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Research on the Multiple Coating Material of Chitosan in the Preservation of Jinqiu Pear Zhi Yuan,Mingli Wang,Yue He,Hong Zhang and Xia Li  Li  (1 Province Key Laboratory of Fermentation Technology and Biological Pharmacy, Guizhou University 550003, Guiyang Gu iyang Guizhou, China; 2 Fruit Resource Institute of Karst Mountainous Region, Guizhou University; 3 Guizhou Center for Fruit Engineering Technology; Guiyang, Guizhou 550003;) Abstract: This study compared the physical and antibacterial capability of chitosan, chitosan/ SiOX  nanoparticals and chitosan/ SiOX  nanoparticals/ glycerin monostearate respectively. Three solutions were coated on the surface of Jinqiu pear to form film, comparing the effect of preserving by measuring the hardness, water content, total sugar, total acids, and vitamin C content. The results indicated that: SiO X  nanoparticals and glycerin monostearate could take effect on the enhancement enhance of the physical and antibacterial capability, and intensify the effect of preserving preservation. Keywords:chitosan; SiOX  nanoparticals; glycerin monostearate; Jinqiu pear; preserving

and physical capabilities are also detected.

1. MATERIALS AND METHODS  1.1 Materials Chitosan: Aoxing chitin Company of Yuhuan County in Zhejiang, China Glycerin monostearate, acetic acid, 95% grain alcohol: Kelong chemical plant in Chengdu,(esculent) China SiOX nanoparticals: Mingri nonaphase materials Co., Ltd in Zhoushan, China Jinqiu pear: Guiyang, China E.coli、S.aureus: Province Key Laboratory of Fermentation Technology and Biological Pharmacy, Guizhou University, China

The fruit of Jinqiu pear’s whose peel is thin, sweet-palatability and has lots of water and some medicinal value. But Jinqiu pear is putrescible, and at room temperature, its storage time is lose onlyquickly. 20 days, then whose variously nutritional ingredients The quality of Jinqiu pear declined rapidly and the decay rate of it rose sharply [1-4]. Therefore, the effective method played an important role in reducing the postharvest losses and increasing the economic efficiency. Chitosan is esculent crude and edible after coating on food. It is a new-style antistaling agent [5]  with better antibacterial capability and can prevent the bacterium after coating. Although some researches about the fruit and vegetable fresh-keeping agent with chitosan have been reported [6-9], there are some defects about the use of chitosan alone such as unstable permeability ratio and poor antibacterial effect. To get the preferable preserving effect, We attempt to add SiOX  nanoparticals and glycerin monostearate into the antistaling agent.SiOX nanoparticals is a white nontoxic, smellless and inorganic nonmetallic  powder [10]. It can prolong the shelf life of fruit and vegetable   in application to food package, purify and vegetable enhance the preserving effect in alcoholic producing and can also be used to prevent the epiphytotic [11]. Research shows that tensile strength and elongation at rupture will be heightened with SiOX  nanoparticals adding[12]. Glycerin monostearate is a highly qualified and   efficient emulsifying agent, which is helpful to promote homodisperse of SiO X  nanoparticals in solution. It is also an internationally recognized food additive which is nontoxic and unrestrained [13] . Chitosan( CTS ) , the solution of chitosan and SiO X  nanoparticals(CTS-SiOX),the compound of chitosan, SiO X  nanoparticals and glycerin monostearate (CTS-C) are used to form a coating on the surface of Jinqiu pear in this study. And the effects of preserving of these solutions are compared by measuring the firmness, water content, total sugar, total acids,  acids,  and vitamin C content. Antibacterial

1.2 Instrumentation: Ultraviolet spectrophotometer: UV2550, SHIMADZU. JP Ultrasonic cleaner: HS10260D, Tianjin hengao science development company, China Electronic multifunctional tester: WDW-20J, Shanghai hualong instrument Co., Ltd, China Sclerometer: GY - 1,Mudanjiang machinery institute, China PH-meter: PHS-2, Shanghai dapu instrument Co., Ltd, China Electronic analytical balance: METTLER AG135, Switzerland Vacuum drying oven: DZF-0, Shanghai yuejin medical devices manufacturer, China 1.3 Methods 1.3.1 Solution preparation 1.3.1.1 Chitosan solution(CTS)  1.5g of chitosan was dissolved into 6.0% (v/v) acetic acid solution (100mL). The pH of the solution was adjusted to 5.6 and stirred continually until chitosan was dissolved completely. And then, the final solution was sonicated for 10min to eliminate any gas bubbles. 1.3.1.2 SiOX / chitosan solution(CTS-SiOX)  0.03g of modified nano-SiOX particles was dispersed into 6.0% (v/v) acetic acid aqueous (100mL) by sonicating. At this point, 1.5g of chitosan was added into the suspended solution and stirred continually until chitosan was dissolved completely. After that, the pH of the solution was adjusted to 5.6 to get SiOX / chitosan mixed solution. 1.3.1.3 Chitosan composite solution(CTS-C)  0.03g of modified nano-SiOX  particles and 0.04g of glycerin monostearate were dispersed into 6.0% (v/v) acetic acid aqueous (100mL) by sonicating. 1.5g of chitosan was added into the suspended solution and stirred continually

