食品科学和技术(英文)

Food

Science

andTechnologyBy

Gilsonl10/23/2002DefinitionFood

science:

Scientific

study

of

food

from“farm

to

fork”.Food

technology:

Use

of

the

informationgenerated

byfood

science

to

produce

safe,nutritious

and

wholesome

food.FOOD

SCIENCEMultidisciplinaryEngineeringChemistry/BiochemistryMicrobiologyNutritionFoods

as

edible

biochemicalsTouches

on

many

other

areasGlobalization

of

world

food

supplyMORE

PEOPLE,

LESSFOODWidespread

food

shortages

will

develop

overthe

next

40

years

as

a

population

explosiongradually

outstrips

world

food

supply.The

food

supply

is

the

most

immediateconstraintonthe

Earth’s

population-carryincapacity.Milestones

&

Projections:1830:

Worldhuman

population

reaches

1

billion1930:

2

billion1960:

3

billion1975:

4

billion1999:

6

billion

[Assuming

a

64-year

human

lifeexpectancy,

of

all

the

people

bornon

earth

since

itcreation,

2/3

are

now

alive.]2030:

9

billionBiggest

increases

are

expected

in

some

of

thepoorest

areas,

such

as

Africa,

southern

Asia,and

South

America.Human

population

of

Africa

will

double

in

23

years.Population

of

South

Americawill

double

in

29

years.Population

of

Europe

will

double

in

343

years.Projection:

Maximum

amount

of

people

earthcan

sustain

=

20.7

billionFood

Science

Achievements:1900

-

19991900s:Vacuum

packaging

-

removes

atmosphere

fromfood

packages.Hydrogenation

-

to

keep

unsaturated

fats

froturning

rancid.U.S.

&

British

patents

issues

for

killing

bacin

food

with

ionizing

radiation

(1905).In

U.S.,

first

commercial

freezing

of

fruit

afish.1910s:In

U.S.,

first

large-scale

commercial

pastaproduction.1920s:Clarence

Birdseye

develops

quick-freezingprocess

for

foods

and

first

commercializesblanched

frozen

vegetables.Food

fortification

begins

by

fortifying

tabwith

iodine

(1924).1930s:Freeze-drying

process

invented

to

preserve

food.Vitamin

D

first

added

to

milk

through

ultravioletradiation

(1933).1940s:Mass

production

of

food

using

automation

takes

offConcentrated,

frozen,

and

dehydrated

foods

producin

mass

quantities

for

shipping

overseas

to

militarFlour

first

fortified

with

vitamins

and

iron

(1940Aseptic

processing

and

packaging

is

developed,increasing

food

quality,

safety,

and

retention

ofnutrients.1950s:Controlled-atmosphere

packaging

(CAP)developed

(CAP

controls

O2

andCO2

in

thepackage

to

limit

respiration

and

ethyleneproduction,

thereby

delaying

ripening

andspoilage).U.S.

Army

begins

food

irradiation

program(1953).Watson

&

Crick

discover

the

double-helixstructure

of

DNA,

laying

the

foundation

forunderstanding

genetics

and

developingrecombinant

DNA

technology1960s:First

commercial

plant

for

freeze-drying

foopens

(1960

-

for

coffee).Computer

control

in

processing

plants

firstintroduced.FDA

approves

irradiation

to

disinfest

wheatand

wheat

flour

(1963),

to

inhibit

sprouting

ipotatoes

(1964),

and

to

extend

the

shelflife

opotatoes

(1965).Aseptic

canning

adopted

by

foodmanufacturers.1970s:Hazard

Analysis

Critical

Control

Point

(HACCP)

syjointly

developed

by

NASA,

Pillsbury

Co.,

and

the

U.Army

Natick

Laboratories.Recombinant

DNA

technology

developed

(1973).1980s:Modified-atmosphere

packaging(MAP)

introduced

tincrease

shelflife

and

protect

them

from

spoilage,oxidation,

dehydration,

weight

loss,

and

freezer

buFDA

approves

irradiation

to

control

Trichinella

sin

pork

(1985),

to

disinfest

and/or

delay

ripening

ifresh

fruits

and

vegetables

(1986),

and

to

controlmicroorganisms

in

spices

and

herbs

(1986).1990s:HACCP

becomes

widely

adopted

by

foodmanufacturers

largely

due

to

regulations

by

FDA

andUSDA.FDA

approves

use

of

irradiation

to

control

harmfulbacteria

in

fresh

and

frozen

poultry

(1990)

