Proceedmgs

of the 7th lnternauonal Workmg Conference on Stored-product Protectum - Yolume 2

Study on microwave drying of grain Su Ya2,

Yu Xiurong",

Youarr", Zheng

Wang

Ttesong", Zhao Simeng' and Huang

Abstract After

rice

are

debranchmg

dned

rmcrowave , the

activities

of

have little change the drymg temperature

below 55°C to maize (except

and urgent

losses.

Accordmg

among the cereal grams purchased

and stored

moisture content grams IS about 2.5 rrulhon tons

The maize WIth

the handlmg capacity of the drymg apparatus

high moisture content can absorb a great deal of microwave

milhon tons.

So tlus kmds maize should be dned with the combmation

rmxed flow, cross flow and concurrent

method of microwave drymg and hot air drymg.

common charactensucs

method

could be used as pretreatment

apparently eficiency

shorten

the heatmg

MIcrowave

of drymg

time , mcrease

gram

which

the drymg

temperature matenals

m the alternatmg mcreasmg

the production

of nce , corn and wheat

rrulhon tons,

10.2207 rmlhon tons respectively very complicated

and reachmg

the microwave

The climate m Chma IS

approachmg

the north

parameter

Studymg the climate records of the mam

IS often found cloudy and ramy whether dunng

the harvest

It results

season.

of microwave

drymg apparatus

It has the

in a second The design of

IS under the studymg and The technological Only a few years

began to study microwave

IS quite limrted.

some expenments of our

These years,

on microwave

expenments

can

the

study

drymg. we have

gram drying. be

probably

used

IS usually at 20% or slightly above; the corn IS usually 25%

references

or so, even as hIgh as 40 % sometImes.

miCrowave drymg techmque and for the development

Consequently,

the

loss of the gram whIch was caused by mould development and germmatIon

for

further

the

heatmg and drymg

stage and no fixed types

Related information Results

nce

Thus

high usage rate of heatmg

has not been published openly

conducted

that the

round-gramed

the

which IS

system

the high temperature

ago, Chmese scientists

the weather

in the south or m

moisture content of the newly harvested

held,

has been studied abroad dunng recent years

m our

IS that

and lead to the rapid

of the whole

the techmque

11. 1986ml1lIon tons and

production areas of the cereal grams m Chma,

electnc

generator,

of heatmg uniformly,

Therefore, country are 18.5226

theory

will be heated wholly at the same time

pecuhanty energy

heatmg

water molecules bemg heated take place at high-

speed activity

Introduction

flow dryers etc. The

of them are usmg hot air to dry

While the microwave

matenals

However,

IS at least 1

The types of the dryer are usually contmuous

created by the microwave

In 1995,

to develop the gram

to reduce post-harvest

by the state around the year 1992, the amount of the high

technology

IS below 50°C to nce and for seeds)

In the senous loss years, the number can reach 15 %

to statistics.

When drymg nee and maize

low-power and long-proceedmg

10 %

So, It IS very necessary drymg technique,

but the cookmg qualities and gelatnuzation

With microwave, IS used,

the yearly loss of the gram on this reason IS on average

enzyme which has effects on the nee qualities

decrease greatly, properties

with

Shezhang''

and

apphcation

as of

of the

eqmpment and technology deSIgn.

because that the grams can not be dned to

Experiment Materials and Method

the safe storage mOIsture content on tIme IS rather senous. Accordmg to the statIstIcs

of the Mlmstry

of Agnculture,

Experiment materials and method 1

Department

Of Gram and all Storage,

142 Shongsan South Rd 2

( 450053), 3

4

of

Internal

Trade

P

R

Chma

and DeSIgn Instttute

153

Nanyang

Rd

Department of InstabIlIty,

a RIce vanety: No 5,

of the

b Corn vanety: Zhengzhou Gram College, 142 Shongsan

South Rd

Zhengzhou (4500052),

Department

of Food Engmeenng,

P

R

Chma

Zhengzhou Gram College,

Zhengzhou (450052),

P

R

142

Chma

P

R

Chma

round- gramed 6811 (all

nce,

Zhengzhou

are newly-harvested

Ye Dan No 2 (seed corn)

