Proceedmqe of the 7th International Working Conference on Stored-product Protection - Volume 2

Detection of spoilage of cereal grain in storage bin

Kiyokazu GOT01, Yoshihiro MIWAi and Motohiro MORIl

Abstract

Recently, the incident of spoilage of gram dunng the storageoccurs a few times a year at the drying and storage facilitiesm Japan. This causes the huge economic damage and thefarmer's cooperative loses the reliance. If the sign ofspoilage can be detected in the early stage, the damage willbe prevented. There are some causes of gram spoilage duringthe storage, for example increase of respiration, dewcondensation, fermentation, mold, microorganism, storedgram insect, mouse etc .. In any case, the concentration ofcarbon dioxide increases in the storage bm. So, themeasurement of CQ concentration will be a one of theeffective methods to detect the spoilage of stored grain. Inthis paper, the characteristics of CQ concentration changewere investigated when the dew condensation occurs m thestorage bin. The probability of spoilage detection was thenconsidered

Introduction

In Japan, there are a few incidents of rice spoilage yearlyduring storage. The causes are the fermentation or breedingof the microorganism etc. When the nce spoilage occurs,the economic damage IS huge and the credit of the farmers'cooperatives will be lost.The causes of rice spoilage are as follows:

a) Paddy tends to be harvested in early stage m Japan, sothe moisture content of received paddy m the facilitiesrecently has been fairly high,b) Early harvesting (August, September) has mcreased, sothe temperature IS high m the harvesting season.c) When the concentration of paddy received is remarkable,a large quantity of wet paddy is piled in the temporarystorage bin. The safe air-flow then can not be kept.d) The final moisture content was set highly by governmentin companson to the preVIOUSvalue So the moisture contentof stored paddy may be fairly high.e) The moisture content of stored paddy may become highsuddenly by the dew condensation caused by weather

IFaculty of Agnculture, Gtfu UruversIty, 1-1 YanagIda GtfU-Shl Gtfu,501-1112, Japan

condition.f) Using the storage drying method, the drying rate is slow,so the duration of wet state is long.In the drying and storage facilities, the nce spoilage hes

in two aspects, one IS the fermentation, another IS thebreeding of rrncroorgamsm. In both cases, the respirationrate of rice or microorgamsm increases. So It can be saidthat the startmg point of rice spoilage is the increase ofrespiration rate. We can prevent the significant spoilage by

the detection of this condition.The cherrucal formulas of respiration of rice are as

follows:aerobic: C6HIZ06 + 6Q-6CCh + 6HzOanaerobic: C6H1206- 2CzHsOH + 2CQWhen the rice respires, carbon dioxide IS generated. So,

we can detect the respiration by the measurement of CQconcentration. Further, even 1£ microorgamsms, forexample mold, or animal, for example mouse, etc.,increase, we can notice that incident by the measurement ofcarbon dioxide. The CQ concentration of carbon dioxide ISthe useful mdex to detect the irregular condition dunng nee

storage.The nee spoilage during storage IS mainly dependent on

the moisture content and temperature of grain. The causesto become high moisture content are as follows.a) A little high moisture paddy IS mixed in the regular

moisture paddyb) Part of paddy IS wetted rapidly for example by dew

condensa tion.We performed detectmg the increase of respiration rate by

the measurement of CQ concentration using the small sizecontainers and the practical gram storage bm,

Experimental Method

Model experiment

Mtxture of htgh moisture paddyThe model of paddy storage bin was set by pilmg 3

standard SIeves (200mm diameter and 50mm height}: upperand lower ends were sealed In the upper and lower SIeves,paddy of regular moisture content (1 kg weight) was put,and moisture content was about 13.5 - 14.0 % W. BPutting the high moisture paddy (15 - 30 %W. B.) m themiddle sieve, the change of CQ concentration at the upperand lower space as SIde of the model storage bin. The CQ

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Proceedings of the 7th Internatwnal Working Conference on Stored-product Protection - Volume 2

concentration meter of infrared type was used.Effect of dew condensationAssuming that regular paddy is wetted suddenly by the

effect of dew condensation inside the storage bm, somemodel experiments were carried out.Experimental device was the same as the experiments of

mixture of high moisture paddy. 2.8 kg of regular paddy waspiled in the model bin. A little amount of paddy m the petndish which absorbs water was put on the top of paddy layerinstead of dew effect. Changing temperature and amount ofwater absorbing, the change of COz concentration wasmeasured in the upper and lower space inside of the modelbin.

