中国农业大学讲义食品学院食品工艺学课件411
食品工艺学教材(PPT 61页)【优质文档】

§3 原辅材料
生产面包所需的原辅材料分为基本材料和辅助材料 两大类。
基本材料:小麦粉、酵母、水、盐。 辅助材料:油脂、糖、乳品、蛋品、改良剂、各种
馅料装饰料、营养强化剂等。
一 小麦粉
1 面粉的化学组成及性质
面粉的主要成分有水、蛋白质、碳水化合物、脂质、 矿物质、维生素、酶。
(1)水分
面粉中的水分以游离水和结合水两种形式存在。面 粉中的水分绝大部分呈游离水状态,面粉中水分的变化 也主要是游离水的变化,它在面粉内的含量受环境温度、 湿度的影响。结合水以氢键与蛋白质、淀粉等亲水性高 分子胶体物质相结合,在面粉中含量稳定。
食品工艺学 (下篇)
第一篇 焙烤制品工艺学 概述 第一章 面包生产工艺 第二章 饼干生产工艺 第三章 蛋糕工艺
第二篇 软饮料工艺学 概述 第一章 原料与材料 第二章 碳酸饮料 第三章 果蔬制品工艺
第一篇 焙烤制品工艺学
概述 第一章 面包生产工艺 第二章 饼干生产工艺 第三章 蛋糕生产工艺
§概述
焙烤制品是泛指糖食制品中采用焙 烤工艺的一个大类产品。产品的范围十 分庞杂,分为许多大类,每类又分为数 以百计的不同花色品种,它们之间即存 在着同一性,又有各自的特殊性。
食品中的淀粉以-淀粉的形式存在。
但是在接近0℃的低温范围中,糊化了的-淀粉分 子又自动排列成序,形成致密的高度晶化的不溶性淀 粉分子,迅速出现了淀粉的化,这就是淀粉的老化。
(4)脂质 小麦中的脂质主要由不饱和脂肪酸组成,容易因氧 化和酶水解而酸败。
(5)矿物质 小麦和面粉中矿物质是用灰分来测定的,国家标准 规定:特制一等粉灰分(以干物计)不得超过0.70%
国家面粉质量标准规定:特制一等粉和特制二等粉 的水分为13.5%;标准粉和普通粉的水分为13.0% 。
(最新整理)食品工艺学培训课件.ppt

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冷藏运输:
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2、冷水冷却
• 浸入式 • 喷雾式 • 淋水式 • 优缺点
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• 营养、方便、卫生、经济 • 市场需求量大,在发达国家占有重要的
地位,在发展中国家发展迅速
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低温保藏食品的历史
• 公元前一千多年,我国就有利用天然冰 雪来贮藏食品的记载。
• 冻结食品的产生起源于19世纪上半叶冷 冻机的发明。
• 1834年,Jacob Perkins(英)发明了以 乙醚为介质的压缩式冷冻机。
• 这些反应产生的大量热量可使鱼体温度 上升2~10℃,如不及时冷却,就会促进 酶的分解作用和微生物的繁殖。
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二、冷却的方法
(一)固体物料的冷却 (二)液体物料的冷却 (三)其它冷却方法
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(一)、固体物料的冷却
1. 冷风冷却
2. 冷水冷却
3. 碎冰冷却
4. 真空冷却
• 酶作用的效果因原料而异 • 酶活性随温度的下降而降低 • 一般的冷藏和冻藏不能完全抑制酶的活性
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三、低温对非酶因素的影响
• 各种非酶促化学反应的速度, 都会因温度下降而降低
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第二节 食品的冷却
一、冷却的目的
食品工艺学教材(PPT 36张)

普通食品:有营养与感观两者功能的食品
特殊膳食用食品:为满足某些特殊人群的生理需要,或 某些疾病患者的营养需要,按特殊配方而专门加工的食 品。
保健食品:具有特定保健功能的食品。即适宜于特定人 群食用,具有调节机体功能,不以治疗疾病为目的的食 品。(营养强化食品:针对某一功能添加营养强化剂。)
第二节 食品加工工艺
3、提高食品的卫生和安全性:食品加工中通过一定的处理
过程和卫生要求,可以减少由原辅料、环境等带来的安全危害。
4、食品加工可以为人类提供营养丰富、品种多样的食 品:食品加工可以最大限度的保留食品原料中含有的各种营养物
质。并通过减少有害物质和无功能成分的含量相对提高食品中营 养成分的含量。
5、提高食品的食用方便性:为了满足现代社会人类快节奏的
食品的分类(图片) 1、按加工工艺分:干制食品、罐头食品、冷冻食品、 发酵食品、焙烤食品、腌渍烟熏食品、软饮料等。
2、按原料种类分:粮油食品、畜禽肉类食品、果蔬 食品、水产品、乳与乳制品、蛋制品、糖果和巧克力 制品 。 3、按保藏方式分:罐头类、干藏类、冷冻类、腌制 品、熏制品、发酵肉制品、发酵乳制品、辐射制品。
第三节食品工业及发展趋势
食品加工和食品工业
食品加工 改变食品原料或半成品的形状、大小、性 质、纯度,使之符合食品标准的各种操作 利用这些操作将食品原料或半成品加工制 成可供人类食用或饮用的物质的全部过程。
食品制造
食品工业
是指以农业、渔业、畜牧业、林业或化学工业的产品或半成品 为原料、制造提取、加工成食品或半成品,具有连续而有组织的 经济活动的工业体系。
二、研究内容和范围 (一)根据食物原料特性,研究食品的加工和保藏 1、食品原料特性:食物化学成分多、体系复杂;除营养成分外还 有其他几十种到上百千种的化合物;胶体,固体,液体,大多数 食物原料都是活体。 蔬菜、水果、坚果等植物性原料在采收或离开植物母体之后仍 然是活的;家畜、家禽和鱼类在屠宰后,组织即死亡,但污染这 些产品的微生物是活的,同时,细胞中的生化反应仍在继续。
中国农业大学食品学院 食品工艺学 课件.ppt

若人体缺乏乳糖酶,将表现为腹泻、呕吐 等乳糖不耐症。由于发酵乳中的乳糖被部 分分解,缺乏乳糖酶的人食用后不再表现 为乳糖不耐症,或仅有轻微表现。
乳糖的分解产物葡萄糖作为人体的能源被 利用或以糖原的形式贮存起来。半乳糖被 肠道、肝脏吸收,变为脑和神经组织的部 分成分,到达小肠下部则成为肠道菌群的 营养物质。
乳糖(Lactose)的分解和乳糖不耐症
乳糖在乳糖酶(Lactase)的作用下分 解成单糖,经微生物分解成酸和其他 成分。
双糖类中乳糖最难利用。乳糖为双糖, 难溶于水,在消化器官内经乳糖酶作 用而水解后才能被吸收,如果乳糖被 直接注射于血管或皮下,则从尿中排 出。
婴儿体内乳糖酶活力大,可以在乳粉 中强化乳糖;母乳化乳粉,乳糖占 50%以上
乳糖的性质和作用
1. 乳糖远较麦芽糖、蔗糖难溶于水
2. 在乳糖酶的作用下分解成单糖,经微生物 分解成酸和其他成分,意义很大
3. 乳糖水解后所产生的半乳糖是形成脑神经 中重要成分(糖脂质)的主要来源,在婴 儿发育期,有重要作用;一部分乳糖被送 至大肠中,由于乳酸菌的作用生成乳酸, 而抑制其他有害细菌的繁殖,对防止婴儿 下痢也有很大作用
2. 乳脂肪的理化特性
1)易氧化 脂肪与氧、光线、金属接触时,氧化产
生哈败;工艺上,避免使用铜、铁设备和 容器,应使用不锈钢设备
2)易水解 含低级脂肪酸比较多,即使稍微水解也
会产生带刺激性的酸败味
水解起因于乳本身的解脂酶和外界污染 的微生物酶
3. 乳脂肪球的构造及其存在状态
1)乳脂肪以脂肪球的形式存在于乳中
第四节 牛乳成分的化学性质
一、水分
结合水:约占2-3%,以H键和蛋白质的 亲水基或和乳糖及某些盐类结合存在
食品工艺学教材(PPT81页).pptx

微生物按生长温度分类
微生物类型
嗜冷微生物 嗜温微生物
最低
-7~5 10~15
温度℃
最适
15~20 30~40
最高
25~30 40~50
嗜热微生物
30~45 50~60
75~80
部分微生物生长和产生毒素的最低温度
食物中 毒性微 生物
粪便指 示剂微 生物
微生物
肉毒杆菌A 肉毒杆菌B 肉毒杆菌C 肉毒杆菌D 梭状荚膜产气杆菌 金黄色葡萄球菌 沙门氏杆菌 埃希氏大肠杆菌 产气杆菌 大肠杆菌类
(1)水分蒸发
❖ 食品在冷却时及冷藏中,因为温湿度差而发生表面 水分蒸发。
❖ 水分蒸发不仅造成重量损失(俗称干耗),而且使 果蔬类食品失去新鲜饱满的外观。 ▪ 减重达到5%时,水果、蔬菜会出现明显的凋萎 现象。
(1)水分蒸发
▪ 肉类食品因水分蒸发而发生表面收缩硬化,形成 干燥皮膜,肉色也有变化。
❖ 肉类在冷藏中的成熟作用。
(5)脂类的变化
冷却贮藏过程中,食品中所含的油脂会发生水 解,脂肪酸氧化、聚合等复杂的变化,使得食 品的风味变差,味道恶化,出现变色、酸败、 发粘等现象。这种变化进行得非常严重时,俗 称为“油烧”。
(6)淀粉老化
微晶形式存在的(20%直链/80%支链)普通淀粉( -淀粉) 糊化 较高温度下(食品加工)
4℃ 24h
宰杀 → 降温至18~20℃→排酸→冷藏链
b.水冷法
▪ 浸渍式、喷淋式
特点
冷却速度快而均匀;
无干耗;
可连续化作业,所需空间小; 易引起微生物污染。
冰水预冷机
适用范围
家禽、水产、部分果蔬、罐头食品
c.碎冰冷却法 ▪ 利用冰块融化吸收相变热,降低食品的温度的 方法。 特点 简便易行;
《食品工艺学第三章》PPT课件课件

(3)注意事项
n 不管是水调面团还是松酥面团,在调制时都应使用 温水。
《食品工艺学第三章》PPT课件课件
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(五)糖浆面团
(亦称浆皮面团,Syrup-mixed dough)
n 用蔗糖制成糖浆或用饴糖与面粉调制而成的面团。 该面团既有一定韧性,又有良好的可塑性。
