Modified Atmosphere Packaging of Fresh Fruits and Vegetables

Extending the shelf-life of fresh fruits and vegetables

MAP modified atmosphere packaging for fresh fruits and vegetables, including Atlanta sprouts, apples, apricots, artichoke, asparagus, aubergine, avocado, bananas, bean sprouts, beetroot, blackberries, broad beans, broccoli, Brussels sprouts, cabbages, cauliflower, carrots, celery, cherries, chicory, courgettes, cranberries, cucumber, cumquats, fennel, garlic, gooseberries, grapefruit, grapes, green berries, guava, kale, kiwi fruit, leek, lemons, lettuces, limes, lychees, mandarins, mango, mangosteen, marrow, melon, mixed fruit salads, mixed vegetable salads, mulberries, nectarines, Olea, onions, oranges, papayas, parsnips, passion fruit, peaches, peas, peppers, pineapple, plums, potatoes, prickly pear, radish, rambutans, raspberries, rhubarb, rocket, shallot, spinach, star apples, strawberries, sweetcorn, swede, tomatoes, turnip, water chestnuts, watercress, watermelon, and yams.

The principal spoilage mechanisms affecting whole and prepared fresh fruit and vegetable products are microbial growth, enzymic browning, and moisture loss. MAP which results in depleted O2 and/or enriched CO2 levels is very effective at inhibiting these spoilage mechanisms, as well as:

1. Reducing respiration
2. Delaying ripening
3. Decreasing ethylene production and sensitivity
4. Retarding textural softening
5. Reducing chlorophyll degradation
6. Alleviating physiological disorders

Unlike other chilled perishable foods that are MAP packed, fresh fruit and vegetables continue to respire after harvesting and any subsequent packaging must take this into account. The products of aerobic respiration are CO2 and water vapour (whereas fermentation products such as ethanol, acetaldehyde and organic acids are produced during anaerobic respiration). Respiration is affected by numerous intrinsic properties of fresh produce as well as various extrinsic factors but, generally speaking, the achievable shelf-life of MA packed produce is inversely proportional to respiration rate. The depletion of O2 and enrichment of CO2 are natural consequences of the process of respiration when fresh fruit or vegetables are stored in a hermetically-sealed package. Such modification of the atmospheric composition results in a decrease in the respiration rate of plant material. If produce is sealed in an impermeable film, inpack O2 levels will fall to very low concentrations where anaerobic respiration will be initiated. Anaerobiosis is usually associated with undesirable odours and flavours and a marked
deterioration in product quality.

If fruit or vegetables are sealed in a film of excessive permeability, little or no atmospheric modification will result within the package. In addition, moisture loss will cause undesirable wilting and shrivelling, and therefore fully permeable films are unsuitable for fresh produce packaging. However, if the film of correct intermediary permeability is chosen, a desirable equilibrium modified atmosphere (EMA) is established when the rates of O2 and CO2 transmission through the package equal the product’s respiration rate. The exact EMA attained will depend on the product’s intrinsic respiration rate, but will also be greatly influenced by various extrinsic factors. These factors need to be optimised for each commodity so that the full benefits of MAP can be realised. Consequently, desirable EMAs can passively evolve within a hermetically sealed package without the introduction of a gas mixture.

Respiration characteristics need to be properly matched to appropriate film permeabilities. Generally speaking, commodities possessing extremely high respiration rates need to be packed in extremely high O2 permeable films. By gas flushing produce packages with 5% CO2/5% O2/90% N2, it is possible to establish a beneficial EMA more quickly than a passively generated EMA. A gas/product ratio of 2:1 is recommended. Such a procedure may be necessary to delay enzymic browning reactions which could result in spoilage before a passively generated EMA has been established. Only fruit and vegetables of the highest quality should be used for MAP. Hygienic preparation, disinfection in chilled chlorinated water, rinsing and dewatering prior to MAP will help to ensure low microbial counts before chilled storage and distribution. In addition, knowledge of the intrinsic properties of fresh produce
(respiration rate, pH, aw, biological structure and ethylene production and sensitivity) and the extrinsic factors to optimise (harvesting, handling, hygiene, temperature, relative humidity, MAP materials and machinery, gas/product ratio and light) will help to ensure the safety and extended shelf-life of MA packed fruit and vegetables.

General Information for Modified Atmosphere Packaging of Fresh Fruits and Vegetables