FAT RICH DAIRY PRODUCTS

Module 5. Quality and preservation of cream

Lesson 13
PACKAGING AND STORAGE OF CREAM

13.1 Introduction

Cream is a high moisture product, and hence is easily perishable. It needs special care to preserve and improve the shelf life. Pasteurization of cream extends the shelf-life to greater extent, but packaging of cream also play in extending the shelf life of cream. Type and characteristics of packaging material used for cream will vary depending on the manufacturing process of cream and also intended use of finished end product i.e. for retail or wholesale marketing.

13.2 General Requirements for Packaging of Cream

Various formats exist for the packaging of pasteurized or fresh cream. The following are the important factors to be considered in packaging of all creams, whether pasteurized, UHT treated or sterilized.

● The exclusion of light is important as light can initiate auto-oxidation of milk fat resulting in the production of rancid flavors. Homogenized cream is particularly susceptible to the action of light.

● Cream may be tainted by the absorption of odors from various sources and packaging material must, therefore, be impermeable to gases.

● The absorption of moisture or fat can cause the quality of cream to deteriorate and packaging must, therefore, be impermeable to both.

● The packaging materials themselves may contain compounds which can migrate into the cream causing a gradual deterioration in quality, e.g. monomers from plastic packaging and printers' inks and dyes used for labels and decoration. Packaging materials should be carefully selected to avoid such problems.

● The design of the container can also influence product quality. With some creams serum separation may occur during storage and the ability to shake the contents to ensure mixing can be important to consumer acceptability.

Table cream

Table cream is packaged for retail sale in units similar to those for milk such as glass bottle, paper carton, low density polyethylene sachet, plastic bottles etc. When table cream is produced for the purpose of coffee whitening, UHT processing is combined with aseptic packaging employing ‘multi-cup tray’ package format, each cup quantity serving as a single dose sufficient for one cup of coffee.

13.3 Packaging for Pasteurized Cream

Retail packaging

Pasteurized cream is packaged in cartons and bottles for retail sale with package size usually being in the range of approximately 100-1000 ml. Pasteurized cream for retail sale was earlier packaged in glass bottles, waxed cartons and polyethylene-coated cartons, but now the most common form of packaging used is the injection moulded polystyrene pot, or flat topped round container. Polypropylene containers are used an alternative as these less likely to cause taint and, when used as a copolymer with polyethylene, it is more robust under chilled condition. However, due to technical difficulties these have limited use.

To improve the barrier properties of plastics packaging for fresh cream, multilayer materials may incorporate an ethylene vinyl alcohol (EVOH) layer. Once filled, the containers are closed with a heat-sealed polyethylene/ aluminium foil laminate and often a clear plastic lid is provided for consumers to reseal the container once opened.

Bulk packaging

It may be used for catering or institutional use. Normally plastic (e.g. polythene) bags contained in plastic crates or cardboard cartons are used for bulk packaging. In this case package size ranges from 5 to 25 liters.

13.4 Sterilized Cream

In case of retort sterilized cream, tin cans and glass bottles are commonly used packaging formats. The simplest method of sterilization is to package the material, then heat the complete package and material to confer sterility. The can and glass bottle have been the traditional containers for such operations, but other retortable plastic materials are now available for packaging. It is normal to give the cream a preheat treatment before packaging to destroy bacterial spores. Sterilization takes place in a retort or hydrostatic sterilizer using temperature-time regimes of 110--120°C for 10-20 min. This severe heating induces gross changes in the cream with protein denaturation, Maillard browning and fat agglomeration may take place to modify texture and flavor. A calcium sequestering agent, such as sodium citrate or a sodium phosphate, may be added to make more casein available for stabilizing the emulsion. The unit packaging volumes have to be relatively small (400 ml) because of the restriction on heat transfer with larger volumes. Normally cream of approximately 23 per cent fat content is the base cream for in-can sterilized cream manufacture. It enjoys a substantial market as a dessert adjunct or ingredient in a number of food items, such as dressings and sauces. It is well known to be a good base for party dips.

