FAT RICH DAIRY PRODUCTS

Module 4. Consumer cream products

Lesson 10
COFFEE CREAM, STERILIZED CREAM AND WHIPPED CREAM

10.1 Introduction

Cream is added as an ingredient to a large number of commercial food products including canned soup, dried bakery mixes, etc. In this context the cream serves as a source of dairy fat and its structural properties are of little importance. There are, however, two major product groups viz., alcoholic cream liqueurs and cream cakes, desserts etc., where cream is both a major ingredient and a major determinant of the properties of the complete product. The major consumer cream products include coffee/table cream, whipped & whipping cream and sterilized cream.

10.2 Coffee Cream

Coffee cream is a low-priced cream with a fat content of 16 to 25 per cent, which is used in coffee and on fruits and cereals. Coffee cream is a long-shelf-life product, similar to UHT milk. It is a special type of low-fat cream processed to minimize 'feathering', the coagulation and release of free fat, which occurs when cream is added to hot coffee. Further, coffee cream is providing an attractive appearance to the coffee with an appropriate modification of flavor.

Production of coffee cream by UHT process: The fat content for coffee cream has to be standardized as per the legal requirements. The standardized coffee cream must be homogenized to prevent fat layer or fat plug formation in the container, thus improving taste, whitening power and stability. Homogenization has a direct influence on the flocculation stability of coffee cream in hot coffee. A double-stage homogenization is optimal for UHT cream. The first homogenization is done before the UHT treatment; the second aseptic one is done after the UHT treatment. For both processes the pressure in the first stage should be about 200 bar and in the second stage about 50 bar. Standardized coffee cream is processed as per the UHT process and is filled aseptically into one-way containers of standard net volumes.

Production of coffee cream by sterilization process: When preserving coffee cream by the sterilization process is carried out, first fat content is stanfderdized, then pasteurized at 90°C, homogenized, filled into bottles, closed by crown corks and finally sterilized in retorts. In the process of sterilizing cream in the pack, homogenization has to take place before the sterilization, which again is a double-stage process using the same pressures (200/50 bar) as per UHT process.

10.3 Sterilized Cream

Sterilized cream is packed in cans and sterilized using similar plant to that used for sterilized milk. In the production of sterilized cream the fat content is standardized, then the cream is preheated to 140°C for 2 s to reduce bacterial spores. The cream is homogenized at 50-75°C using either single or two-stage processes. The stabilizing salts are then added to prevent the 'grainy' texture which is a defect that occurs following sterilization. The cream is filled into cans which are seam closed. The cans are coated on the inside with a lacquer, e.g. an epoxy-phenolic compound suitable for both acid and non-acid foods, which prevents reactions between the cream and the tinned steel of the can. Sterilization may take place in static batch retorts, agitated batch retorts or continuous retorts. If the product is agitated during processing, it increases the rate at which the required can-centre temperature is reached, thereby reducing the overall processing time. Generally for a 170 g can, the time required for a static retort is 40 min to reach 118°C, followed by a further 30 min at this temperature to effect sterilization . In contrast, for an agitating retort only 23 min is required to reach 118°C followed by a further 18 min at this temperature to effect sterilization. A continuous retort requires 26 min at 119.5°C for sterilization. After sterilization the cans are cooled with chlorinated water, dried, labeled, packed in paperboard boxes and stored at ambient temperatures prior to distribution.

10.4 UHT Cream

Indirect process

The Process for the preparation UHT cream is similar to the production process of UHT milk. For the production of UHT cream the heat exchangers used are mainly of plate or tubular design. Homogenizers are placed between the regeneration and UHT sections. The plant with up-stream of the UHT section and holding tube can be regarded as non-sterile, while those downstream are sterile and the plant must be maintained to a high standard of hygiene before use to reduce the risk of bacterial spores contaminating the product. The pre-sterilization of all plant with steam is most effective.

Direct Process

Cream may be UHT processed using methods of direct heat exchange. Apart from diluting the cream by as much as 10-15%, the instantaneous heating of cream and the shear effects occurring, as cream and steam are mixed, can destabilize the milk fat globules. Homogenization is therefore necessary to restore the emulsion, and when direct methods of heat exchange are used the homogenizer is placed downstream of the heat-treatment section. Clearly, a vacuum cooling section is required to remove the water added through the direct contact of cream with steam and this is placed before the homogenizer. Whether cream is homogenized prior to UHT treatment or after, the product temperature should be between 50-75°C. Low-fat UHT creams require high pressure homogenization, whereas other creams may be homogenized at lower pressures.