Main instruments and reagents a VISCOSImeter Brabender Company, Germany b. HIgh-speed

Henan Econorruc Trade School, 4 Yousheng )J"orth Rd , Zhengzhou ( 450053),

pohshed

Huang]mgqmg,

seed nce)

Zhengzhou

P R Chma

Shongsan South Rd 5

Zhengzhou (450052),

Zhengzhou Gram ScIence Research Millistry

Zhengzhou Gram College,

freezmg

centnfuge

20

RD-52D,

HItachI

Company , Japan. c MIcrowave

1096

oven 2450MHz,

NN-86555 type , Kaosheng

Proceedings of the 7th Iniernotumol

d. e. f g.

Workmg Conference on Stored-pmduct Protectioa - Volwrne 2

Brand, Panasomc Company, Japan ER-761 MD type, Hater Brand Qmgdao Refngerator Factory Electnc heatmg blow dry oven DRH-100Sbba type, Guangdong Medical Apparatus Factory Analytical Balance, TB328B type, graduation value o .1mg, Shanghai Balance Factory Pullulan PF-20 Japan Hayshibara Biochemical Standard Amylume, J T Bakeerchenucals

Method (1) Microuxue heatinq nee and corn

Put the rice which contamed 11.5% moisture and the corn with 16.15% moisture content mto ground-m bottle after its moisture being adjusted, and let moisture diffuse to reach an equilibrium state for fifty hours, spread out the nce on the turnmg glass plate of the microwave oven, each sample dried is 250g. Suppose the heatmg power accordmg to the expenment requirements. Then, translate the samples bemg treated mto ground-in bottles and seal up with wax. At last, measure the moisture content, the rate of cracked seeds and germmation percentage after bemg put on for 48 hours (2) Measuring the rate of cracked seeds 48h later, dehusk the nee treated by microwave by hand. Brown nee is put on the glass board under which a 60W light bulb irradiates, check the brown nee one by one With magnifier. The rate of cracked seeds is the number of the nee kernels With cracks selected from each 100 kernels of brown nee Using the Similar method, we get the cracked rate of corn. (Each sample is done three parallel expenments and calculate the average) (3) Measuring the deamylopepectase actl,mty of rice Weight 1. 4g brown nee and pulvenze then Sieve it With a Sieve of 0.2mm bore diameter And then, the sample treated is soaked m active enzyme mixed by orthophosphonc acid buffer, and total enzyme mixed by sodium hydrosulflte buffer solution Then put it m refngerator for a mght Fmally, centifugated it at 94oor. mm for 15 mm (4°C). Draw the supernatant flUidand measure the actiVity The reactiOn system is: o .4% pullulan 0 .8ml, pHS. 5 acetic aCidbuffer solutiOn 0.2 ml, extractiOn of enzyme O.lml, preservatmg heat under 35°C for 30 mm and measunng reduction sugar produced durmg the reaction The enzyme active umt is defined: one enzyme active umt 1Sthe number of the enzyme needed in the reaction to hydrolys1sPullulan and produce lumol maltotrise under the temperature of 35°C. The mh1bitory enzyme activity equals to that total enzyme actiVity subtracts active enzyme actiVity (4) Measunng the amylase actwity of rwe 4.0g sample and lOml O.2molIL orthosphosphnc aCid

