IS 11816-1: Storage of Cereals and Pulses, Part 1: General Recommendations for the Keeping of Cereals

2010·1.3 MB·English

by  Bureau of Indian Standards

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IS 11816-1 (2010): Storage of Cereals and Pulses, Part 1:
General Recommendations for the Keeping of Cereals [FAD 16:
Foodgrains, Starches and Ready to Eat Foods]
“!ान $ एक न’ भारत का +नम-ण”
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IS 11816 (Part 1):2010
ISO 6322-1 : 1996
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Indian Standard
STORAGE OF CEREALS AND PULSES
PART 1 GENERAL RECOMMENDATIONS FOR THE KEEPING OF CEREALS
( First Revision)
ICS 67.060
© BIS 2010
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEWDELH I110002
November 2010 Price Group8
Foodgrains, Starchesand Ready-to-Eat FoodsSectional Committee, FAD16
NATIONALFOREWORD
This Indian Standard (Part 1) (First Revision) which isidentical with ISO 6322-1 :1996 'Storage ofcereals
and pulses - Part 1: General recommendations for the keeping of cereals' issued by the International
OrganizationforStandardization (ISO)wasadoptedbytheBureauofIndianStandards ontherecommendation
ofthe Foodgrains, Starches and Ready-to-Eat Foods Sectional Committee and approval of the Food and
Agriculture Division Council.
This standard was first published in 1986which was identical to ISO6322-1 :1981'Storageofcereals and
pulses - Part 1: General considerations in keeping cereals'. The first revision of this standard is being
brought out to align itwith the latest edition ofISO Standard.
The text of ISO Standard has been approved as suitable for publication as an Indian Standard without
deviations.Certainterminologyandconventionsare,however,notidenticaltothose usedinIndianStandards.
Attention is particularly drawn tothe following:
a) Wherever thewords'InternationalStandard'appear referringtothis standard, theyshouldbereadas
'IndianStandard'.
b) Comma (,) hasbeen used as adecimal markerwhile in Indian Standards, the current practice isto
useapoint(.j asthe decimal marker.
The technical committee has reviewed the provision ofthe tollowinq International Standard referred inthis
adopted standard and hasdecidedthat itisacceptablefor use inconjunction with this standard:
International Standard Title
ISO5527:1995 Cereals- Vocabulary
In reporting the result of a test or analysis made in accordance with this standard, if the final value,
observed or calculated, is to be rounded off, it shall be done in accordance with IS 2 : 1960 'Rules for
rounding off numerical values (revised)'.
IS 11816 (Part 1): 2010
ISO 6322·1 :1996
Indian Standard
STORAGE OF CEREALS AND PULSES
PART 1 GENERAL RECOMMENDATIONSFORTHE KEEPING OF CEREALS
( First Revision)
1 Scope
This part of ISO6322 gives general guidance related to the problems of keeping cereals. Other aspects of the
storageof cerealsandpulsesaredealtwithinISO6322-2andISO6322-3.
2 Normative reference
The following standard contains provisions which, through reference in this text, constitute provisions of this part
of ISO6322. At the time of publication, the edition indicated was valid. All standards are subject to revision,and
partiesto agreements basedonthis part of ISO6322areencouragedto investigate the possibility of applyingthe
most recent edition of the standard indicatedbelow. Members of lEe and ISOmaintain registers of currently valid
InternationalStandards.
ISO5527:1995,Cereets- Vocabulary.
3 DefInitions
Forthe purposesofthis partof ISO6322,thedefinitions givenin ISO5527andthe following definition apply.
3,1 relative humidity: Ratioof the vapour pressure in asample of moist air to the saturation vapour.pressure
with respecttowateratthe sametemperature.
4 Aspectsoftheproblems
4.1 Technicalfactors
Theproblemofkeepingcerealsarisesattwo different stages,asdiscussed in4.1.1and4.1.2.
4,1.1 Immediateiy after harvesting, the cerealsmay sometimes remain moist for periods of time rangingfrom a
lew hourato several months. The product is particularly unstable and as a rule it is at this stage that storage
conditionsareleastfavourable.It isfrequentlyaquestion of storageonthe farm or insmall, not always adequately
equipped,silosandstorerooms, whilstawaiting theappropriatetreatment.
4,1.2 Upto andincludingthe international marketing stage,cerealsarestored for anything from afew months to
severalyears at or below a maximum moisture content. the level of which may be fixed in each country. Such