n 适合制作浆皮包馅类糕点。例如:提浆月饼、广式 月饼、浆酥麻饼等。
该法生产的糕点起酥性好,柔软酥松,入口即化,皮色稍
深。
《食品工艺学第三章》PPT课件课件
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o 冷热水调制法:首先将部分开水冲入油、饴糖等原辅 料➢中此,类乳面化团均蛋匀白后质拌吸入水面胀粉润,受调到成一坨定块限状制。,用淀手粉摊部开 面分团糊,化稍,冷面却筋片网刻络,均再匀逐细次密加,入面冷团水延调伸制性,强反。复加水34➢次产。品将皮面色团适搓中、,拉酥、脆抻不、硬摔。至光滑细腻并上筋后,再 用手摊开面团,静置一段时间使之退筋散热并待用。
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3. 调制方法
目前,国内调制水油面团主要有以下3种方法。
o 冷水调制法 o 温水调制法 o 冷热水调制法
《食品工艺学第三章》PPT课件课件
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1. 冷水调制法:首先搅拌油、饴糖,再加入冷水搅拌均匀, 最后加入面粉。
此法制出的产品皮色浅白,酥层不易断脆,起酥性偏硬。
2. 温水调制法:用40-50℃的水调制面团。
n 油滴作为隔离介质分散在面筋之间,使面团表 面光滑、柔韧。
《食品工艺学第三章》PPT课件课件
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o 水油面团按用油量和用途可分为
烘焙型 油炸型 油炸型的水油面团筋力可低些。
o 水油面团按照用途分为
延伸性面团:单独包馅用的水油面团 弱延伸性面团:与油酥面团制成酥皮面团包馅
食品工艺学PPT课件(共28单元)干制方法

第四节 食品的干制方法
干制方法可以区分为自然和人工干燥两大类
自然干制:在自然环境条件下干制食品的方法:晒干、 阴干、
人工干制:在常压或减压环境中用人工控制的工艺条 件进行干制食品,有专用的干燥设备,如:空气对流 干燥设备、滚筒干燥设备、真空干燥设备 等
B.干端处则与低温高湿空气相遇,水分蒸发缓慢, 干制品平衡水分相应增加,干制品水分难以降到 10%以下;
因此,吸湿性较强的食品不宜选用顺流干燥方式。
两种干燥设备干燥曲线的比较
(3)双阶段干燥设备
基本结构
顺流干燥:湿端水分蒸发率高 逆流干燥:后期干燥能力强,平衡水份低
双阶段干燥:取长补短 特点:干燥比较均匀,生产能力高,品质较好 用途:苹果片、蔬菜(胡萝卜、洋葱、马铃薯 等) 现在还有多段式干燥设备,有3,4,5段等,有 广泛的适应性。
齐。
①喷嘴结构简单、维修方便。 ①喷嘴易堵塞、腐蚀和磨损。
②可采用多个喷嘴(1-12 个) ②不适宜处理高粘度物料。③
提高设备生产能力。③可用于 操作弹性小。
并流、逆流、卧式或立式干燥
机。④动力消耗低⑤制品蓬松
⑥塔径较小。
①可制粒径 5μm 以下的产 ①动力消耗大。②不适宜大型
品,可处理粘度较大的物料。 设备。③粒子均匀性差。
要降低干燥介质的温度,务使食品温度上升到干球温 度时不致超出导致品质变化(如糖分焦化)的极限温度 (一般为90℃)
一般还可降低空气的流速,提高空气的相对湿度(如 加入新鲜空气)进行控制。
(4)干燥末期,干燥介质的相对湿度应根据预期干 制品水分含量指标来加以选用。
干燥结束时食品中水分含量大小是达到与当时 介质温度和相对湿度条件相适应的平衡水分。
食品工艺学课件(PPT 65张)

本课程教材及课程网页
1. 《食品工艺学 》 , 夏文水主编,中国轻
工业出版社,2007,1 国家级规划教材
2. 食品工艺学国家精品课程网页 /jpkc
主要参考书
1. 《食品加工原理》,夏文水等译, 2001,中国轻工业出版社; 2. Principles of Food Processing Dennis R.Heldman and Richard W.Hartel 1997
1. 安全性
• 指食品无毒、无害、无副作用;与“食品
卫生”为同义词;
•有微生物、化学、物理方面
微生物:细菌总数、致病菌、霉菌等;
化学:重金属铅砷汞、农药残留、药残、
激素、滥用化学添加剂或用量超标;
物理:杂质、外形、异物
2. 保藏性
有一定的货架寿命或保质时间
食品在一定时间内保持品质或食品品质降低
食品工艺学其他参考书
1.《肉制品加工原理与技术》,夏文水主编,2003, 化学工业出版社; 2. 《乳制品生产技术》,张国农等译,2002,中国轻 工业出版社; The Technology of Dairy Products,1998,UK, Ralph Early 3.《水产品加工技术》,夏文水等译 , 2002,中国轻 工业出版社; Fish Processing Technology, 1997,UK, G.M.Hall
到不能被消费者接受的时间被定义为食品货 架寿命或货架期;
取决于加工方法、包装和贮藏条件; 消费者选择食品的依据之一;
3. 方便性
便于食用、携带、运输、贮藏;
易拉罐、易拉盖、易拉袋; 外包装、纸盒、箱子等;
净菜、配菜;
开袋即食
四、食品管理
食品工艺学课件(PPT 66页)

多媒体方式、互动、提问、读书报告、讨论、
实践教学
食品工艺实验 实验报告:每人一份,用实验报告 纸写,实验结束后一周交
考核方式
笔试 60% ,平时成绩20%,期中20% 笔试:基本概念、基本理论
第一章 绪论
第一节 食品的概念
一、食物与食品 1. 食物:供人类食用的物质称为食物
是人体生长发育、更新细胞、修补组织、调 节机能必不可少的营养物质,也是产生热量 保持体温、进行体力活动的能量来源。
不同,通常从加工工艺、原料来源、食品特点 等几方面来分类; • 食品的分类方法现还没有统一标准,约俗而成;
通常的食品分类方法
• 按加工工艺分类:反映了食品的加工特点,一 般食品加工厂应用
• 按原料种类分类:反映了食品的原料来源,一 般农业上应用
• 按产品特点分类:反映了食品的消费属性,一 般商业上应用
• 按食用对象分类:反映了食品的适用性,一般 商业上应用
Canned Mushroom 罐头类
dehydrated garlic flake 干藏类
酱黄瓜 腌渍制品
加工工艺分类
芋籽 冷冻类
烟熏制品
发酵肉制品
辐射制品
发酵乳制品
焙烤制品 罐头制品
饮料
加工工艺分类
速冻制品(绿芦笋)
发酵制品
挤压制品 干制品
本课程教材
《食品工艺学 》, 夏文水主编,中国轻工 业出版社,2012,1 国家级规划教材
主要参考书
1. 《食品加工原理》,夏文水等译, 2001,中国轻工业出版社;
2. Principles of Food Processing Dennis R.Heldman and Richard W.Hartel 1997
中国农业大学食品学院 食品工艺学ppt课件

中国农业大学 主讲教师:李博
1
课程简介
• 课程名称:食品工艺学 • 学 时 数:32 • 主要内容:《肉制品加工技术》
《乳制品加工工艺》 《果蔬产品加工工艺》 《面食制品加工工艺》
2
主要参考书
《食品工艺学》
中、下册,轻工业出版社
《畜产品加工学》
农业出版社
《乳与乳制品工艺学》
骆承庠主编,农业出版社
带。约占20%。分子呈球形,称G-肌动蛋 白;300-400个单体集合在一起,呈纤维状, 称F-肌动蛋白
• 能溶于水或稀的盐溶液,等电点pH 4.7 • 作用:为肌肉收缩的主要蛋白质,可与肌
球蛋白横桥形成交联,结合两个调节蛋白 质一起参与肌肉收缩。
36
肌动球蛋白(actomyosin)
• 又称肌纤凝蛋白,由肌动蛋白与肌球蛋白结合
电点,与水的结合力减弱;肌动球蛋白的形 成,使蛋白质间的有效空隙大为减少;蛋白 质某种程度的变性
58
(二)肉的成熟(aging or ripening of
meat)
1.解僵软化的机制
1)钙离子作用
2) 蛋白酶作用
59
2.保水性的变化 pH值为5.6-5.8,即在成熟时离开了 等电点,保水性部分恢复
种类繁多 的传统风味
肉制品
博大精深 的饮食文化
急需工业化 生产
目前向以中式为主、中西结方向发展
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2.国际肉品工业生产概况 食品工业与农业产值的比:日本3.4:1;
美国2.9:1;德国3.2:1;中国0.3:1 1:1
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3.国内外的主要产品类型 国内:腌腊制品,酱卤制品,熏烧烤
制品;干制品,油炸制品,香肠制品, 火腿制品,罐头,其它
食品工艺学课件

⾷品⼯艺学课件Processing of fruitsInstructor: mingfeng zheng(郑明锋) phd.Email:vanheng@/doc/bca037d13186bceb19e8bb68.htmlCell: 138********注意:课件全部根据⽼师提供的ppt整理,在编号上可能会有些问题,所以⼤家将就着看,祝⼤家考试顺利。
