Introduction and Milk Composition PDF

Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 ‫ اي نقط موجودة في المحاضرة هتكملها الني اكيد قولتها او شرحتها‬:‫مالحظة‬ Lecture 1,2 ‫ولعلمك اي اضافة قولتها في المحاضرة عليك بردوه‬ Introduction: 1 Hygiene=...

Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 ‫ اي نقط موجودة في المحاضرة هتكملها الني اكيد قولتها او شرحتها‬:‫مالحظة‬ Lecture 1,2 ‫ولعلمك اي اضافة قولتها في المحاضرة عليك بردوه‬ Introduction: 1 Hygiene= conditions or practices help maintaining health and preventing disease, especially through cleanliness 2 Food hygiene =All conditions and measures necessary to ensure the safety and suitability of food at all stages of the food chain 2 Food safety =Assurance that food will not cause adverse health effects to the consumer when it is prepared and/or eaten according to its intended use. Importance of study Hygiene in the Dairy Industry: 1. Consumer Health and Safety: to safeguarding the health and safety of consumers 2. Increases Product Quality: (suitability) Good milk hygiene practices good milk products maintain their nutritional value, taste, and appearance, thus enhancing consumer satisfaction. 3. Regulatory Compliance: 4. Economic: Poor milk hygiene practices, result in product recalls, increased production costs, and loss of market share. ‫مش عاوزين حاجة ترجع لينا تاني‬ Milk definition It is the normal secretion of the mammary glands of mammals obtained by the complete milking of one or more healthy animals after colostrum The animal that use their milk according to the Egyptian standards ‫ده المواصفة القياسية المصرية بصرف النظري عن ان في ناس بتشرب لبن الحمير‬ The cow is the principle source of milk in many parts of the world. However, may use milk of other animals: as source of milk for the buffalo, goat, Ewes, camel and mare, may use donkey milk in some countries. 1 Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 lactation cycle of cow:  The heifer is bred before 2 years  Secretion of milk in the cow’s udder begins shortly before calving then continues to give milk for about 300 days.  after approx. 300 days’ milk production decreases by about 15 – 25 % of its peak volume.  At this stage milking dried 60 days prior to calving.  To begin a new lactation cycle  The first milk after calving is called colostrum. (It differs greatly form normal milk in composition and properties)  A cow is normally productive for five years. Udder Anatomy of cow: ‫خدت الكالم ده في االناتومي قبل كده لو نسيته هفكرك به زي بعضه انا طيبة‬ The mammary gland of the dairy cow consists of four separate glands. “quarters.” each with a teat. The right and left side of the udder are separated by a median ligament, while each half not as distinctly separated as are the halves. Udder of cow consist of: ‫خدت الكالم ده في الهستولوجي قبل كده لو نسيته هفكرك بردوه ما انا قولتلك اني طيبة‬  The glandular tissue contains a very large number (about 2 billion) of tiny bladders called alveoli. Each alveolus is lining with Milk secretory cells (lactating cell) are located on the inner walls of the alveolus, which surrounded by muscle cells.  Groups of alveoli, are collected by a common duct to form a lobule; which separated from neighboring lobules by connective tissue  The Small ducts of lobule collected in larger milk ducts which lead to a cavity above the teat. “udder cistern”,  The udder cistern has an extension reaching to the teat; ‘’teat cistern’’.  At the end of the teat there is a channel of length (1 – 1.5 cm long).  The channel is closed by a muscular sphincter between milking… which prevents 1- Milk from leaking out & 2- Bacteria from entering the udder.  capillaries bring nutrient-rich blood from the heart to the udder alveoli, in this way the milk- producing cells are furnished with the necessary nutrients for the secretion of milk. Milk formation Milk constituents are synthesized from components obtained from the blood; ‫معلومة حلوة عالماشي كده وانت بتذاكر لو كنت بتذاكر يعني‬ Milking process 1-The cow in correct stimuli, before milking by:  washing the udder,  massaging the udder and fore-stripping milk out of each quarter. 2- leading to release of oxytocin into the cow’s bloodstream 3- that causes the muscle-like cells to compress the alveoli.’’ letdown reflex’’. 4- The milk is forced into the duct system and into the gland and teat cisterns to milking machine or hand milking or suckling calf. N.B. The effect of oxytocin disappearing after 5 – 8 minutes........ what’s happen when oxytocin effect end?? Answer……………………………………………………………………………………………………………………………………………………… 2 Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 Differences between Colostrum and Milk - Colostrum vs. Milk: Casein/4.8% Casein/2.5%  The secretion that produced by the udder immediately after parturition is colostrum, and Usually extends up to 3-5 days post-partum  The colostrum composition is different from the normal milk.  It is brownish-yellow colour, with odd smell and a saltier taste.  High content of whey protein 11%, while normal milk 0.65% So, coagulate when heated??  The colostrum milk is higher in SNF, especially the globulin fractions (protein), minerals like Calcium, phosphorus, magnesium, chlorine, Iron is higher 10 to 17 times greater than normal milk  Vitamin A is 30 times more than in normal milk.  Vitamin D is 2 times more than in normal milk  While less in Lactose % and Potassium  Fat are variable ‫كل اللي فات كان مقدمة البد منها‬ Composition of milk ‫افتكري ادعي لنفسك وادعلي‬ ‫يارب اجيب امتياز في المادة وربنا يباركلك يا دكتورتي‬ 1- water: It constitutes at least about 80% - 90% of milk composition  Water holds the constituents of milk either in colloidal form (e.g. lactose, minerals and protein) or in a form of emulsion (milk fat). water Present in high % ?? 1- to facilitate the milk secretion, milking, suckling, drinking and digestion. 2- helps the technological processing during manufacturing of milk products 3- also facilitates the growth of both desirable and undesirable microorganisms in such suitable media. What’s meant by?? Emulsion: …………………………………………………………………………………………………………… Colloidal: ……………………………………………………………………………………………………………. 3  Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 2- Milk fat ‫اخف مكون واغلي مكون في اللبن‬ Present in milk in form emulsion in milk serum= - Milk fat is the most valuable milk constituent, according to it the price is evaluated. - The higher the fat % the tastier the milk. - Milk fat exists as small globules or droplets in the milk serum. - Fat globules diameters range from 0.1 to 20 um - the largest particles in the milk and also the lightest part - fat globules tend to rise on milk surface to form cream-line - Aggregation of fat globules under the influence of a protein called agglutinin. Fat globule structure: ‫التركيب ده مهم‬ - milk fat globules are particles consisting of a core of neutral glycerides (mainly triglycerides) surrounded by a bilayer membrane of phospholipids and proteins on the outside. The predominant of protein is Glycoprotein - fat globule membrane (FGM)= contains at least 25 different enzymes, - The most abundant enzymes are alkaline phosphatase and xanthine oxidase. Function of the membrane: Acts as 1- natural emulsifying agent, enabling the fat to remain dispersed throughout the aqueous phase of milk, to prevent to some extent flocculation and coalescence. 2- protect fat globules from lipolysis by action of lipase enzyme. Removing of FGM caused by many factors among them, ……………………….. and ………………………. ‫خد بالك‬ Chemical structure of milk fat  The milk fat consists mainly of triglycerides (98%), diacetyl glycerol, phospholipids, and fatty acids  The Triglycerides, are composed of an alcohol called glycerol and various fatty acids.  Fatty acids make up about 90% of milk fat Milk fat is characterized by the presence of relatively large amounts of short-chain saturated, volatile fatty acids, as butyric and caproic acid…. Which are important to the flavor of milk ‫ليه اللبن رايحته لبن ومش رايحته جوافة مثال؟؟‬ products and in off flavors in milk……. why?? ………………………………………………………. Factors affecting fat% in milk: 1- Species, Breed of the animal. 2- Individual variation. 3- Feeding: Over feeding not increase the fat, but under feeding affect. 4- Seasonal variation. 5- Efficacy of milking. ……………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………… 6- Interval between milking.?? ………………………………………………………………………………………………………… ‫ساعات كمية الحليب تقل مع انك‬ ……………………………………………………………………………………………………… ‫مظبط كل حاجة بس السبب ده‬ ………………………………………………………………………………………………………… ‫بسيط وعامل المزرع كسالن بس‬ ……………………………………………………………………………………………………… 4 Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 N.B. fat content decreases slightly during successive lactations, by ~0.2 % over a typical productive lifetime (~5 lactations). Proteins in milk: Proteins are giant molecules built up of smaller units = amino acids, Amino acids in milk characterized by the presence of one amino group (NH2) + one carboxyl group (COOH) in the molecule=== which called Such compounds are called ampholytes??............................. Generally, Proteins are built from a supply of approx. 