Nghien dm. Phdt triin yd ting dung Cone nghe Vat lieu (KC.02/06-10)- Ha Noi 27/11,1009 NGHIEN CUU CHE TAO M A N G BAO GOI K H I QUYEN BIEN D O I (MAP) PHAN 1: A N H HUONG CIIA QUA TRINH PHAN TAN PHU GIA T O l H I N H T H A I
HOC BE M A T CUA M A N G M A P
Pham Thj Thu Ha, Le Van Luong, Nguyen Van Khoi, Dinh Gia Thanh, Nguyln Thanh Tung
Vien Hoa hoc- Vien Khoa hoc va Cong nghe Viet Nam, 18 Hoang Quoc Viet- Ha noi Email: vlpolvme [email protected]
Tom tat. Mang bao gdi khi quyen bien doi (Modified Atmosphere Packaging- MAP) tren ca so
polyetylen bd sung mot so phu gia vd co duac che tao bang phuang phdp dim thdi. Anh hudng ciia phuang phdp tron hap va phan tan phu gia tdi hinh thdi hoc be mat ciia mang MAP duac quan sat
bdng each chup anh kinh hien vi dien tic quet (SEM). Phuang phdp tao me tron goc cho mang MAP vdi be mat nhan vd dong deu hon.
I. Gl6l THIEU
Bao gdi khf quyen bien doi (MAP) la mot cong nghe tru viet dugc sir dung rat pho bien de bao quan thuc pham, dac biet la rau qua, tir khi thu hoach tdi qua trinh du tru va trong toan bo chuoi phan phoi de dam bao chat lugng san pham cho tdi khi den tay nguoi tieu dung [1].
Trong so cac cong nghe sau thu hoach hien nay de duy tri dugc chat lugng ciia rau qua d nhiet do thap, MAP co uu diem la chi phi thap va de trien khai d quy mo thucmg mai. Viec sir dung thanh cong MAP dua tren tinh chat tham khi chpn loc cua mang doi vdi O2 va CO2 de tao ra mot khi quyen phu hop vdi thdi nan bao quan ciia nhieu loai san pham rau qua [2]. Viec lira chon mang chat deo co kha nang duy tri khi quyen mong muon la giai doan quan trong lam nen thanh cong ciia MAP [1].
Mang chat deo bao quan rau qua tuoi neu dugc thilt k l phu hgp co the tao ra va duy tri mot khf quyen bien doi vdi nong do O2 thap va CO2 cao giiip lam giam ho hap va nhung thay doi tieu cue co lien quan den chat luong. De dat dugc khi quyen bien doi toi uu cho moi loai san pham, can bang giua cudng do ho hap ciia san pham va do tham khi qua mang chat deo phai dugc xem xet. Tuy nhien, khf quyen bien doi dugc thilt lap ben trong mot so bao gdi doi khi khong thfch hop cho nhieu loai san pham vi cac loai mang chat deo cd tren thi trudng thudng bj nan che ve do tham O2 va CO2.
Polyetylen (PE) la loai polyme dugc sir dung rong rai trong bao gdi thuc pham va thudng cd gia thanh thap nhat. Mang PE thong thudng cd tdc do tham 02 tir 1.000-4.000cm3/m2/ngay va C 02 tir 3.200-12.260cm3/m2/ngay tuy thuoc chilu day [4]. Do tham khi thap thudng din tdi dong nude ben trong, dilu nay co the lam tang qua trinh hu hong ciia rau qua do sir tan cong ciia nam mlc va vi khuan. Co the tang do tham khf ciia mang bang each due 16. Phuong phap nay la se due tren mang bao gdi mot so lo cd kich thudc nhat dinh de dat dugc do tham khf thfch hgp vdi san pham bao quan. L6 cd the cd nhieu hinh dang khac nhau nhu hinh tron, hinh vuong, ngu giac, luc giac, elip... vdi kich thudc khac nhau. Bang each dieu chinh kich thudc va s6 lugng 16, cd the dilu chinh dugc do tham khf ciia mang [5]. Mot each khac d l tang do tham khf ciia mang la bo sung cac phu gia vo co tro. Cac phu gia nay thudng la cac hgp chat vo ca tren ca sd alumino- silicat dugc dac trung bdi ty le nhom/silicat, dudng kfnh mao quan, dien tfch b l mat rieng, ty trong rieng va phai dap img 3 tieu chuan: tra, x6p va cd kha nang lien k i t vat ly vdi cac khf nhu O2, CO2, C2H4.. .Cac phu gia dugc sir dung d l chi tao mang MAP cd t h i la zeolit [6], khoang set hoat tfnh [7] hay g6m [3,8]. Bai bao nay nghien cuu anh hudng ciia phuang phap tron hop va phan tan phu gia tdi hinh thai hoc be mat ciia cac loai mang MAP.