Chapter one:introductionFruit quality and preprocessingObjectsThrough the introduction, the students knowThe relationship between quality of fruit and the processed product,The relationship between composition of fruit and the processed product,Quality attributes of fresh fruits, and quality measurementspreprocessing methods and technologies1.1 classification of fruitsFruits are commonly classified by growing region as follows. Temperate zone, subtropical, and tropical. Growing region and environmental conditions specific to each regionsignificantly affect fruit quality. Examples of fruit grown in each region are listed below:1) temperate zone fruits2) subtropical fruits3) tropical fruits(1) temperate zone fruitsPome fruits(仁果类): apple, asian pear (nashi), european pear, quince榅桲果Stone fruits: apricot杏, cherry, nectarine, peach, plumSmall fruits and berries: grape (european and american types), strawberry, raspberry, blueberry, blackberry, cranberry (2) subtropical fruitsCitrus fruits: grapefruit, lemon, lime, orange, pummelo, tangerine, and mandarinNoncitrus fruits: avocado, cherimaya, fig, kiwifruit, olive, pomegranate(3) tropical fruitsMajor tropical fruits: banana, mango, papaya, pineappleMinor tropical fruits: carambola, cashew apple, durian, guava,longan, lychee, mangosteen, passion fruit, rambutan1.2 quality of raw materialsThe quality of processed fruit products depends on their quality at the start of processing; How maturity at harvest, Harvesting methods,Post harvest handling proceduresMaintenance in fresh fruits between harvest and process initiation.Quality attributes of fresh fruitsAppearance、exture factors、flavor components、nutritional quality、safety factorsAppearance factorsSize、shape、color、freedom from defects and decay.Texture factorsFirmness, crispness, juiciness.Flavor componentsSweetness, sourness (acidity), astringency, (收敛),bitterness, aroma, off-flavors,Nutritional qualityFruit's content of vitamins (a and c are the most important in fruits), minerals, dietary fiber, carbohydrates, proteins. Safety factorsResidues of pesticides, presence of heavy metals, mycotoxins produced by certain species of fungi, microbial contamination.1.3 losses in fresh fruits after harvastWater loss,Physical injuries,physiological breakdown, decayLoss of acidity, flavor, color, and nutritive valueFactors influence fruit qualityIn the orchard,During transportation,Throughout the handling system (sorting, sizing, ripening, and storage).The total time between harvesting and processingMinimizing the delays throughout the post harvest handling system greatly reduces finality loss, especially in highly perishable fruits such as strawberries, blackberries, apricots, and cherries.1.4 contribution of fruits to human nutritionEnergy (calories)VitaminsMineralsDietary fiberThe us. Department of agriculture and other organizations currently encourage consumers to participate in the "five a day" program which focuses on consumption of five servings of either fruit or vegetables each day.Energy (calories)(1) carbohydrates: banana, breadfruit, raisin葡萄⼲(2) proteins & amino acids: nuts, dried apricot and fig(3) fats. Avocado, olive, nutsFruits typically contain between 10% and 25% carbohydrates, a small amount (less than1.0%) of proteins, and a very small amount (less than 0.5 %) of fat. Carbohydrates, sugars,and starches are broken down to co2, water, and energy during metabolism. Carbohydrates and fats provide most of the calories the body requires for heat and energy.Vitamins(1) fresh fruits and vegetables contribute about 91% of vitamin c, 48% of vitamin a, 27% of vitamin b6, 17% of thiamin硫胺(维⽣素b1) to diet.(2) the following fruits are important contributors (based on their vitamin content and the amount consumed) to the supply of indicated vitamins in the u.s. Diet:*vitamin a: apricot, peach, cherry, orange, watermelon, cantaloupe*vitamin c: strawberry, orange, grapefruit, banana, apple, cantaloupe* niacin烟酸: peach, banana, orange, apricot"*riboflavin核黄素: banana, peach, orange, apple* thiamin: orange, banana, grapefruit, appleMinerals(1) fresh fruits and vegetables contribute about 26% of the magnesium镁and 19% of the iron to the u.s. Diet.(2) the following fruits are important contributors to the supply of indicated minerals in the us. Diet:* potassium钾: banana, peach, orange, apple* phosphorus磷: banana, orange, peach, raisin, fig*calcium: tangerine, grapefruit, orange* iron: strawberry, banana, apple, orangeDietary fiber(1) all fruits and nuts contribute to the dietary fiber in the diet. Dietary fiber consists of cellulose, hemicellulose, lignin⽊质素, and pectic substances, which are derived primarily from fruit cell walls and skin.