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LECTURE PLAN
HISTORICAL CONSIDERATIONS
PRESENT SITUATION
Production data
I GENERAL CONSIDERATIONS ON YOGHURTS MANUFACTURE
II YOGHURTS QUALITY
III KEY POINTS ABOUT YOGHURTS
MANUFACTURE PROCESSES
III.1 - MIXES (CULTURE MEDIUM) PREPARATION
III.2 - FERMENTATION PROCESS
III.3 - COOLING – MECHANICAL TREATMENTS
III.4 - FROM PACKAGING TO COLD STORAGE
III.5 – CLEANING IN PLACE – PROCESS
AUTOMATION
IV CONCLUSIONS
-T 3
HISTORICAL CONSIDERATIONS
_____________________________________________
è APPARITION 8 000 TO 10 000 YEARS AGO (MESOPOTANIA, EGYPT, INDIA, NORTH-EAST OF AFRICA)
Ä LINKED TO ANIMALS DOMESTICATION
Ä A WAY OF MILK PRESERVATION
Ä IMPORTANT BENEFITS FOR HUMAN HEALTH
AND NUTRITION
è CENTURIES AND CENTURIES OF TRADITIONAL HANDICRAFT MANUFACTURE … ACCORDING TO PEOPLE'S TRADITIONS AND ENVIRONNE- MENTAL CONDITIONS
(MORE THAN 400 GENERIC NANES ;
NOT ONLY BASED ON LACTIC FERMENTATION)
è LARGE SPREADING OVER ALL THE WORLD
-T 4
PRESENT SITUATION
__________________________________________________
è INDUSTRIALISATION OF THE YOGHURT MANUFACTURE IS 30 TO 40 YEARS OLD
è LARGE MULTINATIONAL COMPAGNIES ARE INVOLVED
è A LOT OF YOGHURT TYPES AVAILABLE ACCORDING TO CONSUMERS DEMAND
è WELL ESTABLISHED MANUFACTURING
PROCESSES ð BETTER QUALITY CONTROL
ð PROCESS PRODUCTIVITY
IMPROVEMENT
è RESPECT OF THE REGULATIONS ESTABLISHED BY EACH DIFFERENT COUNTRY
-T 5
LACTIC ACID FERMENTATION
______________________________
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LACTOSE
|
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STARTER CULTURE
LACTIQUES
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GALACTOSE
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GLUCOSE
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+
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LACTIC ACID
+
AROMA
COMPOUNDS
+
TEXTURING
COMPOUNDS
|
Þ Symbiotic cultures : Streptococcus
thermophilus and Lactobacillus bulgaricus
Þ Galactose accumulation,
glucose utilisation
Þ The accumulation of the lactic
acid leads to an acidification of
the mix (pH decrease)
Þ Milk coagulation when pH ~ 5.2
Þ Production of aroma COMPOUNDS (acetaldehyde) and of texturing
compounds (E.P.S.)
-T 6
FRENCH YOGHURT DEFINITION
__________________________________________________
è THE FRENCH REGULATION FIXED THE CONCENTRATION OF :
ÄLACTIC ACID ³ 7.0 g/l
ÄALIVE THERMOPHILIC LACTIC BACTERIA ³ 107b/g
(only Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus are allowed)
ÄADDITIVES £ 30% w/w
(fruits, sugar, flavouring agents)
è OTHERS INDICATIONS MUST BE GIVEN :
ÄFAT CONTENT
ÄMILK ORIGIN (ANIMAL)
ÄNATURE OF ALL THE ADDITIVES
Ä STORAGE TEMPERATURE
Ä MAXIMUM STORAGE TIME
è EXCEPT FOR SUGAR, ALL "MIXES" COMPONENTS MUST COME FROM MILK
-T 7
TYPES OF YOGHURTS AVAILABLE
________________________________
1) TEXTURE
ð SET TYPE YOGHURTS
ð STIRRED TYPE YOGHURTS
ð DRINKING YOGHURTS
2) FAT CONTENT
ð LOW FAT
ð MEDIUM FAT
ð FULL FAT
3) FLAVOR
ð PLAIN (NATURAL) YOGHURTS
ð FRUIT ADDITION
ð FLAVOURED YOGHURTS
4) DIVERSIFICATION IN PRODUCTS AND MANUFACTURING CONDITIONS
ð VEGETABLE OILS ADDITION
ð HEAT TREATMENT
ð VITAMIN FORTIFICATION
ð ENZYME HYDROLYSIS
-T 9
SIMPLIFIED YOGHURT MANUFACTURE
FLOW-SHEET
__________________________________________________
3 MAIN STEPS CAN BE DEFINED :
1) PREPARATION AND PHYSICAL
TREATMENTS OF THE MIXES
2) Ö INOCULATION OF THE MIX
Ö LACTIC ACID FERMENTATION
(INCUBATION IN CUPS OR IN TANKS)
3) COOLING, FILLING, PACKAGING*
AND COLD STORAGE
-----------------------------------------------------------------
*FOR SET YOGHURTS FILLING AND PACKAGING
ARE DONE BEFORE FERMENTATION.