20 amino acids, 18 types of which are found in milk proteins. - Milk contain all essential amino acids, (eight and nine for infant), - The milk protein is classified by of grouping milk proteins into casein & whey protein (albumin & globulin) The classification based on acidification of milk at pH 4.6 at 20°C,  In cow’s milk: about 80% of the total protein precipitates at pH 4.6 is called casein. While, the proteins that remain soluble under these conditions are referred to as whey proteins or serum proteins N.B a)- Casein Defined as the protein that precipitated from skim-milk at pH 4.6 at 20C. Characteristics:  It dominant class of proteins in cow’s milk. (79.5%) of total milk protein.  It is precipitated by acidifying to pH 4.6 (isoelectric point)  It is rich in phosphorous (phosphoproteins)  Casein present in molecular complexes that are known as casein micelles. (0.4 microns)  The casein micelles consist of α s-casein, β-casein and k-casein  The casein micelles bind with each with Calcium phosphate Structure of casein 5  Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 ‫تركيب عجيب لل‬ micelles or Why casein micelles are soluble in milk?? Casein micelles - the α s-casein and β-casein are almost insoluble in water, while those of ‫ال تخرج قبل ان تقول سبحان هللا‬ k-casein are readily soluble. - k-casein are dominating the surface of the casein micelles so, the solubility of calcium k-caseinate overcome the insolubility of the other two caseins in the micelles, So …whole micelle is soluble as a colloid. The Kappa casein acts as a stabilizing factor that protecting other caseins from precipitation and make casein more soluble forming casein micelles. So, it holds the casein complex in colloidal suspension Why The Kappa casein acts as a stabilizing factor in ‫ادعلي يا بني قولتلك قبل كده‬ milk?? K-casein appears to be present on the surface of casein micelles linked by hydrophilic C- terminal part of carbohydrates chain that protrude ‫ بارزة‬from the micelle surface, giving it a “hairy” appearance. That chain is highly charged “hairs” (strong negative charge of carbohydrates that physically prevent the approach and interactions of hydrophobic regions of the casein molecules. ‫الحاجات اللي بترسب الكازين وتخلي اللبن يقطع‬ Precipitation of casein = One characteristic property of casein is its ability to precipitate Curdling of milk? ‫عشان الناس اللي علمها عنجليزي‬ 1-Removal of the hairs by cleavage with rennet 2- Precipitation by acid destroys the stabilization effect of K-casein, At Normal pH of milk= 6.6 allowing micelles to interact and aggregate. Casein micelle has a net negative charge. The protein molecules remain separated because identical charges repel each other. At isoelectric point= 4.6 The protein molecules no longer repel each other, Due to the excess presence of hydrogen ions the molecules acquire a net positive that attract to negative charges ……. Form clusters. The protein is then precipitated. 6 Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 Whey proteins= milk serum proteins remain after remove casein 1- they are not precipitated at their isoelectric points. 2- They are denaturated by heating at temperature more than 70C. 3- Not affected by renneting. Why??....................................... 4- Whey proteins especially α-lactalbumin have very high nutritional values. Their amino acid composition is very close to that which is regarded as a biological optimum -lactalbumin:  Constitutes about 3.7% of the total milk proteins  This protein may be considered to be the typical whey protein  It is present in milk from all mammals  It is synthesized in udder  Plays a significant part in the synthesis of lactose in the udder.  It coagulates easily by heat,  and responsible for the skin layer over liquid milk when heated. - lactoglobulin:  constituent about 50% of whey proteins that formed in the udder,  Denaturation begins at 60  C  At high temperatures sulphurous compounds such as hydrogen sulphide are gradually released. Which is responsible for the “cooked” flavour of heat treated over 75C. ‫سبب الطعم المميز اللبان الشركات مع حاجات تانيه‬ ‫لسه هنقولها‬ The ratio of casein: whey proteins shows large interspecies differences; -in human milk, the ratio is c. 40 : 60, ‫لما تشوف النسب ده هتعرف ان مفيش احن من االم عليك‬ -in equine (mare's) milk it is 50: 50 ‫لما تروح تبوس ايد امك ولما تستغرب قولها الدكتورة قالتلي‬ -while in the