Proceednnqsof the 7th International Worktng Conference on Stored-product Protection - Volume 2

Effect of radiation sterilization on pine pollen storage qnality

Fu junjie", Shen Weiqiao' and Zhou Iianhua'

Abstract

Radiation sterilizanon of pine pollen was carried out by dintof 60Co- y ray in this expenment. The storage penod of pinepollen could be prolonged upto more than two years afterradiation. Effect of different radiation doses on pine pollenstenhzation was studied and the nutritive contents, such asprotem, amino acid, trace elements, were determmed andthe stenhzation effect was monitored durmg the course ofstorage. The relation between nutritive elements andradiation dose was determined as well.

Introduction

Pine pollen is one of the outstanding pollen products in theforeign and domestic markets due to Its manual collection,abundant nutrient, stable components, pure quality,msecticide residue-free and animal hormone-free quahty,unlization of pme pollen Will contribute SIgnificant economicand SOCial efficiency to the econonuc development ofmountain areasDurmg the course of pine pollen collection, there IS a

serious bacterium contammanon problem, If the collectedpine pollen was not subjected to sterilization treatment, Itwould be very difficult to fulfill the Hygienic Standard. Thestenlized pine pollen often begins to go moldy and be blockedtwo months later after the treatment of traditionalsterihzation method. Moreover, some nutritive contentswill be destroyed at a temperature higher than 50"C , so it isnot suitable to employ the high temperature stenlizationmethod to conduct pine pollen sterilization Recent years,much researche on the efficiency of radiation stenlization ofpme pollen has been reported However, because of thecollection technology, processmg and storage technology,the researches on the effect of radiation sterilization on ItSstorage quality were scarcely reported. The mam purpose ofthis paper IS to solve the problem of stenhzauon, storageand quality analysis durmg the course of collection andprocessing of pine pollen. In this experiment, pine pollenwas packed in different package matenals and subjected to

1 Institute of Nuclear-Agncultural Sciences, Zhejiang AgriculturalUnrversity, Hangzhou 310029, P R Chma

different radiation doses and stored under the condition ofnormal temperature and pressure, the storage period of pinepollen could be prolonged to more than two years.

Material and Method

Material Resources

The pine pollen provided by Asian Institute of ChineseForestry Academy has a purity of 97 % with water contentof less than 8 % and ash content of less than 3%. Accordmgto the test analysis and storage experiment, certain amountsof samples were put into PE bags, glass bottles, smallplastic palls (2 kg) and large plastic palls (25 kg),respectively.

Radiation device

A 1.6 X 105 Bq 60(0- Y radiation device with a sourceheight of 42.6 mm was employed. Fnckle dose counter andFammer dose meter are used to determine the radiation spotdose. The experimental doses were 1, 3, 6, 9 and 12 kGyrespectively With a dose rate of 3 - 6 X 102 rad/s.

Radiation method

Based on the 2-year storage requirement, the pine pollenin different package material was put into the radiation spotwith a height of 20 em from the ground. In order to obtainthe homogeneity of the radiation dose, the sample wasrotated 1800 after the samples got the half radiation dosewith the radiation spot as its center.

Microbe determination

The radiation samples were Immersed mto the sterilizedwater respectively, and analyses were performed aftercomplete rotation WIth conventional microbe dilutionmethod, 3 con-secutive degrees (l0-1, 10-2, 10-3) foreach were employed. Each tnphcated sample was cultured inagar culture medium and broth culture medium, each With ablank control. The bactenum plates were put mto a 37"Cthermostat and the bacterium numbers were counted after48 hours of culture; meanwhile, the mold plates were alsoput into a 28"C thermostat and the mold numbers werecounted after 72 hours of culture.

Quality analysis

The amount of protem, amino acid, trace elements and

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

other nutritive compositions was determined at a timeinterval of 360 days during storage.

Storage experiment

The pine pollen packed in different package materials (themiddle scale test was performed with a total mount of pinepollen of 8000 kg packed in large plastic pails) was put intoan ordinary warehouse after the radiation sterilization withdifferent doses. Controls were also set among differentpackages. The biological loading capacities of the sampleswere tested at a time interval of 90 days.

