Tetra Pak UHT technology Seminar LTH

Transcription

1 Tetra Pak UHT technology Seminar LTH PSD.TPD&B.BP.1.01, AA10

2 Presented by Andrzej Holanowski, PhD Senior Dairy Technologist Tetra Pak Dairy & Beverage Systems AB Lund, Sweden PSD.TPD&B.BP.1.01, AA10

3 Aseptic processing Product Aseptic environment Container Sterilisation Sterilisation Filling & sealing Aseptically packaged product PSD.TPD&B.BP.2.04, AA10

4 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

5 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

6 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 or 1 of initial 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

7 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

8 Raw milk quality for processability: ph alcohol stability >75% total Count of bacteria for sterility level: limit of heat resistant spores PSD.TPD&B.BP.2.17, AA10

9 Classification of bacteria by temperature preference 45 C 20 C 7 C Thermophilic Mesophilic Psychrophilic Psychrotrophic PSD.TPD&B.BP.2.18, AA10

10 Bacterial formation of spores 1 1 Viable bacterium 2 Nuclear content gathered (at bad growing conditions) A thick wall is formed around the nucleus (the spore) 4 The cell decomposes and the spore is liberated 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

11 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

12 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

13 Heat treatments definitions Pretreatment Thermisation C/15 sec Preliminary heating Pasteurisation 63 C/30 min Pasteur's method rare today (batch pasteurisation) Heat treatment Chilled distributed products HTST pasteurisation C/15 sec Milk HTST pasteurisation C/2 5 sec Cream HTST pasteurisation C/2 5 sec Fermented products Ultra pasteurisation C/2 4 sec Cold storage Ambient distributed products UHT 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

14 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 temperature = constant D time, t Micro-organisms D 121 C B. cereus 2.3 sec. Cl. botulinum sec. B. stearothermophilus 408 sec. PSD.TPD&B.BP.2.09, AA10

15 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

16 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

17 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] Temperature dependance z-value [ C] B. stearothermophilus 10.5 Colour changes 29.0 Losses of vitamin B Losses of lysine z temperature PSD.TPD&B.BP.2.10, AA10

18 Definition of F-value (T 121.1) t F o =. z 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 C PSD.TPD&B.BP.2.11, AA10

19 Definition of B*-value (T 135) t B* = 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

20 Definition of C*-value (T 135) t C* = 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

21 UHT treatment Time-temperature combinations needed for destruction of spores Heating time or equivalent heating time, S Region of in-container sterilisation % Destruction of thiamine 90% Ps- Lipase de-activation 90% Ps-protease inactivation no discolouration 1% Destruction of lysine A Mesophilic spores 30 o C Thermophilic spores 55 o C UHT region B Temperature o C PSD.TPD&B.BP.2.08, AA10

22 Heat effects Decimal reduction time, sec 10 6 Bacteriological destruction 10 5 Enzyme inactivation 10 4 Chemical destruction Temp, C No. TP70:38, 9305BM

23 Heat effects Temperature F o Time C* C minutes (z=10 C) seconds seconds (z=31.4 C) PSD.TPD&B.BP.2.14, AA10

24 PSD.TPD&B.PEH.6.09, AA10

25 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 Time Seconds Time Minutes PSD.TPD&B.BP.2.16, AA10

26 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

27 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

28 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

29 Sensoric changes in UHT milk Duration of storage (week) Off flavour Sulfur Cooked Metal Stale Rancid/Bitter Optimum C Source: Blanc Sulfur Cooked Metal Stale Rancid/Bitter Optimum 25 C No. TP70:61, 9311BM

30 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

31 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

32 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

33 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

34 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

35 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

36 Loss of vitamins in UHT milk Vitamin Losses by (%) UHT treatment Ambient storage Sensitivity to Light Oxygen Notes Ascorbic acid 0 80 Up to Antioxidant Folic acid Up to AA-antioxidant B Up to 100 B Pyridoxine-fortification B 2 (riboflavine) < 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