(2) the dietary fiber content of fruits ranges from 0.5-1.5% (fresh weight basis).(3) dietary fiber plays an important role in relieving constipation by increasing water-holding capacity of feces. Its consumption is also linked to decreased incidence of cardiovascular disease, diverticulosis, and colon cancer.factors influefncing composition and quality of fruitsPreharvest factors(1) genetic: selection of cultivars, differences in raw fruit composition, durability, and response to processing. Fruit cultivars grown for fresh market sale will not be the optimal cultivars for processing.(2) climatic: temperature, light, wind--climatic factors may have a strong influence on nutritional quality of fruits. Light intensity significantly affects vitamin concentration, and temperature influences transpiration rate, which will affect mineral uptake and metabolism. ?(3) cultural practices: soil type, soil nutrient and water supply, pruning修剪, thinning, pest control-fertilizer addition may significantly affect the mineral content of fruit.1. 5 maturity at harvest and harvesting methodMaturity at harvest is one of the primary factors affecting fruit composition, quality, and storage life. Although most fruits reach peak eating quality when harvested fully ripe, they are usually picked mature, but not ripe, to decrease mechanical damage during postharvest handling. Harvesting may also mechanically damage fruit; therefore, choice of harvest methodshould allow for maintenance of quality.Postharvest factors1) environmental,2) handling methods,3) time period between harvesting and consumption(1) environmentalTemperature, relative humidity, atmospheric composition,(2) handling methodsPostharvest handling systems involve the channels through which harvested fruit reaches the processing facility or consumer. Handling methods should be chosen such that they maintain fruit quality and avoid delays.(3) time period between harvesting and consumptionDelays between harvesting and cooling or processing may result in direct losses (due to water loss and decay) and indirect losses (decrease in flavor and nutritional quality).Fruit maturity, ripening, and quality relationshipsMaturity at harvest is the most important factor that determines storage life and final fruit quality. Immature fruits are of inferior quality when ripened. Overripe fruits are likely to become soft and with insipid flavor soon after harvest. Fruits picked either too early or too late in the season are more susceptible to physiological disorders and have a shorter storage life than those picked at mid-season.Maturity and ripeningIn general, fruits become sweeter, more colorful, and softer as they mature.Some fruits are usually picked mature but unripe so that they can withstand the postharvest handling system when shipped long distances. Most currently used maturity indices are based on a compromise between those indices that would ensure the best eating quality to the consumer and those that provide the needed flexibility in transportation and marketing.Carbohydrates(碳⽔化合物)Carbohydrates : fresh fruits vary greatly in their carbohydrate content, with a general range being between 10% and 25%;. The texture, taste, and food value of a fresh fruit is related to its carbohydrate content. Sucrose, glucose, and fructose are the primary sugars found in fruits.Fructose is sweeter than sucrose, and sucrose is sweeter than glucose.Starch is converted to sugar as the fruits mature and ripen.Proteins(蛋⽩质)Fruits contain less than 1% protein (as opposed to 9-20% protein in nuts such as almond, and walnut). Changes in the level and activity of proteins resulting from permeability changes in cell membranes may be involved in chilling injury. Enzymes, which catalyze metabolic processes in fruits, are proteins that are important in the reactions involved in fruit ripening and senescence.Enzymes in fruits:(Organic acids(有机酸)Organic acids are important intermediate products of metabolism. The krebs (tca) cycle is the main channel for the oxidation of organic acids in living cells, and it provides the energy required for maintenance of cell integrity. Organic acids aremetabolized into manyconstituents, including amino acids, which are the building blocks of proteins.Citric acid、malic acid、tartaric acid、oxalic acidPigments(⾊素)Pigments undergo many changes during the maturation and ripening of fruits.