and

redmeats

(1997).Pasteurization

process

for

shell

eggs

by

ohmic

heat(using

electricity).Flash

pasteurization

process

of

fresh

juicescommercially

applied

leading

to

not-from-concentracitrus

juices.Orange

juice

fortified

with

calcium.High-pressure

processed

guacamole

comes

to

U.S.market

(1998).Steam

pasteurization

and

vacuuming

of

beefcarcasses

introduced

to

reduce

microbial

hazardsRecombinant

enzyme,

chymosin,

replaces

rennet

inmost

cheese

manufacture.First

food

from

a

transgenic

plant

(a

tomato

withdelayed

ripening)

comes

to

market

(1994).Active

packaging

systems

introduced

that

interacwith

package

contents

or

the

package’s

internalatmosphere

are

developed

to

enhance

productfreshnessUNIT

OPERATIONSMaterials

handling

-

Harvesting

and

transportation

whilemaintaining

product

quality

to

and

in

the

processing

plant.Low

temperature

storage

to

maintain

perishable

proappearance

and

vitamin

content.Volume

restrictions

due

to

“field

heat”

producedfruits

&

vegetables.Care

of

handling

livestock

and

fragile

products

suceggs.Safety

issues

from

static

electricity

buildup

ignidust

or

fine

flour

transfer

while

avoiding

humiditybuildup

and

caking

of

product.Proper

handling

of

spices

to

retain

desirable

aromacompounds.Cleaning

-

often

required

for

thsimple

removal

of

dirt

and

debris

Brushes,

high-velocity

air,

steam,

water,

vacuum,

magneticattraction

of

metal

contaminants,

mechanical

separation,

filtetc.Water

treatment:

In

soft

drinks,

water

should

be

low

in

inorgasalts,

since

these

minimize

carbon

dioxide

solubility

and

promexcessive

escape

of

gas

bubbles;

often

this

requires

additionatreatment

processes

suchas

microfiltration

and

deaeration.Cleaning

of

food

equipment

surfacesModerately

alkaline

and

neutral

detergents

find

wide

applicatiofood

industry

as

they

remove

soil

and

other

deposits

yet

arenoncorrosive

to

food-contact

surfaces.Many

types

and

combinations

of

detergents

used.SeparatingSolid

from

a

solid

(e.g.,

shelling

nuts;

lye

peeler

fpeaches)Solid

from

a

liquid

(e.g.,

filtration;

centrifugaticrystallization

of

sugar

crystals

from

sugar

cane

juiLiquid

from

a

solid

(e.g.,

extracting

juice

from

a

frpressing

oil

from

peanuts

and

soybeans)Liquid

from

a

liquid

(e.g.,

centrifuging

oil

from

waRemoving

a

gas

from

a

liquid

or

solid

(e.g.,

pullingvacuum)Hand

sorting

and

grading

still

very

common

(e.g.,

fruits

&vegetables),

but

labor

costs

are

high.Electronic

photocell

equipment

used

to

detect

and

reject

off-cproducts

(e.g.,

potato

chips,

peanuts,

eggs);

ultrasonics

also

uscreen

internal

tissue

of

whole

fruits

and

vegetables.DisintegratingBreakdown

of

large

food

particles

into

smaller

parti Examples:

Cutting,

grinding,

pulping,

homogeniziSome

cutting

now

done

with

high-pressure

water

jetand

laser

beams.Disintegration

often

involves

heat

build-up

due

to

fand

some

products

require

cooling

(e.g.,

meats

to

avoprotein

denaturation

and

coffee

to

avoid

burned

flavoGrinding

of

frozen

meat

is

done

to

avoid

this.Or

addition

of

dry

ice

that

dissipates

as

carbon

diHomogenizationPumpingOne

of

the

most

common

operations

in

the

foodindustry(both

liquids

and

solids

suspended

in

liquids)Many

kinds

of

pumps

-

pump

selected

depends

uponnature

of

food

to

be

moved.Rotary

gear

pumps

have

close

tolerances

among

movingparts,

chunk-type

foods

would

be

reduced

to

purees,

asometimes

this

is

the

intent,

so

the

pump

serves

twopurposes.A

single-screw

pump

(with

large

clearances)

best

f

moving

food

with

large

pieces

without

disintegrati

(e.g.,

corn

kernels,

grapes,

small

shrimp).C.

