Free Essay

Essay

In:

Submitted By sela90
Words 1234
Pages 5
JFS R:简明评论/食品科学中的假设

食品包装的作用,材料,
环境问题

丁午MARSH,博士和BETTY BUGUSU,博士

食品技术研究所发出了这样的科学地位摘要食品包装上的更新读者

R:食品科学简明评论
及其对环境的影响。
关键词:食品包装,食品加工

在食品加工和食品包装的进展发挥了主要作用,保持美国的食品供应最安全的
世界。简单地说,包装保持的好处
该过程完成后,食品加工,使食品,以
从他们的起点很长的距离,仍然是安全
有益健康的在时间的消费。然而,封装技术必须兼顾粮食保护等问题,包括
能源和原材料成本,加剧社会和环境
意识和严格的规定的污染物和处置
都市固体废物。

城市固体废弃物(MSW)的项目通常抛出
路程,包括饮料,食物残渣,院子里的装饰,和耐用
如冰箱和电脑。立法和监管力度,控制包装,包装是城市生活垃圾的主要负担的错误认识的基础上。相反,美国
环境保护署(EPA)发现,大约有
只有31%的在2005年产生的都市固体废物是从包装相关
材料,包括玻璃,金属,塑料,纸张和纸板的
百分比,一直保持相对稳定,20世纪90年代以来,尽管城市生活垃圾总量的增加。 Nonpackaging来源
如新闻纸,电话簿,和办公通信产生更多的两倍多MSW(EPA 2006A)。食物是唯一的
产品类别通常消耗,每天3次的每一个人。
因此,食品包装占了几乎三分之二的总包装废弃物体积(亨特和1990年)。此外,
食品包装是约50%(按重量计)的总包装
销售。虽然具体的知识已经改变,因为
出版的第一届科学的状态摘要的关系
包装和城市生活垃圾(IFT 1991年)之间,问题仍然不佳
理解,复杂的努力,以解决被丢弃的包装材料对环境的影响。本文介绍的作用
食品包装在食品供应链中,材料的种类
用于食品包装,食品包装上的影响
环境。此外,该文件提供了一个概述
EPA的固体废物管理指引“和其他废物管理

作者马什是总裁肯尼思·S.沼泽&Associates公司,有限公司,中环,SC,

美国作者Bugusu科学与技术系研究员,
工程,食品技术研究所,华盛顿特区,美国直接
作者Bugusu查询(电子邮件:bbugusu@ift.org)。
? 2007年食品技术研究所
DOI:10.1111/j.1750-3841.2007.00301.x
未经许可,禁止进一步复制
MENT选项。最后,它解决了处理方法和立法
包装处理。

食品包装的作用

食品包装的主要角色是从外界的影响和损失,包含食物,以保障食物产品,
并为消费者提供了成分和营养信息(科尔斯2003)。可跟踪性,便利性和篡改指示
辅助功能的重要性日益增加。食品的目标
食品包装是包含在具有成本效益的方式满足行业的要求和消费的欲望,维护食品安全,
并最大限度地减少对环境的影响。

保护/保护

食品包装能延缓产品变质,保留处理的有利影响,延长保质期,并保持或提高食品的质量和安全性。在这样做时,包装提供
从3个主要类别的外部影响:化学,生物和物理的保护。

化学防护最大限度地减少环境的影响,如接触到气体成分的变化所引发的
(通常为氧),水分(增加或减少),或光(可见光,红外线,
或紫外线)。许多不同的包装材料可以提供
化学屏障。玻璃和金属提供了一个几乎绝对的屏障
化学品和其他环境用药,但几包
纯粹的玻璃或金属,因为闭合装置被添加,以方便
充盈和排空。关闭设备可能包含材料
允许的渗透率的最低水平。例如,塑料盖
有一些气体和蒸汽的通透性,因为这样做的垫片材料中使用的上限,以方便关闭和金属罐盖,让
密封后填充。塑料包装提供了一个大范围的屏障
的性能,但通常是更可渗透比玻璃或金属。

生物保护提供了一个屏障的微生物
(病原体和破坏剂),昆虫,啮齿动物和其他动物,从而预防疾病和腐败。此外,生物屏障的维护条件来控制衰老(成熟
和老化)。这些障碍通过多种机制发挥作用,
包括防止对产品的访问,防止异味传输,并保持内部环境的软件包。

身体防护盾牌食品机械损伤和
包括对遇到的冲击和振动的缓冲

卷。 72,NR。 3,2007年食品科学杂志R39

R:食品科学简明评论
科学的地位摘要 - 食品包装。 。 。

在分配过程中。通常纸板和
瓦楞纸板材料的物理障碍,抵制的影响,擦伤,
和破碎损坏,所以它们被广泛用作船运集装箱
包装精致的食物,如鸡蛋和新鲜水果。适当
物理包装也保护消费者免受各种
的危害。例如,儿童性关闭潜在的阻碍
危险的产品。此外,取代的塑料
从洗发水到碳酸饮料瓶包装的产品范围
从破碎的玻璃容器的危险减少。

