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腐乳之殇
热度 10 bxlh2008 2015-2-9 12:00
腐乳之殇 文/杨国力 导读 : 台湾近日食品安全问题不断,地沟油风波刚刚消停,又出现腐乳非法添加的问题,香港环署食物安全中心在2015年1月6日宣布,台湾一款腐乳查出含有非食用染料二甲基黄。什么是二甲基黄,腐乳中又存在哪些安全隐患。 腐乳是中国流传数千年的传统民间美食,被西方人誉为“东方奶酪”,其是一种将豆腐利用霉菌发酵、腌制,二次加工的豆制食品,在中国大陆、台湾地区及东南亚特别盛行。腐乳起源于北魏末年,当时就有古书记载腐乳简单的制作方法“干豆腐加盐成熟后为腐乳”,在明代就有大量史书记载腐乳的各种制作方法,《本草纲目拾遗》记载:“腐乳又名为菽乳,以豆腐腌过加酒糟或酱制者,味咸甘心”;清朝,关于腐乳的史料更加详实,不仅制作工艺大有改进,并且还有关于腐乳保健方面的介绍,如关于腐乳种类的《随园食单》“广西白腐乳”,关于腐乳详细的制作工艺《湖雅》“腐乳:豆腐腌霉为腐乳胚,出黑镇酱肆,取坯制成腐乳”,关于保健方面的《饮食谱》“腐干而再造者为腐乳,陈久愈佳,最宜病人”。 腐乳通常分为青方、红方和白方三大类,臭豆腐属于青方,是指在腌制过程中加入苦浆水、盐水;大块、红辣、玫瑰等酱腐乳属于红方,是因为在腌制过程中加入红曲色素;甜辣、桂花、五香等属于白方,是在生产过程中不加红曲色素,保持本色。另外还有添加糟米,成为糟方,添加黄酒称为醉方,添加芝麻、玫瑰等称为花方。 腐乳中的微生物世界 腐乳通常使用毛霉菌发酵,如北京著名的王致和腐乳,另外还有风味独特的黑龙江克东腐乳,其是采用小球菌进行发酵的,色泽鲜艳,质地细腻柔软,味道鲜美绵长。 虽然各地腐乳品种繁多,配料不同,但是制作原理基本相同,都是先将大豆通过浸泡、磨浆、滤浆、煮浆、点浆、养花、压榨等工序制作成豆腐,然后压坯切成小块,摆在木盘中接入菌种(蛋白酶活力很强的毛霉菌、根酶、小球菌、枯草芽孢杆菌等)进入发酵和腌坯阶段,等发酵完成后,根据不同品种加入红曲霉、酵母菌、米曲霉等进行密封贮藏阶段,腐乳所有鲜美的风味都是在发酵和贮藏阶段形成的,这期间腐乳中的微生物世界也是多姿多彩,此消彼长,造就了一罐风味独特的腐乳。 接下来我们便进入腐乳中的微生物世界,看看这些小精灵是如何使豆腐块变成鲜美乳腐的神奇过程。在前发酵阶段,接种在豆腐坯上的“小精灵”(毛霉菌、根酶、小球菌或枯草芽孢杆菌等)在合适的条件下迅速攻城略地,占领有利的位置,快速的繁殖,很快毛霉菌或根酶的菌丝便相互交织在一起形成厚密洁白的菌丝层,菌丝上挂着蒸发的水珠,犹如爱丽丝仙境,这些小精灵不仅积累了大量的兵员,也准备了大量的粮草——蛋白酶,使这些豆腐坯“城池”水解为水溶性蛋白质,为后发酵风味的形成奠定了基础;发酵成熟后的一块块“城池”被分开装入坛中,小精灵们也被迫的分家了,经过盐腌后,加入酒、香辛调味料,便进入了最重要的后熟阶段,在这里盐保护了小精灵的家园,使腐乳坯及菌丝收缩,坯体变硬,菌丝形成被膜,保护了腐乳坯,盐如同腐乳坯的保护罩,防止杂菌攻陷小精灵的“城池”,也使蛋白酶作用缓慢,防止内部出现“哗变”,在还没形成香气的时候,腐乳坯就已经糜烂;酒也是小精灵的好帮手,抑制杂菌的攻击,使蛋白酶迟钝,合成芳香的酯类;最后经过漫长的后发酵,色泽鲜明、风味独特的腐乳便形成了。 腐乳中存在的安全问题 腐乳营养价值很高,高蛋白、低饱和脂肪酸、不含胆固醇,并且还含有大豆异黄酮,是不错的健康食品,但是却存在安全问题,香港环署食物安全中心在 2015 年 1 月 6 日宣布,台湾一款腐乳查出含有非食用染料二甲基黄。 二甲基黄是何物?二甲基黄是一种酸碱指示剂,工业用油溶性染色剂,具有神经及生殖毒性,长期摄入二甲基黄会增加罹患肝癌、肺癌及膀胱癌的风险,国际癌症研究署( IARC )将其列为 2B 级致癌物,被严格禁止在食品行业用于食品添加剂。为什么要使用二甲基黄,而不用其他合法的着色剂呢?这是因为食用色素是水溶性色素,不容易着色,使腐乳产品品相差,而二甲基黄是油溶性的,加入乳化剂可以令腐乳有好看的品相。在腐乳类允许使用的添加剂有哪些呢?红曲米(红曲红)可以作为着色剂在腐乳类按生产需要适量使用,甜蜜素可以作为甜味剂在腐乳类按照规定( 0.65g/kg )使用。 臭豆腐乳又称为青方,有媒体报道称不法商贩采用绿矾(硫酸亚铁)和硫化钠快速生产臭豆腐,比传统的苋菜梗发酵卤汁制成的臭豆腐快很多。绿矾、硫化钠和发酵物形成的卤汁快速使臭豆腐上味着色,硫酸亚铁在 GB 14880-2012 中可以作为食品营养强化剂添加在豆腐类食品中,最大添加量为 200~400mg/kg ,然而不法商贩为了利益采用便宜的化工级的绿矾来处理臭豆腐,含有的重金属会对身体造成危害;作为违法添加的非食用物质硫化钠会在消化道被分解出硫化氢,造成硫化氢中毒。 除过非法添加的硫化物,臭豆腐自身也会产生一些硫化物,这也是臭味的来源,臭豆腐乳中的胱氨酸、蛋氨酸及半胱氨酸等在毛霉菌的作用下产生容易气化的硫化氢分子等,产生硫臭和氨臭。臭水中含有较高的硫化物,但是在腐乳中的溶解性无机硫化物含量很低,不至于对身体造成严重的危害,无需特别担心,视臭豆腐乳为洪水猛兽。 腐乳是中国优良的传统小吃,味道鲜美,风味独特,质地细腻,营养丰富,老少咸宜。不能因为不法厂商的非法行为造成“腐乳之殇”,让腐乳从我们这一代人手中消失殆尽。
个人分类: 科普创作|13116 次阅读|14 个评论
Publish or perish下教授之殇
热度 59 outcrop 2014-12-3 18:10
Imperial College London的Stefan Grimm教授逝去了,邮件系统在他逝去之后,按照他的设定,自动群发了一封题为“How Professors are treated at Imperial College”的邮件;读完让人唏嘘。为了保持原汁原味,我就直接引用英文。 在国内不断学习西方科研体制的时候,也许这是一个警钟。邮件原文如下: From: Stefan Grimm professorstefangrimm@gmail.com Date: 21 October 2014 23:41:03 BST To: big-email-list Subject: How Professors are treated at Imperial College Dear all, If anyone is interested how Professors are treated at Imperial College: Here is my story. On May 30th ’13 my boss, Prof Martin Wilkins, came into my office together with his PA and ask me what grants I had. After I enumerated them I was told that this was not enough and that I had to leave the College within one year – “max” as he said. He made it clear that he was acting on behalf of Prof Gavin Screaton, the then head of the Department of Medicine, and