Etiket Arşivleri: Milk

Peynir ve Yoğurt Oluşum Mekanizması ( Prof. Dr. Erdoğan KÜÇÜKÖNER )

PEYNİR VE YOĞURT OLUŞUM MEKANİZMASI
Prof. Dr. Erdoğan KÜÇÜKÖNER
Süleyman Demirel Üniversitesi, Mühendislik-Mimarlık Fakültesi, Gıda Mühendisliği Bölümü, Isparta
erdogankucukoner@sdu.edu.tr

Özet

Peynir ve yoğurt farklı hayvanlardan elde edilen sütlerden üretilebilmektedir. Birer protein jeli olan bu ürünlerde süt proteinleri ürünlerin oluşumunda temel önem arz etmektedirler. Peynir, sütün peynir mayası denilen uygun proteolitik enzimlerle ve/veya zararsız organik asitlerle pıhtılaştırıldıktan sonra; peynir altı suyunun ayrılması, pıhtının şekillendirilmesi ve tuzlanmasıyla elde edilen, taze veya olgunlaştırıldıktan sonra tüketilen bir süt ürünüdür. Yoğurt, fermentasyonda spesifik olarak Streptococcus salivarius subsp. thermophilus ve Lactobacillus delbruecki subsp. bulgaricus’un simbiyotik kültürleri kullanılarak elde edilen fermente bir süt ürünüdür. Yoğurt ve peynirin duyusal, kimyasal, beslenme ve sağlık açısından özelliklerini, üretimde süte uygulanacak işlemler ile depolama sırasında dikkat edilmesi gereken hususlar etkilemektedir.

Anahtar kelimeler: Süt, peynir, yoğurt.

Abstract

Cheese and yogurt are able to be produced from milks of different animals. Milk proteins in these products, being protein-gels, are important to the product formation. Cheese produced by removing whey from curds and salting and giving shape through press just after coagulation (curdling) of milk by proteolytic enzymes and/or harmless organic acids is a dairy product consumed as a fresh or a ripened. Yogurt is a fermented dairy product produced by specifically inoculation of symbiotic cultures of Streptococcus salivarius subsp. thermophilus and Lactobacillus delbruecki subsp. Bulgaricus during fermentation. Applied processes on milk in the production and the subjects watched out during the storage affect the properties of yogurt and cheese in terms of sensory, chemical, nutrition and health.

Keywords: Milk, cheese, yogurt.


Kaynak: http://helalvesaglikli.org/docs/kongre/1/sozlu_bildiriler/4_peynir_ve_yogurt_olusum_mekanizmasi_prof_dr_erdogan_kucukoner.pdf

Peynir Tozu ve Peynir Altı Suyu Tozu Üretimi ( Prof. Dr. Erdoğan KÜÇÜKÖNER )

PEYNİR TOZU VE PEYNİR ALTI SUYU TOZU ÜRETİMİ
Prof. Dr. Erdoğan KÜÇÜKÖNER
Süleyman Demirel Üniversitesi, Mühendislik-Mimarlık Fakültesi, Gıda Mühendisliği Bölümü, Isparta
erdogankucukoner@sdu.edu.tr

Özet
İnsan hayatındaki öneminden dolayı, sütün ürünlere işlenmesi gıda endüstrisinde önemli bir yere sahiptir. Bu süt ürünlerinden biri olan peynir; sütün ısıtılması, starter kültür ilave edilmesi, proteolitik enzimlerle pıhtılaştırılması, pıhtının süzülerek peyniraltı suyundan ayrılması, telemenin tuzlanarak ve baskılanarak şekillendirilmesi ile elde edilen, taze veya olgunlaşmış halde tüketilen besleyici bir süt ürünüdür. Peynir tozları gıda endüstrisinde çok farklı alanlarda kullanılmakla birlikte, en yaygın olarak gıdalara lezzet verme amaçlı kullanılmaktadır. Peynir tozunun bu özelliğinden çerez kaplamaları başta olmak üzere preslenmiş çerezlerde, peynir esaslı soslarda, çorbalarda, patates cipslerinde, tuzlu çeşnilerde ve tuzlu bisküvilerde yaralanılmaktadır. Sütünün peynir yapımından sonra katı kısımdan ayrılan geride kalan sıvı kısmına ise peynir altı suyu denir. Peynir altı suyu tozu gıda sanayinde; şekerlemeler, unlu mamuller, et ürünleri, çorbalar, soslar, içecekler gibi birçok üründe kullanılmaktadır. Ayrıca, hayvan beslenmesinde ucuz ve yüksek kaliteli protein kaynağı olmasıyla beraber karbonhidrat kaynağı olarak da tercih edilmektedir.

