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Principles of industrial production


Commissioning of a new plant

After erection of a new spray drying installation it has to be brought into operation. This phase is called commissioning and proceeds in several stages:

  1. Mechanical test of all individual components,
  2. Test and calibration of control instruments,
  3. Performance test with air,
  4. Performance test on water,
  5. Performance test on the product(s) for which the spray dryer was designed,
  6. Fine tuning of the plant to achieve the design specification (both as to product quality,
  7. consumption of energy and capacity),
  8. Training of operators, and
  9. Final acceptance test and issue of a performance certificate.
With the acceptance test, the plant fulfils the requirements specified by the supplier in the contract. The whole commissioning period normally takes 1 to 4 weeks, depending on the complexity of the installation and number of products. However, on multi-purpose plant drying a number of products, it may take longer.

Causes for trouble-shooting

If during the intended commissioning period, the specified parameters have not been achieved, efforts are concentrated on how to identify, locate and remove the reasons for the problem. This involves a trouble-shooting exercise conducted as part of the commissioning program. 

However, commissioning is usually finalized successfully to time schedule and the plant quickly in commercial production. In factories faced with their first spray drying installation there has to be a training period during which the factory staff learns how to operate the dryer and the overall behaviour of the plant. However, even in factories having long experience with spray drying and possessing high level of technological knowledge, a training period is still needed, during which both the operators, engineers and maintenance staff acquaint themselves with the new plant since every spray drying installation has its own operational features. The experiences from one spray dryer cannot automatically be applied directly to another one. The development in spray drying has been very fast during the last 20 - 30 years. Therefore an existing spray dryer may not represent the best available technology. 

Experience has shown that problems can occur suddenly even in a well-established, well operated and well maintained plant with experienced staff after many years of successful operation. Such situation is in fact the most typical case calling for trouble-shooting and the problems the trouble-shooter is faced with normally fall into following categories:

  1. Lack of capacity 
  2. Excessive deposits somewhere in the system 
  3. Excessive energy consumption 
  4. Product quality defects
  5. Excessive powder stack loss 
  6. Bacteriological contamination
In broader sense, trouble-shooting involves also the development of technology for a new product or a product of upgraded quality. Generally speaking all advances in current technology aiming to upgrade the quality, to reduce the consumption of energy or increase
the capacity can be considered as the outcome of successful trouble-shooting. However, such projects should be planned in advance and conducted in off-peak season. On the other hand, sudden occurrence of problems indicated above requires immediate action, especially if they appear in the peak season.
The first approach to a trouble-shooting operation is to find out when the problem appeared and what changes of technology and/or which modifications of a product composition might have been implemented, just before the problem occurred. For such an evaluation availability of production documentation, such as production log books, installation maintenance books, laboratory analysis records both of raw milk and all raw materials, intermediate control and final product control data, is extremely helpful. It is therefore very important to keep the log sheets and other production records and reports up-to-date at all time.

Production documentation

If a need for trouble-shooting suddenly occurs, the most appropriate approach after briefing about the problem and - if the first routine check of the plant and operation has not brought any explanation - is to find the answers on the above when-what-which questions basis, i.e. to trace when it has appeared and possibly in which consequence. The answers to such questions can be found by interviewing the staff and referring to the records and production documentation. Sometimes it is necessary to go through the documentation of the last few months or even to compare data with the same season of the previous year.

The trouble-shooting is greatly facilitated, if such documentation is readily available and kept intact. 


Production log sheets

It is strongly recommended to keep all production run records containing data written down by the operators with ½ or at least 1 hour intervals. The importance of such practice cannot be emphasized strongly enough, even with modern, computerized plants having full data logging and trend facilities. In the modern electronic data processing it is dangerous to assume that the computer can fully replace the human factor. There are many good reasons to continue with manual operational data recording.

First of all, the tabular type log sheet representing one page for one day operation is easier to survey than a computer print-out. Computer print-outs often involve plenty of paper.

