Release of 1-methylcyclopropene (1-MCP) from Polystyrene Fibers Functionalized with Inclusion Complex Between 1-MCP and α-cyclodextrin

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1 Release of 1-methylcyclopropene (1-MCP) from Polystyrene Fibers Functionalized with Inclusion Complex Between 1-MCP and α-cyclodextrin H. Yoshii, H. D. Ariyanato, T.L. Neoh Food Engineering Laboratory Department of Applied Biological Science Graduate School of Agriculture Kagawa University, Japan

2 Release of 1-methylcyclopropene (1-MCP) from Polystyrene Fibers Functionalized with Inclusion Complex Between 1-MCP and α-cyclodextrin (α-cd) Development of packaging materials for continuous 1-MCP treatment What is 1-methylcyclopropene (1-MCP)? What is Cyclodextrin (CD)? 1-MCP synthesis and formation of inclusion complex Electrospinning of polystyrene fibers functionalized with inclusion complex Release characteristic of 1-MCP from inclusion complex and electrospinning fiber

3 Climacteric vs Non climacteric fruits

4 Ethylene is a plant growth hormone that is active in ripening. Ethylene is a phytohormone that has always been considered detrimental to the storage of fruits. Hence, mitigation of the ethylene effects is of great interest especially for perishable produce. o Decreasing quality of fruits o Flesh softening in fruits o Shelf colour change Physiological Maturity Decreasing Quality o Short life of fruits Development (non edible) Commercial Maturity Overmature Organoleptic quality of a fruit in relationship to its ripening stage Ethylene 1-Methylcyclopropene

5 Mechanism of 1-MCP action Binding of ethylene to receptor Lifting of suppressive Action of receptor Ethylene receptor Competition Ethylene 1-MCP Ripening / Senescence Flesh softening in fruits Pigmentation Self color change Increase of flavor component Ethylene unable to bind to receptor Ethylene receptor Greater affinity of 1-MCP for receptor Suppressive action of receptor remains

6 1-Methylcyclopropene applied Untreated Untreated Control 1-MCP treated 1-MCP treated (a) (b) (a) Don Huber, Jiwon Jeong and Mark Ritenour of University of Florida. (b) Kazuo Ichimura, Hiroko Shimizu, Toshihiko Hiraya and Tamotsu Hisamatsu. 2002, Bull. Natl. Inst. Flor. Sci. 2, 1-8

7 1-Methylcyclopropene applied (c) Untreated 10 ppb 1-MCP 100 ppb 1-MCP 1 ppm 1-MCP Don Huber, Jiwon Jeong and Mark Ritenour of University of Florida. (d) Our experiment Untreated 0.3mM STS 0.1 ppm 1-MCP 1 ppm 1-MCP 10 ppm 1-MCP

8 1-MCP & inclusion complex 1-Methylcyclopropene (1-MCP) Ethylene response inhibitor delay ripening in fruits Effective at levels of ppb Gaseous organic compound Explosive & unstable 1-Methylcyclopropene 1-MCP (gas) α-cd (powder) 1-MCP/α-CD inclusion complex (powder) SmartFresh TM by AgroFresh Inc.

9 Cyclodextrin Cyclodextrins (CDs): 1) natural starch derivatives from enzymatic degradation 2) a family of cyclic oligosaccharides with truncated molecular structure 3) α-, β- and γ-cd consist of 6, 7 and 8 glucopyranose units, linked by α-(1, 4)-glycosidic bonds 4) hydrophilic on the external surface and relatively hydrophobic on the interior cavity 5) capable of encapsulating molecules which are less polar than water α β γ

10 1-MCP synthesis & formation of inclusion complex between 1-MCP & α-cd 1-MCP synthesis Li Lithium diisopropylamide 3-Chloro-2-methylpropene Lithium salt of 1-MCP Host : Aqueous α-cyclodextrin (α-cd) Preparation method : i) Synthesis of lithium salt of 1-MCP 1-MCP/α-CD IC ii) Production of 1-MCP gas iii) Exposure of α-cd solution under 1-MCP atmosphere (closed, agitated vessel with a flat gas liquid interface) iv) Precipitation of inclusion complex (IC)