Anahtar kelimeler: Maya, peynir, süt, peynir altı suyu.

Abstract
Processing of milk has an important place in food industry due to its importance on human-life. One of the dairy product, cheese, produced by heating of milk, addition of starter culture, coagulation (curdling) by proteolytic enzymes, draining of whey, salting and giving shape by press is a nutritious product consuming as a fresh or a ripened. Cheese powder utilized in so many different areas of food industry is widely used as a flavor enhancer
for foodstuffs. This feature of cheese powder is utilized in firstly coating of snack foods, additionally cheese-based sauces, soups, potato chips, salty dressings and in salty biscuits. Remaining aqueous phase, separated from solid part in the cheese production, is named “whey”. In food industry, whey powder is used in different food products like candies, bakery products, meat products, soups, sauces, drinks etc. Furthermore it is preferred for animal-
feeding due to its high carbohydrate content besides to being a cheap and high quality protein source.

Keywords: Yeast, cheese, milk, whey.


Preparing Milk for Processing

Preparing Milk for Processing
Got Milk
What is Milk?
It is the normal secretion of the mammary glands of all mammals
Its primary purpose is to nourish the young of the species
The Cow
Principal source of milk for human consumption in the United States

A great deal of variety among the milk of different animals exists which affects processing
The Cow
The most important factor that determines the composition of milk is the breed of cow.
Dairies are inspected by veterinarians, they are regulated by States and Cities.

Essential to protect public health concerns
Cold temperatures and environmental conditions of cattle are important to milk quality.

Stainless steel is recommended for use in equipment because it does not react with milk to cause off-flavor
The milking operation stimulates muscles in the udder of the cow causing let-down of milk into teat canals.

The machines work like vacuums and suck the milk into receiving vessels that lead to a holding tank
Holding Tanks
Refrigerated to cool the milk to less then 8 degrees C in order to control bacterial multiplication

Milk should not stay in the holding tanks for more than 2 days before transporting.

Tank Trucks
Milk is shipped in sanitized milk cans by trucks from smaller dairies or by tank truck transportation from larger dairies.
Drivers inspect the milk to see if it is cold and has a good aroma.
They also take a sample for further processing
Inspection Standards
Samples are analyzed for fat and solid contents and microbiological data.

Tests are conducted to determine bacterial count, determination of sediment, and evaluation of milk flavor.
Grade A Pasteurized Milk Ordinance
1978 – Recommendations of the U.S. Public Health Services/ Food and Drug Administration is used as a guide to the setting of standards of milk quality
Milk Flavor
Can acquire off-flavor
Cows eating unusual feed and or by absorption of odors and chemicals.
Poor milk handling equipment
Copper causes oxidized flavors that are metallic, oily and fishy.
Health Consideration of Dairy Products
Milk and other dairy products are a significant amount of nutrients for humans.

Milk is a good source of protein, calcium, and riboflavin.
3 C’s of Milk
Always Keep Milk…..

Clean!
Cold!
Covered!
Health Consideration of Dairy Products
Cow’s milk unlike human milk must be modified to meet nutrient requirements of infants.
Milk is low in iron which babies need in order to prevent anemia.
Milk can help to prevent osteoporosis, acne problems, poor eyesight, and fragile teeth.
Trends in Consumption
Since 1975 the available milk supply has increased.
Campaign slogans…..
Got Milk?
Milk does a Body Good!
Three A Day (Milk, Yogurt, Cheese)

Review
What is the most important factor that determines the composition of milk?
Why do we want to keep milk in stainless steel containers?
How long should milk stay in holding tanks?
What can milk help prevent?