Secondly, it is well known that in modern life direct contact with figures can easily be lost. Therefore an operator, who writes down for 8 hours a day about 20 figures every half hour and does that throughout the whole year, can definitely keep in mind the important parameters better than his colleague just watching a computer screen.

The general rules for keeping production log books are:

  1. Separate log-book (or a file of daily log-sheets) for the evaporator and the spray dryer,
  2. Separate log-books for each product,
  3. Headings describing each production run by type of product, required quality (possibly a number of quality specifications, if any), number of operational parameters specification (if any, see later), the plant configuration (as to optional possibilities which remain unchanged during the operation, i.e. size of nozzle inserts or where fines are introduced etc.), the names of supervisor, operators, laboratory worker responsible for the process control and any other information considered of local importance.
  4. A number of vertical columns sufficient to cover the time of reading all the important technological parameters which are shown on the control panel or measured directly by special instruments. It is also very useful to provide columns for the process control of the most important characteristics as final moisture, bulk density, solubility index, and possibly others, as measured by the laboratory or by operators themselves. It is also useful to have some columns expressing the production capacity (as raw milk intake to the evaporator, number of bags or load cell reading of a silo etc.) 
  5. Some space has to be reserved as a last column for remarks which serve for comments as to production irregularities, i.e. reasons for production interruptions with stop and restart times, observations as to component malfunctions which did not stop the production (i.e. if a nozzle blocked and had to be replaced), comments as to operator reaction to such irregularities and replies from maintenance staff regarding reported malfunctions (see Fig. 7.2. columns Faults and Repairs: Reported to: Date Repaired:) etc. 
  6. A number of rows for interval readings. Intervals should not be longer than 1 hour, preferably ½ hour
An example of a production log sheet for an evaporator and spray dryer with fluid bed and fines return for manufacture of instant whole milk powder is shown on Fig. 7.1 and 7.2. 
Evaporator log sheet
Fig.7.1. Evaporator log sheet
Spray dryer log sheet
Fig.7.2. Spray dryer log sheet

General maintenance log book

All components of the whole installation have to be serviced at regular intervals as specified by the manufacturer in the Plant Instruction Manual. Such service comprises oil change, lubrication, replacing of gaskets, filters etc. Beside a routine service there is sometimes a need for break-down service in a case of an accident, which requires immediate action.
Component Inlet Outlet Pressure Inlet °C Outlet °C
Inlet filter 0 -80 80 30 30
Supply fan -80 -150 230 30 35
Steam heater 150 110 40 40 180
Air disperser 90 -5 95 180 180
Main cyclone -60 -275 215 95 89
Suction fan -275 10 285 89 -
Transport filter 0 -40 40 30 -
Transport cyclone -180 -310 130 42 -
Transport exhaust fan -230 60 290 42 -
Component RPM kW AMP Volt % open
Supply fan 1455 28 15 415 100
Suction fan 1455 30 55 415 90
Transport exhaust fan 2850 5.5 10 415 -
Atomizer drive 2870 7.5 13.5 415 -
Feed pump 2870 5.5 10.5 415 -
Rotary valve 1 920 0.37 1.3 415 -
Rotary valve 2 920 0.37 1.3 415 -
Rotary valve 3 920 0.37 1.3 415 -
Conditions Water Feed Water Feed
Test duration (h) 0.5 0.5 TS% 0 43
Feed °C 28 45 Powder 0 255
Inlet air °C 167 167 Moisture - 3.4
Outlet air °C 95 95 PGR 12810 12670
Amount of feed kg 163 289.9 Evap.- 326 321.7
Table. 7.1. Check list for a spray dryer

A log book must be kept to record all service or intervention steps taken with description of the defect and the way the problem was solved. The remarks from the production log book as to malfunction or possible suspicion of malfunction of a component should be followed up by inspection of that component at the next production stop and the results of that inspection should also be recorded. 