遏制和减少食品浪费

食品包装对环境的影响的任何评估
必须考虑的正面效益,减少食物的浪费整个
供应链中。据报道,在大量的浪费食物
许多国家,包括粮食的25%至50%的水果和
蔬菜(FAO,1989)。不足保护/保护,存储,
运输已被列为食品浪费的原因。
包装延伸的食品的保质期,降低总废物
从而延长它们的可用性。 Rathje和其他人(1985)
人均产生的垃圾在墨西哥城中少
包装,更多的食物垃圾,三分之一的废物总量比
在可比的美国城市。此外,Rathje以及其他的
(1985)观察到,包装食品在2.5%的总废物
相比,50%的新鲜食品,部分原因是由于农副产品
收集处理厂的产品被用于其他用途
而在家里,通常被丢弃。因此,
包装可能有助于减少总固体废物。

市场营销和信息

一个包是面对的产品,而且往往是唯一的产品
之前曝光的消费者体验购买。因此,
独特或新颖的包装可以促进销售,在竞争激烈的
环境。包可能被设计,以提高
产品图像和/或不同的产品的竞争。
例如,较大的标签可能被用来容纳
食谱。包装也提供给消费者的信息。为
例如,包装标签的产品满足法律的要求
鉴定,营养价值,配料表,净含量,
和制造商信息。此外,该包传送
有关产品的重要信息,如烹饪指令,
品牌识别和定价。所有这些增强功能
可能会影响废物处置。

可追溯性

食品法典委员会规定的可追溯性“
按照食品流动能力,通过指定的阶段(S)
生产,加工,分销“(食品法典
委员会于2004年)。可追溯性有3个目标:改善供应
管理,便于追溯的食品安全和质量
微妙或检测不到目的,并区分和市场食品
质量属性(戈兰高地等2004)。食品制造业
公司合并的包装标签上的唯一代码
他们的产品,这使他们能够跟踪他们的产品在整个
分配过程。代码可在各种不同的格式
(例如,打印的条形码或电子射频识别
[RFID]),并可以手动读取和/或由机器。

方便

便利功能,例如方便的接入,处理和处置;
产品的知名度;的resealability和microwavability大大
影响包装创新。其结果是,包装起着
一个重要的角色,最大限度地减少准备和提供必要的努力

R40作者食品科学卷。 72,NR。 2007年3

食品。烤箱安全的托盘,蒸发袋,微波食品包装
使消费者能够煮的饭菜,几乎没有任何准备。
新的闭包的设计提供便于打开,resealability,和
特殊的分配功能。例如,一个饼干制造商最近
介绍了柔性袋与刻痕部,其提供
访问的cookies。剥离密封用的膜覆盖
开开盘后才可发售,并允许重合闸。进展
食品包装的发展提供便利的现代零售
1一站式购物的便利为消费者提供的格式
来自世界各地的食品和可用性。这些方便的
功能增加价值和竞争优势的产品
但也可能会影响包装废弃物的数量和类型
需要处置。

篡改迹象

故意的篡改食品和医药产品
导致在特殊包装设计的功能,以减少或消除
篡改和掺假的风险。虽然任何包
可以breeched,防撕功能不能很容易地被替换。
防揭功能包括:带,特殊的膜,
分离的瓶盖,瓶衬及特种印刷
或图形或文字不可逆的改变,如复合罐
在打开。特种印刷还包括全息图,可以不
容易被复制。防窃启包装通常需要
额外的包装材料,这加剧处理的问题,
但带来的好处大于缺点。的一个例子的
防篡改功能,无需额外的包装材料
是医疗包装上使用的是化学和热密封
制定打开时改变颜色。

其他功能

包装可能成为其他功能,例如为载体,保费
(例如,夹杂物的礼物,其他产品,或
优惠券)或家庭使用的容器。包装的潜力
使用/再利用消除或延迟进入废物流。

材料用于食品包装

包装设计和建设发挥了重要的作用,决定
的食品的保质期。正确的选择
包装材料和技术,保持产品的质量
新鲜,分发和存储。材料,其具有
传统上被用于食品包装,包括玻璃,金属(铝,
箔和层压板,马口铁,和不含锡的钢),纸张和
纸板和塑料。此外,更广泛的各种塑料
在刚性和柔性的形式被引入。当今的食品包装
通常几种材料结合起来,利用每一种材料的功能
审美属性。作为研究,以提高食品包装
继续,在该领域的进步可能会影响对环境的影响
包装。

美国食品和药物管理局(FDA)规定包装
根据“联邦食品,药品和化妆品”第409条的材料
行动。监管的主要方法是通过食品
联系通知的过程,需要制造商通知
FDA的120天前销售食品接触物质(FCS)的一个
新的用途。的FCS是“用于与使用任何物质作为成分
使用的材料在生产,包装,包装,运输
或持有的食物,如果使用不打算有技术
在这类食物的影响“(21 USC§348(H)(6))。 ,可能所有FCSS的
预定可使用状态的情况下,合理地迁移到食品
除非归类为一般和监管作为食品添加剂
确认为安全的(GRAS)物质。