THEIR INCUBATION IS DONE IN WARM ROOMS
T 10
MAIN YOGHURT QUALITY CRITERIA
___________________________________________
1) ORGANOLEPTIC EVALUATION
ð ACIDITY
CONSUMERS ARE SELECTING "NON ACID" YOGHURTS
ð TEXTURE
Ÿ KEY PARAMETRE (PIECES OF FRUIT
HOMOGENITY INTO THE BULK)
ŸON SPOON AND IN MOUTH APPRECIATION
ð FLAVOR
THE "YOGHURT TASTE" (BASED ON ACETALDEHYDE) IS VERY COMPLEX
2) OTHERS FACTORS
ð NO SYNERESIS
EXUDATION OF WHEY IS BADELY APPRECIATED BY
THE CONSUMERS
ð GEL HOMOGENITY
MICROSTRUCTURE, GRANULARITY
ð COLOUR
-T 11
METHODS FOR
YOGHURT QUALITY
DETERMINATION
______________________
ACIDITY
Ÿ pH
Ÿ LACTIC ACID CONTENT
ð MEASUREMENT AS A FUNCTION OF :
* FERMENTATION TIME,
* STORAGE TIME (POST-ACIDIFICATION)
ACIDIFICATION RATE (STARTER + PROCESS
PROPERTIES)
Ÿ THE CINAC SYSTEM
* pH = f (TIME)
* dpH/dt = f (TIME)
* KEY DESCRIPTORS :
- Vm : MAXIMUM ACIDIFICATION RATE
- Tm : TIME TO OBTAIN Vm
- pHm : pH CORRESPONDING TO Vm
- TpHi : TIME TO REACH A CERTAIN pHi
-T 12
METHODS FOR
YOGHURT QUALITY
DETERMINATION
_____________________
è A LOT OF MORE OR LESS EMPIRICAL METHODS
· POSTHUMUS FUNNEL
· BROOKFIELD (LARGE INDUSTRIAL UTILISATION)
· BOSTWICK CONSISTOMETER
è TEXTURE (FIRMNESS CARACTERISATION)
· PENETROMETRY
· ROPINESS ASSESSEMENT
è RHELOGICAL BEHAVIOUR
· OSCILLATORY MEASUREMENTS ON A CONE/PLATE INSTRUMENT
· OBTENTION OF THE CHANGE OF COMPLEX VISCOSITY VERSUS STRESS INCREASE
-T 13
METHODS FOR
YOGHURT QUALITY
DETERMINATION
_________________________________________
ANALYSIS OF FLAVOUR COMPOUNDS
· GAS CHROMATOGRAPHY
(+ MASS SPECTROMETRY)
· LIQUID CHROMATOGRAPHY
· COLORIMETRIC TESTS
è4 MAIN CATEGORIES OF COMPOUNDS :
· CARBONYL COMPOUNDS (ACETALDEHYDE, ACETON, ACETOÏN, DIACETYL)
· NON-VOLATILE ACIDS (LACTIC, PYRUVIC, OXALIC)
· VOLATILE ACIDS (FORMIC, ACETIC, PROPIONIC)
· SOME AMINO ACIDS
è ACETALDEHYDE IS THE KEY COMPOUND
(2 TO 75ppm)
· INCREASE IN MIXED CULTURES
· DECREASE DURING STORAGE
· MOST OF THE OTHER COMPOUNDS MUST BE PRESENT
-T 14
METHODS FOR
YOGHURT QUALITY
DETERMINATION
SOME OTHER QUALITY CRITERIA
è MICROBIOLOGICAL COMPOSITION
· GOOD AMOUNT OF ALIVE LACTIC BACTERIA
· AVOID CONTAMINANT FLORA
è COLOUR – COLORIMETRY
· WHITE COLOUR (NATURAL YOGHURTS)
· "FRUIT" COLOUR/FLAVOUR COLOUR
è GEL HOMOGENITY
· AVOID BUBLES AND GRANULAR COAGULUM
è SYNERESIS = VOLUME OF WHEY OBTAINED AFTER SOME DAYS
· LIMIT WHEY EXUDATION AND INCREASE WATER-BINDING CAPACITY
-T 15
METHODS FOR
YOGHURT QUALITY
DETERMINATION
SENSORY ANALYSIS
· EXPERTS TRAINED PANEL (10-20 PEOPLE)
· CONSUMERS TRAINED PANEL (100 PEOPLE)
è VERY TIME CONSUMING AND EXPANSIVE
è AGREEMENT AND TRAINING ON TEST METHODS AND SPECIFIC TERMINOLOGY (YOGHURT ATTRIBUTES)
è HOW TO SELECT ONLY A FEW NUMBER OF KEY ATTRIBUTES
-T 16
CULTURE MEDIUM (MIX) PREPARATION
___________________________________________
1) COMPOSITION OF THE MIXES
Ü GENERAL RULE
ð UTILISATION OF A MILK BASE
ð FAT CONTENT STANDARDISATION
ð PROTEIN ENRICHMENT
Ÿ MILK AND/OR CASEINE POWDER ADDITION
Ÿ CONCENTRATION (EVAPORATION, U.F.)
Ÿ NON-MILK PROTEINS ARE NOT ALLOWED
IN ALL COUNTRIES
Ü FRUIT/FLAVOURED YOGHURTS
ð ADDITION OF PIECES OF FRUIT
ð ADDITION OF SUGAR OR SWEETENING AGENTS
ð ADDITION OF FLAVOURING AGENTS
-T 17
CULTURE MEDIUM (MIX) PREPARATION
___________________________________________
Ü OTHER YOGHURTS
ð ADDITION OF OTHERS ADDITIVES (WITH POSSIBLE
RESTRICTIONS COUNTRY BY COUNTRY)
Ÿ STABILIZERS/EMULSIFIERS (POLYSACCHARIDES)
Ÿ VITAMINS (A, C ….)
Ÿ VEGETAL FAT, FATTY ACIDS
Ÿ PRESERVATIVES (SORBIC AND BENZOIC ACIDS,
SULFUR DIOXYDE)