It is also very useful to have a check list for control of the various components and to conduct such a control at regular intervals preferably each month. Such control involves, for instance, pressure drops across the air filters, cyclones and perforated plates, checking of thermometer and flow meter readings, safety pressure switches, functioning of the fire extinguishing equipment etc. A visual inspection of state of hygiene not only of the plant but of the whole plant building should belong to the everyday routine checks. 

It is also recommendable to organize a yearly inspection for potential hair cracks and welding failures in the dryer walls. An example of a check list for a small spray dryer with pneumatic transport system is shown on Table.7.1.

Product Quality Specification
Product: Instant whole milk powder 28% fat
Package: 500g and 2500g tins
Issued: XX.XX.XX
Property Value Method of Analysis
Moisture max.3% NA A1b
Fat content min.28.2% NA A9a
Titratable acidity max. 0.15% NA A19a
WPNI 2.5-3.0 ADMI
Insolubility index max. 0.3 ml IDF 135-89
Bulk density 650x 470-490 kg/m³ NA A2a
Fraction > 500µm max.8.0% NA A8a
Fraction > 125µm max.20% NA A8a
Sediment disc A ADMI
Free fat content max.1.9% NA A10a
Dispersibility min.94% IDF 89-78
Sludge 85 max.0.15 g
Sludge 20 max.0.15 g
Hot water test max.0.5 ml
Coffee test max.0.5 ml
Lecithin content 0.20-0.25% NA A22a
Vitamin A 2500-3000 IU/100g
Vitamin D3 500-600 IU/100g
Taste min. 15 points
Flavour min. 15 points
Colour min. 10 points
Total plate count max.5000/g
B.coli neg. in 0.1 g
Staphylococcus A. neg. in 0.1 g
Bacillus Cereus max. 100/g
Salmonella neg. in 500 g
Table. 7.2. An example of product quality specification.

Product quality specification

It is seldom that a factory produces only one product. Normally a number of products are produced differing in composition or identical as to composition, but different in quality requirements. For instance, a skim milk powder can be produced as a non-agglomerated, high bulk density powder or agglomerated with various requirements as regards bulk density, high-, medium- or low-heat. It is not unusual that a factory produces skim milk powder in more than ten various quality categories. For each quality a Product Quality Specification has to be elaborated. An example of such specification for Instant Whole Milk Powder is shown on Table.7.2.

Operational parameter specification

For every Product Quality Specification an Operational Parameter Specification is required. The name is self-explanatory. For internal factory communication, these specifications can be referred to by numbers and written in the headings of production log sheets together with numbers of Product Quality Specifications, as mentioned above. 
In modern computerized plants the parameter set points will be stored in ‘Recipes’, which are downloaded in the computer prior to start-up of the plant. Only the production management should have access for changes of these recipes. 
An example of Operational Parameter Specification is shown on Table. 7.3.

Product quality control

The target of any production is to obtain a final product, which meets all the requirements as specified by the appropriate Product Quality Specification and which has been manufactured using conditions as prescribed by the relevant Operational Parameter Specification as outlined above. However the latter has to be considered just as a general guide line. Such a specification usually expresses the operating parameters by a single figure which is valid for average ambient conditions or by a range covering extremes. Throughout the year, atmospheric conditions and milk composition are subject to variations. As to the former, quite considerable seasonal fluctuations occur, but also during a single day’s production. Thus successful manufacture of a product of standard and consistent quality is impossible without well-organized Process Quality Control and Final Quality Control.

