Crop MaturityThe specific maturity of the crop is vital to the fruit growth. the optimal maturity varies with intended use. Only we know the intended use beforehand can we define proper time to harvest crop. Except that we should classify maturity with ripening. “maturity”means ready to harvest, while “ripe”means ready to eat, sometimes they coincide.Maturation: the processes of fruits develop from the immature to the mature state. Maturity: the end of maturation with two interpretations which respectively are Physiological maturity and Horticultural maturity. Here are three important classes of horticultural maturity types: Harvested physiologically immature, harvested firm mature but ripened later, Harvested when ripe.MaturationMaturation consists of physical, biochemical, and physiological changes. The changes of physical include firmness, texture, skin chlorophyll, carotenes, xanthophyll and anthocyanins. The other changes include starch, sugars, soluble solids, soluble pectin, acidity and respiratory activity.The changes follow certain mode during maturation, some increase such as sucrose, carotenes, starch etc, while some decrease for instance malic acid, flesh firmness and respiration. The capacity to withstand physical stress, physiological stress and pathogens decreases too.Indices of maturityHorticultural maturity indices of fruits are flesh firmness, skin color, flesh color, sugar content, content of soluble solids, total content of acids, chlorophyll content, carotene content, full bloom days and heat-unit accumulation.Pear maturityPears are firm when it’s harvested, then stored until they are ripened before fresh consumption or processing. The only index of maturity at harvest is the pressure test for firmness. Optimum firmness will vary with different climates or rootstocks. Sometimes soluble solids may be used but they are more variable. Heat-unit accumulation for 5 to 9 weeks following bloom is inversely correlated with the number of the days from full bloom to harvest maturity. This is true of each cultivar. The most reliable index of pear maturity is flesh firmness with heat units during the post-bloom period.Apple maturityFirmness tests have worth for later harvest and during storage not for early harvest of apples. The number of days from full bloom to harvest is a vital index of apple maturity, especially when used with the color change and the gain of the minimum soluble solids in the juice. Except that it follows another pattern: we can decrease oneday for each 3 days that bloom is later than average otherwise add 1 day in a given year. The flesh of apples should be white and somewhat sweet, but after long storage, apples should not be fully ripe to eat at harvest.Prune and plum maturityOptimum maturity for prunes depends on its purpose, those to be eaten locally or processed directly can be picked more mature than those to be shipped or canned. Ultimate quality depends on post-harvest storage and ripening conditions. Prune cultivars have a characteristic number of days from full bloom to maturity which almost can directs the harvest. About 140 days after full bloom the primary test can be started to decide maturity more precisely. Other indices of maturity are soluble solids, flesh firmness, flesh and skin color etc.Different researchers got different conclusions about the better index of maturity. Some thought it was flesh firmness or sugar content or the soluble solids/acids ratio, some thought it was flesh color change and solids/acids or percent soluble solids etc. The differences between them maybe have resulted from different measuring devices or techniques etc.Peach maturityThe main indices for it are ground color change from green to straw color, flesh firmness, and days from full bloom. The warm weather during the post-bloom period reduces the number of days reaching harvest maturity.Cherry maturityThe soluble solids and fruit color are known for the best indices of maturity, but recent someone found that stem:fruit removal force may be better, and fruit acid level is vital to sour cherries. Optimum maturity varies with intended use too, as referred before.Maturity of nutsFilberts fall off the husk in September, October, or November, and they drop to the ground, then they must cure which includes the decreases of some moisture and increases in fatty acids and changes in flavor components by losing moisture. Oils are formed in walnut when they are mature about 1-4 weeks before hull dehiscence, then they are dried artificially to 3-4 percent moisture immediately after harvest at 38-43℃and 35-40℃for filbert to 8-10 percent finally. Almonds are mature when they are loose enough to be knocked, the longer the delay for harvest, the greater the threat from the navel orangeworm. Pecans