buffer (pH 5 . 8) is gnnned to homogenate. Then frx the capacity to 50ml After centnfugmg at 100r/m for 5 m , we get the supernatant flmd which is the very enzyme fltnd, The system of reaction is: 4ml enzyme fluid (Before measuring the a-amylase activity, the enzyme fluid must be treated by water-bath under the temperature of 70°C for 15 mmutes 1ml orthophosphonc acid buffer solution (pH 5.8), 2ml1 % amylase solution, react at the temperature of 40°C for 5 mmutes Measuring the number of reduction sugar production regardmg The malt sugar as the standard after extermmatmg the enzymes The umt of enzyme activity is defmed as that one of the unit of enzyme activity is the number of enzyme needed to catalysis and produce 1mg malt sugar in 5 mmutes l3-amylase activity equals that total enzyme activity substracts aamylase activity (5) Measuring the steam oualui; of 1"ICe Weight some nee commensurate With the parts dry of 7g Adding water about 120ml after elutriatmg it Then, these index must be measured after steaming the sample in special arrangement for 20 mmutes The first mdex is the moisture absorption rate of nee, the second is the pH value of nee water. The third is the iodineblue-value of nee water. 1ml of the nee water centrifuged is added by 5ml of O.5mollL hydrochlonc acid and 0.2 % iodine fluid, and then fix the capacity to 100mi Finally measure the absorbency at 660nm With 1cm colonmeter, and the iodine-blue-values of nee water is showed by the absorbency (6) Meas'lamg the qeuuinizatuni specl,fl,cdy of rice GB;J14490-93 cereal and starch gelatinization specifier ty method 'viscometry method' (7) Measu1"Lng the content of the amylose shanthy method (8) Measurnu; the nunsiure content Accordmg to GB5497-85, 130°C fixed temperature and fixed time operation (9) Measunng the germinatum percen,tage Accordmg to GB5520-85 (10) Measunng the actiVity of hydrogen perOXidase accordmg to GB5522. 85

Result and Analysis The influence of microwave heating on rice quality We use ER-761 MD mIcrowave oven, the power of whIch is 700W The number of nce treated m batches is 500g and the time is 3 mmutes The result shows that deamylopepectase, total amylose and a-amylase activity reduced obViOuslyafter bemg treated by microwave. At the same time, the mOisture absorptiOn rate of nee, the pH value of nce water, and the iOdme-blue-valueof nce water

1097

Proceedings of the 7 th Internatumal and insoluble

amylase reduce

to a certain

Working Conference on Stored-product Protectwn - Volume 2

extent.

The result of this expenment

All of

too obvious.

Generally

speaking,

good. has lower gelatinizing

the rice whose quality is

temperature,

Approach the microwave condition of rice

final viscosity,

jelling value and relative higher viscosity and damage value. The result of the experiment effect existing simultaneously,

UsingNN-86555 kaoshen

has negative effect and positive

Table 1. The influence of microwavedryingto deamylopepectase

handle part contrast part

6811

handle part

technology

brand microwave oven. suppose Results see Table 4 -

and amylase activItY(fJ-1g).

deamylopepectase

contrast part

With

6.

obVIOUSinfluence on specificity of the nee gelatinization.

Huang jmqmg

drying

5 heating power and 5 heating time.

even they have not enough

sample

IS basically consrstent

that of related reports of overseas (See Table 1- 3).

amylase and soluble amylose rise a bit and the result is not

amylase activity

activity

total

activity

inhibitor

total

enzyme

enzyme

enzyme

enzyme

21.44 7.56 16.19 8.04

10.86 3.78 7.43 3.57

10.58 3.78 8.76 4.47

a-amylase

/3-amylase

4.75 4.00 6.25 2.50

17.50 12.25 18.13 11.88

22.25 16.25 24.38 14.38

Table 2. The influence of microwave drying on the steammg and boiling quality of the rice.

sample

Huang jmqmg

contrast part handle part contrast part

6811

handle part

rice water

nee

absirotuib

waterpH

rate

value

429.3 407.9 451.5 402.9

total

total

rice iodine-

amylopectin

total

soluble

insoluble

starch

amylose

amylose

blue-value

starch

6.97 6.87

0.135 0.131

82.20 82.47

64.70 64.42

17.50 18.05

9.41 10.27

8.09 7.78

7.04 6.83

0.192 0.161

82.01 81.50

65.47 65.14

16.54 16.36

9.65 10.64

6.89 5.72

amylose

Table 3. The influence of microwavedrying on the gelatioruzation of the nce(B. U).