Process quality control

The aim of controlling the selected quality characteristics of both intermediate and final product during production is to provide information to the operating staff about possible deviations from the standard. Based on this information the operator has to evaluate the magnitude of possible deviation from the standard, if any, and decide whether production should either continue under unchanged conditions or whether adjustments have to be taken, i.e. which parameters and to what extent these should be altered to re-establish the standard quality parameter. The results of such process control are of value only when available regularly and shortly after sampling. Therefore in-process quality control has to be organised with rapid routine analysis methods.
Furthermore, the capacity of the installation must be taken into consideration, as it is obvious that with high capacity plant, substantial quantities of product can be lost as non-standard in a short time. Generally the sampling and intermediate quality control should be done in one or maximum two hours intervals. It should involve such properties, which are influenced directly by the spray drying operation and which are decisive for possible downgrading or rejection of the product. The following properties should be controlled:
Operational Parameter Specification
Product: Instant whole milk powder 28%
Evaporator Steam Temperature 92°C
Flow 40000 l/h
Heater I temperature 85 °C
Holding time 150 s
Heater II temperature by-pass
Thermocompressor pressure 5.5 bar
Condenser temperature 44°C
Spray dryer Atomizer wheel curved vane
Atomizer speed 15000 RPM
Feed heater temperature 75°C
Fines return to: wheel
Homogenizer pressure-total 70 bar
-1.stage 50 bar
-2.stage 20 bar
Inlet temperature 180°C
Outlet temperature2) 72-78°C
Powder moisture ex-chamber 5.5±0.1%
Inlet Temperature VF I2) 75-80°C
Inlet Temperature VF II2) 60-65°C
Inlet Temperature VF III2) 30-35°C
Final powder temperature 42-45°C
Mixture lecithin/butter oil 1 : 2
Wetting agent temperature 65°C
Wetting agent dosing - scale 66%
In Process Control: 1) Final powder moisture - IR 2.8±0.1%
Bulk density 1250x (volume) 210±5ml
1): Conduct every 2 hours if within limits otherwise, every hour
Table. 7.3. An example of operational parameter specification.
  1. Milk acidity at the beginning and end of each tank batch,
  2. Concentration from the evaporator,
  3. Scorched particles of the powder from the spray dryer (this is mainly for safety reasons
  4. indicating a fire risk),
  5. Moisture content of the final powder (in the case of a two-stage dryer, also several times
  6. during a day the moisture content after each drying step),
  7. Solubility index,
  8. Bulk density.
The analytical methods for process control are often rapid routine methods with inferior reproducibility in comparison with the methods used for final control. It is therefore useful to compare frequently their results with the results of final control in order to modify their conditions, if necessary. Some of the above mentioned parameters (for instance, moisture) can be measured directly by in-line apparatus or can even control the installation. However, even such instruments need frequent check and calibration for each type of product by established laboratory methods. 
The results of process quality control are preferably recorded in Production Log Book together with processing parameters.

Final quality control

The laboratory for final quality control must be equipped with all apparatus, instruments, chemicals and aids which are prescribed by the appropriate standard testing methods for all properties prescribed by Product Quality Specification. Besides, the laboratory should have facilities for such analytical methods, which are not directly related to the quality standards, but which are essential for special investigations, i.e. trouble-shooting. The laboratory staff should be qualified to conduct all types of analytical work.
The sampling for final quality control has to be done in agreement with the appropriate standard as to sampling frequency, number of samples drawn from a batch, production run, silo, tote bin etc. The results are recorded in a Product Quality Book and are kept separately for each product.
What is meant by the best quality of a product? It might be a subjective evaluation depending on the preferences of the person involved. One of the definitions is, of course, the quality required by the customer. A product is often specified according to more than ten various quality characteristics. However, none of them remains strictly constant during the whole production run. Each one is subject to some variations. A target of good manufacture is to obtain not only a top quality, but also a consistent quality. The judgement of quality is difficult, when comparing two products with ten characteristics, which deviate only slightly from the standard. Therefore it is useful to elaborate a Classification System, in which the whole production run (for instance 20 hours run with one hour sampling intervals) is evaluated as to quality and consistency, using a key based on penalty points deducted from the total sum of points for an ideal product. Such a system has to be elaborated individually and similar systems are in use by various companies in various countries. 
The laboratory manager is one of the key persons of a factory and should report directly to the factory manager. The responsibilities of the laboratory management include:
  1. To follow daily the results of process quality control and its agreement with final quality control,
  2. To inform daily the production manager about the quality development,
  3. To keep the survey of quality development over longer periods expressing averages and deviations,
  4. To control the results of own laboratory by split-sample tests or in cooperation with other, possibly independent laboratories.

