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airport was built during the war, but for some reason it could not be used then. Last year, however, it came into use. Over a hundred people must have been driven away from their homes by the noise. I am one of the few people left. Sometimes I think this house will be knocked down by a passing plane. I have been offered a large sum of money to go away, but I am determined to stay here. Everybody says I must be mad and they are probably right.Lesson22 A glass envelope 玻璃信封My daughter, Jane, never dreamed of receiving a letter from a girl of her own age in Holland. Last year, we were travelling across the Channel and Jane put a piece of paper with her name and address on it into a bottle. She threw the bottle into the sea. She never thought of it again, but ten months later, she received a letter from a girl in Holland. Both girls write to each other regularly now. However, they have decided to use the post-office. Letters will cost a litt1e more, but they will certainly travel faster. Lesson23 A new house 新居I had a letter from my sister yesterday. She lives in Nigeria. In her letter, she said that she would come to England next year. If she comes, she will get a surprise. We are now living in a beautiful new house in the country. Work on it had begun before my sister left. The house was completed five months ago. In my letter, I told her that she could stay with us. The house has many large rooms and there is a lovely garden. It is a very modern house, so it looks strange to some people. It must be the only modern house in the district.Lesson24 It could be worse 不幸中之萬幸I entered the hotel managers office and sat down. I had just lost &50 and I felt very upset. I left the money in my room, I said, and its not there now. The manager was sympathetic, but he could do nothing. Everyones losing money these days, he said. He started to complain about this wicked world but was interrupted by a knock at the door. A girl came in and put an envelope on his desk. It contained &5o. I found this outside this gentlemans room she said. Well, I said to the manager, there is still some honesty in this world !lesson25 Do the English speak English? 英國人講的是英語嗎？