科学的地位摘要 - 食品包装。 。 。

玻璃

玻璃的历史非常悠久,在食品包装中的第一玻璃
用于盛装食物的对象被认为已经出现了约3000
,BC(Sacharow和格里芬1980年)。玻璃容器的生产
涉及加热的二氧化硅的混合物(玻璃前),碳酸钠
(溶剂),和石灰石/碳酸钙和
氧化铝(稳定剂),直到材料的高温融化
成厚的液体物料,然后将其倒入模具中。再生
碎玻璃(碎玻璃)也被用来在玻璃制造中,可能占
高达60%的所有原材料。使用玻璃容器。
在食品包装中往往是表面涂层,以提供润滑
在生产线中,并消除刮伤或表面磨损
和线堵塞。玻璃涂料也增加,保存实力
的瓶子,以减少破损。改进突破阻力允许
制造商使用更薄的玻璃,从而降低重量和
更好的处理和运输(McKown 2000)。

因为它是无味,化学惰性,几乎所有的食品
产品,玻璃有用于食品包装应用的几个优点:
它是不透气的气体和蒸汽,因此它保持产品
了很长一段时间不损害味道或风味的新鲜度。
承受能力高的加工温度,使玻璃
用于两个低酸和高酸食品的加热杀菌。
玻璃是刚性的,提供了良好的绝缘性,并可以生产
许多不同的形状。玻璃的透明度,让消费者
看到的产品,但在玻璃颜色的变化可以保护
光敏感的内容。最后,玻璃包装有利于环境
因为它是再用和循环再造。

喜欢的任何材料,玻璃具有一些缺点。尽管努力
使用更薄的玻璃,它的重量增加了运输成本。
另一个值得关注的是它的脆性和破损的敏感性
内部压力,冲击,热冲击。

金属

金属是最多才多艺的所有包装形式。它提供了一个组合
优良的物理保护和阻隔性能,
成形性和装饰的潜力,可回收性和消费者
验收。最主要使用在包装2金属
是铝和钢。

铝。通常用于制造罐,金属箔,并层叠
纸张或塑料包装,铝是一种轻量的,银白色
来自铝土矿,在那里它的存在结合的金属
氧作为氧化铝。往往添加镁和锰
铝以提高其强度属性(页和其他
2003)。不像许多金属,铝是具有很高的耐最
形式的腐蚀;其自然铝氧化物涂层提供
一个非常有效的阻挡层的空气的影响,温度,水分,
和化学攻击。

除了提供优异的阻隔湿气,空气,气味,
光,和微生物,铝具有良好的柔韧性和表面
的韧性,优良的延展性和可成形性,和出色的
压花潜力。它也是一个理想的回收材料
因为它很容易变成新产品的回收和处理。纯
铝软饮料罐主要用于轻包装,
宠物食品,海鲜,预先刻螺纹关闭。它的主要缺点
铝的成本高,相比其他金属(
例如,钢)和其无法被焊接,使得它有用
只有进行无缝的容器。

铝箔。铝箔是由轧制纯铝板
成非常薄的片材,接着通过退火来实现金属
死耐折性能(在影片中的折痕或折留
代替),这使得它能够紧紧折叠。此外,铝
箔是可在一个宽的厚度范围内,具有较薄的箔
用于食品和较厚的铝箔用于托盘包装。像所有的铝

包装,箔提供优异的阻隔湿气,空气,气味,
光,和微生物。它是惰性的酸性食品,和不
需要漆或其他保护措施。虽然铝是容易
可回收,箔不能再生铝没有
在薄片的针孔形成。

层压板和金属化薄膜。层压包装包括
铝箔,纸或塑料膜的结合
改善的阻隔性能。厚度薄,便于应用。虽然
层压塑料能使热封性,密封
不能完全阻止水分和空气。由于层压铝
是相对昂贵的,它通常用于高价值的食品打包
干汤,药草和香料等。一个更便宜的替代
复合包装,金属化薄膜。金属化薄膜是塑料
含有一层薄薄的金属铝(Fellows和阿克斯特尔
2002)。这些膜已经改善对水分的阻隔性能,
油,空气,和气味,和铝的高反射率的表面的
是对消费者的吸引力。更灵活的复合薄膜,金属化
薄膜主要用于包小吃。虽然单个
覆铜面板及金属化薄膜组件技术上
可回收,分选和分离材料的难度排除
经济上是可行的回收利用。

马口铁。从低碳钢的生产的(即,黑钢板),
马口铁的结果是涂层薄层两侧的黑钢板与
锡。该涂层是通过在熔融浸渍的钢板
锡(热镀马口铁)上电沉积锡或
钢板(电解马口铁)。虽然锡钢
一定的耐腐蚀性,马口铁容器往往涂漆
提供惰性屏障之间的金属和食品产品。
常用的漆是环氧酚醛材料和
油性树脂基和乙烯基树脂。

除了其优异的气体阻隔性能,水蒸气,
光,和气味,马口铁可以进行热处理,并气密地密封,
它适用于无菌产品。由于它具有良好
延展性和可成形性,可用于马口铁容器的许多
不同的形状。因此,马口铁被广泛使用,以形成用于饮料罐,
加工食品,气溶胶,粉状食品的容器,
糖或面粉为基础 的甜点;包关闭。马口铁
是一个优秀的现代金属涂层和基材平印
技术,实现出色的图形装饰。其相对
重量轻,机械强度高,使其易于运输和
存储。最后,马口铁很容易多次循环使用,不损失
及品质的显着较低的成本比铝。