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ISO 6322-1 : 1996
storagecanbehandledbyvery largebulkstorageorganizationswith modern. well-equipped silos. orother types of
bulkstorage facility. Thetype of problem arising varieswith the type of store. its condition. location andexpected
periodof storage.
4.2 Environmental andsociOCeconomlcfactors
Problemspeculiarto the keeping of grainvarygreatly from onecountry to another. These variations depend upon
thefactors listedin4.2.1to 4.2.3.
4.2.1 Climaticconditions
Undoubtedly.climatic conditions areoneof the most important factors affecting the quality of grain.from growth in
thefield tofinalanimalorhuman consumption.
Geographicalareascanberoughlydivided intothe following:
aJ hotanddamptropical climates. where deterioration of the graincanbevery rapid;
b) hot anddry climates, where cereals areharvested naturallydried andwhere. because of this. the problem is
simpler le.g. the southern United Statesof America andthe Middle East);however. inthese regions the grain
canremain hotfor longperiodsafterharvesting,whichexacerbatesinsect infestationproblems;
c) temperate climates, where partof the harvestmaybemoist (e.g.Europe);
d) verycold regionsposing very specialproblems suchascerealswhich havespent some time undersnow.
It isfrequently the casethat some of the developing countries havelessfavourable climates andare therefore at a
disadvantageinthe fight againstgraindeterioration.
4.2.2 Importing/exportingactivitiesofthacountry
Alloountries which produce cereals havestorage problems at the farm level. Those which export and import grain
havefurther problems. Exporting countries, in particular. haveto use storage structures which make it possible to
delivercerealswhich complywiththe often very stringent standardsset byofficial organizations inthose countries
aswell asby the importing oountries (especiallywhere microorganisms and insects are concerned). It should be
remembered, however, that in many exporting countries it is important that anyequipment used should beof low
cost.
4.2.3 Technicalmanagementdevelopment
.
Somedeveloping countries are not well informedabout the manyproblems andare often ill-equippedto dealwith
them. Onthe other hand.thedevelopment of modern harvesting techniques le.g. use of the combine harvester)
considerablymodifies the specific natureof the first storage(4.1.1)because6f the potentialinflux of moistgrain.
The organizationof the storage system is very important because of size differences in the storage structures
used;the presenceofhugequantitiesofgraincanpresent practicalandlogistical problems.
At the present time. varying types of more or less advanced storage systems (bulk or sack) exist side by side
throughout theworldandoften inthe samecountry.
It isdesirableto segregate lots of grainon arrivalat the bulk storage depot according to moisturecontent soasto
avoidmixingdampanddry grain.
4.3 Qualitativefactors
Whether or not acereal is in good condition should bejudged in relation to the ultimate use of the cereal: i.e. for
humanoranimalconsumption, inthenaturalstate orafterprocessing. orfor non-edible industrial products.
The quality factors are usually laid down in regulations which. for each country, determine quality criteria, for
examplethe quality of the grain itselfandthe permissible quantities of foreign substances(other varieties of gram,
insectorrodent residues,residuesof pesticidesortoxins).

