Tetra Pak UHT technology Seminar LTH PSD.TPD&B.BP.1.01, AA10
Presented by Andrzej Holanowski, PhD Senior Dairy Technologist Tetra Pak Dairy & Beverage Systems AB Lund, Sweden PSD.TPD&B.BP.1.01, AA10
Aseptic processing Product Aseptic environment Container Sterilisation Sterilisation Filling & sealing Aseptically packaged product PSD.TPD&B.BP.2.04, AA10
UHT definitions Sterilisation A process applied to a product with the object of destroying all microorganisms (by heat treatment at a temperature exceeding 100 C) Sterile Condition in which living cells are absent or killed Steriliser Equipment used for sterilisation: autoclave, hydrostatic steriliser or aseptic processing plant Commercial sterility Product which is free from micro-organisms that can grow and contribute to its deterioration (Not absolutely sterile) Aseptic Conditions to prevent bacteriological contamination PSD.TPD&B.BP.2.01, AA10
Long-life products Low-acid ph >4.5 milk products, tea, coffee, liquid food products containing vegetables High-acid ph <4.5 juices, fermented milk products, fruit products PSD.TPD&B.BP.2.07, AA10
UHT what do we need to achieve? In low acid foods (specifically milk): Required bacteriological effect expressed as: - Reduction of Clostridium botulinum spores to the level of 10-12 or 1 of initial 10 12 survives - public health requirement (12D reduction or F o = 3 process) - Reduction of thermophilic spores by minimum 9D (B * >1) guarantying commercially sterile product Minimised chemical changes expressed as: - Decomposition of thamin (vit. B 1 ) less than 3% (C * <1) - Lactulose value <600 mg/l - undenaturated ß-Lactoglobulin >50 mg/l PSD.TPD&B.BP.2.01, AA10
UHT what do we need to achieve? In low acid foods (specifically milk): Biochemical stability expressed as: - Maximal reduction of enzymatic activities in the heat treated product Physical and chemical stability: - No phase separation (fat, proteins, serum) - No sedimentation PSD.TPD&B.BP.2.01, AA10
Raw milk quality for processability: ph 6.65-6.80 alcohol stability >75% total Count of bacteria for sterility level: limit of heat resistant spores PSD.TPD&B.BP.2.17, AA10
Classification of bacteria by temperature preference 45 C 20 C 7 C Thermophilic Mesophilic Psychrophilic Psychrotrophic PSD.TPD&B.BP.2.18, AA10
Bacterial formation of spores 1 1 Viable bacterium 2 Nuclear content gathered (at bad growing conditions) 6 2 3 A thick wall is formed around the nucleus (the spore) 4 The cell decomposes and the spore is liberated 5 4 3 5 The spore is free 6 At favourable conditions the membrane of the spore bursts and a new cell will be formed No. TP70:68, 9311BM
Commercial sterility The commercially sterile product must: Keep without deterioration, stable and good commercial value during storage Free from micro-organisms and toxins harmful to the health of consumers Free from any micro-organisms liable to proliferate during storage PSD.TPD&B.BP.2.03, AA10
Legislation and suggestions for heat treated milk products UHT Heat treatment >135 C and >1 s (Council directive 92/46/EEC) -------------------- Lactulose* <600 mg/l ß-Lactoglobulin* >50 mg/l (*IDF and ECC suggestions) Sterile Lactulose* >600 mg/l or ß-Lactoglobulin* <50 mg/l (*IDF and ECC suggestions) PSD.TPD&B.BP.2.05, AA10
Heat treatments definitions Pretreatment Thermisation 63 65 C/15 sec Preliminary heating Pasteurisation 63 C/30 min Pasteur's method rare today (batch pasteurisation) Heat treatment Chilled distributed products HTST pasteurisation 72 75 C/15 sec Milk HTST pasteurisation 85 90 C/2 5 sec Cream HTST pasteurisation 90 120 C/2 5 sec Fermented products Ultra pasteurisation 125 138 C/2 4 sec Cold storage Ambient distributed products UHT 135 150 C/4 15 sec Ambient storage Conventional sterilisation approx. 116 C/20 min Ambient storage HTST = high temperature short time, UHT = ultra high temperature PSD.TPD&B.BP.2.06, AA10
Definition of D-value D-value (decimal reduction time) is the time at a specific temperature necessary to reduce the number of micro-organisms to 1/10 of the original value Number of micro-organisms N 10 5 10 4 10 3 10 2 10 1 10 0 10-1 10-2 temperature = constant D time, t Micro-organisms D 121 C B. cereus 2.3 sec. Cl. botulinum. 12.25 sec. B. stearothermophilus 408 sec. PSD.TPD&B.BP.2.09, AA10
Rate of thermal death of micro-organisms at high temperatures depends on: Type of micro-organism vegetative bacteria (high) viruses (medium) endospores (law) Medium surrounding micro-organisms ph, water activity (a w ), concentration and type of food components i.e. (simple carbohydrates, fats, chemical ions, type of acid and ) PSD.TPD&B.BP.2.01, AA10
Absolute sterility not possible N Bacteria Logarithmic destruction Time/temperature would be too drastic Not possible to prove by random testing Not possible to prove sterility (prove absence) t Time PSD.TPD&B.BP.2.02, AA10