锡自由钢材。也被称为电解铬或镀铬
氧化涂层钢,锡 - 钢需要的有机材料的涂敷
以提供完整的耐腐蚀性。即使
铬/三氧化二铬,锡钢不适合焊接,
这一特性使得它非常适合涂料等粘附
涂料,油漆,油墨。像马口铁,锡钢具有良好的
成形性和强度,但它是很有限的成本要低于
马口铁。食品罐头, 可结束后,托盘,瓶盖和关闭都可以
由不含锡钢。此外,它也可以被用于使
大批量出售和大量储存容器(如鼓)
原料或成品(研究员和阿克斯特尔2002)。

塑料

塑料是由缩合聚合(缩聚)
或加成聚合反应(加成聚合)的单体
单位。在缩聚反应中,在聚合物链的增长通过冷凝
与分子间的反应是伴随着形成
低分子量的副产物,例如水和甲醇。
缩聚涉及单体与至少2个功能
基,如醇,胺或羧酸基团。在加聚,
聚合物链增长的加成反应,其中2个或更多

卷。 72,NR。 3,2007年食品科学杂志R41

R:食品科学简明评论

R:食品科学简明评论
科学的地位摘要 - 食品包装。 。 。

分子相结合,形成一个较大的分子没有解放
的副产物。加聚反应涉及的不饱和单体,双
或三键被打破单体链链接。有
使用塑料食品包装的几个优点。流体和
陶土,塑料片,形状和结构,可以做成
提供的设计灵活性。因为它们是化学
耐磨,塑料是便宜,重量轻,具有很宽的范围内
的物理和光学性质。事实上,许多塑料热
可密封的,容易进行打印,并可以集成到生产过程
包形成,填充,并在同一密封
生产线。塑料的主要缺点是它们的变量
透气性的光,气体,蒸汽,和低分子量的
分子。

有2大类:塑料热固性和热塑性塑料
(EPA 2006年b)。热固性聚合物固化或
设置不可逆的加热时和不能被重塑。因为他们
坚固耐用,他们往往将主要用于在汽车
和建筑应用中,如粘合剂和涂料,
而不是在食品包装中的应用。在另一方面,热塑性塑料
的聚合物暴露于热时软化,并返回到
其原来的状态,在室温下。由于热塑性塑料
可以很容易地成形和模压成各种产品例如
瓶,罐,塑料薄膜,用于食品包装的理想选择。
此外,几乎所有的热塑性塑料是可回收的(融化
为原料生产的新产品中重复使用),虽然
分离带来了一些实际的限制对某些产品。
在回收过程中需要分离树脂型确定
由美国塑料委员会(表1)。

有一些健康问题有关残余
单体和组件中的塑料,包括稳定剂,增塑剂,
和缩合,如双酚A的组件的某些
这些问题的基础上使用非常高的摄入水平的研究;
其他人都没有科学依据。为确保公众安全,FDA仔细
评论和调节物质,用于制造塑料和其他
包装材料。任何物质,可以合理地预期
迁移到食物被归类为间接食品添加剂主题
FDA的规定。调控定义为一个特定的阈值
膳食暴露水平,通常引起的毒性作用,
因此,提出了可以忽略不计的安全问题(21 CFR§170.39)
使用豁免物质用于食品接触材料的
作为食品添加剂的监管。 FDA重新审视的阈值水平,如果新
科学的信息引起了关注。此外,FDA建议
消费者使用塑料按照预期的目的
与制造商的指示,以避免意外安全
关注的问题。

尽管这些安全问题,在食品包装中使用的塑料
继续增加由于成本低的材料和
功能优势(,如thermosealability,microwavability,
光学性能,并无限的尺寸和形状)比传统的
的材料,如玻璃和马口铁(洛佩兹-卢比奥等2004)。

表1 ---塑料回收的树脂识别代码

金额金额
生成的再生
树脂码(万吨)(万吨)

聚对苯二甲酸乙二醇酯1 2860 540
高密度聚乙烯2 5890 520
聚氯乙烯1640
低密度聚乙烯4 6450 190a的
聚丙烯4000 10
聚苯乙烯6 2590
其他树脂7 5480 390

资料来源:美国塑料委员会(2006b)和EPA(2006A)。 aIncludes线性低密度聚乙烯。 R42作者食品科学卷。 72,NR。 2007年3

多种类型的塑料包装材料被用作
食品,包括聚烯烃,聚酯,聚氯乙烯,聚偏二
氯乙烯,聚苯乙烯,聚酰胺,乙烯 - 乙烯醇。
虽然已超过30种的塑料作为包装
,聚烯烃和聚酯材料(刘和黄2000)
最常见的。

聚烯烃。聚烯烃是一个集体期限为聚乙烯,
聚丙烯,2在食品包装中的最广泛使用的塑料,
其他较受欢迎的烯烃聚合物。聚乙烯和聚丙烯
都拥有一个成功的组合属性,包括:
柔韧性,强度,光亮度,稳定性,水分和耐化学性,
和易于加工,并且非常适合用于回收和
重用。