Aseptic packaging

UHT cream must be aseptically packed. The following are the various packages are commonly used:

1. The form-fill-seal laminated carton is used as it contains aluminum layer in the laminate which is essential if the product is to be preserved from the auto-oxidative influences of light during storage.

2. Thermoformed containers made from the coextrusion of polystyrene and polyvinylidene chloride (PVDC) are also used and these containers are closed with heat sealed polyethylene/ aluminium laminate foil.

3. Blow-moulded polyethylene or polypropylene containers formed at the point of filling may be used and for bulk UHT cream, bag-in-box packages made from metallized plastic laminates may be aseptically filled.

10.5 Whipping Cream

Whipping cream is one of the food foams. It is widely accepted due to its taste and multiple applications in decorating and refining of food. Whipping cream can be differentiated into the fresh whipped product as manufactured in the dairy for distribution and the whipped cream. The cream is usually whipped immediately prior consumption, either by the consumer or in the catering outlets. The basic requirements for this product are:

a. Good whippability i.e., short beating time and a volume increase of at least 80%, mostly 100-150%.

b. Good foam stability and firmness of the foam i.e a defined weight of 100 g with defined dimensions should not penetrate more than 3 cm within 10 seconds.

c. Low serum formation i.e., a cube of whipped cream with 6 cm length/width/depth should not exude serum after 1 hour at 180C and should exude a maximum of 1 ml after 2 hour of storage.

Fig. 10.1 Flow diagram for manufacture of sterilized cream

Process

Cream preparation and fat standardization

Standard quality requirements for raw milk must be applied when manufacturing whipping cream. A special point is the fatty acid composition, which depends on the feed situation. Milk fat with a majority of saturated fatty acids i.e., high melting point and a low iodine number (so-called winter cream), results in firmer foam than a softer fat. Fat standardization is done in the separator in the same way as for market milk. Minor modifications can be made by adding whole milk or cream with a higher fat content. Fat corrections with skim milk result in reduced whippability and foam stability. These decisive quality criteria are improving with increasing fat content (> 30%), with 35% being the optimum.

Acidification/ripening

Whippability depends on both the characteristics of fat globular membrane and the state of hydration of the serum protein. Favorable conditions for foaming of the proteins exist at a pH of 6.4-6.2. To set the pH of the cream, butter cultures can be added (0.5-2%), followed by ripening at 10-15 °C, until the preset pH has been reached. The objective of the ripening is to achieve good fat crystallization or fat hardening. Total ripening time (before and after filling/packing) should be a minimum of 1-2 days at temperatures < 10°C.

Homogenization

In general, homogenization improves foam stability and avoids the creaming of the fat, which is an absolute requirement for UHT and sterilized cream with their longer shelf life. Experience has shown that a single-stage homogenization leads to earlier gelation of the product, due to the inherent and additional viscosity caused by the agglomeration of fat globules. A two-stage homogenization is preferable with the following criteria for a 30% fat cream:

a. I-Stage at 70°C and a pressure of 60-70 bar

b. II- Stage at 70 °C and a pressure of 15-20 bar

For pasteurized cream having the same shelf life as fresh milk, homogenization is not necessary.

Heating and cooling: Whipping cream must be heat treated with an approved process. For fresh whipping cream, pasteurization is done mainly with a high-heat process, where temperatures > 95°C are chosen. Whipping cream with an extended shelf life is manufactured by the UHT process and filled aseptically. Sterilized whipping cream is sterilized after the filling operation. After heating, a shock cooling should be applied for fresh cream, using temperatures of < 10°C (optimum 2-4°C) in order to achieve good fat crystallization and foam stability.

Filling is done into glass bottles or into one-way containers (for shelf-stable whipping cream) such as cups or bricks with user-friendly volumes of 150 g, 200 g, 250 g, and 500 g. For large-scale users containers with a net volume of 2 liters up to 15 liters or churns of 20 liters content are used.

Two methods are used in the application of aerosols:

a. Aseptic filling of homogenized, UHT or sterilized cream into spray cans (used as one-way containers)

b. Non-aseptic filling into so called siphon bottles, in which after filling of cream and closing of the bottle, a cartridge with a compressed air is used.