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Mandatory quality standards set by importing countries obviously havean effect on the storage problems facing
exportingcountries. Countries with lessadvancedstorage methods attheir disposal may find difficulty in meeting
thesestandards.
Thus, although each individualcountry may have its own problem, because of international trade there are very
great overlaps and many problems which, at the technical and scientific level, are similar; present knowledge
makesit possibletoformulateguidelinesfor ensuringthe safestorageof cereals.
5 Specificcharacteristics of cereals asproductsto be stored
5.1· .~....._ aoVingorganism
The resting grainis a living caryopsis inwhich the germ andthe aleurone layer have a reduced rate of metabolic
actMtYwIrichmayacceleratevery rapidlywhen the environment isfavourable.Theendosperm cellsarecomposed
8S1llttilllyof reserve substances (carbohydrates,proteins and, in smaller quantities, lipids),which supply energy
forthe metabolicprocesses.
Thefundamentalmetabolic activitiesofgrainareoftwo kinds,asgivenin 5.1.1 and5.1.2.
5.1.1 Respiration,which mainly affects carbohydratesandlipids,occurs under aerobic conditions if the moisture
content andtemperature of the grainare suffICientlyhigh;the respiration produces carbon dioxide, water vapour
andaconsiderableamountof heat(2830kJper moleofglucoseoxidized).
Under _robic conditions, a fermentative metabolic process occurs, producing less heat (92kJ per mole of
gIucoael.Thefermentedgrainliasatypicalsour-sweet alcoholicsmell andhasundergone other changesthat make
it unsuitlblefor humanconsumption, althoughit issuitablefor animalfeeding.
Oxidalion phenomenaare normal in stored grain,but take place only at a low rate if grain is dry; care shouldbe
takenthat noappreciableaccelerationoccurs,sincethis indicatesthatthe grainisunsuitable for further storage.
5.1.2 Germination of the seed, which isthe normal outcome of its metabolic activity in the presence of oxygen
andoptimum conditiorisof moistureandtemperature, occursinseveralsuccessive stages: imbibition, activationof
the enzymes, active cellular multiplication, soonaccompaniedbycell growth and followed by the development of
the'jIOlIlIg~t;onlythe last stageisvisibleexternally.
Germination, even inits initial stages, isaserious changein grainalready stored or to be stored. It occurs most.
freQuently in wet years, while the crop is still standing in the fields. There are two important practical
CQllSlIqUllflC8:
a) chemicalcllange ofthereservesubstances;
bl increaseof enzymicactivities: wheat with higha-8mylasecontent, harvested in northern Europein.Wetyears,
isawel~knownexample.
Suchcerealsareoften unfitfor humanconsumption.
Thegerminationpotential, whichdeterminesthe viabilityof the grainin general, lias to be preserved ~ the grainis
tobeusedinmaltingorfor seed.
5.2 Mlcroftora
The seed is permanent host to a.considerable microfloril; most of these microorganisms are cosmopolitan and
innocuous, but some produce harmful by-products. Microflora communities present on freshly harvested grain
includemanytypesofbacteria,mouldsandyeasts.
.While
the grainis ripening'and its moisture content falling, the number of foeld microorganisms, mainly bacteria,
diminishes.When thegrain isllarvested; it isinvadedby storage microorgariisms andthe field microflora gradually

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ISO 6322-1 :1996
dies out. If the moisture content is below 14% on wet mass basis. the microflora does not multiply. whereas
above14% on wet massbasis it does so rapidly.However. the moisture content limit is temperature-dependent
Isee7.3),
Thus,at harvest, the qualitative and the quantitative compositions of the microflora depend more upon ecological
factorsthanuponthe species of cereal.
Duringtransportandstorage, additions to the microfloralpopulationoccur.
5.3 Weed seedsand otherforeign matter
Most commercial bulks of grain, which have not been screened or aspirated. contain aproportion of other grains,
weed seeds, chaff, straw, stones, sand, etc. The vegetable materials may have physical and biological properties
thatdifferfrom those of the main constituentandmaytherefore affectthe storage behaviour.
5.4 Importantphysicalpropertiesaffecting storage
Themost relevantphysicalproperties affectingstoragearethe moisture andtemperature conditions of the grain.
5.4.1 Abulkof cerealcontains, besides the grains,aconsiderableinterstitialvolume of air;for example, inwheat,
approximately40 %of the total bulkvolume isair.
Thefluid-flow property of bulk grainis such that the graincanbefed into either hoppers or pipelines and makes it
suitablefordryingorcooling byblowing(orsucking)dryairthrough it.
5.4.2 Because of the very low thermal conductivity of the grain 10,125W/(m·K) to 0,167W/lm-KJI. the heat
resulting from metabolic phenomena. in the absence of ventilation, builds up locally. bringing about spectacular
temperature rises, more especially as the specific heat capacity of grain is relatively low (approximately
1,88kJ/lkg·K)for wheat with 15% moisture contentl; however, it increases as the moisture content of the grain
increases.In addition to inherent metabolic activity, heat may be produced by the activity of microorganisms and
insects.
5.4.3 Grain is hygroscopic and gives up or absorbs moisture so as to maintain an equilibrium with the
concentration of moisture inthe airsurrounding it.Therelationshipmay beexpressed asasigmoid CUM!, which is
practicallystraight over most of the significant storage range between 20 % and 80 % relative humidity. Thereis
some variation in the relationship between moisture content of the grain (usually expressed as a percentage on
wet mass basis)and'that of the air (usuallyexpressed asapercentage as relative humidity) with temperature.k
the temperature increases, tha moisture content is lower at a constant relative humidity.. There is also some
difference between grain which is gaining moisture and that which is losing it; i.e. there is a hystereSis
phenomenon in the relationship between the moisture content of the grain and the relative humidity ofthe
intergranularatmosphere. Examplesof adsorption-desorption isothermsaregwen inannex A.
Periodicchanges in the relative humidity of the atmosphere only affect the surface layers of bulks of grain. the
relativehumidityof the interstitial airbetween grains belowthe surface being principally controlled by the original
moisture content andtemperature. Gradientsof equilibrium relativehumidity and moisturecontent may beset up
bypersistent differences intemperature between the surface andthe interior of the grain bulk caused bychanges
in extemal temperature or heating within the grain mass. The moisture flows down the temperature and vapOur
pressuregradients to the coolest partof the grainandraisesthe moisture content there.
5.4.4 Theterms "dry", "moist" and "safe" canbeappliedtograininstoraae.
"Dry" or "safe" indicates that the grain has a moisture content at which, taking into account the likely range of
temperaturetobeexperienced duringstorageandtransport, there isnoriskof appreciable metabolicactivityof the
grainitselfnorof attackbymouldsendother microqrganisms.
"Moist" grainisthat whose moisturecontentisabovethat level.Therangeof ~safe" moisturecontentvarieswith
the.crop and is dependent on the temperature lincluding artificial means of reducing temperature)and period of
sfor<l9&.As ageneral rule,11 "safe" moisture content is one not exceeding that in equilibrium with 65%.relative
humidity.

