Harvesting
Based on a number of research works made in Hawaii a specific terminology for development, maturation, definition of the edible stage and senescence for pineapple was proposed. This proposal was based on physical and biochemical changes that take place during propagation and development of the fruit. There is a time span of 110 days between the end of flowering and the point at which the fruit is at its edible stage. Changes in chemical composition occur when half of the peel turns yellow. Chlorophyll, carotenes, xanthophiles and anthocyanines are the main pigments found in pineapple. Their presence changes the external color of the fruit from green, green-yellow, or yellow, to a mixture of yellow and purple with or without green. External color of pineapple is an important trait in consumer preference. During maturation chlorophyll fades out and total and pulp carotenes increase, while peel carotenes decrease. Both peel and pulp carotenes rise at senescence. These changes define four stages in fruit development.
Changes in maturation stage are evident when peel color turns from green to yellow at the base of the fruit. Pineapple is a non-climacteric fruit and can be harvested as soon as it is ready for consumption. A minimal content of soluble solids of 12% and a maximal acidity of 1% insure a minimal level of consumer acceptance along with size and texture uniformity, absence of rotting, sunburns cracks, bruises internal breakdown endogenous brown spot, gummosis or damage by insects. Crown leaves should be green, medium length and erected. Soluble solids must fall between 11 and 18%, titratable acidity as citric acid from 0.5 to 1.6%, Ascorbic acid should fall between 20 and 65 mg/100g of fresh weight, depending on the cultivar and stage of maturity. Pineapple fruit can be classified in three categories: category A, defined by fruits weighing more than 1.5 kg; category B, fruits weighing between 1 and 1.5 kg; and category C, fruits weighing less than 1 kg.
Harvest maturity is usually based on skin colour and the shape of the individual fruitlets. Colour is not an infallible means of measurement since Smooth Cayenne can be fully mature with yellow sweet flesh while the skin is still green. This has presented a problem in marketing such fruits in Europe and in some cases they have been labelled to indicate they are ripe while the skin is green. Skin colour can vary due to season, rainfall, microclimate and field practices. In other cases estimation of the skin colour can be effective. The eyes turn from green to yellow–orange from the bottom and maturity can be judged on the number of rows of eyes that have changed colour. A common harvest maturity is when two or three rows have changed colour. In Hawaii, skin colour is supplemented by a minimum reading of 12°Brix for fruit destined for fresh consumption. Harvest maturity can also be estimated by relating it to the time after flowering or mid-flowering, but the number of days may vary from place to place. In Madagascar the period from flower induction to ripening varied from 140–221 days and in South Africa from 234–283 days. For Smooth Cayenne in Hawaii, it took 110 days from the completion of flowering to harvest maturity, but it was between 70–120 days, that is, from mid-flowering to the onset of ripening. These variations were attributed to seasonal temperature variations. In Queensland in winter, pineapples are picked at an immature stage to avoid black heart, and this stage is preferable for handling owing to high resistance to bruising.Half ripe (50% of the shell yellowing) Smooth Cayenne fruit can be held for about 2 weeks at 7.5°C and still have about 1 week of shelflife, and at this stage the fruit was suitable for export. Quarter yellow (25% yellowing) pineapples at harvest gain about one additional week’s storage for every 6°C decrease in storage temperature (no temperature range was reported) and at 7°C the maximum storage life is 4 weeks. The sound of a fruit as it is tapped sharply with the knuckle of the finger can change during maturation and ripening. Consumers sometimes use the method of testing fruit. This method may only be used postharvest to determine their maturity since the plants are so spiky that it would be very difficult to get at the fruit.
Kew Pineapple plants flower 10-12 months after planting and attain harvesting stage 15-18 months after planting, depending on the variety, time of planting, the type and size of plant material used and the prevailing temperature during fruit development. Under natural conditions, pineapple comes to harvest during May- August. With a slight colour change at the base of developing fruit, it could be harvested for canning purpose. But for table purpose, the fruit could be retained till it develops satisfactory golden yellow colour. Harvesting is done with a sharp knife, severing the fruit-stalk with a clean cut retaining 5-7 cm of stalk with the fruit in such a way that the fruit is not damaged.
The stage of maturity at harvest is dependent on the required storage or shelf-life and the method of transportation to the export markets. The level of yellow colouration of the "eyes" of the fruit judges maturity.
