Ice cream

Ice Cream

INTRODUCTION

A high incidence of food poisoning in the early part of the 20th century was nearly always attributable to ice cream consumption.

The reasons for the infections were due to:
  • 1. Small scale production by inexperienced people
  • 2. Inadequate storage & temperature control
  • 3. Inferior raw materials
  • 4. Lack of hygiene awareness / education
  • 5. Ice cream is a good media for bacterial growth coupled with the above 3 reasons.
The ice cream heat treatment regulations 1959 suggested time and temperature combinations:
  • 65° c for 30 minutes
  • 71° c for 10 minutes
  • 80° c for 15 seconds
  • 150° c for 2 seconds (UHT = Ultra Heat Treatment)
After heat treatment cooling to 7c or below must be effected within 90 minutes

During the ageing period (The time between heat treatment and freezing of the mixture) The temperature of the mix must not rise above 7c. If it does then the mix must be re-pasteurized.

Psteurizer chart recorders are essential and this record should be inspected and signed and thermometers calibrated.

Ice cream composition regulations

  • 1. Dairy ice cream containing milk fat must contain at least 5% fat and 7.5% milk solids not fat (MSNF). The same regulation applies to non milk fats.
  • 2. The products made from non milk fats (non dairy fats) must state on the packaging:
    a. Contains non milk fat or
    b. contains vegetable fat

Manufacturing basics

The texture of ice cream, 'mouthfeel' (smooth, coarse, etc.) is dependant on its ice crystal structure

The milkfat is in tiny globules that have been reduced in size and distribution by the homogenizer during the mix processing

Emulsifiers are added to ice cream to reduce the stability of this fat emulsion by replacing proteins on the fat surface. When the mix is subjected to the whipping action in the barrel of the freezer the fat emulsion begins to partially break down and the fat globules begin to flocculate or destabilize.

If emulsifiers were not added, the fat globules would have so much ability to resist this coalescing, due to the proteins being adsorbed to the fat globule, that the air bubbles would not be properly stabilized and the ice cream would not have the same smooth texture (due to this fat structure) that it has.

Structure from the Ice crystals

The initial freezing point of the solution is lower than 0° C due to dissolved sugars (freezing point depression), which is mostly a function of the sugar content of the mix.

As ice crystallization begins and water freezes the concentration of the remaining solution of sugar is increased and the freezing point is lowered.

At the typical ice cream serving temperature of -16° C, only about 72% of the water is frozen. The rest remains as a very concentrated sugar solution. This helps to give ice cream its ability to be scooped at freezer temperatures. The air content also contributes to this ability

Critical to ice cream structure is ice crystal size, and the effect of re-crystallization (heat shock, temperature fluctuations) on ice crystal size and texture.

Statutory Instrument 1995 No. 1372 (S.101)
The Dairy Products (Hygiene) (Scotland) Regulations 1995 SCHEDULE 6
Regulations 3(3), 9(6) and 13(1)(b)(vi)

REQUIREMENTS FOR MILK-BASED PRODUCTS

PART I microbiological criteria

  • 1. On removal from the processing establishment milk-based products shall not contain pathogenic micro-organisms and toxins from pathogenic micro-organisms in such quantity as to affect the health of the ultimate consumer.
  • 2. Sterilised or ultra heat-treated milk-based products which are in liquid or gel form and are intended for conservation at room temperature shall meet the following standards after incubation at 30°C for 15 days:-(a) have a plate count at 30°C g 100 per ml; and (b) be organoleptically normal.
  • 3. Subject to paragraph 5 below, milk-based products shall meet the standards referred to in the tables below upon removal from the processing establishment

    TABLE A Product Type of micro-organism Standard (m1,g)
    (i) Cheese, other than hard cheese Listeria monocytogenes Absence in 25g where n = 5, c = 0
    (ii) Milk-based products, other than cheese covered by (i) above Listeria monocytogenes Absence in 1g
    (iii) Milk powder Salmonella spp Absence in 25g where n = 10, c = 0
    (iv) Milk-based products, other than milk powder Salmonella spp Absence in 25g where n = 5, c = 0 The sample of 25g referred to in paragraph (i) of table A above shall consist of 5 specimens of 5g taken from different parts of the same product.