It

is

essential

that

all

food

pumpsbe

easily

disassembled

for

thoroughcleaning

(stainless

steel

is

the

mostcommon

material

used

to

make

pumpsfor

the

food

industry).MixingAgain,

very

common

operation

in

the

food

industrybe

solid-solid,

liquid-liquid,

solid-liquid,

gas-liMany

are

“kitchen-style”

mixers,

just

bigger.Most

common

used

to

mix

solids

into

liquids

to

dissolvthem

is

a

propeller-type

agitator

within

a

stainless

sMixing

usually

involves

the

generation

of

heat

anfoods

it

is

often

desirable

to

minimize

this

temperatuby

some

form

of

cooling.Some

mixing

requires

high

rpmExample:

Mixer/beater

found

in

ice

cream

freezers

toincorporate

air

into

ice

cream

mix

to

produce

desiredvolume

increase

(overrun)

required

to

attain

desiredtextureHeat

exchangingA.

Reasons

to

heat:CookPasteurizePreservation

(e.g.,

blanching)Drive

off

moisture

(evaporate)Develop

flavorsInactivate

natural

toxic

substances

(soybean

meaB. Need

to

control

application

of

heat

(often

necessheat

and

rapidly

cool

the

product)Rapid

heating

and

cooling

often

require

maximumcontact

of

the

food

with

the

heating/cooling

sourceheat

exchangers

in

the

pasteurization

of

milk).Steam-jacketed

stainless

steel

kettle

or

tank

ofteheating

liquid

foods

(mixing

propeller

usually

inclprevent

scorching

and

even

distribution

of

temperatCanning

-

using

a

retort

(pressure

cooker)Roasting

-

circulating

hot

airC.

CoolingAgain,

a

heat

exchanger

can

be

used,

but

with

cold

wapumped

through

the

unit.Commercial

blast

freezers

reach

-26CLiquid

nitrogen:

-196CEvaporation

-

to

concentratefoods

2-

to

3-foldTo

remove

water,

to

recover

desirable

food

volaand

to

remove

undesirable

volatiles.Can

be

solar

(raisins),

heated

kettle

(water

fsugar

syrup).Very

common

in

the

industry:

Vacuum

evaporatio-

reduced

pressure

allows

liquids

to

boil

at

lowertemperatures

(the

lower

temperature

causes

lessdamage

to

food

quality).Drying

-

to

take

foods

to

near

totdryness

(often

2

to

3%

water)ExamplesDriedmilk

processed

by

spray

drying

(atomized

liquid

mixed

wiheated

air);

liquid

foods

are

easiest

to

dry.Mashed

potatoes

and

tomato

puree

processed

by

drum

drying(drum

heated

from

within,

applied

layer

of

food

flashes

off

itmoisture

on

contactwithheated

drum,

and

thin

film

offoodscroff

drum

with

long

knives).Peas

and

diced

onions

dried

by

moving

through

a

long

tunnel

ove(subject

of

overheating

and

shrinkage),

but

a

preferred

methovacuum

freeze-drying

(used

for

coffee),

food

frozen,

dehydraunder

vacuum

from

the

frozen

state.Forming

-

foods

made

intospecific

shapes

(e.g.,

fish

stickApplication

of

pressure

within

an

appropriate

forRange

of

pressures

used,

varies

considerably

depeupon

the

product.For

example:

Extrusion

{Breakfast

cereals

-

Extrucooking}Formulated

dough

or

mash

is

extruded

under

highpressure

with

heat.Packaging

(food

containers)To

protect

food

from

microbial

contamination,

phydirt,

insect

invasion,

light,

moisture

pickup

or

loflavor

pickup

or

loss,

and

physical

abuse

(damage).Containers

include

metal

cans,

glass

and

plastic

bpaper

and

paperboard,

plastic

and

metallic

films,

acombinations

of

these.Packaging

is

automated.New

processesTo

increase

the

range

of

options

withieach

unit

operation,

to

improve

qualityor

increase

efficiency.Examples

include:

supercritical

fluiextraction,

ohmic

heating,

and

highhydrostatic

pressure

processing.QUALITY

FACTORS

INFOODSAppearance

factorsTextural

factorsFlavor

factorsAdditional

quality

factorsAppearance

factorsA.