I arrived in London at last. The railway station was big, black and dark. I did not know the way to my hotel, so I asked a porter. I not only spoke English very carefully, but very clearly as well. The porter, however, could not understand me; I repeated my question several times and at last he understood. He answered me, but he spoke neither slowly nor clearly. I am a foreigner, I said. Then he spoke slowly, but I could not understand him. My teacher never spoke English like that! The porter and I looked at each other and smiled. Then he said something and I understood it. Youll soon learn English! he said. I wonder. In England, each man speaks a different language. The English understand each other, but I dont understand them ! Do they speak English ?lesson26 The best art critics 最佳美術評論家I am an art student and I paint a lot of pictures. Many people pretend that they understand modern art. They always tell you what a picture is about. Of course, many pictures arc not about anything. They are just pretty patterns. We like them in the same way that we like pretty curtain material. I think that young children often appreciate modern pictures better than anyone else. They notice more. My sister is only seven, but she always tells me whether my pictures are good or not. She came into my room yesterday. What are you doing ? she asked. Im hanging this picture on the wall, I answered. Its a new one. Do you like it ? She looked at it critically for a moment. Its all right, she said, but isnt it upside-down ? I looked at it again. She was right! It was!Lesson27 A wet night 雨夜Late in the afternoon, the boys put up their tent in the middle of a field. As soon as this was done, they cooked a meal over an open fire. They were all hungry and the food smelt good. After a wonderful meal, they told stories and sang songs by the camp fire. But some time later it began to rain. The boys felt tired so they pet out the fire and crept into their tent. Their sleeping-bags were warm and comfortable, so they all slept soundly. In the middle of the night, two boys woke up and began shouting. The tent was full of water! They all leapt out of their sleeping-bags and hurried outside. It was raining heavily and they found that a stream had formed in the field. The stream wound its way across the field and then flowed right under their tent!Lesson28 No parking 禁止停車Jasper White is one of those rare people who believes in ancient myths. He has just bought a new house in the city, but ever since he moved in, he has had trouble with