卡拉胶
卡拉胶（ 或 ； ，CAS 9000-07-1），又称鹿角菜胶、角叉菜胶、爱尔兰苔菜胶，是一組从海洋红藻（包括角叉菜属、麒麟菜属、杉藻属及沙菜属等）中提取的線性多糖的统称。這些多糖體由於能夠與食物中的蛋白質穩定結合，所以被廣泛應用於食品产业，例如：作为凝固剂、增稠剂或稳定剂，用於奶類及肉類產品。
卡拉胶的名字来源于爱尔兰苔菜（"Chondrus crispus"，也称角叉菜）在愛爾蘭語的称呼"，原來的意思是指「小石塊」。這種植物作為食品添加劑使用早於15世紀已經開始。卡拉膠是素食主義 及維根主義支持者對明膠使用的另類選擇，因為在甜品中經常使用的明膠是動物製品。
当用于食品时，在包装的卡拉胶以欧洲联盟的E編碼E407（藻酸盐）表示。
卡拉胶是一種无臭、无味的大型（分子量在10万道尔顿以上）的高度彈性分子，相互卷曲在一起形成双螺旋结构。卡拉胶具有亲水性、粘性、稳定性，溶于80摄氏度热水形成粘性透明液体，并能在室温下形成不同形式的凝胶。這使食品工業及其他產業亦廣泛使用卡拉胶作及稳定剂。
All carrageenans are high-molecular-weight polysaccharides made up of repeating galactose units and 3,6 anhydrogalactose (3,6-AG), both sulfated and nonsulfated. The units are joined by alternating α-1,3 and β-1,4 糖苷键。
商業應用的卡拉胶以下列三个类型為主：
影響到這三個類型卡拉膠在其特質上的主要差異在於其硫酸酯在重複性半乳糖單位的位置與數量。
下面是卡拉胶应用的一些例子：
In the U.S., carrageenan is allowed under FDA regulations as a direct food additive and is considered 公认安全 when used in the amount necessary as an emulsifier, stabilizer, or thickener in foods, except those standardized foods that do not provide for such use. FDA also reviewed carrageenan safety for infant formula. The European Food Safety Authority concluded "there is no evidence of any adverse effects in humans from exposure to food-grade carrageenan, or that exposure to degraded carrageenan from use of food-grade carrageenan is occurring", Furthermore, the stated in a July 2014 review of carrageenan "that the use of carrageenan in infant formula or formula for special medical purposes at concentrations up to 1000 mg/L is not of concern".
Although the (NOP) had added carrageenan to its National List of additives allowed to be included in organic foods in 2003, and reviewed and reauthorized it in 2008, noting it as "critical to organic production and handling operations", on November 18, 2016 the NOP's (NOSB) voted to recommend carrageenan be removed from the National List of additives allowed in organic food production.
On April 4, 2018 the (AMS) (美国农业部) published a document to announce the renewal of carrageenan on the National List, allowing its continued use in food products. The document states, “The NOSB recommended removing carrageenan because they determined that alternative materials, such as gellan gum, guar gum, or xanthan gum, are available for use in organic products” continuing, “AMS found sufficient evidence in public comments to the NOSB that carrageenan continues to be necessary for handling agricultural products because of the unavailability of wholly natural substitutes (§ 6517(c)(1)(ii)). Carrageenan has specific uses in an array of agricultural products, and public comments reported that potential substitutes do not adequately replicate the functions of carrageenan across the broad scope of use. Therefore, carrageenan continues to meet the OFPA criteria for inclusion on the National List.” The rule went into effect May 29, 2018.
In the most recent review by an independent panel, the Joint Expert Committee of the 联合国粮食及农业组织 of the 联合国 and 世界卫生组织 on Food Additives released a technical report in 2015 on the use of carrageenan in 配方奶粉 and found that the additive was ‘not of concern’ in infant formula as food for special medical purposes at concentrations up to 1000 千克s per 公升. The use of carrageenan in infant formula, organic or otherwise, is prohibited in the EU for precautionary reasons, but is permitted in other food items.
In the UK, the issued a product recall for sweets containing carrageenan, stating that carrageenan “is not permitted as an ingredient in jelly confectionery products as it presents a choking hazard”.
Degraded carrageenan () has been found to cause inflammation of the gut, altering microbiota, and was found to be a triggering factor of inflammatory bowel diseases such as ulcerative colitis and Crohn Disease.
Food-grade carrageenan has been confused with poligeenan, although they are completely different products, creating a controversy over the food-additive's safety. Food-grade carrageenan's safety has been proven through various studies.