the same light source

(Figure 2b). One of them travels through a sample

cell, and the other passes through a reference cell. The

two beams are measured separately, either by two

matched detectors or by rapidly alternating use of

the same detector. The ratio of the intensity of the

two beams can be obtained by this system. Thus, the

double-beam instrument automatically compensates

for absorbance by the reference, as well as for any

variation of source intensity with time and wave-

length. This instrument provides more accurate quan-

titative measurement of transmittance or absorbance

than a single-beam instrument. There are also spec-

trophotometers equipped with an automatic drive for

scanning the wavelength. An automatic recording

Light

source

Monochromator

Cell

Detector Readout

Light

source

Monochromator

Reference cell

(a)

(b)

(c)

Sample cell

Detector Readout

Light

source

Cell

Dispersing

device

Photodiode array

Readout

fig0002 Figure 2 Designs of various types of instruments for visible spectroscopy: (a) single-beam instrument; (b) double-beam instrument;

and (c) multichannel instrument with a photodiode array detector.

SPECTROSCOPY/Visible Spectroscopy and Colorimetry 5457

of absorbance as a function of wavelength permits an

absorption curve (an absorption spectrum) to

be obtained. The spectrum is useful for the qualitative

identification of a substance and selecting a suitable

wavelength for quantitative analysis. It may also

reveal the presence of impurities that are interfering

in determination.

0024 A conventional spectrophotometer simultane-

ously measures transmittance or absorbance only at

a single selected wavelength. However, a modern

spectrophotometer is a multichannel instrument,

which can monitor any selected wavelength range in

the visible region. This spectrophotometer is usually a

single-beam system with a photodiode array as a

detector (Figure 2c). The photodiode array is designed

with a linear array that has a series of photodiodes

arranged side by side. Each photodiode responds to

visible light. If dispersed light in its component wave-

length is focused on the surface of the array, the

individual photodiode measures the intensity of radi-

ation from a particular section of the spectrum. The

data from photodiodes are then accumulated and

processed by a computer. This instrument allows the

immediate and continuous recording of an entire

spectrum without mechanical wavelength scanning.

This feature is very useful for the analysis of mixtures

of absorbing species and kinetic studies.

0025 Spectrophotometers with a flow cell are often used

as detectors in analytical systems and subsequently

have extended the application of visual spectroscopy.

When linked with a turnable type of sampler and a

recorder, they expedite manual procedures and read

large batches quickly. By directly observing eluate

from a chromatographic column with this detector

or, if the substance to be measured is colorless, after a

color-developing reaction, several constituents can be

concurrently determined by high-performance liquid

chromatography. The photodiode array spectropho-

tometer is an effective detector for this purpose, since

it can obtain essentially continuous spectra of the

eluate and produce an absorption spectrum for any

point on the chromatogram.

0026 There are several types of automated analyzers

equipped with spectrophotometric detectors in

which analytical procedures are entirely automated

to handle large numbers of analyses and routine

work, especially for clinical specimens.

0027 A modern spectrophotometer, incorporating a com-

puter for instrument control, data collection, and data

processing, provides derivative determinations using

derivative absorption spectra and dual-wavelength,

absorption difference methods by simultaneous meas-

urements at two different wavelengths. These methods

lead to analytical approaches that increase both the

sensitivity and selectivity.

0028New absorptiometric techniques, photoacoustic

and thermal-lens spectroscopy, now allow trace

amounts of light absorption to be measured. Photo-

acoustic spectroscopy is based on the detection of

thermal modulations from a light-absorbing sample

as pressure waves in gas surrounding a sample. Ther-

mal-lens spectroscopy utilizes a thermal-lens effect

where, when a laser beam is introduced into a sample,

local heating along the beam leads to a change in the

refractive index in the vicinity of the beam. These

highly sensitive techniques can accurately detect an

extremely small absorption, even lower than 0.001,

by increasing the laser’s power.

