Market requirements for apples

Apples are mostly grown in temperate regions. Most are sold for fresh fruit consumption, though over 660,000 tons of apple juice concentrate is produced annually and smaller amounts are used for cider, dried apple slices, puree, etc.

Generally, fruit quality (color and flavor) is best from fruit grown in climates with warm days/cool nights and high light intensity.

The majority of apples worldwide is grown for the fresh market and is therefore graded at the point of harvest.

Size, shape, color and freedom from blemishes, disorders and diseases are of major importance to the retailer and consumer who are demanding increasingly higher quality fruit, right throughout the year.

Processors, while more tolerant of appearance, also seek good quality fruit. They are more interested in the ripeness, nutritional value, color, texture, flavor type (dessert or culinary), and quality of the fruit, including, level of acidity, and TSS (total soluble solids), mainly sugars.

Fruit quality, for both fresh fruit and processing markets, is closely related to the ripening stage of a fruit. Processors may require unripe or partially ripened fruits, which enable them to extract more juice.

The best time to pick fruit depends upon type of fruit, cultivar, climatic conditions, fertilization, intended use of the fruit and subsequent storage conditions.

However, there is an important distinction between maturation and ripening. Maturity relates to the full natural development of a plant or fruit, whereas, ripeness is the desired stage for consumption.

Thus while an apple may be mature, fully developed and ready to be harvested, it can be far from ripe and require careful ripening conditions to achieve optimum quality.

Fresh Fruit

Appearance

The EU has three classes of apples and pears - ‘Extra’, ‘I’ and ‘II’. Fruit is graded according to size, shape, color, and freedom from defects, blemishes and diseases.

The size is determined by the diameter of the equatorial section or by weight.

Firmness

Firmness is particularly important to the ‘crunch’ and bite quality of the fruit. Firmness is affected by: 

• Temperature. High temperatures stimulate a loose cell structure.
• Crop management. Excessive thinning of fruit can result in a higher number of cells per fruit, increasing firmness in the remaining crop.
• Mineral nutrition. Calcium, nitrogen and phosphorus all have a major role to play in improving the firmness of fruit.

Minimum firmness standards have been established for different cultivars. If more than a defined percentage is below the firmness standard, fruit lots destined for export can be rejected.

Flavor

There are four main groups of compounds that determine fruit flavor, sugars, organic acids, phenols and volatile compounds.

(1) Sugars

The greater the sugar content, the sweeter and better bodied the fruit. Sugars are the major soluble solids in fruit juice and therefore the level of soluble solids is often used as an estimate of sugar content. Typical sugar contents of apples and pears at maturity are around 12 and 10 °Brix respectively. Retailers set minimum sugar contents based on cultivars at delivery.

(2) Organic Acids

The higher the level of organic acids, the more tart the flavor of the fruit and the better the thirst-quenching properties of processed soft drinks. In pome fruit, the main organic acids are citric, malic and lactic acid. In ripe fruits the pH is normally lower than 4.2. Acidity is measured by titration. This, combined with the Total Soluble Solid content (°Brix) provides a sugar/acid ratio. The TSS/Acid ratio is low at the beginning of the ripening process increasing as fruit acids are degraded during ripening.

(3)Phenols

The greater the level of phenols, e.g. tannins, aponins etc., the more bitter or harsh the fruit flavor.

(4) Volatile components

Largely determined by the three groups of compounds above, the volatile components of fruit largely influence its aroma.

Processing

Juice Concentrates

Besides fresh juices, juice concentrates (frozen or dried) are an important product on the world market. Fruit destined for juicing should be of good edible quality, full flavored and at the optimum ripening stage. Over-ripe fruit can spoil flavor and acidity, and lead to problems from microbial contamination of the juice. Frozen concentrated apple juice is prepared from the unfermented, unsweetened, un-acidified liquid obtained from the first pressing of properly prepared, sound, clean, mature, fresh apples. This juice is clarified and concentrated to at least 22.9 °Brix (according to US standards).

Canning

Fruit for canning should be sound, ripe and free from blemishes and disease. Fruits should also be even in size and shape for easy mechanical peeling and the provision of evenly sized pieces or segments.

Bramley is probably the best apple for processing. Golden Delicious will give a product similar to the Bramley providing the acidity of the covering processing liquor is chemically adjusted with citric acid to minimize pulp browning.

Bartlett pears also lend themselves to canning. They have a good texture and flavor with a bright color and uniform size and shape. Pears for canning should be allowed to grow to full size but they should be picked while still green and hard. Ripening is carried out in boxes or crates in a well-ventilated store.

Cider

European ciders are traditionally made from cider apple cultivars resulting in a range of differing end-product properties. It is important that all the starch in the fruit is converted to sugar before milling of the fruit, or fermentation will be affected. Starch analysis using iodine staining is a useful means of assessing remaining levels of starch in fruit prior to harvest. As a result, only ripe fruit is used for cider. However, over-ripe fruit can give rise to significant problems during milling of the apples and subsequent pressing of the mash.

Preserves – jams, dried or frozen fruit slices

Several characteristics are important for fruit used as slices. They should retain their processing characteristics under refrigerated storage for the several months needed to work through the bins in storage. Slices should be free from discoloration before and after cooking and are often infiltrated with brine solutions to inhibit browning due to oxidation. Cultivars that require less brine are less expensive to process. Cooked slices should retain their firmness.