Manual Methods of Analysis of Foods ( Milk and Milk Products )

Contents

Types of Liquid milk

Preparation of sample

Detection of Adulterants

Cane sugar

Quantitative determination of sugar

Starch

Quantitative determination of starch

Cellulose Added Urea

Quantitative determination of urea

Ammonium Sulphate

Glucose

Sodium Chloride

Saccharin

Dulcin

Foreign Fat

Neutralisers

Hypochlorites and Chloramines

Quarterly Ammonium Compounds

Detergent containing Alkyl benzene sulphonic acid

Skimmed Milk Powder

Gelatin 16

Detection of Preservatives

Formalin

Hydrogen Peroxide

Boric acid and Borates

Salicylic acid

Phosphate Test for Pasteurisation in milk

Turbidity Test for Sterilised milk

Determination of Total Solids

Determination of Fat

Cream including Sterilised Cream, Whipped Cream and Malai

Determination of Fat

Thickeners in Cream

MILK AND MILK PRODUCTS MANUAL FOR ANALYSIS OF MILK AND MILK PRODUCTS

Cream Powder

Curd

Determination of Fat

Determination of Total Solids

Channa or Paneer

Cheese (All Varieties)

Ice Cream, Kulfi and Chocolate Ice Cream,

Dried Ice Cream Mix, Dried Frozen Dessert

Condensed / Evaporated (Sweetened, unsweetened and Skimmed) Milk

Milk Powder ( Whole, Skimmed, Partially Skimmed) Infant Milk Food, Milk Cereal Weaning Food etc

Khoa

Table ( Creamery ) and Deshi Butter

Ghee /Butter Fat

Chakka and Shrikhand

Yoghurt

Whey Powder

Edible casein products

Determination of Lactose by Colorimetric method in Milk based Sweets

Source

Milk Microbiology

What is Milk Microbiology?

Basically it’s the study of Milk and its microorganism.

Microbiology?

Is the study of Microorganisms; under this are bacteria, virus, protozoal parasites, and fungi.

What is Milk?

It is a white liquid produced by mammary gland of animals. It is the primary nutrition of the young before they are able to digest more complex food. Throughout the world there are 6 millions consumers in the world.

Milk is sterile at secretion in the udder but is contaminated by bacteria even before it leaves the udder. Further infection of the milk by microorganisms can take place during milking, handling, storage, and other pre-processing activities.

Raw milk – The lacteal secretion, practically free from colostrums obtained by the complete milking of one or more healthy cows (PMO).

“Consumer Milk” products:

– Homogenized milk: ³3.25% fat

– Reduced fat milk: 2% fat

– Low fat milk: 1% fat

– Fat-free milk: skim milk, <0.5% fat

(all with 8.25% solids-non-fat)

Introduction

Fermented milk or dairy products have been part of human diet since ancient times. Various fermented products are made by different strains. Lactic acid fermentation is performed most often by lactic acid bacteria. Due to their abundance in nature, including mucosal surfaces of the human body, and their use in fermented foods they are labeled as GRAS (generally recognized as safe). The main genera that belong to the lactic acid bacteria group are: Lactobacillus, Leuconostoc, Lactococcus, Pediococcus and Streptococcus.

These bacteria ferment the carbohydrates in milk, the major one being lactose, to lactic acid and some other products. The acid precipitates the proteins in the milk and that is why fermented products are usually of thicker consistency than milk. The high acidity and low pH hinders the growth of other bacteria, including pathogens. Some lactic acid bacteria can produce agents with antimicrobial properties. Since milk is rich in many nutrients such as protein, calcium, phosphorus, and B vitamins dairy products are an excellent food.

Physical and Chemical Properties of MILK

It is a white emulsion or colloid of butter fat globules

Has yellow-orange carotene imparts the creamy yellow color to the glass.

Contains 30-35% grams of protein per liter of which about 80% is arrange in casein micelles

Different carbohydrates such as: lactose, glucose, galactose, and other oligosaccharides

Vitamins A, B6, B12, C, D, K, E, thiamine, niacin, biotin, riboflavin, folates, and pantothenic acid are present

Origin of microorganism in milk

  • Commensal micro flora- teat skin, epithelial lining of the teat canal, duct that conveys the milk from the mammary gland to the teat orifice.

  • Environmental contamination- soil, water equipment, dairy farm area are reservoir for many food borne pathogens

YOGURT

a semisolid sourish food prepared from milk fermented by added bacteria, often sweetened and flavored.

Mixed starter culture – S. Thermophilus and lactobacillus delbrueckii or lactobacillus bulgaricus.

Ratio 1:1

Fermentation: lactose content of milk to yield lactic acid, CO2, acetic acid, diacetyl and acetaldehyde

Ph reduce: around 6.5 to 4.5 due to the production of organic acids

Initially streptococcus thermophilus ferments the lactose

Lactobacillus bulgaricus, which is more acid tolerant, continues to ferment the remaining lactose.