Results and Discussion

Effect of radiation on pine pollen nutritive elements

Protein: Figure 1 is the change of the protein contentafter radiation with a storage period of 360 days and 720days, respectively. It could be concluded that radiationsterilization had no direct effects on protein content. After acomplete analysis of the experimental data, the linearregressive equations between the protein content in storageperiod and the absorbed doses were obtained as follows:IgN360d = 11.6406 + 6.8061 x 10-3 Irt = 0.3482IgN72Od=11.8642 + 2.8344xlO-2Dy = 0.7876

N is the total amount of protein; D is the absorbed dose (0::::;;;D::::;;;12 kGy; y IS the correlation coefficient. )Trace element: After the radiation sterilization with

different doses, ten trace elements were determined after astorage period of 360 days and 720 days. As shown in Table1, only some of them had a slight increase in content. Itindicated that radiation had no significant effects on thetrace elementts content within the limit of the sterilizationdose.

13

~0J!le.se0 12uc!0~Co

110

-&-360d-+-720d

2 4 6

Dose/kGy

8 10 12

Fig. 1. Relation between radiation dose and protem content.

Amino Acid: The relation among the 15 kinds of aminoacids and the doses with a storage period of 2 years wasdetermined after the radiation sterilization with differentdoses by 6OCo-ray,as shown in Table 3. It clearly indicatedthat there was no apparent change in the amount of the 15kinds of amino acids with the upper limit of 12 kGy. Fromthe storage period of 720 days, there was also no changingrule between the storage period and the total amino acidamount. As a result, we could see that the radiation dosesand the storage time had no influence on the 15 kinds ofamino acids in the pine pollen.

Effect of radiation sterilization

The total amount of coenobia of biological load in pinepollen was determmed 2 days later, and then the coenobiawas determined 8 times within a storage period of 2 years.It could be seen from Table 2 that 60Co-y ray radiation hadan effective influence on the stenlization and that thenumber of the bacterium contamination decreased with theincrease of radiation doses.

Table 1. Effect of radiation on trace elements content of pine pollen.

Element CK1 kGy 3 kGy 6 kGy 9 kGy 12 kGy

360d 720d 360d 720d 360d 720d 360d 720d 360d 720d

K% 1.12 1.13 1.12 1.12 0.12 1.15 1.17 1.16 1.15 1.11 1.14P% 0.27 0.28 0.29 0.29 0.28 0.28 0.26 0.30 0.30 0.29 0.30Ca 1173 1171 1171 1158 1157 1161 1160 1144 1140 1150 1145Mg 923 923 922 951 950 964 964 1009 1010 1025 1022Fe 225 226 226 229 226 217 215 229 230 231 237Mn 83.1 85.1 85.0 84.7 84.5 84.3 84.4 84.7 84.5 84.8 85.2Zn 44.9 45.1 45.5 44.5 44.6 45.9 46.0 48.0 48.1 44.5 44.9Cu 9.3 10.1 10.0 10.1 10.4 10.1 10.0 10.1 10.1 10.1 10.5Na 68.4 69.8 70.0 78.5 78.3 70.4 70.8 72.3 72.3 71.2 71.4B 4.8 5.3 5.2 5.1 5.0 5.8 5.5 4.9 5.2 5.3 5.1

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Proceedings of the 7 th International Worktng Conference on Stored-product Protection - Volume 2

Radiation With a dose of 6 kGy could achieve 90% results, especially with the doses between 6 - 12 kGy. Insterilization effect and 9 kGy over 97 % . Moreover, the storage period of 720 days, we found that the pine pollenradiation with a low dose could also Inhibit the reproduction had no blocks, molds and mycelia, and had the same color asof the microorganism. The pine pollen without radiation the fresh one. At the same time, we found that low dosestreatment had a heavy number of bacteria contamination, could also control the growth of biological load and hadand began to be blocked two months later, together with the certain effect on storage. With the extension of the storageappearance of molds. period, mycelia appeared and the color of the pine pollen had

Storage resulta positive relation with the storage period.