最简单的和最便宜的塑料制成,加入
乙烯的聚合是聚乙烯。有2个基本类
聚乙烯:高密度和低密度的。高密度
聚乙烯是激烈的,坚强,坚韧,耐化学品和水分,
可渗透的气体,易于加工,并且容易形成。它是用来
瓶用于牛奶,果汁,水,麦片盒内衬,人造黄油
浴缸和杂货店,垃圾和零售袋。低密度聚乙烯
灵活,强大,坚韧,易于密封,耐潮湿。因为
低密度聚乙烯是相对透明的,它是以
在薄膜应用中,在应用程序中使用的其中
热封是必要的。面包和冷冻食品包装袋,软盖,
和挤压食品瓶是低密度聚乙烯的例子。
有时会重复使用聚乙烯袋(包括杂货, nongrocery零售)。的2个类别的聚乙烯,高密度 聚乙烯容器中,尤其是奶瓶,是最再生
塑料封装中。

较硬,密度更高,比聚乙烯更透明,
聚丙烯具有良好的耐化学品和是有效的
限制水蒸汽。其熔点高(160℃),使其适合
热电阻的应用场合是必需的,如
热灌装包装和微波炉。常见的应用包括酸奶
容器和人造黄油桶。当组合使用时,与
氧气阻隔性,如乙烯 - 乙烯醇或聚偏二氯乙烯,
聚丙烯提供了强度和防潮屏障
番茄酱和沙拉酱瓶。

聚酯。的聚对苯二甲酸乙二醇酯(PET或PETE),聚碳酸酯,聚
和聚萘二甲酸乙二醇酯(PEN)的聚酯,其中
冷凝形成的聚合物酯单体的结果
从羧酸和醇之间的反应。最
在食品包装中常用的聚酯为PETE。
聚对苯二甲酸乙二醇酯。对苯二甲酸的反应时形成的
与乙二醇,PETE提供了一个良好的阻隔性气体(氧
和二氧化碳)和水分。它也具有良好的耐
加热,矿物油,溶剂和酸,但不基地。因此,
皮特是成为包装材料的选择
许多食品,特别是饮料和矿泉水。
PETE的使用,使塑料瓶,碳酸饮料
稳步增加(于面包车Willige等2002)。主要的原因
其受欢迎程度是玻璃般的透明度,充分
保留的碳酸化的阻气性,重量轻,和震裂
性。 3个主要的包装应用PETE
容器(瓶,罐,桶),半硬质片材的热成型
(托盘和水泡),和薄膜(袋和
休闲食品的包装)。 PETE同时存在,为无定形的(透明)
和半结晶(不透明和白色)热塑性
材料。非晶,PETE有更好的延展性,但不僵硬
半结晶PETE,具有良好的强度和硬度比,
延性,刚度和硬度。从碳酸饮料瓶的再生PETE
用作纤维,绝缘性,和其他的非食品包装
应用程序。

科学的地位摘要 - 食品包装。 。 。

聚碳酸酯。聚碳酸酯的聚合而形成的
与羰基二氯化(光气),双酚酸的钠盐。
清除,耐热性,和持久的,它主要是用来作为替代
的项目,如大型回收/再充气的矿泉水瓶和玻璃
消毒的奶瓶。清洗时,必须采取聚碳酸酯
因为使用苛刻的洗涤剂如次氯酸钠
不建议,因为他们催化释放的双酚A
A,潜在的健康危害。 VOM大量的文献分析
萨尔和休斯(2005年)表明,需要新的风险评估
该化合物的低剂量效应。
聚萘二甲酸乙二酯。 PEN是一种缩合聚合物
二甲基萘二甲酸和乙二醇。它是一个相对
聚酯家族中的新成员,具有优良的性能
由于其高的玻璃化转变温度。 PEN的屏障
二氧化碳,氧气和水蒸汽的属性都优于
那些和PEN PETE,提供了更好的性能,在高温下,
允许热笔芯,再洗和重用。然而,PEN
成本的3至4倍以上,PETE。由于PEN提供保护
反对转让的口味和气味,它非常适合于制造
饮料,如啤酒瓶。

聚氯乙烯。聚氯乙烯(PVC),加成聚合物
氯乙烯,重,硬,韧性,和一个中等强度的,
无定形的,透明材料制成。它具有优良的耐
化学物质(酸和碱),油脂和油,良好的流动性;
和稳定的电气特性。虽然聚氯乙烯是主要用于
医疗及其他非食品,其食品用途包括
瓶和包装膜。因为它很容易热成型,PVC
片材被广泛地用于如肉制品的泡罩包装
和单位剂量的药品包装。

可以转化为PVC材料具有广泛的灵活性
加入增塑剂,如邻苯二甲酸酯,己二酸酯,
柠檬酸盐,和磷酸盐。邻苯二甲酸酯类化合物主要用于非食用
如化妆品,玩具,医疗器械的包装应用。
安全问题已经出现在某些使用邻苯二甲酸酯
产品,如玩具(FDA 2002年,乳木果2003年欧盟2005年)。
由于这些安全问题,食品中不使用的邻苯二甲酸酯
包装材料在美国(HHS的2005),而可替代 nonphthalate使用增塑剂,如己二酸酯。为 例如,二 - (2 - 乙基己基)己二酸酯(DEHA),用于制造
塑料保鲜包裹。这些替代增塑剂也有
渗入食物,但在较低的水平比邻苯二甲酸盐的潜力。
水平低,DEHA并没有表现出毒性的动物。最后,PVC
是难以回收的,因为它是用于这样的各种产品,
这使得难以识别和区分。另外,
焚烧PVC呈现环境的问题,因为
其氯含量。

