Lec 6 - High hydrostatic pressures as an alternative method of food preservation

Alternative methods of food preservation

- Ionizing radiation (gamma)

- high hydrostatic pressure (HHP)

- pulsed electric field

- microfiltration

- Thermosonificatiom

High pressure processing (HPP)

= high hydrostatic pressure processing (HHP)

= ultra high pressure processing (UHP)

= pascalization

= cold pasteurisation - up to 600 MPa at ambient temperature

General description of the High Pressure Processing

- Solid or liquid products

- Products packaged or unpackaged

Pressure: 100 - 800 MPa

Time: milliseconds to more than 20 min

Temperature: increase 3°C at 100 MPa (3-6°c increase every 100 MPa)

- Reducing the volume of product about 15%

- Packages must endure it without losing the integrity and barrier properties

Mechanisms of effects of HPP on microorganisms

- cell membrane damage

- ATPase inactivation

- doesn’t destroy covalent bonds

- doesn’t damage primary structure of nucleic acids

Factors affecting the survival of microorganisms subjected to HHP

- type of microorganism

- chemical composition, PH, Aw of food product

- Conditions of pressurization:

> Temperature

> Height of pressure

> Treatment time

> The rate of compression and decompression

Cooked sliced ham packed in MAP

- traditional hurdles.

Picture of Graph in doc

Packaging

- types

- goals of packaging

- pre-packed/ packed foods

- vacuum-packs

- other flexible packaging such as plastic bottle

• NO ceramics, glass or metal ...

Goal:

- must be able to withstand the HHP

- without losing seal integrity

- without leaching undesirable packaging chemicals into the product

Flow diagram of HPP

In doc

Overall Goal of HPP

It Is:

a food processing technology which applies high pressure to solid or liquid foods to improve their safety

- and in some cases, organoleptic properties and quality.

Current global production of food using HPP

About 1.5 million tons per year

Products using HPP

- acidic and low acid foods

- products with high water content, including:

> fish products, shellfish, meat, dairy products,

> smoothies, dips, jams and baby food etc.

- to preserve products such as

> salads, soups, ready meals, pizza, etc.

- solid foods mainly vacuum packed

- liquid foods in flexible packaging

Solid foods, mainly vacuum packed

- dry cured / cooked meats

- cheese

- ready to eat meals

- vegetables etc

Food that can not be HPP treated

1. Solid foods with air included:

- Bread, Mousse (pianka)

2. Packaged foods in completely rigid packaging

- glass, Canned

3. Foods with a very low water content

- Spices, Dry fruits

The decision / reasons to introduce HPP

• Spoilage control

• Pathogen control

• Organoleptic preservation/improvement

• Product reformulation - e.g. low salt meats

• Product forming - the binding of many small pieces of meat into one larger piece

• Shucking of shellfish, Oyster Shucking

Improved organoleptic properties

- form smaller fat globules + better texture

(seen in sausages with low fat and salt content)

- pretreatment of beef to reduce cooking time

Advantages of HPP

- no loss of vitamins and amino acids

- longer shelf-life

- without preservatives or artificial additives

- improve the organoleptic characteristics

- process is energy-efficient and environmentally friendly

Challenges in HPP

• reduction of product volume by about 15%

• wide variety of microbiological effects seen

- Bacterial spores may survive

• unfavorable organoleptic changes

• price

• logistics

HPTS

high pressure thermal sterilization

(non-homogeneous temperature distribution in the chamber during pressurization)

microbiological objectives

Inactivation of:

- bacteria

- virus

- yeast + moulds

- parasites

Higher rates of inactivation by HPP = in more complex organisms.

simpler structures, such as bacteria = usually more resistant to inactivation.

Resistance

Parasites = HPP effective in low pressure ranges

Mould + yeasts = intermediate resistance

Foodborne vegetative pathogens =

- varies in sensitivity when low pressures (300MPa)

combined with intermediate temperatures

L. monocytogenes, S. aureus, E. coli, S. Typhimurium

- variations in range 0.5-8.5 log

Spores = great resistance

Viruses

- pressure resistance depending on structure

- enveloped viruses more sensitive than naked virus

- increase in the degree of inactivation at lower

temperatures: 9°C / 250-500 MPa

gram (+) generally more resistant than gram (-)

High Pressure Processing of Bivalve Shellfish and HPP's Use as a Virus Intervention

Non enveloped virus

- Human norovirus (HuNoV)

- hepatitis A virus (HAV)

Virus intervention

• Bleaching effect occurs at 600 MPa at room temperature

• but is minimised at 5°C

• The overall appearance is much better when HPP used because flesh is completely intact.