1

 

Tab Table le 1.

until chitosan was dissolved completely. After that, the pH of the solution was adjusted to 5.6 to get SiOX  / chitosan mixed solution. 1.3.2 Preservation methods The scatheless and completely filled pears were chose. After rinsing and airing, the pears were divided into 4 groups and each of them had 30 pears. One group as a under control was the untreated pears, the other three were treated with CTS 、 CTS-SiOX  and CTS-C respectively. The hardness, water content, total sugar, total acids, vitamin C content of the pears preserving at room temperatu temp erature(2 re(20—25 0—25℃) w were ere measured measured after 3 days, days, repeated 10 times. 1.3.3 Determination of hardness of  Jinqiu pear Using GY-1-type sclerometer to test hardness of  Jinqiu   pear. 1.3.4 Determination of water content of  Jinqiu pear The method we adopted was called low-vacuum drying method in GB5009.3-2003. 1.3.5 Determination of total sugar and total acid of  Jinqiu   pear GBT6194—86 was adopted to determine the total sugar. GB/T 12456-1990 was adopted to determine the total acids. 1.3.6 Determination of vitamin C content of Jinqiu pear Ultraviolet fast measuring method was adopted to determine vitamin C content. 1.3.7 The preparation of chitosan membrane To obtain chitosan composite film, 15ml of the chitosan solutions were poured carefully onto a 7cm×14cm clean glass plates and dried under infrared lamp. After dried completely, the plates were immersed in 0.1mol/L NaOH solution for 30min, and washed with water. Finally, the chitosan film was removed from the plates and then dried at room temperature. The film was stored in desiccators prior to use. 1.3.8 Mechanical properties Mechanical properties of CTS、CTS-SiOX  and CTS-C were measured by WDW-20J Electronic multifunctional tester. 1.3.9 antibacterial property of CTS 、CTS-SiOX and CTS-C composite films According to the GB/T 4789.2-2003, the composition of the nutrient agar medium was as follows: 0.3 %  beefextract, 1% peptone, 0.5%sodium chloride and 1.5% agar, and the pH value was adjusted to 7.2 with 15% NaOH. And then, the medium was sterilized in an autoclave at 120 °C for 20 min. To evaluate the antibacterial properties of CTS and CTS-SiOX  and CTS-C, the solution of chitosan, chitosan/SiOX  and chitosan/SiOX  / glycerin monostearate was poured onto the nutrient aagar gar medium medium and dried in the incubator and then aliquots of fresh culture were added to the nutrient agar plates containing chitosan and chitosan/SiOX, respe respecti ctivel vely. y. Afte Afterr being being incub incubate ated d at 37℃ for 18-24h, the colony forming units were counted and compared with that of control.

 Membrane Thickness (mm)

Measuring of physical physical and antibacterial capability Orthogon Colony total Tensile-str  Elongatio  al-avulsio  n-at-brea ength E.coli  n strength  k (%) (MPa) S.aureus    kN/m 

CTS 0.025   0.025

21.7

7.8

63.3

24.2

8.7

80.9

37.3

9.0

115.3

6 9

0

CTS-SiO X   0.025 CTS-C 0.025   0.025

1 0 0

2. R ESULTS ESULTS AND DISCUSSION  2.1 Physical and antibacterial properties Physical and antibacterial properties of CTS, CTS-SiOX  and CTS-C were measured and the results were shown in table 1. According to table 1, it can be found that with the orderly affiliation of nano-SiOX  and glycerin monostearate, CTS-SiOX  and CTS-C composite film are higher than chitosan membrane in Tensile strength, Elongation-at-break and Orthogonal avulsion strength,even in antibacterial capability. 2.2 Determination of hardness The hardness of Jinqiu pear was one of the important qualities in the evaluation criteria. However, hardness and  brittleness of Jinqiu pear reduced greatly due to that organic materials such as the pectin were decomposed into small molecule nutrients gradually in the storage process. From the figure 1, after 30 days’ storage, we could see that at room temperature the hardness of  Jinqiu  pears coating with three preservation solutions was slightly higher than the control one, and significant difference(P<0.01) was observed with the control. Futhermore, the effect of CTS-C was the best. It was noticeable from middle to late time of storage.  12.0 11.5 11.0