motorists. when he returns home at night, he always finds that someone has parked a car outside his gate. Because of this, he has not been able to get his own car into his garage even once. Jasper has put up No Parking signs outside his gate, but these have not had any effect. Now he has put an ugly stone head over the gate. It is one of the ugliest faces I have ever seen. I asked him what it was and he told me that it was Medusa, the Gorgon. Jasper hopes that she will turn motorists to stone. But none of them has been turned to stone yet!Lesson29 Taxi! 出租汽車！Captain Ben Fawcett has bought an unusual taxi and has begun a new service. The taxi is a small Swiss aeroplane called a Pilatus Porter. This wonderful plane can carry seven passengers. The most surprising thing about it, however, is that it can land anywhere: on snow, water, or even on a ploughed field. Captain Fawcetts first passenger was a doctor who flew from Birmingham to a lonely village in the Welsh mountains. Since then, Captain Fawcett has flown passengers to many unusual places. Once he landed on the roof of a block of flats and on another occasion, he landed in a deserted car park. Captain Fawcett has just refused a strange request from a businessman. The man wanted to fly to Rockall, a lonely island in the Atlantic Ocean, but Captain Fawcett did not take him because the trip was too dangerous.Lesson30 Football or polo? 足球還是水球？The Wayle is a small river that cuts across the park near my home. I like sitting by the Wayle on fine afternoons. It was warm last Sunday, so I went and sat on the river bank as usual. Some children were playing games on the bank and there were some people rowing on the river. Suddenly, one of the children kicked a ball very hard and it went towards a passing boat. Some people on the bank called out to the man in the boat, but he did not hear them. The ball struck him so hard that he nearly fell into the water. I turned to look at the children, but there werent any in sight: they had all run away! The man laughed when he realized what had happened. He called out to the children and threw the ball back to the bank. Lesson31 Success story 成功者的故事Yesterday afternoon Frank Hawkins was telling me about his experiences as a young man. Frank is now the head of a very large business company, but as a boy he used to work in a small shop. It was his job to repair bicycles and