(1) loss of chlorophyll (green color), which is influenced by ph changes, oxidative conditions, and chlorophyllase action(2) synthesis and/or revelation of carotenoids (yellow and orange colors)(3) development of anthocyanins (red, blue, and purple colors.Beta-carotene is a precursor to vitamin a. Carotenoids are very stable and remain intact in fruit tissues, even when extensive senescence has occurred.Phenolic compounds(酚类化合物)Total phenolic content is higher in immature fruits than in mature fruits and is the main substrate involved in enzymatic browning of cut, or otherwise damaged, fruit tissues when exposed to air.Enzymatic browning(酶促褐变)Enzymatic browning occurs due to the oxidation of phenolic compounds and is mediated, in the presence of o2, by the enzyme polyphenoloxidase (ppo). The initial product of oxidation is usually o-quinone, which is highly unstable and undergoes polymerization to yield brown pigments of higher molecular weight. Polyphenoloxidase catalyzes the following tworeactions:Volatiles(挥发性)Volatiles are responsible for the characteristic aroma of fruits. They are present in extremely small quantities (c <100µg/g fresh wt.).Volatile compounds are largely esters(酯), alcohols, acids, aldehydes(醛), an d ketones (low-molecular weight compounds).VitaminsThe water-soluble vitamins includeVitamin c,Thiamin硫胺(维⽣素b1),Riboflavin核黄素,Niacin烟酸, vitamin b6,Folacin叶酸, vitamin b12, biotin维⽣素h. Fat soluble vitamins include vitamins a, d, e, and k.Fat-soluble vitamins are less susceptible to postharvest losses.Vitamin cAscorbic acid is most sensitive to destruction when the commodity is subjected to adverse handling and storage conditions. Losses are enhanced by extended storage, highertemperatures, low relative humidity, physical damage, and chilling injury. Postharvest losses in vitamins a and b are usually much smaller than losses in vitamin c.1.7 biological factors involved in postharvest deterioration (变坏) of fruits ?Respiration (呼吸作⽤)Ethylene productionTranspiration (蒸腾作⽤)Physiological disordersPhysical damagePathological breakdownRespirationStored organic materials (carbohydrates, proteins, fats) are broken down into simple end products with a release of energy. Oxygen (o2) is used in this process, and carbon dioxide (co2) is produced.The loss of stored food reserves in the commodity during respiration hastens senescence as the reserves that provide energy to maintain the commodity's living status are exhausted. ?Food value (energy value) for the consumer is lost; it has reduced flavor quality, with sweetness especially being lost; and salable dry weight is lost (especially important for commodities destined for dehydration). The energy released as heat.Ethylene productionEthylene, the simplest of the organic compounds affecting the physiological processes of plants, is produced by all tissues of higher plants. As a plant hormone, ethylene regulates many aspects of growth development, and senescence and is physiologically active in traceamounts (less than 0.1 ppm).Transpiration or water lossWater loss is the main cause of deterioration because it results not only direct quantitative.Losses (loss of salable weight) hut also in loss of its appearance, loss of cripsness, andjuiciness), and nutritional quality.The dermal system (outer protective coverings) governs the regulation of water loss by the commodity.Physiological disorders(1) freezing injury :usually results in immediate collapse of the tissues and total loss.(2) chilling injury when fruits (mainly those of tropical and subtropical origin) are held at temperatures above their freezing point and below 5-15℃, depending on the commodity. ?(3) heat injury results from exposure to direct sunlight or to excessively high temperatures.Symptoms include surface scalding, uneven ripening, excessive softening, and desiccation. ?