 Blank Sample CTS CTS CTSSiOx CTS-C

10.5

  a 10.0    P    0 9.5    1       × 9.0    /   s   s   e   n 8.5    d   e   a    H 8.0

   5

7.5 7.0 6.5 6.0 1

3

5

7

9

11 13 15 17 19 21 23 25 27 29 31 Storage times(days)

 

2

Fig. 1.

Hardness changing of Jinqiu pear  

 

89.0

0.110

 Blank Sample  CT  CTS  CTSSiOx  CTS-C

88.5 88.0 87.5

 Blank Sample  CT  CTS S  CTSSiOx  CTS-C

0.105 0.100

87.0 86.5    %    /    t 86.0   n   e    t   n 85.5   o   c 85.0   r   e    t   a 84.5    W 84.0

0.095    %    /    d    i   c   a 0.090    l   a    t   o    T0.085 0.080

83.5 0.075

83.0 82.5

0.070

82.0

1

1

3

5

7

9

3

5

7

9

11 13 15 17 19 21 23 25 27 29 31

11 13 15 17 19 21 23 25 27 29 31 Storage times(days)

Storage times(days)

Fig. 2. 2.

  Fig.4 Total acids changing of Jinqiu pear 2.4 Determination of total sugar From the figure 3, all the trends of total sugar were the same basically during the 20 days of storage. But in the  the late storage, the total sugar content of control increased markedly, and after 30 days’ storage, the total sugar content of the other samples treated by preservation solution remained stably at the same time, and significance difference(P<0.05) was observed with the control. This was caused by the loss of the water content of blank sample. It is indicated that the preservation coating solution played a

 

water content content chang changing ing o off Jinqiu pear  

2.3 Determination of water content The peel of Jinqiu pear was thin and so it had a poor water holding capacity. The water lost easily in the storage. The appearance and eating quality was affected seriously. From the figure 2, we could see that the trend of water content between the control and treatment group increased at first, then decreased, rise again and finally became stably. And a significant low-point was shown at the fourth determination (12 days). After 30 days’ storage, we could see that at room temperature the water content of pears coating with three preservation solutions was slightly higher h igher than the control one, and significant difference(P<0.05) was observed with the control. This might be due to that the water lost quickly when the pear was put for the storage  period of 12 days to reach to the respiratory peak. And it is also shown in the figure 2 that the trend of the sample treated by CTS-C was stable, and the water content was higher than other groups obviously at the fourth determination.  11.0

on Jinqiu pear.  better water holding ef fect  acids 2.5 Determination ofeffect total The figure 4 showed that the total acid content of four samples had the similar changes, and after 30 days’ storage, the total sugar content of the other samples treated by  preservation solution remained stably at the same ti time, me, and significance difference(P<0.05) was observed with the control. Furthermore, the CTS-C group was more stable. 2.6 Determination of vitamin C content 18

 Blank sample

 CT  CTS  CTSSiOx  CTS-C

10.5

 Blank Sample  CTS  CTS  CTSSiOx  CTS-C

16 14

8.0

   1   - 12   g    *   g   u    /    t 10   n   e    t   n   o   c 8    C   n    i 6   m   a    t    i    V 4

7.5

2

10.0 9.5    %    /   r   a   g 9.0   u    l   s   a    t   o 8.5    T

0

7.0 1

3

5

7

9

1

11 13 15 17 19 21 23 25 27 29 31 Storage times(days)

Fig. 3.

Total Total sugar changing of Jinqiu pear

3

5

7

9

11 13 15 17 19 21 23 25 27 29 31 Storage times(days)

 

  Fig.5 Vitamin Vitamin C content changing of Jinqiu pear The figure 5 showed that the total vitamin C content of four samples rose firstly, and then declined. After 30 days’ storage, the vitamin C content of the other samples treated  by preservation solution remained highly at the same time, and significance difference(P<0.05) was observed with the control. The peak of the blank sample appeared in the 15 days at storage, which might be the respiratory peak when the total vitamin C content achieved maximum [3].But the respiratory peak of others treated with preservation solution

3

 

delayed 3-6 days. It was indicated that the preservation solution played a role in delaying respiratory peak.