Ÿ MINERAL CONTENT MODIFICATION (Mg2+, Fe2+, Ca+)
Ÿ FOOD COLOURANTS (10 - 15 COLOURANTS)
-T 18
CULTURE MEDIUM (MIX) PREPARATION
___________________________________________
2) PHYSICAL TREATMENTS OF THE MIXES
2.1 – HOMOGENISATION
ð TO OBTAIN A FAT-IN-WATER EMULSION
(NO FAT LAYER AT THE TOP OF THE YOGHURT)
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CONDITIONS
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CONSEQUENCES ON YOGHURT
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VISCOSITY
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ARE IMPROVED
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150 - 200 bars
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SYNERESIS
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60 - 70 °C
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WHITE COLOUR
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MICRO STRUCTURE
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|||
T 19
CULTURE MEDIUM (MIX) PREPARATION
___________________________________________
2.2 – HEAT TREATMENT
ð "HIGH PASTEURISATION" (95°C – some minutes)
ð "LOW PASTEURISATION" (80°C <) AND UHT TREATMENT ARE LESS EFFICIENT
ð EFFECTS : Ÿ DESTRUCTION OF MICROORGANISMS
Ÿ WHEY PROTEINS DENATURATION
Ÿ INCREASE GEL CONSISTENCY AND
STABILITY
ð THE FERMENTATION TEMPERATURE (40-45°C) IS FIXED AT THE OUTSIDE OF THE HEAT EXCHANGER
T 19b
EFFECT OF HOMOGENISATION AND HEAT TREATMENT ON THE CONSISTENCY/VISCOSITY OF YOGHURT
Heat treatment of milk for 30 min at
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Measurement of consistency/visco
sity of yoghurt
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70°C
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78°C
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86°C
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95°C
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||||
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H
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NH
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H
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NH
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H
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NH
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H
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NH
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Falling sphere a (depth, cm)
Posthumus FUNNEL b
(time, s)
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3.0
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>15.0
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1.5
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10.5
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1.2
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6.0
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1.2
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2.7
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9.0
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5.0
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14.0
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7.5
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17.0
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8.5
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18.7
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9.0
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a) Falling sphere : the deeper the sphere sinks into
the yoghurt, the thinner is the product.