Definition of z-value z-value is the increase in temperature, necessary to obtain the same lethal action or the same effect in 1/10 of time time, t [s] 10 3 10 2 10 1 10 0 Temperature dependance z-value [ C] B. stearothermophilus 10.5 Colour changes 29.0 Losses of vitamin B 1 31.2 Losses of lysine 30.9 10-1 z temperature PSD.TPD&B.BP.2.10, AA10
Definition of F-value (T 121.1) t F o =. z 10 60 t = heating time, seconds T = heating temperature, C z = the increase in temperature necessary to obtain the same effect in one tenth of the time. F o = 1 when heated one minute at 121.1 C PSD.TPD&B.BP.2.11, AA10
Definition of B*-value (T 135) t B* =. 10.5 10 10.1 Assumption: Commercial sterility is achieved at B* = 1 (heat treatment at 135 C for 10.1 sec., z = 10.5) = reduction of thermophilic spores = 10 9 PSD.TPD&B.BP.2.12, AA10
Definition of C*-value (T 135) t C* =. 31.4 10 30.5 C* = 1 = heat treatment at 135 C for 30.5 sec. and z = 31.4 C = 3% destruction of thiamine PSD.TPD&B.BP.2.13, AA10
UHT treatment Time-temperature combinations needed for destruction of spores Heating time or equivalent heating time, S 2000 1000 Region of in-container sterilisation 400 200 100 40 3% Destruction of thiamine 90% Ps- Lipase de-activation 90% Ps-protease inactivation no discolouration 1% Destruction of lysine A 20 10 4 2 1 Mesophilic spores 30 o C Thermophilic spores 55 o C UHT region 110 120 130 140 150 B Temperature o C PSD.TPD&B.BP.2.08, AA10
Heat effects Decimal reduction time, sec 10 6 Bacteriological destruction 10 5 Enzyme inactivation 10 4 Chemical destruction 10 3 110 120 130 Temp, C No. TP70:38, 9305BM
Heat effects Temperature F o Time C* C minutes (z=10 C) seconds seconds (z=31.4 C) 121 6.0 360 4.23 130 6.0 45 1.02 135 6.0 14 0.46 140 6.0 5 0.24 141 8.3 5 0.25 PSD.TPD&B.BP.2.14, AA10
PSD.TPD&B.PEH.6.09, AA10
UHT Ultra High Temperature processes Continuous processes Batch sterilisation in container Temp 150 Direct UHT Indirect UHT Temp F 300 Temp C Temp F Continuous processes 100 Pasteurisation 200 50 100 Time Seconds Time Minutes PSD.TPD&B.BP.2.16, AA10
Shelf-life of milk The time the product can be stored before the quality falls below an acceptable and minimum level Subjective criteria: Taste Sedimentation Colour Fat separation Smell Viscosity Gelation PSD.TPD&B.BP.2.19, AA10
Factors influencing shelf-life Quality of raw product (chemical and microbiological) Pretreatment process Type of aseptic processing system used Homogenisation/deaeration Post heat treatment contamination non-sterile Aseptic packaging Barrier properties of packaging material PSD.TPD&B.BP.2.20, AA10
Main factors affecting the flavour of UHT milk Milk quality Type and severity of heat treatment Packaging material Storage temperature and time PSD.TPD&B.BP.2.21, AA10
Sensoric changes in UHT milk Duration of storage (week) Off flavour Sulfur Cooked Metal Stale Rancid/Bitter Optimum 2 4 6 8 10 12 14 5 C Source: Blanc Sulfur Cooked Metal Stale Rancid/Bitter Optimum 25 C No. TP70:61, 9311BM
Sensory Quality of UHT Milk Heated Flavour - four notes Cooked, Sulfurous, Cabbagey Various sulfur compounds Rich, Heated,UHT, Keton-like Products of Maillard reaction Caramelized, Sterilized Non-enzimatic browning Scorched, Burned Burn-on heating suffaces No. TP XX:XXX, JF06
Sensory Quality of UHT Milk Heated Flavour The cooked flavour appears immediately after UHT treatment and is reduced during storage with rate dependant on availability of oxygen an temperature of storage. No. TP XX:XXX, JF06
Sensory Quality of UHT Milk Stale and Oxidized flavour Stale Aldehydes from autooxidation of fat Oxidized, Flat Bland Chalky Cardbordy Ketons, Propanal N-Pentanal N-Hexanal Brownning reactions No. TP XX:XXX, JF06
Sensory Quality of UHT Milk Stale and Oxidized flavour Stale and oxidized flavour develops during storage while the cooked flavour is disappearing. It depends on a large number of different compounds. Aldehydes and ketons play the major role. Formation of oxidised flavour is accelerated by high storage temperature. No. TP XX:XXX, JF06
Sensory Quality of UHT Milk Other off-flavours Bitter flavour Rancidity Proteolitic activities of plasmin and bacterial thermoresistant proteases. Lipolitic activities of native and bacterial lipases. No. TP XX:XXX, JF06
Lactose and heat effects Lactulose Acetaldehyde Formaldehyde Formic acid Acetic acid ph drop Lactic acid Tartaric acid Maillard reactions products brown colour antioxydents No. TP70:49, 9309BM
Loss of vitamins in UHT milk Vitamin Losses by (%) UHT treatment Ambient storage Sensitivity to Light Oxygen Notes Ascorbic acid 0 80 Up to 100 +++ Antioxidant Folic acid 10 20 Up to 100 ++ AA-antioxidant B 12 0 30 Up to 100 B 6 0 20 15 20 Pyridoxine-fortification B 2 (riboflavine) <10 10 +++ Light-induced flavour Thiamine <10 + A D Very low Very low Higher degradation in fortified products E Very low PSD.TPD&B.BP.2.22, AA10