Analytical Applications

0029A visible spectroscopic method is one of the most

powerful and widely used procedures for quantitative

analysis. There are many applications for inorganic,

organic, biochemical, and food constituents. How-

ever, qualitative applications of this method are re-

stricted, since the spectra of most substances in the

visible region are simple and consist of one or a few

broad peaks with no fine structure. Usually, this

method is combined with a more useful quantitative

technique like nuclear magnetic resonance or mass

spectrometry.

Derivatization

0030Naturally colored substances can be directly ana-

lyzed, while most other substances, which are color-

less or weakly colored, must be converted to an

intensely colored derivative. The reaction for color

formation may include enzymatic conversion or

chemical modification of a substance to produce

colored products and a complex formation between

a substance and a color-forming reagent. Color-

forming reagents have been developed and are now

available for analysis of many substances including

inorganic and organic constituents.

Specific Examples

0031Protein (Folin–Lowry method) This is widely used

for the measurement of protein and consists of two

steps: the reaction of a protein with copper ions in

an alkaline solution and the reduction of a Folin–

Ciocalteu reagent by copper-treated protein contain-

ing tyrosine and tryptophan residues.

0032A carbonate-copper solution (0.1 ml) is added to a

sample solution (0.2 ml) in a test tube containing 5–

100 mg of protein. The carbonate–copper solution is

prepared by combining 2% sodium carbonate in

0.1 N sodium hydroxide (50.0 ml) and 0.5% hy-

drated copper sulfate in a 1% potassium tartrate

5458 SPECTROSCOPY/Visible Spectroscopy and Colorimetry

solution (1.0 ml). The sample solution is mixed

vigorously and allowed to stand for 10 min at room

temperature. Folin–Ciocalteu reagent (0.1 ml) (com-

mercially available) is added and mixed. After

30 min, the absorbance of the sample solution is

measured at 750 nm. The protein content is calcu-

lated from a standard curve prepared from bovine

serum or egg white albumin.

0033 Glucose (glucose oxidase method) This procedure,

taking advantage of the specificity of glucose oxidase,

is based upon the conversion of glucose to gluconic

acid and hydrogen peroxide by glucose oxidase and

the subsequent oxidation of o-dianisidine to its

oxidized form, measurable at 420 nm, by hydrogen

peroxide with peroxidase.

0034 A sample solution (0.5 ml), containing 0–50 mgof

glucose, is mixed with glucose oxidase reagent

(3.0 ml) in a test tube and incubated in a water bath

at 37



C for 60 min. The glucose oxidase reagent is

prepared by creating a mixture of glucose oxidase

(125 000units), horse-radish peroxidase (0.5 mg),

and 1% o-dianisidine in 95% ethanol (0.5 ml) to

100 ml with 0.5 M sodium phosphate buffer, pH

7.0, and, if necessary, filtering the solution. After

incubation, the absorbance at 420 nm is measured

against a blank. The sample content is then calculated

from a standard curve.

0035 Iron (di(2-pyridyl)-N,N-di[(8-quinolyl)-amino]-

methane method) Di(2-Pyridyl)-N,N-di[(8-quinoly-

l)amino]methane (DPQAM) is a selective chelating

reagent for iron(II), and under suitable conditions,

the green 1:2 metal ligand chelate formed can be

used to determine iron in an aqueous solution and,

by solvent extraction, in the presence of large

amounts of foreign metal ions.

0036 An aliquot of the sample solution (10–150 ml),

containing 2.5–25 mg of iron(II) and iron(III), is

placed in a separating funnel. A 5% ascorbic acid

solution (1.0 ml) and 0.84 M acetic acid buffer, pH

4.7 (5.0 ml), are added and extracted with one 10-ml

aliquot of 0.1% DPQAM in chloroform. The mixture

is then shaken vigorously and transferred into a 25-ml

flask containing anhydrous sodium sulfate. The ab-

sorbance of the chloroform extract is measured

against distilled water at 693 nm, and the calibration

graph is prepared using standard solutions of iron (II)

treated in the same way.

See also: Chromatography: High-performance Liquid

Chromatography; Spectroscopy: Overview

Further Reading

Dahlqvist A (1961) Determination of maltase and isomal-

tase activities with a glucose-oxidase reagent. Biochem-

ical Journal 80: 547.