聚偏二氯乙烯。聚偏二氯乙烯(PVDC)是一个
偏二氯乙烯的加成聚合物。这是热封,供应

Similar Documents

Premium Essay

Essay

...1 Overview of How to Write an Essay Writing essays is a major element of your education at the university level. Effective writing gives you the ability to express your ideas, theories, arguments, and projects clearly. The skills you acquire at the university level through writing essays will be aimed at practical business applications that you will be able to use in the workplace. The following information provides a succinct overview of the elements you need to know to begin writing an essay. It will help you on your writing journey. Types of Essays Narrative A narrative essay is a story told by a narrator. Generally, a narrative discusses the personal experience of the author (the first person point of view), but it can also be written about things that happen to others (third person point of view). A narrative typically involves characters, a setting, specific and vivid details, and a series of events that can include current incidents, flashbacks, or dialogue. Cause and Effect A cause and effect essay explores why events, actions, or conditions occur (cause) and examines the results of those events, actions, or conditions (effect). For example, a cause could be purchasing a new expensive home. The effect might be fewer family vacations, more time spent on upkeep, or less time with family because of extra work hours to pay for the home. Comparison and Contrast A comparison and contrast essay shows the relationship between two or more elements. The items can be compared...

Words: 6215 - Pages: 25

Premium Essay

Essay

...How to determine custom essay editing company that is legitimate This is the company you will find great editors to provide you with custom essay editing service. Students whose first language is not English may find speaking and writing in English as a difficult task for them. Most of these students are international students who have enrolled in various universities in America and in the UK. The main teaching language is English, American and Standard English respectively. It is essential for students to master well the language of instruction because it is a medium through which they are required to write their assignments and speak in classroom. Competence and fluency in English language will help students to read and understand the teaching material provided to them. It is important therefore for students to ask for support from custom essay editing services which deal with the tips of writing good essays among other academic papers and also to write for them assignment essays. Our writing and editing services is created both for students and professionals. We deal with both the non academic and academic editing and writing services to fulfill your needs. At our custom essay editing, you will find editors who are qualified in linguistics and English language. We are ready to provide you the custom essay editing service at any time of the day or night because we operate as a 24/7 service. Our custom essay editing service comprises of creative thinkers, skillful editors...

Words: 574 - Pages: 3

Premium Essay

Essay

...An essay is usually a short piece of writing. It is often written from an author's personal point of view. Essays can be literary criticism, political manifestos, learned arguments, observations of daily life, recollections, and reflections of the author. The definition of an essay is vague, overlapping with those of an article and a short story. Almost all modern essays are written in prose, but works in verse have been dubbed essays (e.g. Alexander Pope's An Essay on Criticism and An Essay on Man). While brevity usually defines an essay, voluminous works like John Locke's An Essay Concerning Human Understanding and Thomas Malthus's An Essay on the Principle of Population provide counterexamples. It is very difficult to define the genre into which essays fall. Aldous Huxley, a leading essayist, gives guidance on the subject: Like the novel, the essay is a literary Abstract This article will examine the reasons why it is important both linguistically and psychologically to build a vocabulary quickly when learning a foreign language. The article asserts that very little can be achieved or learned in a foreign language with a small vocabulary and that by building a sizable vocabulary quite quickly one can soon be able to function adequately. You may also wish to look at http://www.jalt-publications.org/tlt/files/95/feb/meara.html   Introduction   It is obvious that in order to learn a foreign language one needs to learn many many words. But how many? Educated...

Words: 332 - Pages: 2

Premium Essay

Essay

...There are some teachers who are going to require you to write a 250 word essay. Actually, it is a very short essay for that matter but for some students, it may also be a burden to have a word limit in writing. Let us take a look at the scenarios that you need to understand to compose a well developed essay. For some students, it may be limiting to have a word factor quota in writing an article. There are some individuals who can tell more out of a topic and that having 250 words will not suffice to tell everything in their minds. That is why you need to have the skills in budgeting the words that you have to write without sacrificing the ideas that you have to deliver. There are different essay types that you also need to consider so having a word limit cannot simply be an easy task. Still for some students, a 250 word essay may mean too much because there are also some people who do not want to waste their time writing. No matter what the essay structure may be, these types of people are not really eager to translate their thoughts to written form so they think 250 words simply equates to too much work. Anyway, you need to understand that having this kind of limit will eventually benefit the students as they improve their discipline, being responsible and being resourceful individuals. We can offer you to buy essays from us so you do not have to worry about the number of words in writing. Let our writers make your life easier...

Words: 273 - Pages: 2

Free Essay

Essay

...I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real essay I’m sorry this is not a real...

Words: 256 - Pages: 2

Premium Essay

Essay

...This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is my essay. This is...