Size

and

shapeSize:

Easily

measured

(e.g.,

fruits

and

vegetablbe

sized

according

to

the

openings

they

can

passthrough;

the

basis

for

automated

separating

andgrading

machines).Shape:

Some

of

the

most

difficult

food

engineerinproblems

are

the

designing

of

equipment

to

packodd-shaped

food

pieces.B.

Color

and

glossFood

color:

Helps

determine

quality,

ripeness

and

spoilageColor

and

transparency/cloudiness:

Can

be

measured

witha

spectrophotometer

(measures

light

transmission

througa

liquid).Solids

and

liquids:

Reflected

color

can

be

measured

bycomparison

with

defined

colored

chips.Hunter

colorimeter:

Color

measurement

by

division

intothree

components

-

value,

hue

and

chroma.Value

-

lightness

or

darkness

of

the

color.Hue

-

predominate

wavelength

reflected

(which

determinewhat

the

perceived

color

is).Chroma

-

intensity

strength

of

the

color.Instruments

available

to

measure

shine

or

gloss.C.

Consistency

-

viscosity;

many

typeviscometers

to

measure

consistency.Bostwick

Consistometer

-

time

it

takefor

food

to

flow

down

an

inclinedtrough.Textural

factorsFood

qualities

we

feel.Food

texture

can

be

measured

by

resistance

to

fSqueezing

(compression).Shear

(force

applied

so

that

one

part

of

the

foodpast

the

other).Cutting.Tensile

strength

(pulling

apart).Texture

changes

-

do

not

remain

constant

in

a

foChange

in

water

content

plays

a

major

roleFlavor

factorsCombination

of

both

taste

and

smell

and

largelysubjective

and

therefore

difficult

to

measure,

very

cWide

divergence

of

opinion.Color

and

texture

influence

flavor.We

become

educated

as

to

expect

certain

colors

withcertain

flavors.Greater

intensity

of

color

associated

with

greatersame

with

greater

viscosity

to

perception

of

greateflavor.Salt,

sugar

and

acid

can

be

measured

usinginstrumentation.D.

Taste

panelsAnalytical

instruments

can

be

used,

butthe

human

“test

animal”

is

still

thebest.Use

of

groupsof

people

preferred

overindividual

opinion,

as

differences

ofopinion

tend

to

average

out.1.

People

involved

in

taste

panels.Trained

people

for

specific

products

(e.g.,butter

and

cheese).Consumer

preference

groups

-

panels

notspecifically

trained

but

provide

insight

as

towhat

consumers

prefer.Highly

trained

people

with

heightened

tastesensitivity

and

knowledge

of

what

to

recognizeas

attributes

and

defects2.

Environment

for

taste

panels.Isolation

of

tasters

to

avoid

influenceby

observiother

tasters.Tasters

unable

to

see

how

food

was

prepared

or

whatits

‘identity’

is.3.

Hedonic

scale

(for

quality

factorsRange

from

‘dislike

extremely

to

neutral

to

likeextremely’.4.

ApproachPreference

test:

Choosing

one

sample

over

anothersamples

are

coded

so

that

source

or

identity

of

foodsample

is

unknown

to

taster.Most

common

is

the

triangle

test

(a

preference

tesSelecting

the

sample

that

differs

fromtwoothers

(tof

3

samples).Usually

no

more

than

5

samples

tested

at

one

sittinsense

of

taste

becomes

dulled.

Statistical

analysiresults

is

usually

employed.5.