Escobar R and Cano Pavon JM (1983) Selective spectro-

photometric determination of trace amounts of iron

with di(2-pyridyl)-N,N-di[(8-quinolyl)amino]methane:

Determination of iron in blood serum. Analyst 108: 821.

Harris DC (1998) Quantitative Chemical Analysis, 5th edn,

p. 511. New York: W.H. Freeman.

Hargis LG, Howell JA and Sutton RE (1996) Ultraviolet

and light absorption spectrometry. Analytical Chemistry

68: 169R.

Holme DJ and Peck H (1998) Analytical Biochemistry, 3rd

edn, p. 36. New York: Longman.

Howell JA (1997) Ultraviolet and visible molecular absorp-

tion spectrometry. In: Settle FA (ed.) Handbook of In-

strumental Techniques for Analytical Chemistry, p. 481.

Englewood Cliffs, NJ: Prentice Hall.

Howell JA and Hargis LG (1994) Ultraviolet and light

absorption spectrometry. Analytical Chemistry 66:

445R.

Howell JA and Sutton RE (1998) Ultraviolet and light

absorption spectrometry. Analytical Chemistry 70:

107R.

Long ME, Swofford RL and Albrecht AC (1976) Thermal

lens technique: A new method of absorption spectros-

copy. Science 191: 183.

Lowry OH, Rosebrough NJ, Farr AL and Randall RJ

(1951) Protein measurement with the folin phenol

reagent. Journal of Biological Chemistry 193: 265.

Thomas MJK (1996) Ultraviolet and Visible Spectroscopy,

2nd edn. Chichester, UK: John Wiley.

SPECTROSCOPY/Visible Spectroscopy and Colorimetry 5459

SPICES AND FLAVORING (FLAVOURING)

CROPS

Contents

Use of Spices in the Food Industry

Fruits and Seeds

Leaf and Floral Structures

Tubers and Roots

Properties and Analysis

Use of Spices in the Food

Industry

L A Wilson, Iowa State University, Ames, IA, USA

Introduction

0001 Spices and herbs are valuable commodities that have

played a major role in world civilization; wars were

fought, governments and their economies altered,

cultures enriched, legends created, and new worlds

discovered. Many of the great chronologers and

explorers – Hippocrates, Theophrastus, Marco Polo,

Christopher Columbus, Vasco da Gama, Ferdinand

Magellan – were associated with the use or trade of

spices. Throughout history, the most powerful and

richest countries were those countries that controlled

the spice trade. Mankind has used spices and herbs

to mask spoiled meat and body odor, preserve the

remains of their dead, heal afflictions of the flesh

and mind, and add enjoyment to their food.

0002 Spices and herbs have historically been used to

improved color (turmeric, saffron, paprika, chillies)

and flavor (cinnamon, cloves, cumin, rosemary, sage,

pepper) and, in some cases, improve the shelf-life

(antioxidant and antimicrobial activity) of foods.

Without spices, our diet would be bland, boring,

and unappetizing. The aromatic and pungent prin-

ciples that make spices so valuable are contained in

their essential oils and oleoresins. (See Antioxidants:

Natural Antioxidants.)

Classification

0003 The definition of spices, herbs, and condiments has

created considerable debate over the years. The Inter-

national Standards Organization (ISO) defines spices

and condiments as the natural vegetative products or

mixture thereof, without extraneous matter, that are

used for flavorings, seasonings, and imparting aroma

to food. Spices and condiments are usually grown in

tropical semitropical climates and comprise one

portion of the plant. Spices are the whole or ground

seeds, fruits, bark, or roots of a plant (Table 1). Herbs

are generally defined as the leafy parts of a soft-

stemmed plant whose main stem dies down to the

roots and regrows each year (Table 1). Herbs are

generally found in the more temperate regions of the

world. Herbs generally contain a lower percentage of

volatile (essential) oil than spices (Table 2). The US

Food and Drug Administration (FDA) further speci-

fies that paprika, saffron, and turmeric are colors,

and that they must be labeled with their common

names on food labels. While the legal definition of

spices and herbs may vary between countries and

trade organizations, this article will use the term

spice to describe both spices and herbs collectively.