(4) very low (<1%) oxygen and/or elevated (>20%) carbon dioxide concentration can result in physiological breakdown of all fruits.Physical damageVarious types of physical damage (surface injuries, impact bruising, vibration bruising, etc.) Are major contributors to deterioration. Mechanical injuries are not only unsightly, but also accelerate water loss, stimulate higher respiration and ethylene production rates, and favor decay incidence.Pathological breakdownDecay is one of the most common or apparent causes of deterioration; however, attack by many microorganisms usually follows mechanical injury or physiological breakdown, which allows entry to the microorganism. Pathogens can infect healthy tissues and become the primary cause of deterioration.Environmental factors influencing deterioration of fruits(影响⽔果变坏的环境因素)Temperature,Relative humidity,Air movement,Atmospheric composition,Ethylene,Harvesting procedures Postharvest handling proceduresDumping、Sorting、Sizing、Cooling、Storage、RipeningDumping:Fresh fruits should be handled with care throughout the postharvest handling system in order to minimize mechanical injuries. Dumping in water or in flotation tanks should be used for fruits. If dry dumping systems are used, they should be well padded bruising. Sorting:Manual sorting is usually carried out to eliminate fruit exhibiting defects or decay. For some fruits, it may also be necessary to sort the fruit into two or more classes of maturity or ripeness.Mechanical sorters, which operate on the basis of color, soluble solids, moisture, or fat content, are being implemented and may greatly reduce time and labor requirements. Sizing:In some cases, sizing the fruits into two or more size categories may be required before processing. Sizing can be done mechanically on the basis of fruit dimension or by weight.Mechanical sizing can be a major source of physical damage to the fruit if the machines are not adequately padded and adjusted to the minimum possible fruit drop heights Ripening:Ripening before processing may be required for certain fruits (banana, kiwifruit, mango, papaya, peach, pear, plum, melon) that are picked mature but unripe. Ethylene treatment can be used to obtain faster and more uniform ripening. The optimum temperature range for ripening is 15-25℃and, within this range, the higher the temperature, the faster the ripening. Relative humidity should be maintained between 90% and 95 % during ripening. Cooling:Cooling is utilized to remove field heat and lower the fresh fruit's temperature to near its optimum storage temperature. Cooling can be done using cold water (hydrocooling) or cold air (forced-air cooling or "pressure cooling"). Highly perishable fruits, such as strawberries, bush berries, and apricots, should be cooled to near 4℃within six hours of harvest. Other fruits should be cooled to their optimum temperature within twelve hours of harvest. Storage:Short-term or long-term storage of fresh fruits may be needed before processing to regulate the product flow and extend the processing season. The relative humidity in the storage facility should be kept between 90% and 95%.To reduce decay, elevated c02 (15-20%) may be added to the atmosphere within pallet covers for strawberries, bush berries, and cherries, and sulfur dioxide (200 ppm) fumigation may be used on grapes.1.8 quality measurementsMany quality measurements can be made before a fruit crop is picked in order to determine if proper maturity or degree of ripeness has developed.ColourColour may be measured with instruments or by comparing the colour of fruit on the tree with standard picture charts. TextureTexture may be measured by compression by hand or by simple type of plungers.Soluble solidsAs fruit mature on the tree its concentration of juice solids, which are mostly sugars, changes. The concentration of soluble solids in the juice can be estimated with arefractometer or a hydrometer液体⽐重计.Acid contentThe acid content of fruit changes with maturity and affects flavour. Acid concentration can be measured by a simple chemical titration on the fruit juice. But for many fruits the tartness and flavour are really affected by the ratio of sugar to acid. Sugar to acid ratioIn describing the taste of tartness of several fruits and fruit juices, the term "sugar to acid ratio" or "brix