The pine pollen radiated with different doses had excellent

Table 2. Pine pollen radiation sterihzation and storage results.

kGy CK 1 3 6 9 12 date of examinationcoenobia/g

bacterium Innumerous innumerous 5300 520 115 15

mold innumerous Innumerous 450 340 253 3 Od

E. coli ~2400 ;;;?2400 ~2400 700 <30 <30

bactenum innumerous innumerous 7373 221 13 4

mold innumerous innumerous 4 5 3 2 90d

E. cob <30 <30 <30 <30 <30 <30

bactenum innumerous innumerous 2550 40 3 1

mold innumerous innumerous 145 60 2 1 200d

E. coli <30 <30 <30 <30 <30 <30

bactenum innumerous innumerous 2500 270 110 20

mold innumerous Innumerous 30 20 10 10 300d

E. coli <30 <30 <30 <30 <30 <30

bacterium innumerous innumerous 2480 48 20 10

mold innumerous innumerous 45 80 10 20 400d

E. coli <30 <30 <30 <30 <30 <30

bacterium innumerous innumerous 1330 180 40 20

mold innumerous 320 150 50 <10 10 500d

E. coli <30 <30 <30 <30 <30 <30

bacterium innumerous Innumerous 1600 265 40 10

mold 2500 450 <10 <10 <10 <10 600d

E. coli <30 <30 <30 <30 <30 <30

bacterium innumerous Innumerous 1600 245 30 10

mold 2000 350 <10 <10 <10 <10 720d

E. coli <30 <30 <30 <30 <30 <30

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

Table 3. The relation between amino acid content and dosage.

kGy 1 3 6 9 12 CKAmmo acid 360d nOd 360d nOd 360d nOd 360d nOd 360d nOd 360d nOdAsp 0.9883 0.9973 1.0669 1.0085 0.9505 0.9732 0.8994 1.0266 0.9470 1.0486 1.0186 0.9316Thr 0.4893 0.4823 0.5224 0.5059 0.4646 0.4870 0.4438 0.5116 0.4714 0.5216 0.5156 0.4757Ser 0.5765 0.5399 0.6067 0.5830 0.5352 0.5697 0.5167 0.5967 0.5510 0.6334 0.6022 0.5757Glu 0.9416 0.9780 1.0055 0.9401 0.8981 0.9592 0.8606 1.0051 0.9472 1.0187 1.0158 0.9238Gly 0.5988 0.5771 0.6545 0.6628 0.5829 0.6410 0.5756 0.6795 0.6179 0.6832 0.6679 0.6260Ala 0.6933 0.6959 0.7301 0.6804 0.6584 0.6991 0.6422 0.7481 0.7048 0.7642 0.7417 0.69nVal 0.5928 0.6814 0.8299 0.8411 0.7946 o 8139 0.7468 o 8453 0.8340 0.6500 0.8520 0.7716Met 0.0757 0.0586 0.0467 0.0997 0.0394 0.0833 0.0350 0.1582 0.0811 0.0820 0.0651 0.0531He 0.4667 0.1979 0.4871 0.5056 0.4522 0.4765 0.4348 0.5378 0.5040 0.5123 0.42n o 4509Leu 0.8132 0.3097 0.8324 0.8542 0.7674 0.7889 0.7321 0.8929 0.8546 0.8859 0.6763 0.7775Tyr 0.3622 0.0351 0.3705 0.3802 0.3208 0.3465 0.3050 0.3795 0.3758 0.3935 0.3113 0.3385Phe 0.4580 0.0275 0.4469 0.4768 0.4346 0.1450 0.3871 0.4909 0.4819 0.4747 0.2518 0.3890HJ.s 0.3752 0.3692 0.3443 0.3896 0.3225 0.3915 0.2942 0.4112 0.3535 0.3994 0.3447 0.3830Lys 0.3668 0.4311 0.4127 0.4300 0.3373 0.4110 0.3085 0.4212 0.4190 0.4067 0.4244 0.3879Arg 1.6112 1.4870 1.5327 1.5098 1.3675 1.5415 1.3388 1.5918 1.4600 1.6341 1.4532 1.5323total 9.4096 7.8680 9.6893 9.8657 8.926 9.3274 8.5216 10.2964 9.6032 10.1083 9.3978 9.3138

could have a storage period of 2 years without any change in

Conclusion color and the puffiness.The elements m pine pollen were determmed after

After 2 years of observation and tests m the laboratory, It radiation sterilization. There was no significant differencecould be concluded that 6OCo radiation sterihzation had a within doses between 0 and 12 kGy. No further research onsignificant effect on storage. A radiation dose withm 6 kGy effect of doses of more than 12 kGy on change of pine pollencould kill 90 percent of all the bacteria and reduce the nutritive elements were made.countless bactena to under 520 per gram, which fulfilled the In a word, 60 Co radiation sterihzation is an effectiveHygienic Standard. method of sterilization and storage technique for pme pollen.With radiation doses of 6 kGy or above, the pine pollen

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