Economics

0004Since spices are an agricultural commodity, their

prices are influenced by climatic and political condi-

tions. Wars and national disasters also limit the

exporting of spices.

0005While more than seventy recognized spices are used

to season food, approximately 30% of the total inter-

national trade is accounted for by black and white

pepper. Cloves, cardamon, cinnamon, nutmeg, and

pepper represent about 70% of the world spice trade.

0006In 2000, the USA consumed approximately 1 bil-

lion pounds (453 600 tonnes) of spice per year. Per

capita consumption increased to 3.7 pounds (1.7 kg).

The average consumption has increased by over 50%

from a decade ago due in part to the increased

consumption of spices used to make foods less bland

(e.g., capsicums, oregano, basil). Imported spices rep-

resent more than 70 herbs and spices grown and

processed worldwide under a variety of environmen-

tal conditions. Black, white, and red peppers, mus-

tard seed, capsicum, cassia, paprika, coriander,

5460 SPICES AND FLAVORING (FLAVOURING) CROPS/Use of Spices in the Food Industry

ginger, and oregano accounted for approximately

75% of the weight and 63% of the dollar value of

these imported spices. The USA domestically pro-

duces 35–40% of its spice needs, including onions,

shallots, chives, garlic, parsley, dill, basil, tarragon,

mustard seed, mild and chilli peppers, cayenne (cap-

sicum), spearmint, and peppermint leaves each year.

0007 In the marketplace, similar spices from different

geographical locations do not necessarily demand

the same prices. European oregano (Greek and Turk-

ish) demands a higher price than Mexican oregano.

0008Spices obtained from different plant parts have

different volatile characteristics owing to differences

in spices, environmental conditions, geographical

origin, and processing. Milling also significantly

influences the characteristic volatile oil content,

composition, aroma, flavor, and color.

Spice Quality

0009Spice quality typically includes its degree of excel-

lence and uniformity, as measured against specific

tbl0001 Table 1 Geographic origin of common spices and herbs and plant parts used

Name Latinname Plant part Countryof origin

Allspice Pimenta dioica L. (formerly Pimenta

officinalis)

Unripe berry Jamaica, Guatemala, Mexico,

Honduras,

Anise seed Pimpinella anisum L. Seed Spain, Egypt, Turkey

Basil Ocimun basilicum L. Leaves France, Egypt, USA

Bay leaves Laurus nobilis L. Leaves Turkey, Greece

Capsicum peppers Capsicum frutescens L. Includes red pepper, chilli pepper

and sweet bell peppers

Hottest varieties: Africa, China

Milder varieties: China, Japan,

the Middle East, India, USA,

Mexico

Chilli pepper: California, New

Mexico, Mexico

Caraway seed Carum carvi L. Fruit Native to: Europe, Asia, North

Africa Primarily exported from

the Netherlands

Cardamon Elettaria cardamomum Fruit India, Ceylon

Celery seed Apium graveolens L. Fruit France, India, USA

Cinnamon Cinnamomum zeylanicum Nees,

Cinnamomum cassia

Bark Indonesia (Korintyi), China

Cloves Eugenia caryophyllata Thunb Unopened flower buds Madagascar and Brazil

Coriander seed Coriandrum sativum Ripe fruit. Leaves known as

cilantro

Coriander: Morocco, Romania

Cumin Cuminum cyminum L. Fruit Middle East, India, Turkey

Dill Anethum graveolens L. Dillweed, seeds Egypt, India, USA

Fennel seed Foeniculum vulgare Mill. Dried fruit India, Egypt, Turkey

Fenugreek Trigonella foenumgraecum L. Pod India, Morocco

Ginger Zingiber officinale Rhizomes China, India, Jamaica

Marjoram Majorana hortensis, Moench Leaves France, Egypt, Europe, South

America, USA

Mustard seed Brassica hirta Seeds Canada, Northern plains of USA

Nutmeg and mace Myristica fragrans, Houtt Seed. Mace is a lacey netlike

orange covering over the seed

Indonesia, East Indian Islands of

Grenada and Trinidad

Oregano Origanum vulgare L. Leaves Greece, Turkey, Mexico

Parsley Petroselinum crispum L. Curly leaf variety California

Paprika Capsicum annum L. Ground fruit pods California, Spain, Hungary

Pepper Piper nigrum L. Berries, Green (immature), White

(ripe with black hull removed),

Black.