Nghien cim, Phdt trien va Lfng duns Cons nshe Vdt lieu (KC 02/06-10)- Hd Ndi 27/11/2009
IT. THUC NGHIEM 2.1. Nguyen lieu
Bentonit (Tuy Phong, Binh Thuan), kich thuoc hat trung binh 4-5um; zeolit A (nhan tao), ty le Si/Al 1,2/1, kich thuoc hat trung binh 4-5 um; silica (Cong ty OCI, Han Qu6c), kich thuoc hat trung binh 4-5um; axit stearic (Trung Quoc); nhua hat LLDPE QAMAR (Saudi Arabia), etanol 90° (Viet Nam).
2.2. Phuong phap tien hanh 2.2.1. Hoat hoa phu gia
80g axit stearic dugc them vao binh phan ung chua 0,51it etanol 90°, gia nhiet den nhiet do 40-45°C va khuay trong khoang 2 gid cho tan hit axit. Pha loang dung dich nay bang H20 . Cho h6n hop g6m 1kg phu gia va dung djch axit stearic va zeolit vao binh phan ung, gia nhiet din 75°C va khuay trong 30 phut. Loc san pham, tiln hanh rira bang hon hgp nude- etanol cho hit axit du sau do say d 100°C din k h l i lugng khong d l i . San pham sau khi say dugc nghien min den kich thudc 4-5 pm.
2.2.2. Qua trinh thdi mang
* Phuong phap tron true tiep: Trong phuong phap nay phu gia hoat hoa dugc tron vdi nhua hat LLDPE theo ty le nhat dinh va dua vao bo phan nap lieu ciia may dim thoi 1 true vit.
Cac hat phu gia va nhua PE dugc tron vdi nhau va dim ra thanh dang chay mem va dugc bo phan thoi khf thoi thanh ong mong, sau do dugc thu lai dudi dang mang. May thoi mang 1 true vit cd ti le L/D = 24, nhiet do ciia may dim 158-170°C, toe do true vit 50 vong/phiit, toe do nap lieu 15kg/gid, toe do thu cuon 200v6ng/phut.
* Phuong phap tao me tron goc (masterbatch): Trong phuong phap nay, phu gia hoat hoa 'dugc tron vdi hat nhua PE vdi ti le thich hgp roi dua vao may diln tao hat 2 true vit b6 tri lien
hop vdi bo phan cat hat d l tao hat PE-phu gia (masterbatch) cd kich thudc dai l-4mm, O - 2mm vdi ham lugng phu gia toi da trong masterbatch la 40%. May dim 2 true vit cd ti le L/D
= 28, nhiet do khoang tron tir 120-160°C, tic do true vit 50 vong/phut. Hat nhua PE nguyen sinh dugc tron vdi masterbatch vdi ti le thich hgp de dat dugc ham lugng phu gia mong muon, sau do dugc thoi thanh mang bang may dim thoi mot true vit nhu mo ta d tren.
2.2.3. Hinh thdi hoc be mat cua mang MAP
Hinh thai hoc be mat ciia cac mang MAP dugc theo doi bang each chup anh tren kinh hien vi dien tir quet Hitachi S4800 (Singapore).
III. KET QUA VA THAO LUAN 3.1. Phuong phap tron true tiep
Phuong phap tron true tilp dugc ap dung doi vdi phu gia zeolit vdi ham lugng phu gia
trong mang la 5%. Anh SEM ciia mang MAP tren co sd LLDPE- zeolit d cac do phong dai khac nhau dugc dua ra trong hinh 1.
Quan sat anh SEM rang thay be mat ciia mang khong nhan va dlu. Dilu nay chung to qua trinh tron hop true tiep khong tot va phu gia khong the phan tan dlu trong nln nhua PE. Cac hat phu gia phan tan khong tot de lai nhung 16 thiing tren be mat mang (mui ten tren anh d) Phuong phap tron true tiep khong phu hop de phan tan phu gia trong nln polyme.
