想像一下，有一種塑膠披薩外包裝盒，這層塑膠是番茄做的，你可以連披薩帶盒子一起進烤箱烤，烘烤過後就變成披薩的一部分。
國營巴西農業研究公司Embrapa Instrumentation和巴西農業部合作，用菠菜、木瓜、芭樂和番茄，開發出這種可食用的塑膠。
巴西科學家Luiz Henrique Mattoso（左一）和其學生展示一塊用木瓜做的可食用塑膠。（來源：Flavio Ubiali／Embrapa）
食材不浪費 兼顧包材永續
「我們可以讓食材回收業製作材料。可食塑膠技術可以確保兩方面的永續性：食材不浪費，並取代用過即丟的合成材料。」研究計畫的協調科學家Luiz Henrique Capparelli Mattoso說。
Mattoso說，Embrapa公司用熱帶水果製作塑膠膜，是全球首創。
這種材料的韌性和質地等物理特性類似傳統塑膠，同樣能保持食物乾淨。可食用塑膠也為包裝產業開啟更多可能性。Mattoso說，禽肉包裝塑膠膜同時也可以有調味功能，而湯品的塑膠包裝也可融化於滾水。
可食塑膠是由脫水食材和奈米材料混合製成，其中奈米材料的功能是讓結構穩定。「這個研究最大的挑戰是找出理想的配方，原料的食譜和比例，讓材料具有我們想要的特性。」Embrapa參與計畫的材料工程師José Manoel Marconcini說。
Marconcini解釋，原材料需在冷凍後以一種特殊的脫水法處理，讓所含的水份從固態直接變成氣態，中間不經過液態。如此，食材可以保持原有的營養。
這種脫水法可以用於水果、蔬菜、豆類甚至部分香料，因此可食塑膠也可用來幫食物調味和調色。
從可分解到可食 塑膠包材再進化
可食塑膠的開發始於20年前，當時Mattoso才開始在Embrapa研究材料科學。「一開始是想要用可再生材料當做石油衍生聚合物的替代品。」Mattoso回憶道。為了達成這個目標，研究團隊開始在合成塑膠中加入天然纖維，以兩種原料製作複合材料。
研究團隊試過劍麻、棉花、黃麻、椰殼纖維和蔗渣等各式材料。Mattoso說，在實驗室中，這些材料比較能耐拉扯和撞擊，此外也比100%合成聚合物要強韌3倍。
開發可食塑膠前，為因應讓包裝材料可以快速被環境分解的需求，這個研究團隊開發出可生物分解聚合物。為了再提高製造過程的安全和衛生標準，團隊最終發展出可食塑膠。
現在科學家透過添加殼聚醣（chitosan）──存在於螃蟹外骨骼的抗菌多醣（antibacterial polysaccharide）──增加食品的保存期限。這種天然分子可以抗菌，因此可以延長食品在貨架上的時間。
Brazilian Lab Turns Fruits, Veggies Into Edible Plastic
BRASILIA, Brazil, January 14, 2015 (ENS)
Imagine putting a pizza in the oven without having to remove the plastic casing that protects the pizza from contamination. The plastic film consists of tomatoes and, when heated, it will become part of the pizza.
This edible plastic has been developed by researchers at the Brazilian Agricultural Research Corporation, Embrapa Instrumentation, a state-owned company affiliated with the Brazilian Ministry of Agriculture.
In fact, the researchers have made edible plastic films from foods such as spinach, papaya and guava as well as tomatoes.
“We can use the waste food industry to manufacture the material. This ensures two features of sustainability: the use of food waste and replacing synthetic packaging that would be discarded,” says the coordinating scientist on the project, Luiz Henrique Capparelli Mattoso.
Mattoso says that Embrapa’s work to develop plastic films from tropical fruits is a world first.
The material has physical features similar to conventional plastics, such as resistance and texture, and is equal in its ability to protect food.
The fact that it can be eaten opens a vast field to be explored by the packaging industry. Mattoso pictures spiced wrapping material for poultry, and soup packages that can dissolve with their contents in boiling water.
The edible plastic is made of dehydrated food mixed with a nanomaterial which has the setting function.
“The greatest challenge of this research was to find the ideal formulation, the recipe of ingredients and proportions so that the material had the features we needed,” says materials engineer José Manoel Marconcini, an Embrapa researcher who participated in the work.
He explains that the food used as the feedstock passes through a type of dehydration in which, after the food is frozen, all the water contained in it turns from a solid state directly into gas, without passing through the liquid phase.
The result is a completely dehydrated food with the advantage of keeping its nutritional properties.
It can be applied to many different foods such as fruits, vegetables, legumes and even some types of seasonings, which explains the great diversity of edible raw materials that can flavor and color the plastic.
The development of the edible plastic material was the result of work that started two decades ago, when Mattoso began his studies in materials science at Embrapa.
“In the beginning, the concern was to use materials from renewable sources studying alternatives to synthetic polymers derived from petroleum,” recalls Mattoso. To accomplish this, the group began to add natural fibers to synthetic plastics, generating composites with the two types of raw material.
Sisal, cotton, jute, coir and bagasse were some natural fibers tested. Mattoso says that in laboratory testing they were more resistant to traction and impacts, in addition to being up to three times stronger than the 100 percent synthetic polymers.
Before discovering how to make edible plastic, the research team developed biodegradable polymers, driven by the demand for packaging easily absorbed into the environment in a short time.
Finally, they arrived at edible plastic, after incorporating higher standards of safety and hygiene in the manufacturing process.
Now the scientists have increased the food’s shelf life by adding added chitosan, an antibacterial polysaccharide found in the exoskeletons of crabs. This natural molecule has antibacterial properties which can extend the length of time food can remain fresh on the shelf.
※ 全文及圖片詳見：ENS
文章@http://e-info.org.tw/node/104697