Malabar Coast of India, Lampong

district of Sumatra in Indonesia

and Brazil

Rosemary Rosmarinus officinalis Leaves Former Yugoslavia, France,

Spain, Portugal

Saffron Crocus sativus L. Dried stigmas of the flower Spain

Sage Salvia officinalis L. Leaves Former Yugoslavia (Dalmatia),

Albania, Turkey

Savory Satureja hortensis L. Leaves Former Yugoslavia, France

Tarragon Artemisia dracunculus L. Leaves California, France

Thyme Thymus vulgaris L. Leaves Spain

Turmeric Curcuma longa L. Rhizomes India (alleppey)

SPICES AND FLAVORING (FLAVOURING) CROPS/Use of Spices in the Food Industry 5461

standards and specification (sensory properties,

cleanliness, and safety). The quality attributes of

spices can be divided into specifications concerning

microbiological quality and safety, filth/contamin-

ation, foreign material, granulation, color, flavor,

total ash and acid-soluble ash, moisture level, and

volatile oil content. Specific tests (American Spice

Trade Association (ASTA) color, Scoville heat units,

curcumin content, piperine content, phenolic con-

tent) may also be used for certain spices. These speci-

fications are set by the processor on the basis of

international, federal, and trade standards.

Microbiology

0010 A large percentage of the spices supplied to the world

are produced in countries where sanitary conditions

and hygienic handling and storage of spices are poor.

Bacteria, insects, and bird and rodent droppings are

common sources of contamination. Often, spices are

laid out in fields or in backyard areas around houses

to dry where they are subject to a high degree of

contamination from animals and humans alike. It is

not uncommon to find standard plate counts on black

pepper of up to 10 million per gram. Spices with high

microbial counts include allspice, caraway, celery

seed, cumin, pepper, paprika, and onion powder.

Standard plate count, yeast mold, coliform (Escher-

ichia coli), and Salmonella tests are typically used to

evaluate the microbiological quality of raw and pro-

cessed spices. It is not uncommon to find metal wires

and scrapings, dirt, sand, glass, bird feather, whole

insects, and insect fragments in raw spices. Therefore,

ISO, ASTA, and the US FDA have set cleanliness

specifications (or guidelines) that all imported spices

should meet. These are usually referred to as Defect

Action Levels (DALs) and ASTA Cleanliness Specifi-

cations. Both of these specifications are designed to

take into account that spices are a natural agricultural

commodity that cannot be totally free of insects and

foreign material. These numbers reflect the maximum

amount of material that can be found under good

manufacturing practices. Heavy and light filth testing

procedures are used to evaluate the amount of filth

and foreign material present in the spice (whole and

ground spices). Total ash after ignition of the spice is a

measure of metal, sand, rocks, and minerals naturally

occurring in the spice. Acid-insoluble ash is the resi-

due remaining after the total ash has been treated

with hydrochloric acid, leaving only the sand. (See

Contamination of Food.)

Moisture

0011High moisture levels in a dried spice are indicative of

improper storage. High moisture levels lead to micro-

biological growth of molds and bacteria. Both

degrade the quality of the spice and may lead to

the presence of toxins (such as aflatoxin). Moisture

testing is usually determined by vacuum oven drying

for capsicums and dehydrated vegetables with low

volatile oils. Toluene distillation of spices is used to

determine the moisture of spices with high volatile oil

contents (the procedure minimizes the loss of volatile

oils that would contribute to a higher moisture deter-

mination). (See Mycotoxins: Occurrence and Deter-

mination; Water Activity: Effect on Food Stability.)