Practical bin experiment

Using the practical storage bin (capacity: 250t) m thegrain drying and storage facilities, the experiment ofdetection of COz concentration change was performed.Diameter and height of the bin were 10m and 7m,respectively.Measuring methodThree COz meters were set m the upper space of the bin,

one of them was set near the surface of stored paddy, andtwo at the upper part m the space. Two COz meters wereset below the paddy layer; one was just below the perforatedfloor, and another was at middle pomt in the lower space.Temperature and relative humidity were measured in the

upper and lower space of bin and outside of the bm. Theouthne of measuring system is shown in Fig. 1.

Upper space

Piled dry paddy

--------- ......

Lower space

Fig. 1. Measurement of practical bin.

Experimental procedurea) Experiment AThe change of COz concentration in the upper and lowerspace of the bm was measured without putting the wettedpaddy. Therefore, this experimental result IS the standardfor companson of the change of COz concentration of each

experiment.b) Experiments B82 kg of water was added to 500 kg of regular paddy. Thiswet paddy, which IS assumed to be affected by the dewcondensation, was put on the surface of plied paddy. Thistype of expenment was done twice.c) Experiment CPuttmg COz gas into the upper space of the bin, the changesof COz concentration m the upper and lower spaces weremeasured. This experiment was done to investigate thediffusion of COz gas through the plied paddy in the bin. Ifthe change of COz concentration can be detected at any pomtm the bm, one COz meter IS sufficient per bin for thedetection

Results and Discussion

Model experiment

Mlxture of high moisture paddya) Effect of moisture contentThe changes of COz concentration when the moisture

content of high moisture paddy ranged from 15 to 20 % W.B. are shown in FIg. 2. When the moisture content was lessthan 16 %W. B. , the change of COz concentration was verylittler beyond 16 %W. B. , the increasing rate became highdrastically. Moreover, the values of the upper and lowerspaces were almost the same, so the measurement at onepoint per bin was aright.

S6COO0...!7

16"

Temperalure 25 ~ ~c of mixed paddy ;

: : 20" :.......................... _ ~ :...,~~.·..····i:----~ :..................) ;7-C.::.<-.\ i

/~~ : 18":................. ., ......82COO

15"OL-------'-------'--------'o 10 20

Time elapsed (h)

Fig. 2. Effect of Me of rruxed wet paddy.

30

b) Effect of storage temperaturePaddy of 18 and 20 % W. B. was used as the high moisture

paddy. The changes of COz concentration were measuredwhen the storage temperatures were 15, 25 and 35°C; theresults are shown in Fig. 3 and Fig 4. The higher thetemperature IS, the higher the increasing rate of COzconcentration is; since the respiration rate increases. If theCOz meter IS sensitive, even the mixture of half dned

paddy, about 18 %W. B can be detected.

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Proceedings of the 7 th Internatwnal Working Conference on Stored-product Protection - Volume 2

g 60008c5 4000u 2!i'C

2000 ::::::::::==--..-:~:.--_:--_. r rrc . .:O'---------''---------'---~----'o 10 20

Time elapsed (h)

Fig. 3. Effect of storage temperature (1).

12000 ··MC·~f·~i~~d·~~dd;;·i(;%vi~B·.-··1'''Temperature: :10000 ; ;..... . 3 fi'C ;

g 60008c5u

10 20Time elapsed (h)

Fig. 4. Effect of storage temperaturel Z)

Effect of dew condensationa)Effect of amount of added waterAdding 5, 10 or 20 g of water to 50 g of regular paddy,

the changes of COz concentration were measured and theresults are shown in FIg. 5. Changes of 10 g and 20 gaddingare similar, so we decided that the amount of added water tothe regular paddy is 20 % of paddy,

1()(XX) Regular paddy: 50g ; ; "';Temperature: 25 t i./: :.......... '1' 'r ··········7··iOg··T···········~

, • I • ,

..................... __ pi .1_ _.......... ~ : ~. .

" 8QCX)S0.0..'-'" 6(X)()

13c:8 4(0)....oU 2<XX>

. .._ ... :._._ .. _Jig~

, ', '. ,·1··.. ··.. ····(····· ~ ~: : : :oc:....:...---.o------'------'-------'-------'

o 10 15Time elapsed (h)

Fig. 5. Effect of quatrty of water added.