BENEFITS of Yogurt

– Easier digestibility,

– The ingested organisms enhance bioavailability of nutrients

– Ensure gastrointestinal balance,

– Promoting colon health

– Accelerates the healing of gastrointestinal tract disorder

– Reduction in cholesterol level.

Changes in milk by microorganism

Gas production: Fermentation occurs at faster rate, then raw milk present a foamy layer on the upper surface Air bubbles becomes entrapped and gas becomes saturated throughout the body of the milk. Colliforms, clostridium and bacillus species.

Roppiness or sliminess: Milk viscosity is increased, rope like structure is formed

Change in the color of milk

Blue color – pseudomonas synciani

Red color –  brubibacterium erythrogenes,  sarcinia marcense

Yellow color – pseudomonas synxantha

Brown color – pseudomonas putrificians

Green color – pseudomonas  aurogenosa

Change in the Flavor of Milk

Sour Flavour:
It is due to acidic changes in the milks:

– Clean: Low contents of acids, Streptococcus lactis

– Aromatic:  streptococci and aroma- forming Leuconostoc sp. , moderated type of acidic components.

– Sharp: coliform bacteria, clostridium species,  volatile fatty acids, high acidic contents

Bitter Flavour:
It is due to alkaline changes in the milk.Potato-like Flavour:
Pseudomonas mucidolense

Fishiness:
Acromian hydrophila, It is due to formation of tri-methyl amine

IMPORTANCE OF BACTERIA IN MILK

  1. Bacteria – Are microscopic, unicellular, occurs in the form of spherical, cylindrical or spiral cells; Size 1-5m.  Sore forming bacteria produce trouble in dairy industry because of their resistance to pasteurization & sanitization produces. Greater the bacteriological count in milk, the lower is its bacteriological quality. Pasteurized milk should have a SPC (Standard Plate Count)/ml (org) not exceeding 30,000.

  2. Moulds/ Molds – Multi-Cellular; in maturity are as Mycelium. Used in cheese making which is responsible for defect in butter and other milk products. Spores are destroyed by pasteurization. It should also be noted that moulds, mainly of species of Aspergillus , Fusarium , and Penicillium can grow in milk and dairy products.

  3. Yeast – Unicellular; Larger than Bacteria. Destroyed during pasteurization.

  4. Viruses – Are ultra-microscopic forms of like can be destroyed by pasteurization or higher heat treatment.

GROWTH OF MICROORGANISM

Bacteria multiply during production and holding of milk, depending on storage time and conditions.  The changes take place in the physico-chemical properties of milk are result of the activities of the individual microbial cells during their period of growth and reproduction or of substances produced during such activity.

Stages of growth :

  1. i. Initial stationary phase

  2. Lag phase (Phase of adjustment)

iii. Accelerated growth phase (log phase)

  1. Maximum stationary phase

  2. v. Phase of accelerated death.

Products of Microbial Growth :

  1. i. Enzymesii. Decomposition products (fats, proteins, sugars).

iii. Pigments

  1. Toxins

  2. v. Miscellaneous changes.

Destruction of Micro-organisms :  May be done by following means.

  1. i. Heat – Most widely used. Pasteurization & sterilization.

  2. Ionizing radiation – Such as ultraviolet rays etc.

iii. High frequency sound waves – Supersonic and ultrasonic.

  1. Electricity – Microbes are destroyed actually by heat generated.

  2. v. Pressure – Should be about 600 times greater than atmospheric pressure.

  3. Chemicals – Includes acids, alkalis, hydrogen peroxide, halogens etc.

Factors Influencing Growth :

  1. i. Food supply – Milk and its products are good food source, provides all food requirements.

  2. Moisture – Milk contains adequate moisture to development.

iii.  Air – Supplies O2  to aerobic bacteria and moulds.

  1. Acidity or pH – Preferably range 5.6 to 7.5.

  2. v. Preservatives – Check growth depending upon concentration.

  3. Light – More or less harmful.

vii. Concentration – High sucrose or salt content check growth.

viii. Temperature – Important means for controlling growth.  According to their optimum growth temperature, bacteria can be classified into :

  1. Psychotropic – can grow at refrigeration temp. 5-70C.

  2. x. Mesophilic – can grow at temp. 20-400

  3. Thermophilic – can grow at temp. above 500C.

Results of Microbial Growth in Milk :

  1. i. Souring:- Most common, due to transformation of lactose into lactic acid & other volatile acids & compounds, principally by lactic acid bacteria.