Huang jinqing

6811

lowest

last

damage

jelling

viSCOSIty

viscosity

viscosity

date

date

61.0 63.0

394 505

228 290

440 518

166 215

212 228

62.5 63.5

475 500

270 280

480 514

205 220

210 234

gelatinize

sample

temperature contrast part handle part contrast part handle part

highest

Table 4. The influence of microwave drying on the grain's moisture removal under dIfferent power and different time( %).

850W

drying time

refore

after

595W dIfference refore

after

467W dIfference refore

after

255W dIfference refore

after

85W difference refore

after

dIfference

1

15.58 13.35 2.23 15.58 13.84 1.74 14.08 13.83 0.25 17.22 16.99 0.23 17.21 17.14 0.07

2

14.08 13.18 0.9

17.22 16.41 0.81 17.21 16.82 0.39

3

15.58 12.27 3.31 14.08 12.46 1.62 17.22 15.81 1.41 17.21 16.35 0.86

4

17.22 15.19 2.03 17.21 15.90 1.31

5

17.22 14.51 2.71 17.21 15.40 1.81

15.58 10.7 4.88

1098

Proceedings of the 7th lnternationat

Workwg Conference ail Stored-product Protection. - Volume 2

Table 5. The influence of microwave drying on the gram's cracked seeds rate of the gram under different power and different

tunet %). drymg time 1

85W 255W 850W 595W 467W before after difference before after difference before after difference before after difference before after difference 17

53

36

17

49

32

2 3

17

80

63

12

22

10

13

13

0

13

13

0

12

28

16

13

14

1

13

13

0

12

37

25

13

15

2

13

13

0

13

18

5

13

14

1

13

32

19

13

14

1

4 5

17

94

77

Table 6. The influence of microwave drymg on the germmation

rate of the gram under different power and different time

(% ) drying time 1

85W 255W 850W 595W 467W before after difference before after dIfferencebefore after difference before after difference before after difference 94

26

68

94

72

22

2 3

94

40

54

94

83

11

94

93

1

94

94

0

94

68

26

94

90

4

94

94

0

94

50

44

94

87

7

94

94

0

94

82

12

94

93

1

94

68

26

94

93

1

4 5

94

1

93

Flam the charts, we know that suitable heatmg power and drying trme can control moisture decreasing 3 % once time, cracked seed rate mcreasmg 5% , and can guarantee ItS seed value

Approach the technology conditions moisture com dealing with microwave Using ER-761MD

microwave

oven

of

Settmg

high

different heatmg powers and five different heatmg time It shows that under the same power, the changing ranges WIll increase WIth the increasing of the heating power, and first of all IS to determme the heatmg power The results see Table 7 -10

up SIX

Table 7. The mfluence of mIcrowave drymg on the mOIsture removal of corn under dIfferent power and dIfferent tIme( %) drying time

before

70W 140W 210W 280W 350W 700W after dJfference before after dJfference before after dJfference before after dJfference before after dJfference before after dJfference

o

1

25 41 24 64

2

25 41 23 85 1 56 25 36 22 45 2 91 27 81 24 60 3 21 25 53 22 12 3 41 24 72 21.08 3 64 24 03 14.05 9 38

3

25 41 23 43 1 98 25 36 21 95 3 41 27 81 24 16 3 65 25 53 21 48 4 05 24.72 19.47 525

4

25 41 23 03 2 38 25.36 21 45 3 91 27 81 22 51 5 30 25 53 20 07 5 46 24 72 18.21 6 51 24 03 11 90 12.13

5

25 41 22 16 3.25 25 36 20 84 4 52 27 81 21 53 6 28 25 53 18 83 6 68 24 72 17 30 7 42

77 25 36 23 50 1 86 27 81 25 50 2 31 25 53 22 91 2 62 24 72 21 87 2 85 24 03 18.08 5 95