REFERENCES [1]  Yuanji Huang, “Pear tree of new varieties of  Jinqiu pea r ,”Journal ,”Journal of Fruit Science,vol. 13, no. 1, pp. 62-63, January 1996. [2]  Yong Zou and Zhengkai Wen.“Analysis of the major nutritional components infruit of Jinqiu Pear,” Qiandongnan Teacher’s Training College Journal,vol. 23, no. 6, pp. 18-19, December 2005. [3]  Bo Zou, “Changes of quality and nutrient content of  Jinqiu pear  and   and  Huanghua pear  after  after refrigeration,” China Southern Fruit,vol. 34, no. 4, pp. 71-72, July 2005. [4]  Peirong Xie,Guifang Xu and Juying Ouyang, “Research on harvest time and storage methods of  Jinqiu pear ,” ,” China Southern Fruit,vol. 32, no. 4, pp. 72-73, July 2003. [5]  Yang Yang,Zheng Ruan, “Study on chintosan and apply to fruit and vegetable fresh – keeping,” Guangxi Light Industry, no. 1, pp. 6-8, January 2002. [6]  Po-Jung Chien,Fuu Sheu and Hung-Ren Lin, “Coating citrus (Murcott tangor) fruit with low molecular weight chitosan increases  postharvest quality and shelf life,” Food Chemistry, vol. 100, no. 3,  pp. 1160-1164, 1160-1164, February 2005 2005.. [7]  Po-Jung Chien,Fuu Sheu and Feng-Hsu Yang, “Effects of edible chitosan coating on quality and shelf life of sliced mango fruit,” Journal of Food Engineering, vol. 78, no. 1, pp. 225-229, March 2005. [8]  Pilar Hernández-Muñoz,Eva Almenar,  María José Ocio and Rafael Gavara, “Effect of calcium dips and chitosan coatings on postharvest

3. CONCLUSION  3.1The addition of Nano-SiOX, significantly enhanced the tensile strength, elongation-at-break and orthogonal Tear strength of the chitosan composite membrane, including 72 % increased tensile strength, 14 %   improved elongation-at-break and 82 %   advanced orthogonal Tear strength. And the nano-SiO X that had antibacterial activity increased the antibacterial effect of the composite membrane further. 3.2 The using of glycerin monostearate made the nano-SiOX  dispersed uniformly in the chitosan composite solution, and also played a certain role to improve the antibacterial properties of the membrane, increase the water-holding capability and transparence, decrease the aerobic respiration, delay the appearance of respiratory peak, maintain the fruit flavor and play a good role in  preservation. The chitosan composite membrane could extended the shelf life of Jinqiu pear from 20 days to 40 days, and had no decay phenomenon. 3.3 Based on the treating with coating, if we adopted other methods, such as cold storage, plastic packaging. The effect of Jinqiu pear preservation would be better.

life of strawberries  (Fragaria x ananassa),”Postharvest Biology and Technology, vol. 39, no. 3, pp. 247-253, July 2005. [9]  Mingli Wang,Lina Yang and Jing Huang, “Study on vegetable fresh-keeping with chitosan coating,”Food Industry Technology Technology,, vol. 24, no. 9, pp. 31-33, September 2003. [10]  Yulong Zhang,Shuli Gao, Nano-modifier, Beijing: Defense industry Press,2004. [11]  Huanbin Liu,Xiaoquan Chen, Nano Science and Technology Introduction, Beijing:Chemical Industry Press,2006. [12]  Yongping Chen,Jianhe Liao, “Study on chitin/SiO2  heteropolymer,”chinese journal of tropical agriculture, vol. 22, no. 2,  pp. 21-23, April 2002. 2002. [13]  Jintao Wu,Shaoqi Zhang, Fruit and vegetable preservation and  processing, Beijing: Beijing: Chemical Industry Press,2001. Press,2001.

ACKNOWLEDGE   The financial support provided by the National Natural Science Foundation of China(31060229), Guiyang agricultural Science and Technology Foundation (20092-006) and Graduate student innovation foundation of Guizhou university (2010012) .  

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