Table of contents

  1. 1.Introduction
  2. 2.Evaporation
    1. 2.1. Basic principles
    2. 2.2. Main components of the evaporator
    3. 2.2.1. Heat exchanger for preheating
    4. Spiral-tube preheaters
    5. Straight-tube preheaters
    6. Preheaters to prevent growth of spore forming bacteria
    7. Direct contact regenerative preheaters
    8. Duplex preheating system
    9. Preheating by direct steam injection
    10. Other means to solve presence of spore forming bacteria
    11. Mid-run cleaning
    12. UHT treatment
    13. 2.2.2. Pasteurizing system including holding
    14. Indirect pasteurization
    15. Direct pasteurization
    16. Holding tubes
    17. 2.2.3. Product distribution system
    18. Dynamic distribution system
    19. Static distribution system
    20. 2.2.4. Calandria(s) with boiling tubes
    21. 2.2.5. Separator
    22. Separators with tangential vapour inlet
    23. Wrap-around separator
    24. 2.2.6. Vapour recompression systems
    25. Thermal Vapour Recompression – TVR
    26. Mechanical Vapour Recompression - MVR
    27. 2.2.7. Condensation equipment
    28. Mixing condenser
    29. Surface condenser
    30. 2.2.8. Vacuum equipment
    31. Vacuum pump
    32. Steam jet vacuum unit
    33. 2.2.9. Flash coolers
    34. 2.2.10. Sealing water equipment
    35. 2.2.11. Cooling towers
    36. 2.3. Evaporator design parameters
    37. 2.3.1. Determination of heating surface
    38. 2.3.2. Heat transfer coefficient
    39. 2.3.3. Coverage coefficient
    40. 2.3.4. Boiling temperature
    41. 2.4. Evaporation parameters and its influrence on powder properties
    42. 2.4.1. Effect of pasteurization
    43. Bacteriological requirements
    44. Functional properties of dried products
    45. Heat classified skim milk powders
    46. High-Heat Heat-Stable milk powders
    47. Keeping quality of whole milk powders
    48. Coffee stability of whole milk powders
    49. 2.4.2. Concentrate properties
  3. 3.Fundamentals of spray drying
    1. 3.1. Principle and terms
    2. 3.1.1. Drying air characteristics
    3. 3.1.2. Terms and definitions
    4. 3.1.3. Psychrometric chart
    5. 3.2. Drying of milk droplets
    6. 3.2.1. Particle size distribution
    7. 3.2.2. Mean particle size
    8. 3.2.3. Droplet temperature and rate of drying
    9. 3.2.4. Particle volume and incorporation of air
    10. 3.3. Single-stage drying
    11. 3.4. Two-stage drying
    12. 3.5. Expansion of air bubbles during drying
    13. 3.6. Extended Two-stage drying
    14. 3.7. Fluid bed drying
  4. 4.Components of a spray drying installation
    1. 4.1. Drying chamber
    2. 4.2. Hot air supply system
    3. 4.2.1. Air supply fan
    4. 4.2.2. Air filters
    5. 4.2.3. Air heater
    6. Indirect: Gas / Electricity
    7. Direct heater
    8. 4.2.4. Air dispersers
    9. 4.3. Feed supply system
    10. 4.3.1. Feed tank
    11. 4.3.2. Feed pump
    12. 4.4. Concentrate heater
    13. 4.4.1. Filter
    14. 4.4.2. Homogenizer/High-pressure pump
    15. 4.4.3. Feed line
    16. 4.5. Atomizing device
    17. 4.5.1. Rotary wheel atomizer
    18. 4.5.2. Pressure nozzle atomizer