milks of the cow, goat, sheep and buffalo it is c. 80: 20. ‫ساعتها هتقولك هم بقوا يدرسوا مادة الدين في الجامعة‬ ‫قولها اه‬ Just for your information: Camel milk was the most acidic due to high content of vitamin C and the richest in total proteins and ash whereas donkey milk had a neutral pH (7.03±0.02) and characterized by low proteins and fat content, being very close to human milk. Human pH (7.15) However, protein profile of camel milk was very similar to that of human milk. So camel milk was suggested to be the most suitable substitute for cow milk when considering preparation of infant formulas. https://www.researchgate.net/publication/280494239_Comparison_of_composition_and_whey_protei n_fractions_of_human_camel_donkey_goat_and_cow_milk Lactose is a sugar found only in milk Lactose (milk sugar) is a disaccharide, consist of two monosaccharides glucose and galactose. Compared with many other sugars, 1- Lactose is only about 1/6 as sweet as can sugar (sucrose). 2- lactose is relatively less soluble in water; what’s the result of?? ………………………….. This relatively low solubility can cause some manufacturing problems because lactose crystallization are  gritty in texture. ‫رملي‬  also responsible for caking and lumping of dried milk during storage, particularly if moisture is absorbed from the air. 7 Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 3- Lactose, if milk is heated to a high temperature, and is kept at that temperature, it turns into brown colour and acquires a caramel taste, ‘’caramelisation’’ ‘’ Maillard reaction.’’ ………………. Why? …………………………………………………………………………………………………………………………………………………………………......................................................................................................................................................................... 4- Formation of lactic acid by action of bacteria that convert lactose into lactic acid, acidity help in absorption of Ca ion in intestine. Lactose intolerance Lactose intolerance= is caused by lactose malabsorption, A condition in which small intestine makes low levels of lactase that can’t digest all the lactose. Symptoms vary from person to person, but may include: gas, diarrhea, bloating, belly pains and nausea. There is no treatment for lactose intolerance, but symptoms can be managed through diet changes…… can eat dairy products as yogurt and cheese N.B: By aging …..some persons found difficulty with dairy product digestion be can develop?? ……………………………………………………………………………………………………………………………………. Glactosemia ‫الزم تعرف انها قليلة علي مستوي العالم بس‬ ‫اعرفها بردوه‬ it is caused by the inability to metabolise galactose due to a hereditary ‫عيب يا بني انت دكتور الزم تبقي عارف‬ deficiency of galactokinase, The incidence is about 1:40,000 Lack of the enzyme leads to the accumulation of galactose in eye lens, causing cataract in adults In young, it interferes with the synthesis of glycoproteins and glycolipids (important for membranes, e.g., in the brain) that causes results irreversible mental retardation within 2–3 months and eye cataract. Minerals and salts in milk - The total concentration is less than 1%. - Mineral present in milk into forms soluble from: as Salts exist in a true solution, and other mineral as, potassium and chloride) partially associated with casein molecules (cases of calcium, phosphate, magnesium and citrate) …. Calcium is present in colloidal solution or bound to proteins. , 50 of Ca with phosphorus % is bound in colloidal bound to casein, and , 35% of calcium is solubilized, Special technological significance of calcium, as it must be present in sufficient quantities for protein coagulation to occur. When milk is boiled or pasteurized, ……………10 to 20% of the calcium becomes less available to the body. 8 Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 Milk fever Time of occurring: usually occurring in high-producing dairy cows, but also less commonly in ewes and sows the first four days after giving birth, but can occasionally occur before the cow calves or months afterwards. Causes: Milk fever is caused by a calcium deficiency. Sings: ‫الصورة عشان لما تشوف الحالة في المزرعة وتخد فلوس انك علجتها تفتكرني وتدعلي‬ Hindquarters sway ‫ رعشة في االرجل الخلفية‬with slight increase in body temperature then decease, she usually lies on her ‫رعشة ترقد وتلف رقبتها وممكن تموت لو ملحقتهش بالكالسيوم؟‬ brisket with her head turned into her flank, dull eye, weak ‫ليه بقي ممكن تموت من نقص الكالسيوم؟ اسأل دكتور الفسيولوجي عشان تستفيد‬ ‫واكتب االجابة هنا وتعالي قولي عليها بردوه عشان اعرف انك استفدت‬ heartbeat, then death Treatment It is essential to get calcium into the blood as quickly as possible. The standard treatment is calcium intraveneously or subcutaneously., with magnesium and phosporus. ______________________________________________________________________________ The amounts of salts present are not constant. Depend on  the stage of lactation  nutritional status of the animal,  environmental and genetic factors,  contamination from the equipment during processing Towards the end of lactation, and case of udder disease, the sodium chloride content increases and gives the milk a salty taste ,‫اللبن ممكن يبقي مالح سيكا‬ phosphates about with 1% bound to lipids (in the fat globule membrane). Milk and dairy products are considered very poor sources of iron and copper and can supply smaller quantities of zinc Minor milk constituents 1- Phospholipids: e.g. Lecithin 2- Sterols: e.g. Cholesterol 3- Non protein nitrogenous substances: About 5% of the total nitrogen in milk, present as non- protein nitrogenous substances and includes ammonia, urea, creatinine, creatine and uric acid. 4- Vitamins: (a)- Water soluble vitamins: ………..B1, B2, B6, B12, nicin and pantothenic acid. There is also a small amount of vitamin C (ascorbic acid) present in raw milk but is very heat- labile and easily destroyed by pasteurization. (b)- Fat soluble vitamins: ……A, D, E and K. Vitamin D also is essential for the utilization of calcium. 5- Pigments: (a)- Water-soluble pigment as lactoflavin (b)- Fat soluble pigment as carotene. 9 Dr. Eman Fathi, food hygiene department, lecture 1,2, course 341 6- Enzymes: ‫مهمة ولسه هنشرحها بالتفاصيل‬ (a)- Of economic importance (e.g. Proteinase, lipase). (b)- Of heat treatment importance (e.g. Phosphatae, Peroxidase). (c)- Of sanitary importance (e.g. Reductase and catalase). 7- Gases: constitutes from 7 to 10% by volume as CO2, O2 and N2 from the surrounding atmosphere. 8-Cells: Body cells, degenerating epithelial cells, lymphocytes and leukocytes. Nutritive value of milk Milk Fat: -The most valuable part of milk components concerning the price as well as the caloric value. -Milk fat is more easily digested and absorbed without producing digestive disturbances than any other common edible fat. As it has low melting point. (less than 40oC) - About 97% of milk fat ingested is utilized by the body. - Milk fat increases the absorption of Calcium from the intestine in presence of Vitamin D. - Milk fat is a rich source of vitamins A, D, E and K (fat soluble vit.). - 1 gram of milk fat produces about 9 calories. Milk Protein (Nutritive value) - Proteins are built from approximately 20 amino acids, 18 of which are found in milk proteins. - A milk protein contains all the essential amino acids ‫(الزم تبقي عارفهم عيب بقي‬tryptophan, leucine, isoleucine, lysine, methionine, phenylalanine, therionine and valine) in sufficient amount as well as histidine which is essential for infants. - Casein is used as a reference protein with which nutritional quality of food protein is generally compared. - Milk proteins are rich in phosphorous as well as sulpher. - One-gram milk protein produces 4.3 calories. Lactose (Nutritive value) 1. As a source of energy, it splits into glucose and galactose, glucose is used for providing energy ‫ هرد عليك واقولك براحة ياعم بفكرك‬,‫قولي ما انا عارف‬ while galactose is considered as it nourishes the brain, especially the infants. ‫ده جديدة اظن بقي‬ 2. Fermentation of lactose leads to formation of lactic acid which: a). Kills the putrefactive bacteria. b). Favors the absorption of calcium from intestine as well as phosphorous and magnesium. 3. One gram of lactose provides 3.9 calories. Minerals  Milk is the best nutritional source of calcium; 1 quart (250 ml) of milk/day supplies the most daily requirement of most people except for pregnant and lactating woman.  lactating woman needs more calcium than that of pregnant one. ‫ قولنا بفكرك‬,‫هنا بردوه ما انا عارف‬  Calcium has an influence upon the clotting power of the blood, and it is necessary for normal regulation of the heartbeat.  Also, phosphorus is an important element for all body cells.  Milk is deficient in iron. ‫مهمة المعلومة‬ ‫عيب لما تقول اشرب لبن عشان‬ ‫يعوضك نقص الحديد او توصفه لالنيميا‬ ‫عيب يا بني انت دكتور متكسفناش‬ ‫المحاضرة اهي بدون لت وعجن‬ 10‫متنساش‬ ‫تدعلي وتدعلي لنفسك‬ ‫لو ذكرت المحاضرة قولي علي الجروب اعمليلي سؤالين كده يا دكتور اعرف بيهم نظام االسئلة بس‬ ‫بشرط اخد بيهم درجات منتظرة كومنتات علي الجروب المحاضرة جميلة وسهلة وخلصنها‬