The Raisin Industry / A practical treatise on the raisin grapes, their history, culture and curing

by Gustavus A. Eisen

Drying on Trays.

—As soon as the grapes begin to ripen, the trays should be distributed along the rows in the vineyard. They may either first be placed in piles at every row where the roads cross the vineyard, or at once distributed along the vines. The former method is to be preferred, as it protects the trays from dirt and dust, and in distributing afterwards it gives the pickers a more varied labor, often welcome as a change from the cramped position necessary in picking. Muscat vines in proper bearing require one or two trays to the vine, while for young vines one tray will suffice. The probable quantity needed should be ascertained beforehand in order that the trays may be properly distributed. The ripe grapes are always placed directly on the trays, and not previously picked in boxes. In placing the bunches on the trays, the proper way for each picker should be to have two trays, one for each grade. On one tray he places all the large bunches that promise to make first-class bunch raisins; on the other tray he places again all inferior bunches and loose berries. The smaller bunches and loose berries may be placed any way almost, as long as they are not heaped on top of each other. The largest bunches should be placed with the stem side down, as this side will, when cured, become the finest and will eventually by the careful packer be placed upwards in the box. That part of the raisin which in drying touches the tray will also present, when cured, a flat surface with several concentric layers, which are considered a prominent feature in the perfect raisin.

The general method of drying is, however, to place good, bad and indifferent bunches together on the same tray, with no attempt at assorting. While this method may do when superior raisins are not required, and when no higher price is paid for better grades, it will be found a very inferior practice when the grower desires to pack himself, in order to reap all the benefit he can out of his crop. For all superior raisins, I therefore strongly recommend the assorting of the raisins on the trays as having the following advantages. It requires less handling of the large bunches. The large bunches dry the slowest, and by having them from the beginning separated from the small and the loose the latter can be brought away to the sweatboxes, when ready, without necessitating the reassorting and handling from the trays, which at this time, when the stems are very brittle, is always expensive as well as injurious to the fine bunches. The larger bunches, which are to produce layer raisins, require less drying, as they are to be sweated or equalized before being packed. The smaller and inferior bunches, on the contrary, must be stemmed and assorted by machinery before they are equalized, and immediately after they are taken from the trays. In order to “stem” readily these raisins must be rather overdried, as if soft they would tear from the stems instead of having the latter broken. We can therefore perceive the advantage of having the two grades on different trays. Without the necessity of assorting we can simply take up our “layer” trays when they are ready and allow our “loose” to remain as long out as necessary, without fear of having the layers overdried. By this assorting when green, each grade can be treated separately in a quick and effective way.

A tray two by three feet may be made to comfortably hold from eighteen to twenty pounds of grapes. The first crop should be placed pretty close on the trays, not allowing any part of the tray to be visible, as the reflected heat will be too great and may injure the raisins. The second crop should be packed less close, as the reflected heat from the surface of the tray will help to dry the grapes. This of course only refers to localities where the temperature during the first drying is very high. The warmer it is the closer should the bunches be packed on the trays, and on the contrary when later on in the season, or when the drying weather is unfavorable, plenty of space should be given the grapes. It is often said that grapes, to make good raisins, should not only dry, but cure. There is much truth in this. Good raisins should dry and cure at the same time, by which is meant that a chemical process is taking place, which is something else than the mere evaporation of the water in the grape. The heat necessary and favorable for drying the grapes is different in different localities. At certain temperatures the raisins will get cooked and spoil, assume a red color, lose their sweetness, become sour and hard, and covered with large, sharply defined corrugations,—signs of a very inferior or even entirely worthless raisin. In Riverside the grapes are said to cook at from 98 to 100 degrees Fahrenheit in the shade. In Fresno the grapes dry and cure well up to a temperature of 105 degrees, and in El Cajon they do not spoil until 103 degrees are reached. I would think that from 90 to 103 degrees in the shade would be the best temperature for drying perfectly ripe and sweet Muscat grapes. When the grapes are very ripe, a much higher temperature will not injure them, while unripe and sour grapes, especially of the second crop, will burn or cook at a lower temperature than would be the proper one for ripe grapes.

It is not always advisable to stop picking when the heat becomes too great. A better method is to stack the trays in the field, so as to protect the raisins from the sun. When the heat subsides, the trays are again spread. The expense and trouble of stacking the trays is not as great as may be supposed, and a few hours will generally suffice to stack a large vineyard with the regular picking gang. Some packers have suggested that to secure good raisins the trays should be stacked for several weeks in the beginning of the period of drying. For the production of our usual dark-colored raisins this is not necessary nor even advisable, except when the heat is such that the raisins would cook and spoil. With a little experience this cooking of the grapes can be readily detected by the smell emitted by the grapes. As soon as they are in the least injured by the heat, a cooked flavor begins to pervade the whole vineyard. When this peculiar flavor is noticed, and when the berries begin to show small red and soft blotches on the side facing the afternoon sun, the stacking should be commenced as quickly as possible. If the trays are kept in piles for several days, the injured grapes will partially recover and at least to some extent regain their color. Greatly injured grapes will dry much slower, sometimes remaining several weeks behind those which were not injured by the sun. Slightly discolored raisins may partially regain their color by sweating, but they will not improve otherwise.

After the trays are filled with grapes, the best way is to put several rows of trays together, or rather to place the trays from three rows of vines along one of the spaces between the rows. This gives more compactness to the crop, makes it easier to handle the trays, and facilitates the stacking of the trays, their turning and reversing, or any labor with the trays that may be required. By thus clearing some of the spaces between the rows, admission for trucks and wagons is had close to the trays.

Turning.

—After the grapes have been exposed to the sun for some days, they must be turned. By this time it will be found that the grapes have dried principally on the upper side, while the lower side is yet comparatively green. The time when the turning of the grapes should be done depends entirely on the weather. One-half of the drying process should be over, and this requires a longer or shorter time. When the time for turning is at hand, it will be found that the under side of the grapes, or rather the side of each berry that was placed against the trays, has flattened out and shows concentric circles, which are considered of much beauty, and greatly valued in all good raisins. When they are well formed and established, it is generally time to turn. If the grapes are turned before these concentric circles are hardened, the latter will open and become less distinct. Another objection to turning too early is that the upper side of the grapes, if not properly dried before turning, will dry but very slowly afterwards, and often so slowly that the raisins may have to be turned a second time, which will prove both expensive and to the disadvantage of the raisins. One turning is always enough, and the only one proper. There are several ways to turn. The Malaga grower, with his raisin floors, must turn his raisins by hand. The great advantage of our trays is that we can turn much quicker. The turning is done in our vineyards by placing one tray on the top of another and then turning them quickly over, when in changing the tray the bottom side of the bunches will be found to be up.

Raisin Tray Catcher.