b) Posthumus funnel : the longer the time required for
the yoghurt to pass through the funnel, the more viscous is the product.
h : HOMOGENISED MILD – NH : NON-HOMOGENISED MILK
(From TAMIME, 1999)
-T 21
FERMENTATION PROCESS
_______________________
3) MIXED CULTURES PROPERTIES
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· IMMEDIATE ACIDIFICATION
· IMPORTANT AND FAST BACTERIA GROWTH
· RAPID AND LONG-TIME ACIDIFICATION
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CONTROL OF FERMENTATION LENGTH
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||
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· SMALL (OR NONE) POST ACIDIFICATION (COOLING, PACKAGING, STORAGE)
· SUITABLE TEXTURE AND VISCOSITY
· GEL RESISTANCE TO MECHANICAL DESTRUCTURATION
· APPROPRIATE FLAVOUR
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CONTROL YOGHURT QUALITY
|
-T 22
FERMENTATION PROCESS
_______________________
B - FERMENTATION IMPROVEMENT
è MODIFICATION OF THE STRAINS INVOLVED IN THE STARTER
· INTRODUCTION OF NEW STRAINS WITH KNOWN PROPERTIES
· OTHER RATIO OF THE SAME STRAINS
è MODIFICATION OF THE STARTER PRESENTATION AND/OR INOCULATION AMOUNT
è OPTIMISATION OF THE YOGHURT MANUFACTURE CONDITIONS
-T 23
FERMENTATION PROCESS
_______________________
PROCESS MONITORING
è TEMPERATURE CONTROL IS QUITE IMPOSSIBLE :
· FIXED BY THE OUTSIDE TEMPERATURE OF HEAT TREATMENT
· A VERY "HEAT SENSIBLE" PROCESS
è pH AND ACIDIFICATION RATE ARE KEY PARAMETERS
· pH ON-line MEASUREMENT IS NOT AVAILABLE
· THE CONCEPT OF ACIDIFICATION RATE IS NOT YET POPULAR
è FERMENTATION END-TIME INITIATE THE COOLING STEP
· STRONG EFFECT ON YOGHURTS QUALITY
· DEFINED FROM pH MEASUREMENTS AFTER SAMPLING
-T 24
FERMENTATION PROCESS
FUTURE INNOVATIONS IN PROCESS MONITORING
1) INDIRECT pH MEASUREMENT
· pH CLASS PROBES ARE NOT ALLOWED
· ELECTRICAL CONDUCTIVITY METHOD
· THERMAL METHOD
2) PREDICTION OF FERMENTATION
END-TIME
· PREDICTION OF pH DECREASE VERSUS FERMENTATION TIME
3) OPTIMISATION OF YOGHURT QUALITY
SEE CONCLUSION
T 25
COOLING
_____________________________
è TWO TYPES OF PROCESSES FOR :
ÄSET YOGHURT
ÄSTIRRED YOGHURT
è SET YOGHURT
ÄSMALL UNITS : WATER BATH OR CABINETS
ÄLARGE UNITS : ROOMS INCUBATION TEMPERATURE,
AND TUNNELS (WARM AND CHILLED)
· AIR TEMPERATURE CONTROL, AIR CIRCULATING
CONDITIONS, AND COOLING CAPACITY ARE IMPORTANT
è STIRRED YOGHURT
ÄAGITATION IN TANK AND CONTINOUS COOLING
(HEAT EXCHANGERS)
· RAPID COOLING
IMPORTANT SHEAR STRESS
(MIXER, PIPES, PUMPS, EXCHANGER…)
COAGULUM
DESTRUCTURATION (LOSS OF VISCOSITY)
-T 26
PACKAGING
______________________________
1) MAIN FUNCTIONS OF PACKAGING :
ë PROVIDE PROTECTION
ë BRING A MESSAGE TO THE BUYER
ë FACILITATE THE HANDLING