to acid ratio" are commonly used. The higher the brix the greater the sugar concentration in the juice; the higher the "brix to acid ratio" the sweeter and lees tart is the juice.1.9 preprocessing1.9.1 harvestingThe above and other measurements, plus experience, indicate when fruit is ready for harvesting and subsequent processing.1.9.2 reception - quality and quantity1.9.3 temporary storage before processing1.9.4 washingHarvested fruit is washed to remove soil, micro-organisms and pesticide residues.Fruit washing is a mandatory processing step; it would be wise to eliminate spoiled fruit before washing in order to avoid the pollution of washing tools and/or equipment and the contamination of fruit during washing.1.9.5 sortingFruit sorting covers two main separate processing operations:Removal of damaged fruit and any foreign bodies (which might have been left behind after washing);Qualitative sorting based on organoleptic criteria and maturity stage.Mechanical sorting for size is usually not done at the preliminary stage. The most important initial sorting is for variety and maturity.1.9.6 trimming and peeling (skin removal)This processing step aims at removing the parts of the fruit which are either not edible or difficult to digest especially the skin.Up to now the industrial peeling of fruit and vegetables was performed by three procedures: Mechanically;By using water steam;Chemically; this method consists in treating fruit and vegetables by dipping them in a caustic soda solution at a temperature of 90 to 100°c; the concentration of this solution as well asthe dipping or immersion time varying according to each specific case.1.9.7 cuttingThis step is performed according to the specific requirements of the fruit processing technology.1.9.8 blanchingA brief heat treatment to vegetables some fruits to inactivate oxidative enzyme systems such as catalase, peroxidase, polyphenoloxidase, ascorbic acid oxidase, and lipoxygenase. ?When the unblanched tissue is disrupted or bruised and exposed to air, these enzymes come in contact with substrates causing softening, discoloration, and the production of off flavors. ?It is most often standard practice to blanch fruits in order to prevent quality deterioration. ?Although the primary purpose of blanching is enzyme inactivation.There are several other benefits blanching initially cleanses the product;Decreases the microbial load,Preheats the product before processing.Softens the fruit, facilitates compact packing in the can.Expell intercellular gases in the raw fruitImproved heat transfer during heat processing.Water blanching is generally of the immersion type or spray type as the product moves on a conveyor.Steam blanching often involves belt or chain conveyors upon which the product moves through a tunnel containing live steam.adequacy of blanching is usually based on inactivation of one of the heat resistant enzymes (peroxidase or polyphenol oxidase).During the blanching process, it is imperative that certain enzymes that have the potential to cause flavour and textural changes be inactiviated. The process involves a brief heattreatment applied to most vegetables and also to some fruits in order to inactivate oxidative enzyme system such as catalase, peroxidase, polyphenoloxidase,ascorbic acid oxidase, and lipoxygenase.When unblanched tissue is disrupted or bruised and exposed to air,these enzymes come in contact with substrate causing softening,discoloration, and the production of off-flavours.Since this action can potentially occur during the period prior to heat processing, it is most often standard practice to blanch fruits in order to prevent quality deterioration.1.9.9 ascorbic/citric acid dipAscorbic acid or vitamin c minimises fruit oxidation primarily by acting as an antioxidant and itself becoming oxidised in preference to catechol⼉茶酚-tannin compounds.It has been found that increased acidity also helps retard oxidative colour changes and so ascorbic acid plus citric acid may be used together. Citric acid further reacts with (chelates) metal ions thus removing these catalysts of oxidation from the system.1.9.10 sulphur dioxide treatmentSulphur dioxide may function in several ways:Sulphur dioxide is an