Volatile Oil

0012The terms volatile oil and essential oil are synonym-

ous and are used interchangeably in the flavoring

industry. These oils volatize at low temperatures and

are the main contributors to the aroma and flavor of

spices. Volatile oils are a complex mixture of organic

compounds, hydrocarbons (terpenes, sesquiterpenes),

oxygenated compounds (alcohols, esters, aldehydes,

ketones), aromatic benzenoids, and compounds con-

taining nitrogen or sulfur, present in droplets of cell

sap and in glandular hairs. In plants, essential oils are

functional enigmas; some may act as insect attract-

ants and so aid in pollination, whereas others may

protect plant tissue against parasites and animal dep-

redation. For example, oregano and thyme essential

tbl0002 Table 2 Volatile oil content (% v/w)

Spice or herb Volatile oil content (% v/w)

Anise 1.5–3.5

Allspice 2–4.5

Basil 0.1–1.1

Bay leaves 1.5–2.5

Caraway 1.5–3.5

Cardamon 3–8

Cassia (cinnamon) 0.5–4.0

Celery seed 1.5–3

Cloves 15–20

Coriander 0.1–1.5

Cumin 1.5–5

Dill seed 2–5

Fennel seed 1–3

Ginger 1.5–3

Mace 5–25

Marjoram 0.7–3

Nutmeg 5–16

Oregano 2.0–4.4

Pepper, black 0.6–5.0

Pepper, white 1.0–3.0

Rosemary 0.5–2.0

Saffron <1

Sage 1.5–2.5

Tarragon 0.2–1.5

Thyme 0.8–2.0

5462 SPICES AND FLAVORING (FLAVOURING) CROPS/Use of Spices in the Food Industry

oils have been shown to inhibit molds and foodborne-

illness bacteria. (See Essential Oils: Properties and

Uses.)

0013 The percentage of volatile oil in spices usually

ranges from 0.5 to 3.0%, with the seed spices typic-

ally having higher values than the herbs (Table 2).

The volatile oil content of spices is influenced by crop

year, origin, milling technique, age, and extraction

technique. Owing to these variations, a standard

method and a minimum level of volatile oil are speci-

fied for the determination of volatile oils. ASTA

Method 5 Modified Clevenger Trap Method) is typ-

ically used to steam-distill off the volatile oils from

the spices and collect them to be measured.

0014 The percentage of volatile oil has long been the

method of choice for defining spice quality, but the

validity and sensitivity of this method are question-

able, as research has shown that consumers and

analytical methods are able to detect differences not

identified by the percentage of volatile oil. The steam

distillation process often produces conditions that

may distort volatile oil composition. The composition

of the oil can be more important than the total

amount of oil present in the spice. On-column cryo-

genic focused gas chromatography of the spice head-

space and/or heat gas-chromatography injections of

the volatile oil can be used as a supplemental tech-

nique for the determination of spice flavor quality.

(See Chromatography: Gas Chromatography.) Elec-

tronic nose technology is also being used as quality-

control instrument to differentiate different spices

based on their volatile patterns. Typically, one to 32

sensors, of different types, are exposed to the head-

space over the spice. If the volatiles bind with a

sensor, they change its electrical resistance, which

can be measured. The patterns produced from this

measurement can be related to spices from different

geographical locations and aroma quality. Many of

these units have neural networks, which can be

trained (using sensory or chemical data) to recognize

these differences.

0015 The relative heat of red peppers is measured by

Scoville heat units. This procedure uses five trained

taste panelists to determine the threshold hotness of

ethanol extracts of red pepper: the higher the number,

the hotter the red pepper. Unfortunately, the variation

in Scoville numbers between laboratories can be as

high as 50%. Newer instrumental methods using

high-performance liquid chromatography have been

developed to determine the amount of specific

capsaicinoids present to try to reduce the variation

found with taste panels. (See Chromatography: High-

performance Liquid Chromatography.)