at that time he used to work fourteen hours a day. He saved money for years and in 1938 he bought a small work-shop of his own. During the war Frank used to make spare parts for aeroplanes. At that time he had two helpers. By the end of the war, the small work-shop had become a large factory which employed seven hundred and twenty-eight people. Frank smiled when he remembered his hard early years and the long road to success. He was still smiling when the door opened and his wife came in. She wanted him to repair their sons bicycle! Lesson32 Shopping made easy 購物變得很方便People are not so honest as they once were. The temptation to steal is greater than ever before--especially in large shops. A detective recently watched a well-dressed woman who always went into a large store on Monday mornings. One Monday, there were fewer people in the shop than usual when the woman came in, so it was easier for the detective to watch her. The woman first bought a few small articles. After a little time, she chose one of the most expensive dresses in the shop and handed it to an assistant who wrapped it up for her as quickly as possible. Then the woman simply took the parcel and walked out of the shop without paying. When she was arrested, the detective found out that the shop-assistant was her daughter. The girl gave her mother a free dress once a week !lesson33 Out of the darkness 沖出黑暗Nearly a week passed before the girl was able to explain what had happened to her. One afternoon she set out from the coast in a small boat and was caught in a storm. Towards evening, the boat struck a rock and the girl jumped into the sea. Then she swam to the shore after spending the whole night in the water. During that time she covered a distance of eight miles. Early next morning, she saw a light ahead. She knew she was near the shore because the light was high up on the cliffs. On arriving at the shore, the girl struggled up the cliff towards the light she had seen. That was all she remembered. When she woke up a day later, she found herself in hospital.Lesson34 Quick work 破案“神速”Ted Robinson has been worried all the week. Last Tuesday he received a letter from the local police. In the letter he was asked to call at the station. Ted wondered why he was wanted by the police, but he went to the station yesterday and now he is not worried any more. At the station, he was told by