2) TWO STAGES FOR PACKAGING :
ë SET YOGHURT : BEFORE FERMENTATION
(LOW VISCOSITY)
ë STIRRED YOGHURT : AFTER FERMENTA-
TION AND PRECOOLING (HIGH VISCOSITY)
-T 27
PACKAGING
___________________________
3) TWO KINDS OF PACKAGING EQUIPMENT :
ë FILL – SEAL TECHNIQUE (FS)
ë FORM – FILL – SEAL TECHNIQUE (FFS)
4) PACKAGING EQUIPMENT CHARACTERISTICS:
ë MECHANICALLY SOPHISTICATED
ë FULLY AUTOMATION
ë CLEAN, ULTRACLEAN OR ASEPTIC
MACHINES
ë VERSATILY (FLAVOR, SIZE, PRODUCT
PRESENTATION)
ë IMPORTANT INVESTMENT
-T 28
OVER PACKAGING – PALLETISATION –
COOLING – STORAGE
_____________________________________
è OPERATIONS FULLY AUTOMATED IN LARGE PLANTS
è FIVE STEPS :
· PLACEMENT OF YOGHURT CUPS IN CARDBOARD TRAYS
· PALLETISATION OF THE TRAYS
· COOLING OF THE PALLETISED YOGHURTS (CHILLED TUNNEL)
· PLASTIC OVERWRAPPING OF THE COOLED PALLETISED YOGHURTS
· COLD STORAGE (4°C) BEFORE DISTRIBUTION AND RETAILING
è THE LOW TEMPERATURE CHAIN MUST BY RESPECTED TO OBTAIN HIGH QUALITY AND SAVE YOGHURTS
-T 29
CLEANING – IN – PLACE (C.I.P.)
è GENERALISED PROCEDURE : MANUAL WASHING HAS DISAPPEARED
è PLANTS AND MACHINES ARE DESIGNED TO ALLOW C.I.P.
è MAIN AGENTS/ACTIONS
· HEAT TREATMENT (STEAM)
· CHEMICAL AGENTS (DETERGENTS, SURFACE ACTIVE, STERILISING…)
· MECHANICAL ACTION (PRESSURE, FLOW RATE)
· WATER (ONLY FOR RINCING).
-T 30
PROCESS AUTOMATION
è INDUSTRIAL PLANTS ARE LARGELY AUTOMATED
· CONTROL LOOPS (TEMPERATURE, FLOW RATE, WEIGHT…)
· SEQUENTIAL MONITORING (INCLUDING C.I.P.)
· PROCESS SUPERVISION WITH KEY DATA
è OPTIMAL QUALITY CONTROL DOES NOT EXIST : SOME STRATEGIC DECISIONS ARE ON THE OPERATOR RESPONSABILITY
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BENEFITS
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DRAWBACKS
|
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ð SECURITY
ð PRODUCT TRACEABILITY
ð LABOR COST REDUCTION
ð CENTRALISED
INFORMATION
|
ð EXPENSIVE
ð SPECIFICITY
ð POOR FLEXIBILITY
|
-T 31
CONCLUSION
MANUFACTURING A HIGH QUALITY YOGHURT IS EASY
YOU REQUIRE FOLLOWING TAMIME AND ROBINSON ADVICE (1999)
· MILK OF GOOD QUALITY AND ADEQUATE FORTIFICATION
· CORRECT HEAT TREATMENT,
· AN ACTIVE, WELL-BALANCED AND CONTAMINANT-FREE STARTER CULTURE,
· A CLEAN AND WELL-MAINTAINED PLANT,
· CORRECT INOCULATION RATE
· CORRECT INCUBATION TIMES AND TEMPERATURES,
· AVOIDANCE OF ROUGH HANDLING OF SET YOGHURTS,
· THE USE OF HIGH QUALITY FRUIT OR OTHER INGREDIENTS
· CORRECT STORAGE OF RETAIL PRODUCT BELOW 5°C
A PERTINENT GOOD MANUFACTURING PRACTICE
-T 32
CONCLUSION
è THE OPTIMISATION OF YOGHURT QUALITY STAYS AN INDUSTRIAL CHALLENGE
è IT NEEDS AN INTEGRATED APPROACH OF THE PROCESS, FROM CULTURES SELECTION AND MIXES PREPARATION TO COOLING AND MECHANICAL OPERATIONS
