How to grade fruits and vegetables after picking?

Artificial grading of fruits and vegetables after harvest can minimize the mechanical damage of fruits and vegetables.

Suitable for all kinds of fruits and vegetables, but work efficiently.

Low, the level standards are sometimes not strict. The biggest advantage of mechanical gradingMechanical grading is that it is highly efficient and suitable for those fruit and vegetable products that are not easily injured. Sometimes, in order to make grading standards more consistent, mechanical grading is often combined with manual grading.

At present, China has developed a fruit grading machine, which has greatly improved the grading efficiency. Mechanical grading in the United States started earlier, and most of them are computer-controlled. There are several types of mechanical grading equipment for fruits and vegetables:

1) The weight sorting device sorts according to the weight of the product. Grading is performed by comparing the weight of the selected product with the pre-set weight. The weight sorting device has mechanical scale type and electronic scale.

formulas and other different types. The mechanical scale sorting device is mainly fixed on the conveyor belt.

It consists of a pallet that can be rotated and a fixed scale arranged at the opening of different weight classes. The fruit is placed individually into the rotary tray, and when it moves into contact with the fixed scale, and the weight of the fruit on the scale reaches the set weight of the fixed scale, the tray is flipped over and the fruit falls. It is suitable for spherical fruit and vegetable products, but the disadvantage is that it is easy to cause damage to the product, and the noise is very high.

The electronic scale weight sorting device has changed the mechanical scale device to set up a scale for each weight level, the shortcomings of noise, an electronic scale can sort the products of each weight grade, the device is greatly simplified, and the accuracy is also improved. The weight sorting device is mostly used for apples, pears, peaches, tomatoes, melons, watermelons, potatoes, etc. (2) The shape sorting device sorts according to the shape and size (diameter, length, etc.) of the selected fruits and vegetables.

There are different types such as mechanical and photoelectric. Mechanical shape sorting devices mostly classify products by the size of the gap or sieve hole. When the product passes through the gap or sieve hole that gradually grows from small to large, the small one is sorted out first, and the largest one is selected last.

Packing plants should be set up in large fruit and vegetable producing areas, and after the picked products are transported to the packing plant, the rotten, broken and diseased products are removed, washed and dried, graded and packaged according to specifications and standards. Manual grading is a commonly used grading method in China. There are two kinds of grading methods, one is to divide the product into several grades according to the color and size of fruits and vegetables based on human visual judgment alone.

For products graded in this way, the grade standard is easily affected by human psychological factors, and the deviation is often large. The second is to use the fruit selection board to grade, there are a series of holes with different diameters and sizes on the fruit selection board, and the grading is carried out according to the different transverse diameter and coloring area of the fruit. For products graded in this way, the size of the fruit of the same grade is basically the same, and the deviation is small.

There are many kinds of photoelectric shape sorting devices, some of which use the shading light when the product passes through the photoelectric system, measure its outer diameter or size, and compare the measured parameters with the set standard value for grading. The more advanced device is to use a camera to shoot, through the electronic computer for image processing, to find the area, diameter, height and so on of the fruit. For example, the shape sorting device for cucumbers and eggplants neatly arranges the fruits one by one on the tray of the conveyor belt, and when they pass through the detection device, the black-and-white camera mounted on the conveyor belt takes the image of the fruit, and the length, thickness, and degree of bending can be quickly obtained through computer processing, and the size and quality (bending, deformity) are graded at the same time.

The photoelectric shape sorting device overcomes the shortcomings of the mechanical sorting device that is easy to damage the product, and is suitable for cucumbers, eggplants, tomatoes, kidney beans, etc.

1. Harvest maturity and optimal harvest time.

1) Classification and criteria for maturity.

1. Physiological maturity.

In the case of the product itself, it means that the plant organs have reached full physiological maturity, i.e. they have reached maximum growth and have begun to mature.

of the stage. The seeds are fully ripe, the flesh becomes soft, due to the strengthening of fruit respiration and hydrolysis of chemical components, the fruit taste becomes light, even tasteless, and the nutritional value is reduced, so it is not suitable for consumption, and it is not resistant to storage, but it has the requirements of being reserved for seeds. For nuts.

Seeds, kernels or seeds are suitable for harvesting at this stage, otherwise the yield and quality of fruits and vegetables will also be affected.

It is based on the time of flowering and pollination or the time of emergence after sowing as the standard for the number of days to be calculated, such as eggplant enters the fruit ripening period 18 days after flowering, and enters the seed maturity period 35 days.

2. Consumption maturity.

Also known as food ripeness.

For retailers and consumers of products, it refers to the stage when fruits and vegetables are fully ripe, showing unique color, aroma, taste, flavor and texture, and have the best edible value. It is based on the quality of the product to transform into the standard. Fruits and vegetables that lack or have no post-ripening effect, such as most vegetables and fruits such as peaches, plums, apricots, grapes, etc., are suitable for harvesting at this stage, and can be marketed after harvesting, but are not suitable for long-term storage or long-distance transportation.