a smiling policeman that his bicycle had been found. Five days ago, the policeman told him, the bicycle was picked up in a small village four hundred miles away. It is now being sent to his home by train. Ted was most surprised when he heard the news. He was amused too, because he never expected the bicycle to be found. It was stolen twenty years ago when Ted was a boy of fifteen !Lesson35 Stop thief! 捉賊！Rov Trenton used to drive a taxi. A short while ago, however, he became a bus-driver and he was not regretted it. He is finding his new work far more exciting. When he was driving along Catford Street recently, he saw two thieves rush out of a shop and run towards a waiting car. One of them was carrying a bag full of money. Roy acted quickly and drove the bus straight at the thieves. The one with the money got such a fright that he dropped the bag. As the thieves were trying to get away in their car, Roy drove his bus into the back of it. While the battered car was moving away, Roy stopped his bus and telephoned the police. The thieves car was badly damaged and easy to recognize. Shortly afterwards, the police stopped the car and both men were arrested. Lesson36 Across the Channel 橫渡海峽Erna Hart is going to swim across the English Channel tomorrow. She is going to set out from the French coast at five oclock in the morning. Erna is only fourteen years old and she hopes lo set up a new world record. She is a strong swimmer and many people feel that she is sure to succeed. Ernas father will set out with her in a small boat. Mr Hart has trained his daughter for years. Tomorrow he will be watching her anxiously as she swims the long distance to England. Erna 年產(chǎn)10萬噸酸奶設計說明書 目　錄 一、設計說明書 第一章 總論 第一節(jié) 前言…………………………………………………………………1 第二節(jié) 建設規(guī)模及產(chǎn)品方案………………………………………………2 第三節(jié) 廠址選擇概述………………………………………………………4 第四節(jié) 總平面布置情況……………………………………………………………5 第二章 工藝設計 第一節(jié) 工藝流程設計………………………………………………………6 第二節(jié)　物料衡算……………………………………………………………11 第三節(jié)　車間設備選型………………………………………………………14 第四節(jié)　主要生產(chǎn)車間設計…………………………………………………15 二、附件 圖1　總平面設計圖……………………………………………………附圖1 圖2　設備工藝流程圖…………………………………………………附圖2 圖3　生產(chǎn)車間設備布置圖……………………………………………附圖3 表1　設備選擇表……………………………………………………………………17 表2　物料衡算表……………………………………………………………………17 一、設計說明書 第一章 總論 第一節(jié) 前言 1.1 酸奶簡介 民以食為天，食以乳為先。牛乳自古以來即被人類飲用，牛乳的組成最為接近人乳，含有人體所需要的全部營養(yǎng)成分，營養(yǎng)最為均衡，在人們的膳食結(jié)構中具有其他食品無法替代的地位和作用。