Laboratory scale of HPP

• Chamber working volume = 1,5 l

• Constant process temperature = 4°C

• Time for pressure generation = 15-20 s

Generating pressure

• direct method - piston plunging into the chamber

• indirect method - use of special pumps

Modeling the inactivation

- salmonella + e.coli

Inactivation of salmonella in ground chicken using HPP

- 5-10g cFU/g

- 450 MPa,

- 10 min.

inactivation of Escherichia coli 0157:H7 and Uropathogenic E. coli in ground beef by high pressure processing

- >5-10g cFU/g

6D-value

Effects of high hydrostatic pressure on Campylobacter jejuni in poultry meat

- 6-10g CFU/g reduction

- 300 Mpa/ 8.73 min, or

- 400 Mpa/ 4.37 min

Possibility of Campylobacter jejuni inactivation in smoked salmon by HPP

- 6-10g CFU/g reduction

- 300 MPa/ 17.10 min, or

- 400 Mpa/ approx. 5 min

USA regulations

USDA → approved HPP „for Listeria contaminated pre-packed ready-to-eat (RTE) meat products"

FDA → accepted the commercial use of PATS for LAF (2009)

(PATS, ang. pressure-assisted thermal sterilization)

(LAF, ang. low acid foods; pH > 4.6)

PATS and HPTS stands for?

PATS = Pressure-assisted thermal sterilization

HPTS = High pressure thermal sterilization

Product description (HACCP)

> Product selection

> Product characteristics (pH, aw, composition...)

> Safety - Public Law & Private Law

> "Pre & post pressure processing" (or with heat treatment?)

> Packaging

> Storage temperature of the product

> Shelf life

Small vs large-scale manufacturer

Large:

- professional service for HPP technology

- microbiological laboratory with experience in chelange test

Small, HPP outsourced:

- often look for a published HPP process that closely matches their product

Product vs process

- HPP pasteurisation

Vs

- HPP Sterilization

Table in doc

HPP

- processes and foods for these processes

1. Sterilisation = PATS, LAF

2. Pasteurisation = RTE foods

3. Shelf life extension = fruit + veg products

Food safety risks associated with food types

1. Chilled food with PH below 4.2

- shelf life = long

- risk = survival of vegetative cells of pathogenic bacteria

- equivalence target = pasteurisation

2. Chilled acid food PH 4.2 - <4.6

- Sl = long

- R = above risk + potential growth of vegetative cells

- Et = pasteurisation

3. Low acid chilled foods

Shelf life 0-5d

- R = above risks

- Et = Cook time as recommended for this food

Shelf life 5-10d

- R= Above risks + Listeria monocytogenes

- Et = Listeria-safe cooking process

Shelf life 10+d

- R = Above risks + cold tolerant C. botulinum

- Et = psychrotrophic C. botulinum cooking process

4. Low acid shelf stable foods

- Sl = long

- R = Above risks + conventional C. botulinum

- Et = suitable retorting process

PH

Shelf-stable (commercially sterile) products:

- pH < 4,0

- Pressure - 580 MPa

- Time - 3 min

Reduction at the 6D level for

- E. coli 0157:H7, Listeria sp., Salmonella spp., Staphylococcus spp.

- in salsa sauce and apple juice.

• As pH is lowered most microbes become susceptible to HPP inactivation and sublethally injured cells fail to repair.

Water activity (aw)

Reducing water activity

→ protect microbes against inactivation by HPP

however...

→ recovery of sublethally injured cells can be inhibited by low water activity

Temperature

45-50°c

- increased rate of food pathogen activation + spoilage

- so need process that has uniform initial food temp in this range

90-110 °C + 500-700 MPa →

- inactivate spore forming bacteria such as C. botulinum

Fat content vs Temperature change

The temp. of water & most of the high- moisture food materials :

- 3°C per 100 MPa at 25°C

Increase fatt conc. = increase temp.

- fatty foods have higher compression heating

Requirements for HPP manufacturer/operator

• Appropriate premises and equipment

• knowledge and experience

• competent staff

Records

Records of Individual cycles should:

- be accessible

- clear link between batch no. + process cycle no.

Shared responsibility for subcontract

HPP processing

1. The processors must have?

2. Records of the relevant cycles should?

1. The processor must have:

• adequate premises and equipment

• knowledge and experience

• competent personnel to carry out the work

2. Records of the relevant cycles should:

• be available to the manufacturer

• clear link between the manufacturers batch no. and processors cycle no.’s

• records relevant to assessing the quality of a product in the event of complaints or a suspected defect are accessible

HPP - The role and responsibilities of food business operators

1. Include the pressurization step in procedures based on HACCP principles

2. Document how the selected HPP pressure and time parameters have been validated and verified

3. Validation

-> durability studies / challenge tests

4. Laboratories

- use accredited labs

5. Test plan

- Appropriate microbiological parameters selected and tested E.g. L. Monocytogenes