enzyme poison against common oxidising enzymes;It also has antioxidant properties; i.e., it is an oxygen acceptor (as is ascorbic acid);Further so2 minimises non enzymatic maillard type browning by reacting with aldehyde醛groups of sugars so that they are no longer free to combine with amino acids;Sulphur dioxide also interferes with microbial growth.In many fruit processing pre-treatments two factors must be considered:Sulphur dioxide must be given time to penetrate the fruit tissues;So2 must not be used in excess because it has a characteristic unpleasant taste and odour, and international food laws limit the so2 content of fruit products, especially of those which are consumer oriented (e.g. Except semi-processed products oriented to further industrial utilisation).5.2.11 sugar syrupSugar syrup addition is one of the oldest methods of minimising oxidation.Sugar syrup minimises oxidation by coating the fruit and thereby preventing contact withatmospheric oxygen.Sugar syrup also offers some protection against loss of volatile 挥发性的fruit esters 酯and itcontributes sweet taste to otherwise tart fruits.It is common today to dissolve ascorbic acid and citric acid in the sugar syrup for addedeffect or to include sugar syrup after an so 2 treatment.QuestionsWhat factors influence the quality of fruits after harvest?How to maintain the fruit in good quality before the processing begin?第⼀节果蔬原料特性新鲜果蔬原料的特点 ? 果蔬原料的化学成分原料的化学成分与加⼯的关系1.新鲜果蔬原料的特点易腐性、季节性、区域性2.果蔬中的化学成分(chemical composition in fruits and vegetables )3.化学成分与加⼯的关系(relation between chemical composition and processing )3.1 ⽔分(water)果蔬中⽔的含量:⼤多数在80%以上,含⽔量⾼的如冬⽠(wax gourd)可达96%以上。
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专用小麦粉的生产
小麦粉的用途
(一)主食品:馒头、
包子、面条、饺子、烙饼、 油条和各种面包、糕点等。 (二)其它加工品:谷 朊粉、小麦淀粉、胚芽产 品 、麸皮制品、其他辅 料等。
主食
2.国外专用小麦粉的分类方法
美国小麦粉根据用途和原料分4大类:第1类— 面包用粉(硬质小麦粉),第2类—糕点用粉 (软质小麦粉),第3类—面制食品用粉(软质 小麦粉),第4类—通用粉。
(六)矿物质
矿物质:以灰分来测定 矿物质(钙、钠、磷、铁等)以盐类存在, 将小麦或面粉完全燃烧之后的残留物绝大部分 为矿物质盐类,也叫灰分。麦粒中1.5%-2.2% 面粉中灰粉很少,灰分大部分在麸皮中,小 麦粉以灰分来分级,表示麸皮的除去程度。
(七)面粉中的酶类
1. 淀粉酶:α-和β-淀粉酶,两种在焙烤食品上重要的 酶。 β-淀粉酶含量充足,而α-淀粉酶不足。可以使一 部分α-淀粉(糊精)和β-淀粉水解转化为麦芽糖,作为 酵母发酵的主要能量来源。
面筋:将面团在水中轻轻揉洗时,可溶部 分溶解于水,淀粉和麸皮微粒等呈悬浮态脱 离出来,最后剩下的具有一定弹性和延伸性 的软胶物质就是面筋。
面筋中的蛋白质主要是麦胶蛋白和麦谷蛋 白,约占80%。
1. 影响面筋形成的主要因素
面团温度(30-40℃) 面团放置时间 面粉质量
谢 谢 各 位 聆 听
3. 脂肪酶:这种酶对面包,饼干制作影响不大,但 对已调配好的蛋糕粉有影响,因为它可分解面粉里 的脂肪成为脂肪酸,易引起酸败,缩短储藏时间。
三、小麦粉的品质规格与标准
(一)面粉的营养价值
1.纤维素、蛋白质、维生素、矿物质主要在表皮和糊 粉层中,而淀粉在胚乳中,脂肪在胚芽中。
2.小麦加工精度要高,营养素大幅度降低,碳水化合 物和热量增加。 3.出粉率80%以下,纤维素、维生素B1、B2、烟酸、 矿物质及总灰分都很低,出粉率80%以上,上述营 养成分都明显地增加。制作面包的面粉需要面筋含 量高,筋力大,颜色白,出粉率必须在75%以下。
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中国农业大学食品 学院食品工艺学课 件411
主要内容
第一章 原辅材料 第二章 面包 第三章 糕点
第一章 原辅材料
第一节 小麦面粉
➢小麦的品种与品质规格 ➢面粉的化学成分及性质 ➢面粉的种类和等级标准 ➢面筋及其工艺性能
一、小麦的品种与品质规格
小麦规格标准:我国小麦分冬小麦和春小麦, 各类小麦按体积质量分为五等,以三等为中 等标准,低于五等为等外小麦 。
β-淀粉酶热不稳定,糖化水解作用在酵母发酵阶段;
α-淀粉酶将可溶形淀粉变为糊精,改变淀粉的流变 性。它对热较为稳定,在70~75℃仍能进行水解作用, 温度越高作用越快。α-淀粉酶大大影响了焙烤中面团 的流变性,在烤炉中的作用可大大改善面包的品质。
2. 蛋白酶:面粉中蛋白酶分为两种,一种能直接作
用于天然蛋白质的蛋白酶,另一种是能将蛋白质分 解过程中的中间生成物多肽类再分解的多肽酶。搅 拌发酵过程起主要作用的是蛋白酶,它的水解作用 减低面筋强度,缩短和面团时间,使面筋易于完全 扩展。
加拿大小麦品种规格按蛋白含量区分,贮 藏时从12.5%到14.5%,分为三等,每增加1% 为一等,按等级分别流通。澳大利亚小麦规 格也分为七种类,每种又有等级,等级也按 含蛋白的量区分。
二、面粉的化学成分及性质
(一)水分:国标规定13±0.5%
(二)蛋白质:8-14%
✓麦胶蛋白:醇溶性蛋白,pH 6.4-7.1 不溶性蛋白,占80% ✓麦谷蛋白:溶于稀酸或稀碱, pH 6-8 面筋的主要成分 ✓麦球蛋白 ✓麦清蛋白 溶于水和稀盐酸溶液中,属于可溶性蛋白 ✓酸溶蛋白
英国小麦粉根据用途分为:面包用粉、乔利伍 德面包用粉、饼干用粉、糕点用粉、家庭用粉。
日本的小麦粉根据蛋白质含量高低分为5类:强 力、准强力、薄力、普通、特殊小麦粉。每类又
根据灰分高低分为特、松、梅3个等级。
四、面团及其工艺性能
面团:面粉加适量水经机械搅拌或手工揉 搓后得到的,具有一定弹性和延伸性,柔软 而光滑的团块。
粗纤维:大多在麸皮中,不能为人体吸收,一 般影响面粉质量,制粉工程中应除去。
(四)脂肪
脂肪:存在胚芽和糊粉层中,含量少,小 麦中1~2%,虽是营养成份,多由不饱和脂 肪酸组成,易氧化酸败使面粉或制品变味, 制粉过程中一般除去。面粉中脂肪更少,低 于1%。
(五)维生素
维生素:小麦中维B1、B2、B5较多,还含有 少量的维E 、维A ,微量的维C,但不含有维D。
(二)小麦粉的分类
按用途划分工业用和食品专用面粉:
工业用面粉一般为标准粉和特二粉,用于生产 谷朊粉、淀粉、粘结剂等。
食品用面粉分成三大类:通用粉、专用粉和配 合粉。
1.通用粉指可以制作一种或多种一般性的食品, 适用范围广 ,等级粉和标准粉就是通用粉;
2.专 用 粉 是 按 照 制 造 食 品 的 专 门 需 要 加 工 的 面 粉 , 品种有低筋、高筋、面包粉等;
(三)碳水化合物
占麦粒重的70%,面粉中的75%,包括淀粉、 糊精、纤维素、游离糖和戊聚糖
溶解性碳水化合物:指碳水化合物中能为人 体消化利用部分包括淀粉、糊精和游离糖类。 淀粉主要在胚乳,糖在胚芽及糊粉层,这两种 占麦粒70%以上,以淀粉为主,糖约占10%, 随着麦粒成熟,糖大多转化为淀粉。
小麦淀粉由19~26%直链淀粉和74~81%支链淀粉 构成,前者50~300个葡萄糖基,后者300~500。直 链淀粉易溶于温水,几乎无粘度,而支链淀粉易 形成粘糊。
3.配合粉是以小麦粉为主根据特殊目的添加其他 一些物质而调配面粉,包括营养强化、预混合面 粉等。
1.我国面粉的分类标准
专用小麦粉分为:面包用粉、面条、馒头、 饺子、酥性饼干、发酵饼干、蛋糕、糕点 用粉等
面粉品种是按灰分多少,粗细度等为标准 进行分类。
长期以来,我国的面粉种类单一,各项指 标并不是针对某种专门的特殊的食品来制 定的,实际上仍是一种“通用粉”,而不 是专用粉,不适应制作不同食品的需要。