Words: 401 - Pages: 2

Premium Essay

Essay

...Process and Procedure Essay Samples are Helpful Guides in Writing Saturday, June 20th, 2009 Process and Procedure Essay Samples will Assist You in Understanding this Essay Format First of all let’s find out what essay is called process and procedure essay. It is an essay which sometimes called “how to” essay for it guides in certain activities or gives instructions as how to do some job (procedure) or complete a certain task. When you feel difficulty with this essay type, you can find process and procedure essay samples which can give you useful tips into creating an essay which will be have high rating. Process and procedure essay outlining certain procedures or directions to perform certain activity is an important task if one needs to learn how to compile clear instructions to serve the needs of professionals in different fields. These can be helpful for engineers, teachers, doctors and even housewives when it concerns cook books which are also some kind of instructive writing. Procedure essay writing is a useful skills for managerial personnel as they need to organize people and direct them toward certain activities. Process and procedure essay samples can be found online in abundance. Through these essay examples one can get some notion about procedure writing and take some notes how to complete a good piece of process essay. One may note that procedure can include descriptions, warnings and recommendations to the procedures described. To provide guidelines for...

Words: 539 - Pages: 3

Premium Essay

Essay

...Essay Writer can provide students with the exact answers to their essay assignments through our free essay section as well as our custom essay writing services. All of Essay Writer’s free essays are uploaded to our site by some college and university students in the UK to serve as informative guides and comparative templates to help you finish your own essay writing tasks with greater ease and clarity. These sample essays are readily downloadable and very easily accessible; just simply select a subject area or topic from our list of available subjects. You can then go through our list of available essay titles under that subject. Welcome to Essay Writer’s free essays section! You can now access our very extensive collection of free essays. These essays are all original and previously not made available to anyone, and are excellently written and submitted by some well meaning college students who wish to share their knowledge to help you do better in writing your own essays. Below is the list of the subject areas we cover in our free essays section. Simply select the subject that corresponds to your need. You will then be shown a list of all the essay titles available for that specific subject. Essay Writer regularly updates its free essay database. Keep checking back for additional subjects or topics. You may also bookmark our Free Essays page to make it easier to check back on the availability of our free essays. To bookmark this page, simply click on the bookmark...

Words: 314 - Pages: 2

Premium Essay

Essays

...HOW TO READ ESSAYS YOU MUST ANALYZE 1. Take a pencil in your hand. 2. Read the essay over once, quickly, looking for the main idea, for what the essay is about in general, and for what the author seems to be saying. Don't get bogged down in details. (If you come to an unfamiliar word, circle it but go on reading). 3. Check the meaning of unfamiliar words. If they seem to be key words, i.e., if the author uses them more than once, scribble a brief definition at the bottom of the page or at the end of the essay. 4. Now re-read more slowly and carefully, this time making a conscious attempt to begin to isolate the single most important generalization the author makes: his thesis. Follow his line of thought; try to get some sense of structure. The thesis determines the structure, so the structure, once you begin to sense it, can lead you to the thesis. What is the main point the author is making: Where is it? Remember, examples or "for instances" are not main points. The thesis is the generalization the author is attempting to prove valid. Your job, then is to ask yourself, "What is the author trying to prove"? Another way of identifying the thesis is to ask yourself, "What is the unifying principle of this essay"? or "What idea does everything in this essay talk about"? or "Under what single main statement could all the subdivisions fit"? If the author has stated his thesis fully and clearly and all in one place, your job is easier. The thesis is apt to be stated...

Words: 971 - Pages: 4

Premium Essay

Essay

...to write A Level Sociology Essay Assessment With reference to the present AEB syllabus, there are three main skills being assessed in your essays. 1. Knowledge and Understanding (9 marks) 2. Interpretation and Application (9 marks) 3. Evaluation (9 marks) What Does This Mean? What this means is that for writing an essay is that the content (studies, names of researcher, dates, figures, concepts, although important need to be organised coherently, applied to a variety of social situations and interpreted, and expressed in a critical fashion. You must be aware of the skills being highlighted in the question in order to use the appropriate skills in your essays. You should also practice writing essays regularly and develop a technique which addresses the skills required so that you can actually answer the question set. I hope that this handout should allow you to achieve this. Stage One Many students are too quick into diving into an answer. They have focused on certain key terms and ‘assumed’ what the essay requires from a quick look at the question. Instead, the question should be read a number of times. Task One With the title provided. Analyze the question by underlining the key features in the essay title Double underline the skills being assessed, e.g., describe and explain Identify any terms or concepts contained in the question. These terms will need to be defined, i.e. concepts such as interactionists. Essay questions will also include...

Words: 1452 - Pages: 6

Premium Essay

Essay

...from these events? How have they affected your personality or how you deal with situations now? Remember the focus of the essay is on the contrasting impacts of these events in your life. These events do not have to be major events, they could be minor in nature but their impact on you could be great and long lasting. Undertake the task of pre writing for this topic. Select your two events. Describe them in point form. Consider their diverse impacts on your life. By the end of this class you should have completed your pre writing and make sure you get your sheet signed by me. You have the week to work on your first draft. Those of you who would like to show me the first draft are free to submit it to me online and I shall hand them back to you online. I will tell you whether you are on the right track, however this is optional and you will not be penalized if you do not show me your first draft. You need to give me Draft 1 by Tuesday, Feb 26. This will be an online submission under Assignments on ilearn. I will correct it and give it back to you by Sunday March 3, and then you will work on changing the draft according to my corrections and bring it to class on Tuesday, March 5 when we will have a peer review session. So after our class today you need to upload your first drafts of the essay in a week, by Feb 26 in an area marked out as Essay 1 under Assignments on Ilearn. You need to exchange your second drafts with two of your classmates on Tuesday, March...

