At present, walnut kernels have become one of consumers’ favorite dried fruits. Regular consumption of walnuts can supplement brain nutrition, which in turn plays a role in protecting brain cells and enhancing memory. However, every year when the walnut harvest season comes, walnut growers are not only worried about the harvest, but also have a headache for walnut peeling.
In the past, when agricultural technology was underdeveloped, a large number of growers often used manual methods to remove the green peel of walnuts. Specifically speaking, they used knives or rolling stones to peel, then scrubbed them with plenty of water. The methods used in the past are low in efficiency,labor intensive and harmful to manpower. The conventional peeling methods are only suitable for small-scale growers.
At present, with the continuous development of agricultural science and innovative design of various nut processing machines, the removal of walnut green peel is becoming more and more mechanized, and the efficiency is constantly improving. There are four common types of large-scale peeling methods:
1. Mechanical Peeling Method
The mechanical peeling method is mainly carried out with walnut peeling machine.
At present, according to the peeling force, the commonly-used peeling machines on the market are divided into scraping type, cutting type, extrusion type and impact type.
■ Scraping type peeling machine has strong adaptability but low efficiency, and the contradiction between the walnut net crushing rate and the total crushing rate is more prominent;
■ Cutting type walnut peeling machine has relatively low procurement costs and adaptability, but is greatly affected by the maturity period. The walnut fruit will break during the cutting process;
■ The extrusion mechanism mainly uses the internal structure device to break the outer peel of walnuts. However, in actual applications, the size of the walnut is different, which leads to more crushing situations and weak adaptability;
Kingston Food Machinery recommends you to select the walnut peeling machine according to its ripeness, size and specifications.
2. Frozen Peeling Method
This method uses low temperature to freeze the green walnut skin and melt it. When the green skin is completely frozen, the temperature will rise to 0℃ or higher. At this time, the green peel will be removed manually or mechanically.
3. Composting Peeling Method
This method has simple operation and low equipment requirements, and has been widely used. Specifically, after the walnut is harvested, it is stacked in a large pile of 50 cm, and at the same time, a layer of mulch (straw, hay, etc.) of 10 cm. Put it on it for 4 to 6 days. When the green skin is peeled off or cracked to about 50%, hit it with a stick or other methods to make it fall off. However, pay attention to the composting time to prevent the bacteria and molds produced by the long-term walnut composting from invading the walnuts and polluting the walnut kernels, resulting in a decline in the performance of walnut products and reducing the economic benefits of growers.
4. Chemical Peeling Method
This peeling method is faster, more convenient, and can significantly reduce labor intensity. Specifically, ethylene is sprayed on the surface of the harvested walnuts, or soaked in a 3% 5% ethylene solution for 5 minutes, and then taken out for 3 days in a stacked degumming manner. During the accumulation process, temperature and humidity need to be controlled. The temperature is generally around 30℃, and the humidity is between 80% and 90%.
Compared with the composting method, this method not only saves a lot of manpower, but also has a higher shelling efficiency, which can reach more than 95%. It should be noted that the chemical substances on the walnut surface should be removed using this method. It is necessary to repeatedly wash the walnuts with a large amount of water to avoid failing to meet the relevant food safety requirements of the market.
The above-mentioned walnut peeling method is currently used by large-scale growers and belongs to the category of commercial use.