205

b) Effect of storage temperatureThe change of COz concentration when 12 g of wetted

paddy was put on the surface of piled paddy is shown m FIg.6; temperatures were 10, 20 and 30t:. When thetemperatures were 20 and 30t: , COzconcentration began toincrease linearly. When 30t:, since the wetted paddy wasdried gradually, the increase of COzconcentration stopped,

and that started to decrease after that. When lOt:, smcethe respiration rate was low, It was difficult to detect thedew condensation.

e0..-3-2000 .... 1. ~ L :~

: e-i--·--r- 20·c. ,---- : . .: /',. : : :

--:--_.·;1<-: :·:-·:T·::-~:~_:t-::-_._:-_::--:j::::~-- -- -_.;: : : : 1oc :: : : • I

30uc:ou

<51000U

10 W ~Time elapsed (h)

40 50

Fig. 6. Effect of storage temperature.

30

c) Effect of amount of wetted paddyPutting the wetted paddy of 0, 1, 2.5, 5, 10 and 20 g on

the surface, the changes of COz concentra tion weremeasured; storage temperature was 20t: (Fig, 7 and Fig.8) As shown m FIg. 8, the increasing rate is in proportionto the wetted paddy amount.

5000

.,.......4000e0...3'300013c:8 2000c5U 1000

Temperature:.20'C ··········r··········..r···········:Dry paddy: 28kg : : :

.... """'1" ·..Wt·.. ·~f:·;~t·P~·dd;··20i·····~···..·····1.. ," I.----- - •• o. , ._ .. __ ~ _ .. _ __ ". . . .I , t t• I , •It. • I

_.. .. .. _ .~. . .. . _: __. .. ~ .. ,... . .. 1.. 1Og . '" _' :. .. .5g ~.

Ol-.-_-~--_'O"'------"---_.&..--_-'o 10 20 30 40

Time elapsed (h)50

Fig. 7• Effect of quantity of wetted paddy (1) .

800 ...... - _ ..,- - ,· ,, .Dry paddy' 2 Bkg: Wt f tt d ddv: 25 :: . 0 we e pa y. .og .

-r·_·- i i 19.J~?_.j

, ., .· .· .· .

e&:700'-'"

25

13c8600c5U

500

400 ..~ __ ---'- -'- __ ---''-- __ -.o-__ --'o 10 20 36 40 5C

Time elapsed (h)

Fig. 8. Effect of quantity of wetted paddy (2).

The change of COz concentration differs also according tobm capacity, and amount of stored paddy. In this model bincondition, If there is about 2.5 g of wetted paddy to 2.8 kg

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Proceedsnqs of the 7 th International Working Conference on Stored-product Protectwn - Volume 2

of regular paddy (0.9 % by weight), the generation of COzcould be detected. This rate IS equal to that of 180 kgwetted paddy to 200 t of regular paddy.This fact shows that even if the wetted paddy ISso little,

the detection is possible.

Practical bin experiment

Conditions of experimentMoisture contents of the regular paddy and water added

paddy were 13.8 % and 21.0 % W. B. respectively.Temperature and humidity during the expenment are shownin Figures 9 and 10 Since weather was cloudy duringexpenment, the change of ambient temperature was small;that was less than 2"C (14.5 -16"C ) especially inside thebin.

18

Lower space

,.....16 Upper spacee

.......... - - - ... - ...... _ .. _ .. "

12"==""_---''-- __ -'--__ --'-__ --'- "'--_----'

12 00 00 00 12 00 00 00 12'00 00 00 12 00

~;-------~~I«- -----;;;j*~:____--Apr. 3 5 6

Fig. 9. Change of temperature inside and outside of the bm.

100

00

~e-~ 80e::I::z::IJG

70

(j()'-- __ -'-- __ --'- __ --L "'-- __ ...L-__ --'

1200 00 00 12 00 00 CXJ 12 00 00 00---?<>t(t!:--------''X------~,---

Apr 3

1200

5 G

Date-TIme

Fig. 10. Change of RlhuIlUdlty inside and outside of thebm.

Detection of carbon dwxulea) Experiment AThe change of COz concentration when there was no

wetted paddy In the bm is shown InFig.Tl . The value In the

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upper space was stable; however that of lower spacedecreased slowly. When only regular paddy existed in thebin, the increase of COz concentration was not found at anyposition. It was clanfied that COz concentration Just on thepaddy surface was higher than that at upper location in thesame space.b) Experiment BThe change of COz concentration when wetted paddy was

put on the piled paddy are shown In FIg. 12 and Fig. 13.This type of experiment was done twice. The measuredvalue of COz concentration fluctuated for the first 3 hourssince the COz meter was set Just above the wetted paddy. Atevery measuring pomt In the upper space, the COzconcentration started to increase about after 3 hours fromthe starting. Though the COz concentration were differentbetween upper and lower part m the upper space, themcreasmg rates were almost the same; those were about100 ppm/lO hours.