  2. Souring & gassiness:- Caused by coil group, indicates contamination of milk and its products.

iii. Aroma production:-  Due to production of desirable flavour compounds s.a. diacetly.

  1. Proteoloysis:- Protein decomposition leading to unpleasent odour.

  2. v. Ropiness:-  Long threads of milk are formed while pouring. Mainly Alkaligenous viscus.

  3. Sweet curdling:- Due to production of a remain like enzyme curdles milk without souring.

DISEASES Outbreaks ASSOCIATED with MILK PRODUCTS

Microbiology Analyses

Standard Plate Count (SPC):

Aerobic plate count of total colony forming units of bacteria per milliliter or gram of raw, processed liquid and dry dairy products utilizing “SMEDP” 17th edition.

Bactoscan Analysis:

an NCIMS approved alternate test for SPC ( Standard Plate Count) on Raw Milk. Bacterial cells in a sample are lysed, liberated DNA is stained, and passed through light. The signal from the DNA is converted to an estimate of Bacteria and CFU’s in the original

Microbiology Analyses

Coliform Colony Forming Unit (CFU) Test:

Agar plate method employing a media (VRB) optimizing the growth of coliform organisms

Yeast and Mold Plate Analysis:

Determination of yeast and mold cell forming colonies in a dairy sample under specified conditions utilizing “SMEDP” 17th edition.

Microbiology Analyses

Direct Micro Count (DMC):

Direct microscopic count examination of stained preparation of milk, or certain other dairy products, to identify and enumerate the number of bacterial clumps present

Lab Pasteurized Count (LPC):

Raw milk in test tubes heated to 62.8C +/- 0.5C, survivors counted by standard plate count method utilizing  “SMEDP” 17th edition.

Microbiology Analyses

Pre-Inc Plate Loop Count (PI):

Raw milk sample undergoes preliminary incubation at 13 degrees Celsius for 16-18 hours before analysis to stimulate the growth of psychrotrophic organisms and subsequently a Plate Loop Count (PLC). Is performed utilizing “SMEDP” 17th edition.

Antibiotic Sensitivity Test:

Test for sensitivity/resistance to antibiotics used in treatment of mastitis infections using the Kirby Bauer (agar diffusion) method.

Microbiology Analyses

E-Coli:

VRB-MUG Agar plate test

E-Coli 0157:H7:

(AOAC Official Method) for identification and presumptive identification of E Coli H157:H7

PRESERVATION of MILK

METHODS

Pasteurization

Sterilization

Dehydration

1) Pasteurization

is a process of heating a food, which is usually a liquid(milk), to a specific temperature for a predefined length of time and then immediately cooling it after it is removed from the heat. This process slows spoilage caused by microbial growth in the food.

– Inactivation of bacterial pathogens (target organisms Coxiella burnettii)

– Assurance of longer shelf life (inactivation of most spoilage organisms and of many enzymes)

– Does not kill all vegetative bacterial cells or spores (Bacillus spp. and Clostridium spp.)

– Pasteurization temperature is continuously recorded

HISTORY OF PASTEURIZATION

The French scientist Louis Pasteur invented pasteurization.

To remedy the frequent acidity of the local wines he found out experimentally that it is sufficient to heat a young wine to only about 50–60 °C (122–140 °F) for a brief time to kill the microbes.

Pasteurization was originally used as a way of preventing wine and beer from souring, and it would be many years before milk was pasteurized.

Pasteurization of milk was suggested by Franz von Soxhlet in 1886.

Louis Pasteur

Sterilization

is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents (such as fungi, bacteria, viruses, spore forms, etc.) present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media.

Dehydration

Dehydrated milk is manufactured dairy product made by evaporating milk to dryness.

Dehydration

Purpose: to preserve it; milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content.

– First invented by Russian physician Osip Krichevsky in 1802.

– Commercially available in 1832 by Russian chemist M. Dirchoff.

Milk drying methods

Spray Drying – Pasteurized milk is first concentrated in an evaporator to approximately 50% milk solids. The resulting concentrated milk is then sprayed into a heated chamber where the water almost instantly evaporates, leaving fine particles of powdered milk solids.

Spray Drying

Drum Drying – Milk is applied as a thin film to the surface of a heated drum, and the dried milk solids are then scraped off. However, powdered milk made this way tends to have a cooked flavor, due to caramelization caused by greater heat exposure.

Freeze Drying – Same as drum drying but involves freezing which retains more amount of nutrition.