由鮮牛乳發(fā)酵成的酸乳由于其豐富的營養(yǎng)、特殊的風味、爽滑的質(zhì)構和良好的生理功能，備受人們青睞。聯(lián)合國糧農(nóng)組織（FAO）、世界衛(wèi)生組織（WHO）與國際乳品聯(lián)合會（IDF）于1977年對酸乳作出如下定義：酸乳，即在添加（或不添加）乳粉（或脫脂乳粉）的乳（殺菌乳或濃縮乳）中，由保加利亞乳桿菌和嗜熱乳酸鏈球菌進行乳酸發(fā)酵制成的凝乳狀產(chǎn)品，成品中必須含有大量的、相應的活性微生物。通常根據(jù)酸乳成品的組織狀態(tài)來進行分類，具體可分為凝固型酸乳（發(fā)酵過程在包裝容器中進行，從而使成品因發(fā)酵而保留其均勻一致的凝乳狀態(tài)）、攪拌型酸乳（成品先發(fā)酵后灌裝而得，發(fā)酵后的凝乳已在灌裝前和灌裝過程中攪碎而成黏稠且均勻的半流動狀態(tài)）和飲用型酸乳（類似攪拌型酸奶，但包裝前凝塊被分散成液體）。飲用酸乳制品對身體有很多益處，乳中許多成分具有很高的營養(yǎng)價值，而且微生物菌群產(chǎn)生的許多代謝產(chǎn)物對人體也極為有益。⑴營養(yǎng)作用：牛奶中乳糖經(jīng)乳酸菌發(fā)酵，其中20%～30%被分解為葡萄糖和半乳糖。前者進一步轉(zhuǎn)化為乳酸或其他有機酸，這些有機酸有益于身體健康；后者被人吸收利用，可參與幼兒腦苷脂和神經(jīng)物質(zhì)的合成，并有利于提高乳脂肪的利用率。牛奶中的蛋白質(zhì)經(jīng)發(fā)酵作用后，乳蛋白變成微細的凝乳粒，易于被人消化吸收。酸奶中的磷、鈣和鐵易被吸收，有利于防止嬰兒佝僂病和老人骨質(zhì)疏松病。牛奶中的脂肪經(jīng)乳酸菌作用后，發(fā)生解離或酯鍵被破壞，易于被機體吸收。發(fā)酵過程中，乳酸菌還會產(chǎn)生人體所必需的維生素B1、維生素B2、維生素B6、維生素B12、煙酸和葉酸等營養(yǎng)物質(zhì)。⑵緩解乳糖不耐癥：乳酸菌產(chǎn)生的乳糖酶能降解牛奶中的乳糖，因此乳糖不耐癥患者飲用酸奶就不會出現(xiàn)飲用牛奶時發(fā)生的乳糖不耐癥，如腹脹、腹痛、腸道痙攣、下瀉等。⑶整腸作用：人體腸道內(nèi)存在有益菌群和有害菌群。在人體正常情況下，前者占優(yōu)勢；當人患病時，有害菌群占優(yōu)勢。飲用酸奶可以維持有益菌群的優(yōu)勢。⑷抑菌作用：嗜熱乳桿菌和雙歧桿菌不受胃液和膽汁的影響，可以進入腸道，在腸道內(nèi)存留較長時間。這兩種乳酸菌以及在這些乳酸菌影響下生長起來的腸道中的其他乳酸菌，可以產(chǎn)生嗜熱乳菌素等抗菌物質(zhì)，這些物質(zhì)大都對大腸桿菌、沙門氏菌和金黃色葡萄球菌等有明顯的抑菌作用。⑸改善便秘作用：進入腸道中的活的乳酸菌能產(chǎn)生乳酸、醋酸等有機酸。這些有機酸有刺激腸道，加強蠕動的作用，故可以改善便秘。⑹降低膽固醇：牛乳中的乳清酸、乳糖和鈣，以及酸奶中存在的羥基戊二酸都有降低膽固醇的作用。⑺抗癌作用：酸奶有抑制3種酶的活性作用，這些酶能引起癌變。另外，酸奶還能激活巨噬細胞，抑制腫瘤細胞，從而起到抗癌作用。 1.2 酸奶的發(fā)展前景 盡管目前我國的乳業(yè)市場不斷擴大，乳品消費觀念在不斷提高，但我國年人均乳制品不足20kg的消費量與世界人均100kg、發(fā)達國家人均140kg的消費量相比還有較大差距。中國的乳品消費在整體上并沒有進入完全理性的軌道。由于營養(yǎng)知識的欠缺，許多人不了解乳品對改善營養(yǎng)、平衡膳食、補鈣和增強體質(zhì)的重要作用，包括對酸乳的認識也不夠，因而市場占有率也不太高，不過隨著人們對酸乳營養(yǎng)價值的認識，人們對酸奶的態(tài)度發(fā)生了改變，市場占有份額也逐年增加。隨著我國居民生活水平和消費觀念的轉(zhuǎn)變，酸奶的消費在以后的較長時間內(nèi)仍舊會保持迅速的增長勢頭，這種超常的增長速度在全球酸奶發(fā)展史上是非常罕見的，市場前景極為廣闊。 1.3 本次設計范圍 本設計主要是年產(chǎn)10萬噸酸奶廠車間的工藝設計。設計范圍包括廠址選擇，制定產(chǎn)品方案，各產(chǎn)品工藝流程的確定，工藝論證，根據(jù)物料衡算進行設備選型，對水、電、汽等生產(chǎn)車間必備的生產(chǎn)要素的配給和優(yōu)化，企業(yè)組織及勞動力組成，全廠輔助設施及公用系統(tǒng)，車間生產(chǎn)工藝流程圖、車間平面布置圖、工廠總平面布置圖各一張，經(jīng)濟核算及效益分析。 第二節(jié) 建設規(guī)模及產(chǎn)品方案 2.1 生產(chǎn)規(guī)模 年產(chǎn)10萬噸酸奶。 2.2 產(chǎn)品方案 2.2.1 產(chǎn)品方案確定說明 本設計根據(jù)產(chǎn)品的種類、包裝種類和各產(chǎn)品的產(chǎn)量，并且符合生產(chǎn)向機械化、自動化、連續(xù)化發(fā)展方向的要求，最終確定了本設計的產(chǎn)品方案。 由于酸奶工廠原料基本采用奶牛當日產(chǎn)的牛乳，并且酸奶是消費者每日飲用的產(chǎn)品，因此酸奶工廠全年沒有停產(chǎn)時間，按照365日計算。為平衡每月生產(chǎn)的產(chǎn)量，避免出現(xiàn)部分月停產(chǎn)，部分月加工任務過于繁重，結(jié)合主要加工酸奶的品種成熟時間情況，初步安排產(chǎn)品生產(chǎn)方案如下（注每月以30天計）：其中玻璃瓶（200g/瓶）和塑料杯（125g/杯）的班產(chǎn)量為50t；屋頂包（500g/包）的班產(chǎn)量為10t；其他品種的班產(chǎn)量均為20t。 