ESL milk theory and practice of shelf life extension

Transcription

1 ESL milk theory and practice of shelf life extension Andrzej Holanowski, PhD Senior Dairy Technologist Tetra Pak, Lund, Sweden

2 General definition of Shelf life Shelf life it is the time during which food products: Remain safe Retain desired sensory, chemical, physical and microbiological characteristics Comply with any label declaration when stored and handled under the recommended conditions. / 2

3 Product stability / 3

4 Microbiological shelf life of milk The microbiological shelf life of milk is determined by: Number of psychrotrophic thermoduric micro-organisms including psychrotrophic spores present in the raw milk Reduction of these by the process applied. Potential recontamination with micro-organisms after the treatment Storage and distribution temperature / 4

5 Acceptance criteria or quality limits at last day of declared shelf life are defined in regulations of different countries or by customers. This may be: Organoleptic acceptance or / and Microbiological limit e.g. TPC not higher than X cfu/ml E.g. total count not higher than X= cfu/ml at the last day of the declared shelf life / 5

6 Microbiological status of raw and processed milk TVC (Total Viable Count) cfu/ml Thermoduric count (TDC) e.g cfu/ml (Swedish milk example) Thermoduric Psychrotrophic Literature estimate 1% of TDC 10% Spores 70% Corynebacteria 20% Cocci Psychrotrophic aerobic spores cfu/ml cfu/l e.g. Bacillus cereus Viable Thermoduric psychrotrophic cfu/ml If process efficiency e.g. 4 log (MF 1.4 µm) Result: cfu / 1 L If process efficiency e.g. 4 log (MF 1.4 µm) Result: cfu / 1 L / 6

7 Some new concepts

8 Concept of potential defect rate Process survivors e.g. B. cereus spores, micrococcus PPC e.g. pseudomonas, Enterobacteriaceae even B. cereus Sub class of PPC: In filler contamination e.g. as above even B. cereus / 8

9 Concept of potential defect rate Process survivors e.g. B. cereus spores, micrococcus PPC e.g. pseudomonas, Enterobacteriaceae even B. cereus Sub class of PPC: In filler contamination e.g. as above even B. cereus / 9

10 Systems to reduce microbiological growth Complete growth inhibition 1. Raw milk with low numbers of psychrotrophic bacteria and spores. 2. Near to complete inhibition of growth of psychrotrophic survivors of HTST pasteurization by strict cold chain equal or below 4 C / 39 F at all times 3. Near zero PPC (post pasteurisation contamination) 4. Complete inhibition preserves product in all packages despite of presence of psychrotrophic bacteria. / 10

11 Systems to reduce microbiological growth Exclusion and growth slowdown 1. Raw milk with low numbers of psychrotrophic bacteria and spores. 2. Significant reduction of psychrotrophic survivors of HTST by filtration rather than centrifugation, plus liberal cold chain (5-8 C / F) 3. Near zero PPC (post pasteurisation contamination) 4. Allows to achieve very low numbers of psychrotrophic spores in the final product on the level like 1 per 100 or 1 per 1000 litres or better. This significantly reduces the statistical risk of claims about spoiled packages. / 11

12 Predicting shelf life is it possible? Modelling example

13 The influence of log reduction 2 days 1 Log / 13

14 The influence of temperature 8 C 10 days 5 C At 4 C all growth lines may be basically flat. Achieving stat of commercial hibernation / 14

15 The influence of temperature and PPC / 15

16 Microbiological efficiency of processing solutions

17 Best-practice lines for chilled dairy products for customized shelf life Validated technology Up to 10 days Up to 15 days Up to 30 days 30 days or more / 17

18 Comparison of process technologies Log reductions, estimated shelf life and potential defect rate Parameter Process Pasteurization 72 C/15 sec Pasteurization + centrifugal bacteria removal Pasteurization + Double and extended centrifugal bacteria removal Pasteurization + Microfiltration 1,4 µm Pasteurization Microfiltration 0,8 µm HTT 130 C/1 sec 127 C/2 sec Total plate count reduction Thermoduric count reduction Psychrotrophic Spore count reduction 1-1,5 log 1) 2-3 log 3-4 log 5-6log > 7 log Destroy all vegetative cells No reduction 1-2 log 2-3 log 4-5 log 6-7 log Destroy all vegetative cells No reduction 1-2 log 2-3 log 4-5 log 6-7 log >7 log Achievable shelf life 2) 7-10 days days days days days >30 days Number of 1L packages with at least one process survivor able to grow in 8C 100% 100% 100% 1% to 100% 1 in 1000 up to 1 in 100 Less than 1 in 1000 Hygiene design level Base line (standard design) High Hygiene High Hygiene Ultra-High Hygiene or Aseptic Ultra-High Hygiene or Aseptic Ultra-High Hygiene or Aseptic / 18

19 The key to ESL M I N I M I S E Process Survivors Re-infection C Growth in Cpackages Raw material quality Processing condition Hygienic design & operation Chilled operation & distribution / 19