Nghien ciat. Phdt triin va Ung dun% C d n g n°h i V d t — (M£M/Q(hlQk HA Noi 27/11/2009
(c) (d) Hinh 1. Anh SEM cua mang MAP vai 5% zeolit duac phan tan bang phuang phdp tron true tiep
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Hinh 2. Anh SEM cua mang MAP vdi phu gia zeolit ham luong 3 (3a, 3b), 5 (5a, 5b) vd 7% (7a, 7b) duac phan tan bang phuang phdp tao masterbatch
3.2. Phirong phap tao me tron goc (masterbatch)
Phuong phap tao masterbatch dugc su dung de phan tan cac phu gia zeolit, bentonit va silica trudc khi thdi mang. Anh SEM ciia mang MAP tren co sd LLDPE vdi cac loai phu gia va ham lugng khac nhau dugc dua ra trong cac hinh tir 2 den 4.
Ket qua cho thay mang MAP dugc che tao theo phuong phap tao masterbatch cd be mat mjn va dong deu. Dieu nay chirng to rang cac hat phu gia da phan bo tot trong nhua nen PE.
Do vay phuong phap tao masterbatch thich hop cho qua trinh phan tan phu gia va thoi mang va se dugc sir dung trong cac nghien cim sau nay.
So sanh anh SEM d cac hinh 2, 3 va 4 nhan thay rang d cac anh SEM cd do phong dai thap, phu gia tron hop va phan tan kha tot trong nhua nen, be mat mang kha min, hau nhu khong cd khuyet tat. 6 cac do phong dai 5.000 va 10.000 cd the quan sat thay su k i t tu ciia cac hat tai mot so vj tri trong mang do phan tan khong dlu. Tuy nhien nhung vi tri nay khong
Nghien cim, Phdt trien va Ung dung Cong nghe Vdt lieu (KC 02/06-Wi- Ha Noi 27/11/2009 mang tfnh dai dien. Trong 3 loai phu gia cd cung kfch thudc hat, mang MAP chua zeolit cd bh mat min nhat do cac phu gia dugc tron hgp va phan t i n dong deu nhit.
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jffin/i 3. ^4n/z S£M cua mang MAP vdi phu gia bentonit ham luong 3 (3a, 3b), 5 (5a, 5b) va 7% (7a, 7b) duac phan tan bdng phuong phdp tao masterbatch
Hinh 4. Anh SEM ciia mang MAP vdi phu gia silica ham luong 5% dugc phan tan bdng phuong phdp tao masterbatch
IV. KET LUAN
Mang MAP dugc che tao bang phucrng phap dun thdi nhua polyetylen (PE) vdi cac phu gia vo co dugc hoat hoa be mat bang axit stearic. Bang phuong phap tao masterbatch, cd thi tron hop va phan tan dong deu phu gia trong nen polyme. Anh SEM cho thay bk mat mang kha min, khong cd khuyet tat. Trong so 3 loai phu gia sir dung, zeolit cho kha nang tron hop va phan tan tot nhat.
Loi cam on
Cong trinh nay dugc thuc hien vdi su hd trg ve kinh phf cua Bo Khoa hoc va Cong nghe
Chuong trinh KC02/06-10 trong khuon khd de tai KC02.20/06-10. ' ' Tai lieu tham khao
I. Y. Wang, A. J. Easteal and X. D. Chen, 'Ethylene and oxygen permeability through
Nghien cim. Phdt triin vd ting dune Cong nshe Vdt lieu (KC.02/06-10)- Ha Noi 27/11/2009
2. D. Sivakumar, L. Korsten, "Influence of modified atmosphere packaging and postharvest treatments on quality retention of lichi cv. Mauritius", Postharvest Biology and Technology, 41, 135-142, (2006).
3. J. H. Yun, D. S. An , K. E. Lee, B. S. Jun and D. S. Lee, "Modified atmosphere packaging of fresh produce using microporous earthenware material", Packag. Technol. Sci., 19, 269-278, (2006).
4. A. P. Jacomino, R. A. Kluge, C. I. G. Sarantdpoulos and J. M . M . Sigrist, "Evaluation of plastic packages for guava refrigerated preservation", Packag. Technol. Sci., 14, 11- 19, (2001).
5. L. Zanderighi, "How to design perforated polymeric films for modified atmosphere packs (MAP)", Packag. Technol. Sci., 14, 253-266, (2001).
6. S. N . (Aktas) Dirim, A. Esin, A. Bayindirli, "A new protective polyethylene based film containing zeolites for the packaging of fruits and vegetables: Film preparation", Turkish J. Eng. Env. Sci., 27, 1-9, (2003).
7. M . A. Camiss , G. Russo, "Activated earth polyetylen film", US Pat. 5,221,571, (1993).
8. D. S. Lee, P. E. Haggar, K. L. Yam, "Application of ceramic- filled polymeric films for packaging fresh produce", Packag. Technol. Sci., 5, 27-30, (1992).