0016 Solvent extraction methods are typically used to

determine the color of paprika (carotenoid pigments)

and turmeric (curcumin content). These procedures

utilize acetone to extract the color pigments, which

are then measured spectrophotometrically. The

results are then expressed as ASTA color units. (See

Spectroscopy: Overview.)

Spice Processing

0017Spices are treated as an agricultural commodity and

shipped in bags, bales, or totes. Upon arrival, they

must meet the cleanliness specifications of that coun-

try. Processors first check the whole spice for cleanli-

ness by pulling a representative sample from multiple

containers and determining the amount of foreign

material (stones, metal, hairs, excreta, glass, insects)

and microbiological load. If a product is found to

have these items present in excess of the DALs, the

spices must be cleaned or treated. Infestations due to

insects and high microbial loads can be reduced by

ethylene oxide, propylene oxide or irradiation treat-

ment. Steam sterilization procedures are also used by

a few spice companies, especially in Europe, to reduce

microbiological loads. Wet steam sterilization re-

quires drying of the spice after treatment. The use of

ethylene oxide in sealed chambers usually reduces the

microbiological load by 90%. However, ethylene

oxide has been classified as a carcinogen, and the

FDA has set a maximum residue tolerance of

50 p.p.m. in spice. Owing to the undesirable toxico-

logical effects of ethylene and propylene oxide, alter-

native methods for sterilizing spices are being

investigated. Irradiation of spices using ionizing radi-

ation up to 30 kGy is allowed in the USA. The FDA

requires that an irradiated spice must be labeled with

the irradiation logo and the statement ‘treated with/

by irradiation.’ However, if the irradiated spice is

used in a food as an ingredient, the finished product

does not have to be labeled as being irradiated. Irradi-

ation of spices is very effective (killing 95–100% of

microorganisms); however, many consumer groups

are opposed to this procedure, owing to concerns

about radiation, nuclear wastes, and unknown

byproducts in the food. After the sterilization proced-

ures (if required), the spices can be cleaned to remove

foreign material. Magnets are used to remove ferrous

metal during the cleaning and grinding operations.

Nonmetallic foreign material can be removed from

spices using a variety of methods, depending upon the

foreign material present and the type of spice. Three

basic types of cleaning techniques are typically used,

alone or in combination with each other: air, gravity,

and centrifugal separators. Each of these methods

uses the difference in weight or specific gravity of

the spice to separate it from the lighter or heavier

foreign material. Gravity separators or air tables are

SPICES AND FLAVORING (FLAVOURING) CROPS/Use of Spices in the Food Industry 5463

the most commonly used pieces of cleaning equip-

ment. This technique uses air forced through a porous

moving plate (deck) to suspend the particles into

layers of different densities. The lighter material

moves downhill, and the heavier material moves

uphill. Proper adjustment of this system allows the

processor to separate the product into many different

density fractions (dust, lights, heavies, stones, etc.).

(See Irradiation of Foods: Basic Principles; Steriliza-

tion of Foods.)

0018 After cleaning, the spice is checked for cleanliness

and other quality attributes. If the spice meets these

specifications, it can be packaged and sold as whole

spice or ground into smaller particles.

Spice Milling

0019 Since ancient times, milling has been used to release

the natural aromatic compounds contained by the

plant’s protective cell wall. Milling shatters the cellu-

lar material, starting the slow release of volatile aro-

matic compounds. During milling, not all the plant

cells are disrupted; consequently, ground spices retain

a portion of their original aromatic components

during processing and storage.

0020 Using a variety of milling techniques and equip-

ment, millers encounter a wide range of different

physiological material. The use of high-speed mills,

which generate large quantities of heat with rapid air

movement, results in the loss and/or deterioration of

volatile components. Therefore, milling is carried out

using as little grinding as possible with high-speed

disintegrators, various types of hammer mills, and

slow-speed vertical and horizontal burr stone mills

in a wide range of sizes and capacities. During trad-

itional milling, the frictional heat of grinding can

increase to 93



C, causing the loss of volatile oil and

the development of off-aromas and flavors. Volatile

oil losses of up to 1.5% during the milling of different

spices between 42 and 95



C are common. (See

Milling: Characteristics of Milled Products.)