    TABLE B Product Type of micro-organism Standard (m1,g)
    (i) Cheese made from raw milk or from thermised milk Staphylococcus aureus n = 5, c = 2, m = 1,000, M = 10,000 Escherichia coli n = 5, c = 2, m = 10,000, M = 100,000
    (ii) Soft cheese made from heat-treated milk Staphylococcus aureus n = 5, c = 2, m = 100, M = 1,000 Escherichia coli
    (iii) Fresh cheese Staphylococcus aureus n = 5, c = 2, m = 10, M = 100 Powdered milk Staphylococcus aureus Frozen milk-based products including ice-cream Staphylococcus aureus
  • 4. The definition of the symbols specified in paragraph 3 of Part II of Schedule 3 shall apply for the purposes of the tables in paragraph 3 above.
  • 5. Testing of the milk-based products referred to in table A of paragraph 3 above shall not be compulsory for sterilised milk, preserved milk-based products and milk-based products where the heat-treatment was applied after wrapping or packaging.
  • 6. Sampling programmes shall be drawn up by the occupier of the dairy establishment in the light of the nature of the dairy products and the principles of risk analysis.
  • 7. In all cases where the standards in table A of paragraph 3 above are exceeded, the dairy products shall be excluded from human consumption and withdrawn from the market.
  • 8. In all cases where the standards in table B of paragraph 3 above are exceeded, there shall be a review of the implementation of the methods for monitoring and checking critical points applied in the processing establishment. The occupier of the processing establishment shall inform the food authority of the corrective procedures included in the production monitoring system to prevent any repetition of the occurrence.
  • 9. Wherever the standard M in table B of paragraph 3 above is exceeded in the case of cheese made from raw milk, thermised milk or soft cheese, testing shall be carried out for-(a) the possible presence of strains of enterotoxigenic Staphylococcus aureus or Escherichia coli that are presumed to be pathogenic; and(b) if necessary the possible presence of Staphylococcal toxins in such products, by a method determined in accordance with Article 31 of Council Directive 92/46, as specified in paragraph 2 of Chapter II of Annex C to that Directive.
  • 10. If the strains referred to in paragraph 9 above are identified or staphylococcus enterotoxins are found, then all the batches of the cheese involved shall be withdrawn from the market. In this case the occupier shall inform the food authority of such findings, of the action taken to withdraw the batches in question and the corrective procedures introduced into the production monitoring system to prevent any repetition of the occurrence.

PART II pasteurised cream

1. Pasteurised cream shall be heated-(a) to a temperature of not less than 63°C and retained at that temperature for not less than 30 minutes;(b) to a temperature of not less than 72°C and retained at that temperature for not less than 15 seconds; or(c) to such other temperature for such other period of time as has equivalent effect to sub-paragraph (a) or (b) above necessary for the elimination of vegetative pathogenic organisms in the cream.
2. The cream shall-(a) be cooled as soon as practicable after pasteurisation, and(b) show a negative reaction to the phosphatase test using the method of analysis specified in paragraph 5 of Schedule 11.

PART III sterilised cream

1. Sterilised cream shall be heated-(a) to a temperature of not less than 108°C and retained at that temperature for not less than 45 minutes; or(b) to such other temperature for such other period of time as has equivalent effect to sub-paragraph (a) above necessary for the elimination of vegetative pathogenic organisms.
2. The cream shall be cooled as soon as practicable after sterilisation.
3. Sterilised cream shall meet the standard referred to in paragraph 2(a) of Part I of this Schedule.

PART IV ultra heat-treated cream

1. Ultra heat-treated cream shall be heated-(a) to a temperature of not less than 140°C and retained at that temperature for at least 2 seconds; or(b) to such other temperature for such other period of time as has equivalent effect to sub-paragraph (a) above necessary for the elimination of vegetative pathogenic organisms.
2. The cream shall be cooled as soon as practicable after being ultra heat-treated.
3. Ultra heat-treated cream shall meet the standard referred to in paragraph 2(a) of Part I of this Schedule.

PART V pasteurised ice-cream

1. Pasteurised ice-cream shall be obtained by the mixture being heated-(a) to a temperature of not less than 65.6°C and retained at that temperature for not less than 30 minutes;(b) to a temperature of not less than 71.1°C and retained at that temperature for not less than 10 minutes; or(c) to a temperature of not less than 79.4°C and retained at that temperature for not less than 15 seconds; and then reduced to a temperature of not more than 7.2°C within 11 hours and kept at such temperature until the freezing process begins.
2. If the temperature of ice-cream has risen above minus 2.2°C at any time since it was frozen it shall not be sold or offered for sale unless-(a) it has again been subjected to the heat-treatment to which as a mixture it was required to be subjected under paragraph 1 above; and(b) after having again been frozen, it has been kept at a temperature not exceeding minus 2.2°C.
3. In the case of a complete cold mix which is reconstituted with the addition of water only, it shall not be necessary for it to be subjected to further heat-treatment by pasteurisation as specified in paragraph 1 above.
4. If a complete cold mix reconstituted with the addition of water only is frozen, it shall comply with paragraph 2 above.

PART VI sterilised ice-cream


1. Sterilised ice-cream shall be obtained by the mixture being heated to a temperature of not less than 148.9°C for at least 2 seconds.
2. After the mixture has been sterilised as specified in paragraph 1 above, it shall be reduced to a temperature of not more than 7.2°C within 1½ hours and shall be kept at such a temperature until the freezing process begins.
3. Paragraph 2 above shall not apply to a mixture which has been sterilised in accordance with paragraph 1 above if immediately after the mixture has been sterilised it is placed in sterile airtight containers under sterile conditions and the container remains unopened.
4. If the temperature of ice-cream has risen above minus 2.2°C at any time since it was frozen it shall not be sold or offered for sale unless-(a) it has again been subjected to the heat-treatment to which as a mixture it was required to be subjected to under paragraph 1 above; and(b) after having again been frozen, it has been kept at a temperature not exceeding minus 2.2°C.
5. In the case of a complete cold mix which is reconstituted with the addition of water only, it shall not be necessary for it to be subjected to further heat-treatment by sterilisation as specified in paragraph 1 above.
6. If a complete cold mix reconstituted with the addition of water only is frozen, it shall comply with paragraph 4 above.

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