    19. 4.5.3. Two-fluid nozzle atomizer
    20. 4.6. Powder recovery system
    21. 4.6.1. Cyclone separator
    22. 4.6.2. Bag filter
    23. 4.6.3. Wet scrubber
    24. 4.6.4. Combinations
    25. 4.7. Fines return system
    26. 4.7.1. For wheel atomizer
    27. 4.7.2. For pressure nozzles
    28. 4.8. Powder after-treatment system
    29. 4.8.1. Pneumatic conveying system
    30. 4.8.2. Fluid bed system
    31. 4.8.3. Lecithin treatment system
    32. 4.8.4. Powder sieve
    33. 4.9. Final product conveying, storage and bagging-off system
    34. 4.10. Instrumentation and automation
  5. 5.Types of spray drying installations
    1. 5.1. Single stage systems
    2. 5.1.1. Spray dryers without any after-treatment system
    3. 5.1.2. Spray dryers with pneumatic conveying system
    4. 5.1.3. Spray dryers with cooling bed system
    5. 5.2. Two stage drying systems
    6. 5.2.1. Spray dryers with fluid bed after-drying systems
    7. 5.2.2. TALL FORM DRYER™
    8. 5.2.3. Spray dryers with Integrated Fluid Bed
    9. 5.3. Three stage drying systems
    10. 5.3.1. COMPACT DRYER™ type CDI (GEA Niro)
    11. 5.3.2. Multi Stage Dryer MSD™ type
    12. 5.3.3. Spray drying plant with Integrated Filters and Fluid Beds - IFD™
    13. 5.3.4. Multi Stage Dryer MSD™-PF
    14. 5.3.5. FILTERMAT™ (FMD) integrated belt dryer
    15. 5.4. Spray dryer with after-crystallization belt
    16. 5.5. TIXOTHERM™
    17. 5.6. Choosing a spray drying installation
  6. 6.Technical calculations
    1. 6.1. Evaporation and product output
    2. 6.2. Heating of atmospheric air
    3. 6.3. Mixing of two air stream
    4. 6.4. Dry air rate, water vapour rate and air density
    5. 6.5. Air velocity in ducts
    6. 6.6. Air flow measurements
    7. 6.7. Barometric distribution law
    8. 6.8. The heat balance of a spray dryer
  7. 7.Principles of industrial production
    1. 7.1. Commissioning of a new plant
    2. 7.2. Causes for trouble-shooting
    3. 7.3. Production documentation
    4. 7.3.1. Production log sheets
    5. 7.3.2. General maintenance log book
    6. 7.3.3. Product quality specification
    7. 7.3.4. Operational parameter specification
    8. 7.4. Product quality control
    9. 7.4.1. Process quality control
    10. 7.4.2. Final quality control
  8. 8.Dried milk products
    1. 8.1. Regular milk powders
    2. 8.1.1. Regular skim milk powder
    3. 8.1.2. Regular whole milk powder
    4. 8.1.3. Whole milk powder with high free fat content
    5. 8.1.4. Butter milk powder
    6. Sweet butter milk powder
    7. Acid butter milk powder
    8. 8.1.5. Fat filled milk powder
    9. 8.2. Agglomerated milk powders
    10. 8.2.1. Agglomerated skim milk powder
    11. 8.2.2. Agglomerated whole milk powder
    12. 8.2.3. Instant whole milk powder
    13. 8.2.4. Agglomerated fat filled milk powder
    14. 8.2.5. Instant fat filled milk powder
    15. 8.3. Whey and whey related products
    16. 8.3.1. Ordinary sweet whey powder
    17. 8.3.2. Ordinary acid whey powder
    18. 8.3.3. Non-caking sweet whey powder
    19. 8.3.4. Non-caking acid whey powder
    20. 8.3.5. Fat filled whey powder
    21. 8.3.6. Hydrolysed whey powder