In

addition

to

flavor,

taste

panelsjudge

texture,

color,

packaging,

samplearrangement,

etc.Additional

quality

factoNutritional

qualityChemicalorinstrumental

analyses

for

specific

nutrient;however,

often

animal

feeding

tests

must

be

used,

especiallquality

of

protein

sources

(biological

value).Sanitary

qualityAnalysis

for

bacteria,

yeasts,

molds

and

insect

fragments.X-rays

to

detect

physical

contaminants

(e.g.,

glass

chips,metal

fragments).C. Keeping

quality

(storage

stability)Measured

under

storage

and

handling

conditions

to

matchconditions

encountered

in

normal

distribution.Normal

storage

tests

may

take

a

year;

extreme

conditions

mabe

used

to

speed

things

up.FOOD

DETERIORATIONAND

ITS

CONTROLFood

deterioration

includes

declinesorganoleptic

desirability/aesthetic

apnutritional

value,

and

safety

(i.e.,

prquality);

occurs

under

the

best

ofconditions.Some

of

the

most

important

advances

infood

technology

have

occurred

as

a

resulof

war.Nicolas

Appert

-

developed

thetechnology

of

canning

(1809)

as

a

resultof

prize

money

offered

by

Napoleon

forpreservation

of

food

for

the

French

armyand

navy.Shelf-life

and

dating

of

fooDefinition

of

shelf-life:

The

time

it

taka

product

to

deteriorate

toanunacceptablelevel

(what

is

unacceptable

is

sometimes

amatter

of

opinion).A

better

definition: Length

of

time

aproduct

remains

salable.It

is

common

for

a

food

manufacturer

to

definea

minimum

acceptable

quality

(MAQ)

for

aproduct.Actual

length

of

shelf-lifedependentonProcessing

method,Packaging,Storage

conditions.Dating

system1.

Different

code

dates:Date

of

manufacture

(pack

date),Date

the

product

was

displayed

(display

date),Date

by

which

the

product

should

be

sold

(sellby

date),Last

date

of

maximal

quality

(use

by

date),Date

beyond

which

the

product

is

no

longeracceptable

(use

by

date

or

expiration

date).2. Use

of

these

code

dates

requires

a

needto

predict

and

monitor

shelf-life.Models

for

predicting

shelf-life

are

particulauseful

for

new

products

without

a

distributionhistory.V.

Major

causes

of

fooddeteriorationMicroorganisms

(bacteria,

yeasts

and

molds)Insects

and

rodentsHeat

and

cold

-

can

cause

deterioration

of

foodnot

controlled.Moisture

and

drynessOxygenLightTimeA.

Microorganisms(bacteria,

yeasts

and

molds)More

types

of

microorganisms

can

spoilfood

than

cause

foodborne

disease.Sources

of

these

microorganisms:

soilwater,

air,

food

itself,

humans,

foodequipment

environment.Healthy

living

tissue

(internally)

is

usually

stehence

the

presence

of

spoilage

organisms

is

mostly

tresult

of

contamination.Bacterial

endospores

are

most

difficult

to

inactiHeat

and

moisture

will

increase

growth

and

activitmicroorganisms.Molds

as

compared

to

bacteria

can

generally

grow

alower

pH

(more

acid

conditions),lower

moisture

contents

(dryer

conditions),higher

salt

concentrations,

andlower

temperatures

(in

refrigerated

foods).Moldsusually

only

a

problem

with

spoilage,

not

safebut

Aspergillus

flavus

and

Aspergillus

parasiticusproduce

aflatoxins

which

are

potent

hepatocarcinogMolds

require

oxygen

for

growth.B.

Insects

and

rodentsInsects

destroy

5

to

10%

of

U.S.

grain

crop

annually

(iother

parts

of

the

world

it

can

reach

50%);

insectsdamage

crops

so

that

spoilage

microorganisms

aremore

of

a

problem.Rodents

both

consume

and

contaminate

food;

control

iscritical

since

mice

and

rats

can

reproduce

very

quicrodents

can

spread

diseaseFood

enzymesEnzymes

inherent

in

food

continue

to

function

afterdeath

of

animal

or

plant;

some

enzymatic

activitiesbe

accelerated

following

death.Can

be

controlled

by

refrigeration

or

blanching.C. Heat

and

cold

-

can

causedeterioration

of

food

if

notcontrolledExcessive

heat

denatures

proteins,

breaks

emulsions,out

foods,

and

destroys

vitamins.Uncontrolled

cold

will

damage

fruits

&

vegetables

ifallowed

to

freeze

resulting

in

discoloration,

and

tchanges;

freezing

milk

will

break

its

emulsion

andcasein

will

curdle;

bananas,

lemons,

squash

andtomatoes

are

subject

to

“chill

injury”

at

<10C.D.

Moisture

and

drynessExcessive

moisture

can

lead

to

undesirable

microbialgrowth.Surface

moisture

from

high

relative