Freeze Drying

New bacteria discovered in raw milk

Chryseobacterium oranimense, which can grow at cold temperatures(7°C)  and secretes enzymes that have the potential to spoil milk.“

  1. haifense and C. bovis

END

By : Gladys Jane Aguhayon

BsBiology – Microbiology

İçme Sütü Üretimi Aşamalarında Trans Yağ Asitlerinin Belirlenmesi ( Emine ALKIN )

ÖZET

Bu araştırmada; içme sütü üretim aşamalarındaki trans yağ asitlerinin belirlenmesi amaçlanmıştır. Bu amaçla; örnek bir süt fabrikasına gelen ve işlenen sütlerin trans yağ asitleri cins ve % miktarları yağ asidi metil esterleri şeklinde GC ile belirlenmiştir. Sonuçlar istatistiksel olarak değerlendirilmiştir.

Sütün bileşimi üzerine; hayvanın ırkı, laktasyon periyodu, meme hastalığı, sağım aralığı, beslenmesi ve mevsimler olmak üzere çeşitli faktörler etkili olmaktadır. Süt yağı; sütün en değerli bileşenlerinden biridir ve diğer hayvansal yağlardan çok çeşitli yağ asitlerini (doymuş ve doymamış) içermiş olması özelliği ile ayrılmaktadır. Süt yağındaki yağ asitlerinin gıda değerinin yanında, aroma ve tekstür oluşumu açısından da büyük önem taşıdığı da bilinmektedir. Ülkemizde süt ve trans yağ asitleri üzerine birçok araştırmalar yapılmasına rağmen, üretim aşamalarının trans yağ asidi üzerine etkileri incelenmediği görülmüştür. Yağların fiziksel, duyusal ve fonksiyonel özellikleri, insan sağlığına etkileri ve muhafaza koşulları kimyasal yapıları ile ilgilidir. Yağlara farklı özellikler kazandıran kimyasal yapı, trigliseritler ile içerdikleri yağ asitleri çeşit ve miktarları ile ifade edilmektedir. Yağların bu değişik etkilerinde farklı yağ asidi bileşimine sahip oluşları ve herhangi bir teknolojik işleme tabi tutulmuş iseler, bu işlem sonucu uğradıkları değişim önemli rol oynamaktadır.

Yapılan çalışmada; toplam trans yağ asidi miktarları; çiğ sütlerde %2.86–6.30, pastörize sütlerde %1.85–6.55, sterilize sütlerde %2.50–9.77, 1 hafta 50C’de depolanmış sütlerde %3.28–11.67, 1 hafta 200C’de depolanmış sütlerde ise %5.32–7.12 arasında tespit edilmiştir. Elde edilen sonuçlar istatistiksel olarak değerlendirildiğinde üretim aşamalarının trans yağ asitleri oluşumu üzerine etkisi önemsiz bulunmuştur.

Anahtar Kelimeler: İçme sütü, trans yağ asidi, kalite

ABSTRACT

Determination of trans-Fatty Acids on the Milk Processing Stages

In this study, it has been aimed to determine trans fatty acids in drinking milk processes. With this aim, the trans fatty acids percent amount and type in the milk come and processed from a sample milk factory have been determined as a fatty acids methyl ester forms by GC. The results are evaluated by statically.

The composition of the milk is related with assorted factors like strain of animal, period of lactation, diseases of nipple, hiatus of milking, nutrition of animal and seasons. Milk oil is one of most valuable composition of the milk, separates from other animal fat with containing many various fatty acids (saturated and unsaturated). The fatty acids in the milk oil are also known with being an important role on the creation of texture and aroma. Physical, sensorial and functional properties of oils, their affect on human health, and their conservation conditions are related with their chemical composition. The chemical composition which gives them different properties finds voice in triglyceride and type and amount of fatty acids of it. The different composition of fatty acids and the mutation under any technological process have important role on this various influence of oils.

In this study, total trans fatty acid amounts of raw, pasteurized, sterilized, storages of 50C at one week, storages of 200C at one week were within the ranges 2.86–6.30%, 1.85–6.55%, 2.50–9.77%, 3.28–11.67%, 5.32–7.12%. The results of obtained were evaluated by statically; there were found that the effect of milk production processes is unimportant.