    22. 8.3.7. Whey protein powder
    23. 8.3.8. Permeate powders
    24. 8.3.9. Mother liquor
    25. 8.4. Other Dried Milk Products
    26. 8.5. Baby food
    27. 8.6. Caseinate powder
    28. 8.6.1. Coffee whitener
    29. 8.6.2. Cocoa-milk-sugar powder
    30. 8.6.3. Cheese powder
    31. 8.6.4. Butter powder
  9. 9.The composition and properties of milk
    1. 9.1. Raw milk quality
    2. 9.2. Milk composition
    3. 9.3. Components of milk solids
    4. 9.3.1. Milk proteins
    5. 9.3.2. Milk fat
    6. 9.3.3. Milk sugar
    7. 9.3.4. Minerals of milk
    8. 9.4. Physical properties of milk
    9. 9.4.1. Viscosity
    10. 9.4.2. Density
    11. 9.4.3. Boiling point
    12. 9.4.4. Acidity
    13. 9.4.5. Redox potential
    14. 9.4.6. Crystallization of lactose
    15. 9.4.7. Water activity
    16. 9.4.8. Stickiness and glass transition
  10. 10.Achieving product properties
    1. 10.1. Moisture content
    2. 10.2. Insolubility index
    3. 10.3. Bulk density, particle density, occluded air
    4. 10.4. Agglomeration
    5. 10.5. Flowability
    6. 10.6. Free fat content
    7. 10.7. Instant properties
    8. 10.7.1. Wettability
    9. 10.7.2. Dispersibility
    10. 10.7.3. Sludge
    11. 10.7.4. Heat stability
    12. 10.7.5. Slowly dispersible particles
    13. 10.7.6. Hot water test and coffee test
    14. 10.7.7. White Flecks Number (WFN)
    15. 10.8. Hygroscopicity, sticking and caking properties
    16. 10.9. Whey Protein Nitrogen Index (WPNI)
    17. 10.10. Shelf life
  11. 11.Analytical methods
    1. 11.1. Moisture content
    2. 11.1.1. Standard oven drying method (IDF Standard No.26-1964 [32])
    3. 11.1.2. Free moisture
    4. 11.1.3. Total moisture
    5. 11.1.4. Water of crystallization
    6. 11.2. Insolubility index
    7. 11.3. Bulk density
    8. 11.4. Particle density
    9. 11.5. Scorched particles
    10. 11.6. Wettability
    11. 11.7. Dispersibility
    12. 11.8. Other methods for determination of instant properties
    13. 11.8.1. Sludge
    14. 11.8.2. Slowly dispersible particles
    15. 11.8.3. Hot water sediment
    16. 11.8.4. Coffee test
    17. 11.8.5. White flecks number
    18. 11.9. Total fat content
    19. 11.10. Free fat content
    20. 11.11. Particle size distribution
    21. 11.12. Mechanical stability
    22. 11.13. Hygroscopicity
    23. 11.14. Degree of caking
    24. 11.15. Total lactose and α-lactose content
    25. 11.16. Titratable acidity
    26. 11.17. Whey Protein Nitrogen Index (WPNI)
    27. 11.18. Flowability (GEA Niro [31])
    28. 11.19. Lecithin content
    29. 11.20. Analytical methods for milk concentrates
    30. 11.20.1. Total solids
    31. 11.20.2. Insolubility index
    32. 11.20.3. Viscosity
    33. 11.20.4. Degree of crystallization
  12. 12.Troubleshooting operations
    1. 12.1. Lack of capacity
    2. 12.2. Product quality
    3. 12.3. Deposits in the system
    4. 12.4. Fire precaution
    5. 12.5. Principles of good manufacturing practice
    6. 12.6. The use of computer for quality control and trouble-shooting
  13. References
Reference: Schlünder,E.U.:Dissertation Techn.Hochschule Darmstadt D 17, 1962.