told me that I would have a meeting with him soon to be sacked. Without any further comment he left my office. It was only then that I realized that he did not even have the courtesy to close the door of my office when he delivered this message. When I turned around the corner I saw a student who seems to have overheard the conversation looking at me in utter horror. Prof Wilkins had nothing better to do than immediately inform my colleagues in the Section that he had just sacked me. Why does a Professor have to be treated like that? All my grant writing stopped afterwards, as I was waiting for the meeting to get sacked by Prof Screaton. This meeting, however, never took place. In March ’14 I then received the ultimatum email below. 200,000 pounds research income every year is required. Very interesting. I was never informed about this before and cannot remember that this is part of my contract with the College. Especially interesting is the fact that the required 200,000.- pounds could potentially also be covered by smaller grants but in my case a programme grant was expected. Our 135,000.- pounds from the University of Dammam? Doesn’t count. I have to say that it was a lovely situation to submit grant applications for your own survival with such a deadline. We all know what a lottery grant applications are. There was talk that the Department had accepted to be in dept for some time and would compensate this through more teaching. So I thought that I would survive. But the email below indicates otherwise. I got this after the student for whom I “have plans” received the official admission to the College as a PhD student. He waited so long to work in our group and I will never be able to tell him that this should now not happen. What these guys don’t know is that they destroy lives. Well, they certainly destroyed mine. The reality is that these career scientists up in the hierarchy of this organization only look at figures to judge their colleagues, be it impact factors or grant income. After all, how can you convince your Department head that you are working on something exciting if he not even attends the regular Departmental seminars? The aim is only to keep up the finances of their Departments for their own career advancement. These formidable leaders are playing an interesting game: They hire scientists from other countries to submit the work that they did abroad under completely different conditions for the Research Assessment that is supposed to gauge the performance of British universities. Afterwards they leave them alone to either perform with grants or being kicked out. Even if your work is submitted to this Research Assessment and brings in money for the university, you are targeted if your grant income is deemed insufficient. Those submitted to the research assessment hence support those colleagues who are unproductive but have grants. Grant income is all that counts here, not scientific output. We had four papers with original data this year so far, in Cell Death and Differentiation, Oncogene, Journal of Cell Science and, as I informed Prof Wilkins this week, one accepted with the EMBO Journal. I was