are mature when the nuts break away husks, it is essential to use mechanical shakers to bring them down.Maturity of small fruitsThe sugar/acids is the best index of grape maturity, it varies with the cultivars and the intended use which are for juice, jelly, fresh or wine.The strawberries are mature for shipment when they are almost all-over red and firm,however they need more mature for immediate processing.Raspberries and blackberries can be picked when they are fully colored and break away from the stem but the former are not crumble and the latter’s tips of the druplets are entirely filled.Gooseberries can be picked for pie at the firm green stage, they sunburn easily so should not be left uncovered after harvest.The currants should be picked slightly immature to decrease tartness when they are for jelly.Blueberries are mature when the stem end are fully blue and are loose on the pedicels. They can be picked only once a week over 6 to 7 weeks because they hang well. Cranberries are harvested during September and October, they will color up at 13°-16°if well ventilated but do not color at 0.5°-1.0°or not well ventilated also leading to chilling injury. both sugars and acids decline at 2°-5°during storage, while the tart flavor is maintained if they are sound. The sugar content is higher the quality better.Fig maturityThe treatment with ethephon which releases ethylene and the sprays with auxins which stimulate endogenous ethylene synthesis can hasten the growth of figs markedly.Fruit colorThe fruits take on different colors and lose their green undercolor when they mature which indicates the change of both quality and stage of maturity. Some pigment changes need direct light and others do not. Red, blue, and purple result from synthesis of anthocyanin, some fruits such as apple peach nectarine and apricot need direct light for red color and others do not. Yellow dose not need direct light to form. Pruning, fertilization, light etc can affect red pigmentation, factors that lead to more carbohydrates before harvest can increase anthocyanin pigments. Improper conditions that prevent light can reduce color by decreasing carbohydrate. The leaves at intense light can produce maximum photosynthate while others only less than 30 percent. Factors that lower incoming radiation can affect light-requiring pigment synthesis. Consumer preferenceThe customers preferred to buy red apples even though the red ones are higher and the internal conditions are more important than color, but yellow and green ones such as Golden delicious, Y ellow Newtown are well accepted by customers too. Their preferences vary with the local customs and the nature of the main cultivars. Pigment synthesisThere are two light-requiring phases to form idaein, the first of which does not form pigment and the second does, they both had action spectra near a wavelength of 650 nanometers. The researchers said that the photoreceptor is a flavor-protein. The ultraviolet light is most important for forming pigment.Influence of environmentSolar radiation consists of 7.5 percent ultraviolet, 41 percent visible and 51.5 percent infrared, they will be modified in 4 ways while passing through the atmosphere. 43 percent of incoming light that reaches the earth is important to the pigmentation of fruits. Ultraviolet and blue light are more important than longer wavelength in forming anthocynin pigments. The adequate exposure of the fruits to light is beneficial to the good pigmentation.The recent works indicate that red light is needed too in at least one step, and enough red light is available in all orchard situations.ATMOSPHERE CONDITIONS heavy smoke, rain, or smoke can diminish light the leaves will not be effective when they receive less than 30 percent light. In dry air, the blue end of the spectrum is scattered much more than red. Diffuse sky radiation percent varies with local atmospheric conditions and latitude. The most highly colored fruits the higher quality.TEMPERATURE the clear bright days and cool nights before harvest is helpful to apples color.CULTURE pruning, tillage, fertilizer use etc maybe affect fruit color, fruit with low sugar content and low leaf/fruit ratio can’t color well. If the fruits and leaves are exposed to 70 percent or more of full sun, the apple can be colored best.Excess nitrogen can reduce color, and delay mature. But when they mature in the trees, their color is perfect. The foliar sprays of urea later than early summer can reduce red and yellow colors.Genetic potential and fruit colorThere is an apple cultivar which can form red in the dark after harvest. During the last 30 years many more colored genetic mutants have been selected, so they can be harvested at maturity with optimum color.General references。