1300 Upper spaceLower posltion(l)

U 900

05 ~~p~.r..~??.'.~~?~ . .- ... -., ... ,. .. -oU 700 Piled pady. 250t. 135%WB

Wet paddy' NothingSOOL----'-----'-----'-----'-----'-------'2200 0000

Apr. 30200 ().I co 0600 0800

AprA

Fig. 11.

Date-Time

Change of ~ concentration Without wetted

paddy.

1400 Piled paddy 250t. 13.5%WB Upper spaceWet paddy 5OO~g. 24%WB

Lower posltlon(l)EI2000-0-

"-0/

g 100:>ouoU eco Upper POS It! .O.~•••••••••.••••• ,

..........

600'----'----'- __ '--_-'-_--'- __ "'--_--'-_----'1600 1800 2000

AprA22 00 00 00 02 00 0400 0600

Apr. 508 co

Date-Time

Fig. 12. Change of m concentration With wetted paddy(1) .

The change of COz concentration of Experiment B wasquite different from that of experiment A, so that it wasclanfied that the existence of wetted paddy can be detected.Moreover, unless the storage bin ISsealed tightly, detectionISpossible.

Proceedmqs of the 7th International Worklng Conference on Stored-product Protection - Volume 2

1100

Plied paddy' 2501, 13.5%WB

Wetted paddy 500kg, 22 %WB

Upper space

Lower posiuon Ll l...... ------_ ....e0-

.3- 700Uc::ouoU50Q

upper posiuon

• Ill .. ••••

" "_ ................-.."

3)JL..-----'-----'------'----'-----'12:30 16'30 1830

Apr 5

Fig. 13. Change of COz concentration WIth wetted paddy.

c) Experiment C

The changes of C~ concentration in upper and lowerspace after puttmg carbon dioxide in the upper space areshown in FIg 14. The C~ concentration m the upper spacedecreased very slowly; the C~ concentration m the lowerspace did not change, so It was thought that the diffusionrate of carbon dIOXIde through piled paddy IS very low.

lCXXXl

&XX>

Upper space

Lower posiuon (1) , (2)

Sf:l.X1J~ ."

g 40008<5UZOOJ

............. - ..- ..••........••..••..•.Upper posuion

Lower space <I), (2)--~.- --- ..--- ..--_.-OL-_---'L...-_--''--_--' __ --'__ ---L __ --'

23.00 01:00 03.00 0000 07.00 ro.OO ll:oo-*-----------

Apr. 5 Apr.6

Fig. 14. Diffusion of carbon dioxide in the bm.

Summary

The mcrease of respiration IS the SIgn of startmg of neespoilage, Carbon dioxide IS generated by the respiration inboth aerobic type and anaerobic type So the detection ofcarbon dioxide was performed dunng storage using themodel storage bm and the practical storage bm.When the high moisture paddy was mixed m the regular

paddy, change of C(h concentration was detected accordmgto moisture content and temperatureAssummg that a part of paddy IS wetted suddenly by dew

condensation, the generation of carbon dioxide by therespiration was surveyed Increasmg rate of C(hconcentration IS dependent on the temperature and amountof wetted paddy. If 0 . 1 % of the regular paddy IS wetted bydew condensation, it is possible to detect the generation ofcarbon dioxide. ThIS change is quite different from thatwhen there is no wetted paddy. Therefore It was concludedthat detection of C(h generation is possible It was,however, found that the dIffUSIOnof carbon dioxide IS veryslow m the piled paddy. So, If the detection is done at onlyone location per bm, it IS necessary to adopt some idea, forexample the aeration before the measurement of C(hconcentration.

References

Fujunaki M. , 1984. SCIence and technology of post-harvest(in Japanese), Konn. Yamashita R., 1992. Physicalproperty of cereal gram (m Japanese), Japanese Society ofAgricultural Machinery.Taguchi R., 1964. Outlme of plant physiology (mJapanese), Yoken-doEbisawa I On the technical problems of country elevator (mJapanese ) , Joumal of Agncultural warehouse andprevention of disasters, No. 39, 40 and 41.

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