also the editor of a book and wrote two reviews. Doesn’t count. This leads to a interesting spin to the old saying “publish or perish”. Here it is “publish and perish”. Did I regret coming to this place? I enormously enjoyed interacting with my science colleagues here, but like many of them, I fell into the trap of confusing the reputation of science here with the present reality. This is not a university anymore but a business with very few up in the hierarchy, like our formidable duo, profiteering and the rest of us are milked for money, be it professors for their grant income or students who pay 100.- pounds just to extend their write-up status. If anyone believes that I feel what my excellent coworkers and I have accomplished here over the years is inferior to other work, is wrong. With our apoptosis genes and the concept of Anticancer Genes we have developed something that is probably much more exciting than most other projects, including those that are heavily supported by grants. Was I perhaps too lazy? My boss smugly told me that I was actually the one professor on the whole campus who had submitted the highest number of grant applications. Well, they were probably simply not good enough. I am by far not the only one who is targeted by those formidable guys. These colleagues only keep quiet out of shame about their situation. Which is wrong. As we all know hitting the sweet spot in bioscience is simply a matter of luck, both for grant applications and publications. Why does a Professor have to be treated like that? One of my colleagues here at the College whom I told my story looked at me, there was a silence, and then said: “Yes, they treat us like sh*t”. Best regards, Stefan Grimm 来自: http://www.dcscience.net/2014/12/01/publish-and-perish-at-imperial-college-london-the-death-of-stefan-grimm/ 学校于是展开了对其死亡的调查,相关报道如下: Imperial College London has launched an investigation into the treatment of one of its academics, who was found dead after telling colleagues that he felt under intense pressure from the university. Stefan Grimm, professor of toxicology in the Faculty of Medicine, was found dead in Northwood, Middlesex, in September. Two academics who knew the 51-year-old have now said that he had complained of being put under undue pressure by the university in the months leading up to his death and that he had been placed on performance review, according to Times Higher Education. Professor Grimm is understood to have been unsuccessful in a number of grant applications and to have been told that his job would be at risk unless this situation improved. The academics said the professor felt let down by Imperial College. A spokeswoman said the college would provide “all the assistance it can” to the investigation into Professor Grimm’s death. She added that the university had launched an investigation to see if “wider lessons” could be drawn. 来自: http://www.independent.co.uk/news/uk/home-news/university-inquiry-into-professor-stefan-grimms-death-9891687.html 这件事只是冰山一角,科研体制问题,无论中外,也许值得进一步的探讨和完善。 延伸阅读 Publish or Perish过分应用把科学家搞Perish
个人分类: 科学网大学|49824 次阅读|148 个评论

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