It's long been known that consumers choose apples based on fruit colour. Although colour does not affect the flavor, taste, and texture of apples, colour influences consumer buying decisions and, in turn, apple growers' bottom lines. For many red and bicolored apple cultivars, including Gala, Delicious, and Fuji, red colour (the intensity and quality of red skin) and fruit size are also important characteristics for fruit grading standards. Even when apples are of adequate size, poor fruit colour can result in lower-grade fruit and decreased consumer approval.
Apple producers recognise that clear days with temperatures of around 25 °C and cool nights below 15 °C are ideal growing conditions for apples to develop bright red colours. Under these conditions, apples are capable of increasing canopy photosynthesis, and respiration rates decrease at night. Commercial apple growers in southern regions can be challenged by warm, dry summers that are not favourable to apple fruit colour development; these warmer climates can have a definite negative effect on production and profits.
'Gala' apples have become very popular in Europe, where the high quality of this fruit is increasingly appreciated by consumers. To meet consumer demand, apple growers in southern Europe (mainly Spain and Italy) are looking for ways to turn out high-quality, cost-effective apple crops despite a climate that is not particularly conducive to apple production.
To address producers' issues of warmer climates, increased consumer demand, and high apple quality, Iglesias and Alegre designed a 3-year experiment using 'Mondial Gala' apples grown in orchards in northeastern Spain. Their objective was to determine how different types of reflective film affect orchard temperature, skin-colour development, fruit quality, light canopy distribution, and, ultimately, apple crop profitability.
Based on the fruit size and colour required to meet European Union grade standards, the use of ExtendayTM or SolarmateTM films resulted in an increase of 26% and 17%, respectively, when compared with the control, for the number of fruit picked at first harvest.
The researchers concluded that "season clearly affected fruit colour development, whereas harvest date, fruit firmness, fruit size, soluble solid concentration, titratable acidity, and maturity were not consistently affected by the use of reflective film." According to Iglesias, the study results are promising, but long-term benefits of the technique will largely depend on fruit prices.