2403

1284

1119

Table 8. The mfluence of microwave drying on the germmation rate of corn under different power and different timet % ). 70W

drying time

before

1

140W

700W 350W 280W 210W after cW:ferencebefore after dnlerence before after dJfference before after difference 89 0 53 36 89 89 26 76 89 63 13

after dJfference before

after difference before

89

88

1

89

83

6

89

2

89

85

4

89

71

18

89

59

30

89

49

40

89

53

50

89

0

89

3

89

72

17

89

59

30

89

46

43

89

32

57

89

19

70

89

0

89

11

78

89

0

89

4

89

63

26

89

51

38

89

35

54

89

20

69

89

5

89

54

35

89

27

62

89

21

68

89

1

88

89

1099

88

Proceednno«of the 7th International

Worhng Conference on Stored-product Protection, - Volume 2

Table 9. The mfluence of microwave drying on the cracked seed rate of the corn under different (%)

power and different

drying time

70W

140W

210W

280W

350W

700W

1

o

o

o

o o

1

2

o

1

2

18

4

o o o

o o

o

2

o o

o

1

1

3

36

5

o

1

2

3

4

3

Table 10. The mfluence of microwave drying on the activity of hydrogenperoxidase different tIme(mgHzOz/lg) drymg

before

time

of the corn undeer different

time

power and

70VV 140VV 350VV 700VV 210VV 280VV after difference before after difference before after difference before after difference before after difference before after difference

42.93 40 20 2 73 41 62 38.58 3 04 43.05 37 20 5 85 41.65 35.16 6.49 42 83 31 52 11.31 42 23 31.03 11 20 2

42.23 11 90 30.03

3

42 93 37 56 5 37 41.62 35 27 6 35 43 05 24 35 18 70 41 65 18 62 23.03 42 83 13 40 29 43

4

5

42 93 34.41 8 52 41.62 32.30 9.32 43.05 19.75 23 30 41 65 7 65 34 00 42.83 4.68 38.15

The effect of microwave drying and hot air drying on the drying rate of corn Based on the analysis of the effect of microwave drying on the drying rate, percentage. 140W

the cracked kernel ratio and germination

Choosmg

the power of microwave

According to the report of matenals,

drymg

temperature

IS 55°C after bemg dned.

quality as good as Its ongmal condrtion. It takes about five hour to reduce

the corn whose

the moisture content of

by microwave,

temperature.

When we treat the corn

it takes only eleven mmutes

The curve of

the change of moisture content IS shown as Fig. 1.

Moist. Content (%

27 25 23 21

19 17 15~"'------------------------::::~Drying I1min 2 3

o

Fig 1.

MOIsture content of com handling WIth rrucrowave and hot air drymg

I

140V rrucrowave drymg curve

II

55t

hot air drying curve

1100

the

In the expenment,

corn from 25.24 % to 15 % by hot air flow drying m 55°C dry oven at constant

as

It can preserve

time (h) 4

5

Proceedin.gsof the 7th lntematumol

Working Conference on Stored-produd Protectv»i - Volume 2 hot air MIcrowave drymg IS a succeed method to dry high moisture matenal and casmg matenal