11 1-MCP synthesis & formation of inclusion complex between 1-MCP & α-cd 1-MCP synthesis Li Lithium diisopropylamide 3-Chloro-2-methylpropene Lithium salt of 1-MCP Formation of inclusion complex 1-MCP/α-CD (molar ratio) MCP/α-CD 1500

12 Preparation method of inclusion complex i) Synthesis of lithium salt of 1-MCP ii) Production of 1-MCP gas iii) Exposure of α-cd solution under 1-MCP atmosphere (closed, agitated vessel with a flat gas liquid interface) iv) Precipitation of inclusion complex (IC) Formation of inclusion complex 1-MCP/α-CD (molar ratio) MCP/α-CD 1500

13 Release characteristic of 1-MCP from IC MCP retention MCP retention : 35%RH 25 o C : 55%RH : 75%RH Time (day) o C : 30%RH : 45%RH : 73%RH Time (day)

14 SEM Phtographs of 1-MCP/α-CD crystal 3500 Initial crystal After 10 days storage 5μm 5μm Reelease condition: Temp. 50 o C Relative humidity,73%rh

15 Electrospinning of polystyrene fibers functionalized with inclusion complex Syringe Syringe pump High voltage generator Electrospinning solution Stainless steel needle Collector plate Voltage = 10 kv Inner needle diameter = 0.84 mm Chloroform : Toluene * 1.5 wt% Tetrabutylammonium chloride (TBAC) with respect to PS.

16 Polystyrene fibers functionalized with inclusion complex PS 17.5 wt%, Complex 50 wt%, TBAC 1.5 wt% Average fiber diameter = 2.6 ± 0.6 μm > g-1-mcp/g-fiber

17 Confocal laser scanning microscopy PS 20.0 wt%, Complex 50 wt%, TBAC 1.5 wt%

18 Release experiment of functionalized fibers N 2 Water bath Bubbling bottle Heater Air bath Electrospun Copper coil fiber heat exchanger Gas sampler Hygrometer N 2 outlet Air actuator Timer Compressed air Programmable temperature controller GC Release of 1-MCP Column : PEG20M packed-column Carrier gas : N 2 Column temp. : 130 ºC Detector : FID N 2 flow rate, v 1-MCP release rate, N 76 mm N = v C g N : Release rate [µg/s] v : N 2 flow rate [ml/s] C g : 1-MCP conc. [µg/ml] F = N / m F : 1-MCP flow [µg/s g-complex] m : Complex mass [g]

19 Crystal structure changes of inclusion complex with humidity ramping 1-MCP/α-CD 1500 RH 0 % RH 40 % RH 60 % 20kV µm Humidity ramping rate 0.33 %/min Initial content 28 mg-1-mcp/g-cd 20kV µm RH 60 % 20kV µm

20 Structure change of polystyrene fibers Before 50⁰C 0.33 %/min After humidity ramping 20kV µm 20kV µm 20kV µm 20kV µm

21 Release characteristic RelativeRelease = A = E a 10 = 106 kj/mol Ramping RH (0.33%/min), 20 wt% PS s -1 Ae Ea - βrh RT i β 1 RH i-1 β 2 RH i-2 Relative Release [1/Ms] ºC β = β β 1 2 = = ºC β = β β 1 2 = = ºC β = β β 1 2 = = RH [%]

22 Conclusion The release rate of 1-MCP from the inclusion complex powder increased slowly until 40-50% RH which the release rate was accelerated exponentially. The release was disturbed at about 65% RH at 40ºC and subsequently retarded at RHs above 90% RH. These collapses could be improved by coating with polystyrene. PS 17.5 wt% 1-MCP/α-CD ± 0.7 μm