13.5 UHT Cream

A number of different packaging options are available for packaging the UHT cream to pack and the following are some of the packaging options:

● Aseptic canning was probably the first to be utilized with cream

● Plastic (polythene), paper and foil laminate cartons

● Plastic ( polystyrene or polypropylene) form-fill-seal packages are most widely used

● Lacquered aluminum or tin-plate cans are used for Aerosol cream

● Preformed pots or with laminates

● Plastic ( polythene) bag contained within a cardboard carton (bag-in-box) is used for bulk packaging of UHT cream with unit volumes are in the range 5-1000 liters.

For aseptic packaging the packaging material is first treated with hydrogen peroxide solution, later removed by squeezing or natural drainage. Residual solution is removed by heat; while the evaporating and decomposing peroxide sterilizes the material. The sterilized product must then be filled in a sterile environment. In Tetra Pak system, the laminate is in the form of a continuous tube and the evaporating peroxide above the filler forms a natural aseptic barrier. Individual packages are formed by heat sealers and cutters at the base of the filler. Most other systems incorporate laminar air flow cabinets for filling operations. Unit sizes range from 7·5 ml (coffee cream) to 1000 ml.

13.5.1 Storage and distribution

* Fresh cream can be stored at 5ºC and the shelf-life is 14 days. Cream is distributed as early as possible but preferably within 3 hours of removing it from cold storage.

* Frozen cream can be stored for 18 months.

* Sterilized cream can be stored for 6 months.

* Sterilized UHT creams have a shelf-life of several months at 5°C.

In addition to pasteurization, sterilization and UHT treatment of cream, the cream can also be preserved and stored for several months by freezing and drying of cream.

13.5.2 Freezing

Bacterial spoilage of cream can be inhibited by freezing of cream however this process leads to destabilization and gross separation of fat and serum resulting on thawing. Freezing of cream is done by two process:

Plate freezing

The plates contain circulating refrigerant are arranged vertically, in parallel, with bottom and end seals to form a series of moulds with hydraulic pressure maintaining the plates in place. The cream is poured into gaps between plates, and surface freezing is instantaneous at the pre-cooled plate surface; this is essential to prevent adhesion of the cream to the plate. The cream freezes progressively towards the centre with refrigerant in the plates absorbing the heat, so that finally slabs of frozen creams are formed. The slabs are removed for packaging and subsequent storing by separating the plates.

Drum freezing

A rotating drum containing recirculating refrigerant is immersed in a vat of cream to form a frozen film. The frozen cream is then removed from the drum with a knife, and a flaked product is obtained. Such a process gives somewhat more rapid freezing than plate freezing and is less damaging to the cream and is continuous. The cream flakes are packaged in heat-sealed plastic bags as used for frozen vegetables.

A temperature less than -18°C is recommended for long-term storage of frozen cream.

Uses

Frozen cream may be used as

* An additive for 'cream soups

* In recombined milk and ice cream

13.5.3 Drying (spray dried cream)

Removal of water from cream gives a product with an extended shelf-life. The most common method of producing dry products from liquids is through spray drying. The particular problem in the production of spray dried cream is the high fat: SNF ratio in the finished product. The fat is in a liquid state at the temperature at which it would exit a spray drying chamber, so it is essential that the fat globules are encapsulated and protected by the non-fat solids. For cream, this normally requires the addition of extra protein, usually sodium caseinate, and the addition of a suitable carbohydrate (e.g. lactose, dextrose, maltodextrin or sucrose) to act as a carrier. Cooling of the powder is necessary to solidify the fat and prevent caking, which will occur if the thin protective membranes are ruptured. Cyclone collection of the powder results in mass caking of powder on the cyclone walls, and bag filters soon become impervious if fat is deposited. A Filtermat drier has a continuous woven belt for collecting powder from the primary chamber and cool air can then be directed on to the powder in subsequent (fluid bed) stages of the drier. This drier is used extensively to dry powders with high fat contents; these powders are usually based on vegetable fats.

The high fat content of cream powder renders it susceptible to deteriorations which impair the flavour. It is essential that the cream is given sufficient heat treatment to destroy lipases. Oxidation of the fat is also a potential problem, and addition of antioxidant extends shelf life. Storage of cream powders should be at low ambient temperatures, as an elevated temperature gives high proportions of liquid fat, resulting in caking problems, as well as more rapid flavour deterioration. The addition of free-flowing agent is recommended to help prevent caking.

Dried cream can be used as an ingredient for dried soup, dessert, ice cream or packet cake mixes.