0021 Cryogenic milling has been utilized to reduce these

problems. In this procedure, spices are ground

with liquid nitrogen to reduce the loss of volatile oil.

The liquid nitrogen cools both the spice and grinding

zone by instantaneous evaporation, absorbing any

frictional heat. Grinding zone temperatures well

below 73



C with theoretical grinding zone tem-

peratures approaching 195



C have been reported.

0022 There are several advantages to the ‘Cryomill’

process of spice milling.

0023 It reduces the oxidation of spice oil, thereby in-

creasing stability and flavor intensity by expelling

air from the grinding zone.

0024It permits production of exceedingly fine particle

size because the low temperatures solidify spice

oil, making the spice very brittle.

0025The fine spice particles disperse uniformly

throughout the finished product to give a uniform

flavor, eliminate speckling, and reduce settling in

liquid products.

0026It reduces the loss of volatile aromatic compounds,

increasing flavor intensity.

0027The low-temperature treatment may reduce the

microbial load.

0028The milling rate is increased, by reducing spice

stickiness.

0029Cryogenically milled spices show a reduced cost

when the increased flavor strength is factored into

the cost.

Spice Oleoresins

0030Spices can also be solvent-extracted to produce oleo-

resins or steam-distilled to produce essential oils.

Oleoresins are liquid, semisolid, or a solid residue

composed of volatile oils, fixed oils (nonvolatile

plant oils), pigments, pungent constituents, and nat-

ural antioxidants. Because oleoresins contain all of

the volatile and nonvolatile flavor components of the

spice, they provide a more rounded, closer duplica-

tion of the original spice. For example, the oleoresin

of ginger contains pungent (hot sensation on the tip of

the tongue or back of the throat) gingerol, shogal,

paradol, and zingerone; white and black pepper con-

tain piperine, and hot chillies (capsicum) contain cap-

saicinoids such as capsaicin, dihydrocapsaicin, and

nordihydrocapsaicin. The oleoresins also contain

natural antioxidants such as romaridiphenol and

romariquinone in rosemary. Mace, sage, thyme,

cloves, oregano, allspice, and cinnamon have also

been reported to have antioxidant properties.

0031Both oleoresins and essential oils are very concen-

trated flavors and can be difficult to use in food

processing. Extractives are typically used at levels of

less than 0.01% of the finished food product. Stand-

ardization of the extractive is necessary, owing to

crop year, geographical origin, age and lot-to-lot vari-

ation. In order to overcome these difficulties, extrac-

tives are usually incorporated into food products by

being (1) dispersed on a dry carrier (salt, dextrose,

flour), (2) solubilized with Polysorbate 80, (3) encap-

sulated inside vegetable gums or food starches (spray-

drying), and (4) made into a water-dispersible liquid

using emulsifiers. The amount of residual solvent

in the spice oleoresin is also of concern, and levels

are monitored by federal agencies. For example, in

the USA, Title 21 of the Code of the Federal Regula-

tions, parts 173 and 182.20, gives essential oils and

5464 SPICES AND FLAVORING (FLAVOURING) CROPS/Use of Spices in the Food Industry

oleoresin generally recognized as safe (GRAS) status

and defines the maximum solvent residue for hexane,

acetone, isopropyl alcohol, and ethylene dichloride

(25, 30, 50, 30 p.p.m., respectively) allowed in the

spice extract. The label of a food containing oleoresins

or essential oils need only state ‘natural flavors.’

See also: Antioxidants: Natural Antioxidants; Colorants

(Colourants): Properties and Determination of Natural

Pigments; Contamination of Food; Essential Oils:

Properties and Uses; Flavor (Flavour) Compounds:

Structures and Characteristics; Irradiation of Foods:

Basic Principles; Milling: Characteristics of Milled

Products; Mycotoxins: Occurrence and Determination;

Sensory Evaluation: Aroma; Spectroscopy: Overview;

Sterilization of Foods; Storage Stability: Mechanisms

of Degradation; Water Activity: Effect on Food Stability