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ISO 6322-1 : 1996
5.5 Preservation of grain quality
It is essential to retain certain indispensable properties ingrain which is to be used for human or animalfood, for
malting orfor seed:
al acertain levelof enzymic activity, especiallya-amylase, inthe caseof cereals to be used for bread making;
bl the originalnature ofthe various protein constituents, asthese determinethe rheological properties of dough;
cl the pElrcentage germination and germinative energy, which should be kept very high for seed and malting
barley.
These requirements preclude any intense heat treatment such as heat sterilization which denatures the proteins
andlimitsthe useof high-temperaturedrying systems.
Forutilization infood (human or animal) it isobviously essential to maintain the food value of the product (flavour,
nutritive elements, nutritious effectiveness) at the highest possible level. It is also necessary to safeguard product
hygienewith regardto any possible toxic substances (toxins)andpesticide residues.
6 Deteriorativechanges which occurin grain
Causesof changeswhich occurduring storage canbedividedinto two quitedistinctcategories:
a) the immediatecauses of the deteriorativechanges;
b) the environmentalfactorsaffectingthese causes.
6.1 Causesofchange
6.1.1 Enzymicchanges
Enzymicchanges produced within the grain manifest themselves in a variety of ways. Such changes to proteins,
carbohydratesandlipidsmay occurduring storage, but these areinsignificantunless the grain is moist.
However, some enzymes, for example the lipases,canbeactive indrygrainover along period.
6.1.2 Otherchangesof biochemicalandchemicalorigin
Bytheir very nature, reactions of biochemical andchemical origin arevaried. These reactions generally requirefairly
hightemperatures such as are encountered during drying or as the result of "heating" caused by the activity of
insects, moulds andothermicroorganisms:
al Maillard reactions which produce many intermediate compounds, the physiological activity of which hasbeen
recognized,eventually leadto non-enzymicbrowning;
b) deterioration of the starch granule structure, which involves very substantial changes, for example damage to
the granule andformationof dextrinsatthe timeof drying;
c) denaturation of proteins, which leadsto the loss of specific properties such assolubility, rheological properties
inthe hydrated state andenzymic activities;
d) diminutionof the quantityof availablelysine;
el destructionof vitamins (B Eandcarotenoids).
"
Some reactions. especially non-enzvmic oxidation of lipids, may take place within the normal range of storage
temperatures.
I 6.1.3 Externalcauses:Uving organisms
Deterioration may be caused by living organisms; i.e. vertebrate and invertebrate animals and microorganisms.
Although the direct effects of attack by living organisms are important. certain indirect effects may be much more
i
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