Discussion The change rice enzyme activity IS related with the stalmg process of the nee The produce of soluble amylose which mfluenced the quality of the nee IS probabaly the result of the activtty of deamylopepectase. It IS sensitive to the microwave After bemg dned by microwave the activity of deamylopepectase mcreased obviously The contents of msoluble amylose appear descent tendency But, these has not so big mfluence on the eatable quality and gelatnuzation property The results of the experiment are basically Identical with the reports on this subject pubhshed m the foreign countnes So we conclude that drymg gram by microwave ISan effective method of purify deamylopepectase and will not effect on nee quahty as well. MIcrowave drying gram shall choose surtable low heatmg power, longer heatmg time, and the highest temperature shall be less than 50 C The expenment done by the Gram Bureau of Pmgchang County, SIchuan Provmce , IS a good proof that proved condrtion above ISrational They first used a microwave oven, which had an effective heatmg length of 1.5 meters, belt speed IS0.7 m/mm, and the power 4kW to dry the gram. However, some of the grams puffed, then changed the power 4 kW to 3 kW, the puffmg phenomenon disappeared, The result of their expenment IS moisture content from 16.7% to 14.7%, cracked seeds rate decreased from 94% to 48% Conclusion ISthat the heating space should be lengthened; the heatmg power and belt speed should be designed to be adjustable. So you can adjust to the best operating condition accordmg to the concrete condition of the drying gram. It's considered by some scholars that the microwave quantum energy rate IS only 0.0000162eV, yet, the weak chemical combmed energy of H-OH, H-CH3, H3C-CH3 has energy of 3 - 6 eV It's ImpossIble that the mIcrowave radiation wIll damage the chemIcal element structures of the gram contents. The heatmg effect IS the only possIble factor mfluencmg the gram quahty. Dunng the expenment, If the power IS too hIgh or the time IS too long. EIther wIll change the quahty of the protem Because of the heatmg effect, the hydrogenperoxldase actIvIty WIlldecreased, then lead to the droppmg of the germmatIon rate (so the com for food use and for feed use, both can be drIed by mIcrowave For the seed corn, further study and expenment are needed) Because the mIcrowave drymg IS fast, when drymg hIgh mOIsture content corn, we can use the mIcrowave drymg combined Wlth the tradItional drymg apparatus to reduce the drymg time and save the energy. As shown m chart No.1, when the corn IS m preheat stage, usmg mIcrowave heatmg can decreased mOIsture content from 25.5% to 19%, It needs sereval mmutes, savmg 3 hours than that drying by a

References Chmese statistics almanac Chma's Statistics Bureau. Beijmg Chma Statrstics Press 1996,371. He jmgbang The present situation and developing tendency of Chmese gram drymg apparatus used m rural areas. Proceedmgs of 93 international acadermc seminar on the techmque of gram drymg and storage Pekmg Chmese Agriculture Engmeenng AsSOCiatIOn.1993. 252 - 259. LI fengchun. The relationship between the gram drymg and the property of husk nee Gram Storage. 1995(5 - 6): 156 -159 The complete collection of Chinese gram storage. The Department of Gram Storage and Transportation of the State Admnustration of Gram Reserves Chongqing, Chongqmg Urnversity Press 1994,536 - 537 LI weimm The present srtuation and development of grain drying and moisture lowenng m China. The Proceedmgs of 93 Intemational Academic Semmar on the Techmque of Gram Drying and Storage Beijing. Chmese Agriculture Engmeenng Association 1993, 262 WESLEY, R. A Some effects of microwave drying on cotton seed. J.Mlcrowave Power 1974(9) 329 FANSLOW,G. E et al. Drying field corn with Microwave Power and Unheated air J. MIcrowave power 1971,6 (3) : 229. CAMPANA, L. E et al Effect of MIcrowave energy on drying wheat Cereal Chern 1986,63(3) :271. CAMPANA, L. E. et al Physical. Chenucal and bakmg properties of wheat dned WIth microwave energy. Cereal Chern, 1993, 70(6) :760 Wadsworth JI, et al RIce Drying by Microwave-Vaccum. RIceJ 1990,93(6): 20-23. Zhou rUlfang The Research of the actiVIty changes of deamylopepectase m nce Chmese Gram and Oil journal 1995, (10), 10-13. J Ia henglong The relationshIp between the pullulanase in nce and msoluble amylose Zhengzhou Grain College Journal 1994 15(4): 1 - 9 Zhou relfang. The research of the influence on deamylopepectase m nce amylose structure and quahty, Chmese AcademICPenodical Digest. 1995(2) 87 - 88. Wadsworth JI, et al. PhySIcochemIcal properties and cookmg quahty of mIcrowave-dried nce. Cereal Chern. 1986, 63(4) :346 - 348. LI LIte The apphcatIOn and speCIaleffect of mIcrowave on food processmg Food Industry ScIence and Technology. 1992(2): 3 - 6.

1101