Key Words: Milk, trans-Fatty Acids, Quality

Milk Powder

It is beyond doubt that the milk powder market, or more correctly: the market for milk powder, is an exciting and promising market that has shown tremendous growth that will not come to an end in the near future. However, it remains to be seen how fast this market will develop and what volume it will reach. There is an increasing rate in production and consumption of milk powder according to the tables. That show as milk powder marketing will replace the milk marketing. Milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content and r its low bulk that is benefit for economy of transportation. Because of all these profits, milk powder marketing will instead of milk marketing.

Type of milk powder changes according to amount of fat is included. That is the another benefit of milk powder. However, there is some critical point. For example moisture content, storage temperature. The moisture content of materials plays a very significant role. Because it has a direct influence on product quality and the processing of semi-finished and end products.

Finally, this project informed me about milk powder which is developed day by day and an alternative dairy product for the new world. Thus, I would like to send my regards and pleasure to my advisor Y. Doc. Dr. Çiğdem SOYSAL for encouraging me in this project.

….

Laboratory‎ > ‎Milk

PURPOSE:

The purpose of this experiment was to investigate the coliform in milk and learn methylene blue reduction test and direct microscopic count method for milk.

THEORY:

The Standard Plate Count (SPC) procedure is used to determine the number of bacteria in a sample. In most cases the initial day SPC represents those bacteria that survive pasteurization (thermoduric), although gross contamination after pasteurization can cause high counts. The regulatory standard of < 20,000/ml is generally easily achieved. Most initial day bacteria counts are <500/ml while counts higher than 1000/ml suggest a potential contamination problem, either in the raw milk supply or within the processing equipment.

The ideal milk shows no increase in bacteria counts during refrigerated storage. When milk is held under refrigeration, only bacteria capable of growth under these conditions will grow. While most bacteria prefer warmer temperatures for growth, some bacteria, referred to as psychrotrophs (“cold-loving”), are capable of growth at 45oF or less. The most common types of psychrotrophic bacteria that rapidly spoil milk do not survive pasteurization; thus their presence in milk is the result of post-pasteurization contaminants due to less than adequate sanitation practices. The initial day SPC of fresh pasteurized milk is not a good indicator of the numbers of psychrotrophs present since most bacteria that survive pasteurization are not psychrotrophic (a few types of thermoduric bacteria will grow slowly under refrigeration conditions). A significant increase in the SPC after 7-10 days of refrigeration storage is evidence of psychrotrophic growth and suggests that post-pasteurization contamination has occurred and that shelf-life will be shortened. Generally, when the SPC exceeds 1 – 100 million, the product will become unacceptable due to flavor defects related to bacterial growth. The key to preventing spoilage and extending the shelf-life of a product is to prevent post-pasteurization contamination through a well-designed quality assurance program. It only takes one psychrotrophic bacteria per container of milk to cause spoilage.

The coliform bacteria (coli) count is used as an index of sanitation during the handling and processing of milk products. Coliforms are killed by pasteurization, thus when present in milk, they are regarded as post-pasteurization contaminants resulting from poor sanitation.  Though the standard is “not to exceed 10/ml,” detection of any coliform bacteria suggests that there is some point in processing that has been neglected in regard to effective cleaning and sanitation procedures. As a rule, the detection of coliforms in milk will indicate the potential for a shortened shelf-life due to concurrent contamination with psychrotrophic bacteria. Milks with coliform counts exceeding 10/ml are not tasted on subsequent days in this program.

MATERIALS:

  • Tcyptone glucose yeast agar

  •  Milk

  •  Methylene blue solution

  •  Tubes

  •  Pipette

  •  Spreader

  •  Bunsen burner

  •  Test tube rack

  •  Etuv

  •  Ethyle alcohol

PROCEDURE 1:

1 – Total Count:

Firstly; milk was diluted from non dilution milk to 10-5 dilution in the test tube. In order to make 1 ml non-dilution milk was taken and it was added to 9 ml distilled water and thus 10-1 milk dilution was occurred and this process was continued to 10-5 dilution. After that; 0, 2 ml dilution was taken with pipette from each dilution (non-dilution, 10-1, 10-2, 10-3, 10-4, 10-5) these were inoculated to tcyptone glucose yeast agar with spread plate method. Then; these were incubated at 37 oC for 24 hours. After incubation, between 300 – 30 being microorganisms were counted and in ml numbers of microorganisms were calculated.

2 – Methylene Blue Reduction Test:

Secondly; raw milk and pasteurized milk were studied separately. 10 ml milk was put in the test tube and 3 – 4 drops methylene blue solution was added to milk. Then; milk and methylene blue solution were mixed vigorously, then; these tubes were incubated at 37 oC for 30 minutes. Milk was examined and observed whether decolorization was occurred or not.

