Pre-prepared food is big business in a modern society where demanding work and social activities have put the squeeze on meal times. For ready meal producers, product integrity and an appetising look is key to success in this market. Consumers demand first class appearance, even spread of ingredients and product integrity and, according to many producers, a ‘smashed up’ ready meal is the biggest driver of lost custom.
A ready meal line can be made up of many processing and packaging options as the diverse range of ingredients, either fresh or frozen, are handled and then presented to the consumer. In terms of processing, pumps can be deployed for operations such as transfer and mixing to produce powerful suction with low shear, low pulsation and gentle handling for such products as mashed potato. Also, depositors have to cope with filling multi-component meals and deposit precise portions of product into trays, cartons or pouches. Browning grills can then be used to give a baked-like finish to ready meals.
In terms of packaging, the tray as been one of the most popular formats for ready meals which use either a modified atmosphere or gas flushing on fresh ingredients. Once the trays have been filled, they are sealed and then tested for any leaks to ensure product integrity at all times. Many meals are then placed in cartons to provide optimum shelf impact.
In recent times, there has been a plethora of other packaging formats used for ‘fresh meal kits’ including pouches and rigid plastics pots but the traditional, more high volume ready meal continues to be packed in trays.
A line can compose of tray denesters that feed trays to single or twin lane conveyors and arrive at a volumetric filler which can be used for bulky ingredients such as rice and pasta. Filled trays can then move to another filling station which applies a pre-mixed sauce.
Trays are then vibrated, to help settle the contents, before moving on to the distribution system below a multihead weigher, through which the most costly ingredients are generally added. These are often the main protein content of the meal such as meat, poultry or seafood.
Trays can then pass on to other ingredient adding stations or straight to the traysealer, where they are sealed under vacuum before then being checkweighed. Often, trays then proceed to an autoclave for retorting to provide a shelf life of three months.
As well as rotary lobe pumps, ready meal producers are now using MasoSine SPS pump technology which has a clever sinusoidal rotor to provide enough suction to cope with high viscosity levels. The large pumping chambers within these pumps allows product integrity to be preserved and maintained even for very fragile product such as pre-cooked meat or chicken.
Cooked pasta and rice can be deposited via a volumetric filling head into trays, cartons and pouches in precise portions.
Modified atmosphere packaging (MAP) is also known as protective gas packs, and is created by evacuating some or all of the air and replacing it with a protective gas mixture (gas flushing). The pack is then hermetically sealed with special barrier films to prevent modified atmosphere from escaping or air getting back into the pack. This technique is used to extend shelf lives of the ingredients used.
In vacuum skin packaging the product is placed on a base film or a pre-made tray. After evacuation, the top film which has specific skinning properties wraps around the contours of the product and seals to the bottom film or the pre-made tray.
Single and multiple lane adjustable magazine pick and place denesters are available as well as fixed and adjustable rotary wheel/scroll style compact footprint models for different tray types and speed requirements. Vertical denesters can be integrated into other line equipment and chain infeeds with varying capacities.
Automatic traysealers have to match the current market requirements for more efficient packaging procedures and an optimum price-performance ratio. This high speed can be achieved through optimised machine sequences and new die technology or by three dimensional tray positioning systems.
The most critical requirement for all sealing equipment among the majority of food manufacturers remains speed but also the effective integration of the tray sealer with other equipment on the line.
Ready meal lines can often include tray denesters, conveyors, volumetric fillers, multihead weigher and checkweigher and today’s traysealers can monitor and control the entire operation.
Automatic seal integrity testers and converger systems are designed to give each pack the longest possible test time in order to identify and reject the smallest possible seal defects. Every pack is tested on some systems and only those with leaks are rejected. Seal testing has, of course, the potential to reduce waste by eliminating product recalls and as all packs are tested on line, rejected packs can be reworked allowing for reductions in product loss.
Many sophisticated systems have now been devised where visual inspections can be combined with mechanical pressure testing to achieve accurate results. In operation, the mechanical control module uses special software to analyse the results of the pressure test, which measures the vibration of the top film on the pack to determine the durability and integrity of the seal.