表1-1 工廠日生產(chǎn)產(chǎn)品方案 產(chǎn)品種類 包裝 包裝規(guī)格 灌裝機能力 產(chǎn)品名稱 產(chǎn)量（噸/天） 凝固型酸奶 玻璃瓶 200g/瓶 12000瓶/小時 風味、果料酸奶 6個品種（3個/天） 90 攪拌型酸奶 塑料杯 125g/杯 12000杯/小時 風味、果料酸奶 10個品種（5個/天） 85 20000杯/小時 150g/杯 9000杯/小時 風味、果料酸奶 6個品種（3個/天） 40 屋頂包 200g/包 6000包/小時 風味、果料酸奶 10個品種（4個/天） 24 500g/包 12 1000g/包 24 　 　 合計 　 　 275 表1-2 年產(chǎn)100000t發(fā)酵乳制品工廠的產(chǎn)品方案一覽表 產(chǎn)品 名稱 包裝 種類 一月 二月 三月 四月 五月 六月 七月 八月 九月 十月 十一月 十二月 年產(chǎn)量 （t） 凝固型酸奶 玻璃瓶 200g 32850 攪拌型酸奶 塑料杯 125g 31025 塑 料 杯 150g 14600 屋 頂 包200g 8760 屋頂包 500g 4380 屋頂包 1000g 8760 第三節(jié) 廠址選擇概述 項目廠址選擇在蚌埠高新技術產(chǎn)業(yè)示范區(qū)，蚌埠位于東經(jīng)11712"、北緯3257"，淮河中下游，面向長三角，蚌埠是安徽省最大的城市之一，也是安徽省第一個建市的地級市，同時也是安徽省經(jīng)濟命脈，全國重要的交通樞紐，經(jīng)濟腹地十分寬廣?？缰袊媳狈纸缇€，擁有千里淮河第一大港口，是京滬高速鐵路一等客站所在地、同時京滬高速鐵路由蚌埠火車原上海鐵路局蚌埠鐵路分局，現(xiàn)上海鐵路局蚌埠鐵路辦事處仍駐蚌埠。蚌埠是中國著名的水陸交通樞扭城市，也是安徽省重要的工業(yè)基地。常住人口360萬人，其中市區(qū)人口近100萬人。蚌埠鐵路縱橫交錯，公路如網(wǎng)般密布，臨近淮河交通極為便利。此外示范區(qū)地勢平坦，工程基礎條件良好，周圍沒有污染源等不利于建廠的環(huán)境因素。廠址與原料基地之間均為高級公路相通，保證了原料采收期對運輸時間的限制。而銷售地區(qū)也在上述中心城市，便于冷鏈運輸和分銷，適于建酸奶加工廠。 第四節(jié) 總平面布置情況 項目占地15000m2，其中生產(chǎn)區(qū)占地6000 m2，位于廠區(qū)中心；生活區(qū)占地1500m2，位于廠區(qū)東北角。工廠坐北朝南，從南大門進廠，豁然呈現(xiàn)在眼前的是一個橢圓形的花壇，花壇中心設置有噴泉、假山，這種色彩鮮明、動靜結(jié)合的搭配，給人一種清新潔凈、生機盎然的感覺，烘托出項目產(chǎn)品新鮮、方便、衛(wèi)生的底蘊，廠區(qū)總平面布置見圖1。花壇往北便是占地1440m2 的主生產(chǎn)車間，寬敞明亮，布置有現(xiàn)代化的生產(chǎn)線。洗手間、空氣凈化設備、衛(wèi)生隔墻等設施一應俱全，全面適應生產(chǎn)的需要。廠區(qū)東側(cè)是機修間和鍋爐房。廠區(qū)西側(cè)布置的是原料庫、成品庫和辦公樓、實驗室。工廠的道路均按照工廠設計的標準進行布置，主干道路寬6m，兩側(cè)布置有綠化帶，環(huán)繞整個廠區(qū)。并設有人行道和緩沖區(qū)，充分做到人車分離、安全生產(chǎn)。廠區(qū)的綠化帶布置合理，栽種常綠樹木和草類，使整個廠區(qū)四季如春，顯得生機盎然。廠區(qū)總平面設計圖見附圖1。 現(xiàn)在食品工廠大多采用輕鋼結(jié)構的廠房，輕鋼建筑材料重量輕、建設周期短，相對建筑成本比較低，同時，輕鋼結(jié)構廠房相對跨度大，對設備在廠房中的布置影響小，框架結(jié)構對于不同功能分隔和以后的變更都非常的方便，因此，本設計也將采用輕鋼結(jié)構廠房進行設計。 我國夏季多為東南風，冬季多為西北風，因此本設計將動力系統(tǒng)和污水處理系統(tǒng)放置在整個廠區(qū)的東側(cè)，避免因為風向的問題影響產(chǎn)品質(zhì)量，同時根據(jù)乳制品GMP要求，本設計的廠房具有通排風系統(tǒng)，避免外界的污染進入到車間內(nèi)部。 主車間物流為南北走向，人流為東西走向，因此，在主廠房北側(cè)設置原輔料倉庫和容器整理中心，對原、輔料進行儲存和瓶、箱等包裝容器的初步滔滔和整理.原料經(jīng)過加工處理，生產(chǎn)出的成品由主廠房南側(cè)經(jīng)過冷庫儲存和恒溫月臺分配后由物流配送系統(tǒng)運送出廠。恒溫月臺能夠避免成品在分配過程中處于高溫環(huán)境，從而造成對產(chǎn)品質(zhì)量的影響。 主場房人流方向為東西走向，人流經(jīng)過主廠房一次換鞋、更衣、二次換鞋、消毒池以及風淋間后通過人流通道進入各個生產(chǎn)崗位進行生產(chǎn)。設計中人流路線與物流路線沒有交叉，因此能夠避免事故和操作失誤。 