Words: 547 - Pages: 3

Premium Essay

Essay

...tutorial x 13 weeks)     Level: Foundation/Matriculation     Lecturers: Ms Fazidah Abdul Jamil., Mdm Goh Wan Chen, Ms Saratha Thevi Ramasamy, Ms Norzaireen Shamsul Kamar Synopsis: This course is designed for students who require the necessary skills for tertiary studies. Some basic grammatical concepts are taught and students are to apply them in their writing. Writing will focus on the development of coherent paragraphs. Reading skills will cover such strategies as scanning, skimming, main ideas, contextual clues and inferences. Learning Outcomes: Upon completion of this subject, student will be able to: 1. write summaries as well as process, comparison-contrast and cause-effect essays 2. apply basic grammatical concepts in writing 3. answer questions based on academic texts 4. give oral presentations Textbook: 1. Daise, D., Norloff, C., and Carne, P., (2011). Q: Skills for Success 4 : Reading and Writing Oxford University Press, UK 2. Paterson, K, and Wedge, R., (2013). Oxford Grammar for EAP. Oxford University Press, UK Recommended References: Cambridge International Dictionary of English (1997), Cambridge University Press, UK Mode of Assessment: [1] Class participation 5% [2] Quiz 1 15% [3] Quiz 2 10% [4] Oral Presentation 10% [5] Mid-Term Examination 20% [6] Final Examination 40% Syllabus – FDENG001 |Week |UNIT |Topics ...

Words: 469 - Pages: 2

Premium Essay

Essay

...Define Your Thesis For essays that are part of an Early Years Care & Education Degree, it is important to clearly define a thesis statement within the first paragraph of the essay. Even if you are given a topic to write, such as the importance of preschool classes in low-income neighborhoods, you need to develop a strong thesis in your own words. Here is an example: "Preschool classes in low-income neighborhoods are a crucial step in helping all children enter elementary school at the same educational level, regardless of the income of the family." Once you have defined a clear thesis, you can proceed to the rest of your essay. However, without a clear thesis, your essay will not hold up. Use Examples The majority of your essay should be a careful and clear argument that supports your thesis statement. Do research and cite as many examples as possible to prove your point. For an essay about the merits of all-day educational opportunities for preschool-aged children, check trustworthy sources such as the National Association for the Education of Young Children and national PTA. Provide each point in a strong and complete paragraph. Each paragraph should have a main statement, supporting information and a conclusion. Tie In Conclusion After you have made your argument, state your conclusion in a clear and concise manner. Whether you have proven that the teacher ratio in a preschool setting should be lower than 4 to 1 or made a case for more national funding for the education...

Words: 281 - Pages: 2

Free Essay

Essay

...Carmen Hollow Mr. Beurskens College English Critique Essay: The Morals of the Prince May 3, 2011 The Grey Area between Good and Evil: A Critique of “The Morals of the Prince” by Niccolo Machiavelli Introduction We’ve all made a promise that we couldn’t keep and we have all felt bad about breaking those promises. Whether it was a promise to our parents, our children or a co-worker, we don’t feel good about it, but sometimes it can’t be helped. Usually if we couldn’t keep a promise it was for a good reason and not a selfish one. To the person that we made the promise to, we may be viewed as uncaring or unreliable, but to ourselves we know that we had to make a decision that could hurt someone but at the same time our decision could help that same person or persons. Making a promise and not being able to keep it for one reason or another, is one of the few topics that Machiavelli writes of in his essay “The Morals of the Prince”. He also tells why he believes a prince should be feared rather than loved, and why a prince should be stingy and not generous. He wants us to know how a “perfect” prince should act and behave so that the prince will be viewed upon as a great prince. Summary Machiavelli writes about how he believes a prince should act and behave to be considered a successful prince, one that is loved and feared, liberal and stingy, one that knows when to keep his word and when to break it. In his essay, Machiavelli writes “a prince who wants to keep his post...

Words: 1138 - Pages: 5

Premium Essay

Essay

...Basic techniques for generating ideas. Brainstorming. Brainstorming consists in writing series of words or sentences just as they flow from our mind, although they have no logical order or connections. Once the words are written down, we have to establish relationships among them. This is the embryo of the future text. Free writing. Free writing is a similar technique to the brainstorming. Consists in writing a text without previous decisions or ideas about how we want to write it. Just choosing a topic and writing about it, and then we can summarise the main ideas. Organisation of information. There are some basic rules for writing a well - structured text. The text should be organised in a clear way; it must not be a twisted or an incomprehensible lot of ideas. We have to try to write according to certain conventions about hoe the text is organised. We have to structure our text in paragraphs. Each paragraph must express one idea. Some rules referring to the paragraphs: A paragraph must be clearly separated from other paragraphs, either by an empty line or by indenting the first line, or both. There must be no blank spaces or half-empty lines inside the paragraph. A paragraph in academic prose does not begin with a dot, a line or a kind of mark, except in special circumstances. Each body paragraph must normally have a topic sentence, and more than one sentence. Types of paragraphs. The introductory paragraph. There must be at least one...

Words: 1285 - Pages: 6