RESULTS 1:

Total Count:

 

non

10-1

10-2

10-3

10-4

10-5

A – raw milk

TNTC

359

284

65

38

9

B – paste. Milk

TNTC

47

2

0

0

0

C – raw milk

TNTC

TNTC

TNTC

198

33

7

Group A)         For 10-2 dilution: (284*102) / 0, 2 ml = 142000

For 10-3 dilution: (65*103) / 0, 2 ml      = 325000

For 10-4 dilution: (38*104) / 0, 2 ml      = 1900000

(142000+325000+1900000) / 3 = 789000

Group B)         For 10-1 dilution: (47*101) / 0, 2 ml      = 2350

Group C)         For 10-3 dilution: (198*103) / 0, 2 ml = 990000

                        For 10-4 dilution: (33*104) / 0, 2 ml      =1650000

(990000+1650000) / 2 = 1320000

Methylene Blue Reduction à this method depends on the ability of microorganisms to change oxidation-reduction potential of medium. Bacteria consume dissolved oxygen in medium and produce some enzyme. These enzymes oxidize substrate and hydrogen removed from substrate and hydrogen was held with methylene blue solution and light blue of milk converted to white or colorless.

PROCEDURE 2:

3 – Coliform Test:

Firstly; milk was diluted from non-dilution to 10-5 dilution, then 0, 2 ml diluted and milks were spread out on violet red bile agar with spread plate method then plates were incubated at 37 oC for 48 hours. After 48 hours number of colonies was counted and in ml number of microorganisms was calculated.

4 – Direct Microscopic Count Method:

In here; firstly; slide was taken and on slide 1 cm2 area was determined and one loopful raw milk was put on this area and raw milk was spread out with distilled water in this area. Then; on slide milk was waited to get dry in air. After that; one loopful xylol was added on each square and waited for 1 min then slide was washed with water. Afterwards; 1 – 2 drops methylene blue was added onto each square and waited for 2 min and again slide was washed with water. Next; slide was got dry in air. Finally; on each square, one drop iol immersion was added and milk was examined under 100X objective.

RESULT 2:

Coliform Test:

 

non

10-1

10-2

10-3

10-4

10-5

A – raw milk

TNTC

TNTC

TNTC

165

16

2

B – raw Milk

TNTC

TNTC

TNTC

TNTC

10

3

C – raw milk

TNTC

TNTC

TNTC

50

15

2

Group A)         For 10-3 dilution: (165*103) / 0, 2 ml = 825000

Group C)         For 10-3 dilution: (50*103) / 0, 2 ml = 250000

Direct Microscopic Count Method:

 

1st region

2nd region

3rd region

4th region

5th region

1st half slide

3

6

8

14

21

2nd half slide

2

4

5

10

15

1st half slide à 3+6+8+14+21 = 52

2nd half slide à 2+4+5+10+15 = 36

Average number of microorganisms = (52+36) / 10 = 8, 8

Average number of m/o’s = 8, 8 * 15700 * 100 = 14130000

In here 100 is 0, 01 ml milk.

DISCUSSION:

        In this experiment; we examined microbiological properties of milk. In milk number of microorganisms was calculated with total count method and coliform bacteria were investigated with coliform test. Also; methylene blue test was applied the milk. In this test one drop methylene blue solution was dropped into milk and colour of milk was slightly blue. After 30 minute slight blue colour of milk converted to white, this transformation was related with number of microorganisms in milk. Microorganisms were used the dissolved oxygen and microorganisms produced certain enzymes. These enzymes oxidize the substrate, thus hydrogen was removed from substrate. Hydrogen was held with methylene blue solution and color of milk was colourless this process was called decolourization. In addition; while raw milk decolorized for 30 minutes pasteurized milk decolorized for 4 – 5 hours. This showed that; in raw milk, number of microorganisms was more than in pasteurized milk.

        Secondly; number of microorganisms was determined with total count method. In each milk dilution, number of microorganisms was calculated with accordance to between 30 – 300 microorganisms and as a result; we observed that raw milk was to contain more number of microorganisms than pasteurized milk.

        Next; coliform test was applied the milk and in here number of microorganisms was calculated. Finally; in milk microorganisms was examined with microcopy and dark blue microorganisms were observed and at five regions average number of microorganisms were calculated, and these were determined at the result and calculation.