第二章 工藝設計 第一節(jié) 工藝流程設計 1.1 凝固型酸奶的工藝流程 鮮乳或還原乳 驗收 預處理 奶倉 牛乳 白砂糖 溶解 調(diào)配 預熱 60～65℃ 15～20MPa 均質(zhì) 加熱滅菌 90～95℃、3～5min 冷卻 快速冷卻至42～45℃ 直投式發(fā)酵劑 接種 灌裝 直投式菌種：43℃ 發(fā)酵 4～6.5h 速冷 速冷至15～20℃ 冷藏 后熟：4℃冷藏過夜 保持冷鏈貯存或銷售 1.2 攪拌型酸奶的工藝流程 鮮牛乳 驗收 預處理 奶倉 牛乳 白砂糖溶解調(diào)配 預熱（60℃～65℃） 均質(zhì)（15MPa） 殺菌(95℃，5min) 冷卻(42℃～45℃) 直投式發(fā)酵劑 接種 發(fā)酵（終點pH4.6） 破乳、冷卻（15℃～20℃） 溶解 殺菌 冷卻 混合 穩(wěn)定劑、水、白砂糖 均質(zhì)（15MPa） 冷卻（15℃～20℃） 灌裝、冷藏 保持冷鏈貯存或銷售 1.3 操作要點說明 （1） 預處理 凈化可以除去原料乳中的雜質(zhì)，使牛乳達到最高的純凈度。為使原料乳中脂肪和無脂干物質(zhì)之間的比例關系符合制品的要求，可通過閃蒸操作調(diào)整其比例關系。 （2） 預熱 預熱一方面可以殺菌，而且由于適當加熱，可以使一部分乳清蛋白凝固，提高酪蛋白的熱穩(wěn)定性，以防止滅菌時凝固，并賦予成品以適當?shù)酿ざ?。同時可以鈍化酶并降低均質(zhì)后乳脂肪球的直徑，防止均質(zhì)后的產(chǎn)品中脂肪上浮，增加產(chǎn)品的穩(wěn)定性。預熱溫度控制在60℃～65℃。 （3） 均質(zhì) 均質(zhì)主要是使原料充分混合均勻，阻止奶油上浮，提高酸乳的穩(wěn)定性和稠度，并保證乳脂肪均勻分布，從而獲得質(zhì)地細膩、口感良好的產(chǎn)品。均質(zhì)壓力控制在 15MPa。 （4） 殺菌 殺菌目的在于殺滅原料乳中的雜菌確保乳酸菌的正常生長和繁殖，鈍化原料乳中的天然抑制物；使乳清蛋白變性，以達到改善組織，提高黏稠度和防止成品乳清西出的目的。殺菌溫度控制在95℃，保溫5min進行殺菌。 （5） 冷卻 冷卻主要是為接種的需要。經(jīng)過熱處理的牛乳需要冷卻到一個適宜的接種溫度，此溫度控制在42℃～45℃內(nèi)。 （6） 接種 接種是造成酸乳受微生物污染的主要環(huán)節(jié)之一，因此嚴格注意操作衛(wèi)生，防止細菌、酵母、霉菌、噬菌體及其他有害微生物的污染。接種時充分攪拌，使發(fā)酵劑與原料乳混合均勻。 （7） 發(fā)酵 發(fā)酵溫度控制在42℃～45℃，從而為微生物代謝提供最適的溫度環(huán)境，發(fā)酵時間2.5h～3h，且期間不攪拌。 發(fā)酵終點判定：觀察發(fā)酵乳表面的狀態(tài)，只要表面呈均勻的凝固樣，并且又少量乳清析出，即可初步判斷接近發(fā)酵終點，再測定pH4.6時即可停止發(fā)酵。 （8） 破乳、冷卻 破碎凝膠體，使凝膠體的粒子直徑達到0.01mm～0.4mm，并使酸乳的硬度和黏度及組織狀態(tài)發(fā)生變化。攪拌速度不可過快，時間不宜過長。 冷卻目的是抑制乳酸菌的生長、降低酶的活性、防止產(chǎn)酸過度、使酸奶逐漸凝固、降低和穩(wěn)定脂肪上浮和乳清析出的速度。將發(fā)酵乳迅速降溫至15℃～20℃。 （9） 混合 將經(jīng)溶解和殺菌的穩(wěn)定劑、水和白砂糖輔料與發(fā)酵乳進行混合。 （10） 均質(zhì) 使混合料液滴微細化，提高料液黏度，抑制粒子的沉淀，并增強穩(wěn)定劑的穩(wěn)定效果。均質(zhì)壓力控制在15MPa,均質(zhì)溫度為60℃左右。 均質(zhì)是為了充分將添加入混合罐中的穩(wěn)定劑、水和白砂糖輔料混合均勻，從而獲得質(zhì)地細膩、口感良好的產(chǎn)品。 （11） 灌裝和冷藏 采用相應灌裝機進行灌裝后的成品置于0℃～5℃冷藏12h～24h，進行后熟，以產(chǎn)生良好的風味。 1.4 酸奶質(zhì)量標準 表2-1 酸奶質(zhì)量標準 項目 純酸牛奶 調(diào)味酸牛乳、果料酸牛乳 全脂 部分脫脂 脫脂 全脂 部分脫脂 脫脂 色澤 呈均一一致的乳白色或微黃色 呈均一一致的乳白色或調(diào)味乳果料應有的色澤 滋味和氣味 具有酸牛奶固有的滋味和氣味 具有調(diào)味乳或果料乳應有的滋味和氣味 組織狀態(tài) 組織細膩均勻，允許有少量乳清析出 果料酸牛乳有果塊或果粒 脂肪，% ≧3.1 1.0-2.0 ≦0.5 ≧2.5 0.8-1.6 ≦0.4 蛋白質(zhì)，% 2.9 2.3 非脂乳固體，%≧ 8.1 6.5 酸度，T≧ 70 苯甲酸，g/kg≦ 0.03 0.23 山梨酸，g/kg 不得檢出 ≦0.23 硝酸鹽（NaNO3計） mg/kg≦ 11 黃曲霉毒素MI,ug/kg≦ 0.5 大腸菌群MPN/100ml 90 致病菌（指腸道致病菌和致病性球菌）≦ 　 　 　 不得檢出 　 　 第二節(jié)　物料衡算 根據(jù)工廠設計規(guī)模、產(chǎn)品方案，通過物料平衡計算，可確定單位時間生產(chǎn)過程中主要原輔料的需求量以及水、蒸汽、能源等流量與耗量，據(jù)此就可以計算出全年主要物料、包裝材料的采購運輸和倉儲容量。同時通過物料衡算，還可以根據(jù)計算數(shù)值經(jīng)濟合理地選擇生產(chǎn)設備，并進行車間的工藝布置和各工序勞動力的安排，也是進行經(jīng)濟分析不可缺少的根據(jù)。 為平衡每月生產(chǎn)的產(chǎn)量，避免出現(xiàn)部分月停產(chǎn)，部分月加工任務過于繁重，結(jié)合主要加工酸奶的品種成熟時間情況，初步安排產(chǎn)品生產(chǎn)方案如下（注每月以30天計）： 根據(jù)酸奶基礎配方： 2.1 凝固型酸奶 鮮牛奶85%，蔗糖7%，穩(wěn)定劑0.5%，菌種3%，水：余量。 凝固型酸奶的日產(chǎn)量為90噸，因此生產(chǎn)凝固型酸奶的原料使用量（以最高使用量）如下： 鮮牛奶：90噸*85%=76.5噸