Colour stages are categorised as follows:
CS1: all eyes green, no traces of yellow;
CS2: 5 to 20% of the eyes yellow;
CS3: 20 to 40% of the eyes yellow;
CS4: 40 to 80% of the eyes yellow;
CS5: 90% of eyes yellow, 5 to 20% reddish brown;
CS6: 20 to 100% of eyes reddish brown.
The harvest operation is done using special devices to draw the fruit from the field by breaking the fruit that shows proper maturity stage and placing them at the edge of the field where they are manually sorted by size. The fruit is carried in trucks placing the crowns downwards for cushioning. From 50 to 80 dozens may be transported, depending on the size. Fruit are marketed by the dozen; those intended for industrial processing are placed in crates at the edge of the parcel and the crowns are chopped off, after which they are transported in bulk in larger trucks to the processing plant. Fruit for export markets use different systems, depending on the buyer. Some buyers require green fruit (color 0) which means soft green color near the peduncle, with 12°Bx, porosity of 1.5 and translucency 0 to 0.5. Other buyers demand ripened or off-green fruit with a minimum of 12°Bx, porosity of 1.5 and translucency of 1 to 1.5. When Ethephon is applied at 1 ounce in 20 litres of water, sprayed on the fruit one week prior to the harvest. When color turns golden yellow fruit are harvested with care to avoid mechanical damage. Fruits are carried to a truck with 2 inches of polyfon in the bottom and 1 inch on the sides. From 3 to 5 layers of pineapples are placed crowns facing to avoid damage. Another way to harvest is using a mechanical harvester which may cut the process time to one fourth and produces minimal damage to the fruit by handling.
Sugar content should be assessed in the field prior to harvesting to ensure adequate sugar development. A minimum of 10 % is generally required although this may vary with the market. Sugar content is not always related to the colour stage as agronomic and production factors will affect sugar development. For the export market where sea-shipment for seven to fourteen days is used, fruits should be harvested at CS1, where the fruits show no yellow colour development on the eyes (ensuring that checks have been made on the sugar content). For airfreighted shipments, although generally cost prohibitive, harvesting can be carried out at CS2 to CS3. Those harvested at more advanced stages are more susceptible to mechanical damage and over-ripeness. Fruit maturity can also be assessed on random samples by determination of the flesh condition. This is carried out by slicing the fruit horizontally at the point of largest diameter; in fruit for sea-shipment export; the fruit should show limited development of translucent areas. Where more than half of the area is translucent, the fruit is considered beyond optimum maturity. Pineapples harvested by hand are snapped from the stalk using a downward motion. The fruit should be placed in field crates and while in the field, left in shaded conditions. Collection in the field and field to pack house transport using sacks or bags will cause mechanical damage and increase the level of rejection. On arrival at the packing facility, the stems and the crowns should be trimmed to 2 cm (0.5") and 10 cm (4") respectively. Out grading should be made of all fruits which are undersize, oversize, over-ripe, under-ripe (depending on the market requirements), damaged, bruised or show fungal or insect damage.
Pineapple is a perennial fruit crop and the returns continue, usually, for a period of 3 years in case of variety ‘Mauritius’. Under natural conditions, pineapple comes to harvest during May- August. With the application of Ethephon and fertilizers the first yield is obtained within 10-12 months. Pineapple plants flower 7-8 months after planting and attain harvesting stage in a year, depending on the variety, time of planting, the type and size of plant material used and the prevailing temperature during fruit development. Observing the colour change is the most common method of determining the maturity of fruits. For long distance transportation, fully mature fruits in green itself just before colour change are harvested. With a slight colour change at the base of developing fruit, it could be harvested for canning purpose. But for table purpose, the fruit could be retained till it develops satisfactory uniform golden yellow colour. Harvesting is done with a sharp knife, severing the fruit-stalk with a clean cut retaining 5-7m of stalk with the fruit in such a way that the fruit is not damaged. Fruits are stacked in piles or on to the vehicles with the crown facing down. Fruits for fresh fruit market are often marketed with crowns.
The yield of pineapple fruit varies with the variety, agroclimate, agrotechniques and planting density. The fruit yield with a plant density of 20000-25000 plants/ha is about 25-35 t, 35000-40000 plants/ha about 40-50 t and that of 43,300-50000 plants/ha is 50-60 t/year, with the yield decreasing progressively from first year to third year which is the normal economic life span of Mauritius pineapple.