Vacuum frying machines are highly synchronized, stable low-temperature vacuum frying food processing equipment that emerged in the late 1960s to early 1970s. They were initially used in potato chip production and saw rapid technological development after the 1980s, significantly expanding their application fields. They are suitable for processing snack foods such as fruit and vegetable chips, dried fruit slices, meat jerky, nuts, etc. The equipment adopts an integrated continuous operation design for heating, frying, and de-oiling, with a core structure that includes a vacuum system, an oil circulation heating system, and a PID temperature control system. By operating in an 80-120°C vacuum environment, oil oxidation is reduced, and the product’s oil content is controlled between 10% and 20%, while preserving color and flavor. A typical model, such as the JS-600, has a single batch capacity of 600 kg and is equipped with an automatic oil filtration and replenishment system, supporting continuous production. Its technical advantage lies in reducing the resistance to water vaporization under vacuum sealing and using technologies such as oil-water mixture to avoid scorching and contamination.
Basic Introduction
Advanced vacuum frying machines should operate at frying temperatures below 95°C, avoiding the issue of waste oil generation caused by excessively high temperatures (80–120°C) in previous generations of vacuum frying. Due to the lower frying temperatures in vacuum frying, using electricity as a heating method is not advisable, as it would produce large amounts of waste oil due to high temperatures. This is clearly stipulated in the industry standards for fruit and vegetable chip equipment. Additionally, large-capacity vertical vacuum frying machines have many drawbacks, as both de-oiling and heat transfer can cause serious issues, resulting in poor initial puffing of fruit and vegetable chips and excessively high oil content. The industrialization of large-capacity vertical vacuum frying machines is not yet mature.
Types of Processed Foods
① Fruits: apples, kiwis, bananas, jackfruit, persimmons, strawberries, grapes, peaches, pears, etc.;
② Vegetables: tomatoes, sweet potatoes, potatoes, green beans, garlic, carrots, bell peppers, pumpkins, onions, etc.;
③ Nuts: jujubes, peanuts, etc.;
④ Aquatic products and livestock meat, etc.
Main Features
- Integrated design for heating, frying, oil storage, de-oiling, dehydration, and oil filtration, all completed continuously under vacuum. The product has low oil content and is in a negative pressure state. Processing food under such relatively oxygen-deficient conditions can reduce or even avoid the hazards caused by oxidation (e.g., fatty acid rancidity, enzymatic browning, and other oxidative spoilage). In a negative pressure state, with oil as the heat transfer medium, the moisture inside the food (free water and some bound water) evaporates rapidly and is expelled, creating a loose, porous structure in the tissue.
- Automatic control of temperature and pressure (vacuum degree), with no overheating or overpressure, ensuring product quality and safe production.
- De-oiling uses variable frequency speed regulation, suitable for all products, whether with low or high oil content.
- The oil-water separation system cools and separates evaporated water and oil, reducing pollution in water circulation, improving water reuse rates, and minimizing oil loss.
- Oil filtration system: upper and lower oil tanks, dual-chamber heating system, independently controlled heating, and cyclic oil filtration during frying keep the oil clean and reduce waste.
- The machine is made of stainless steel, featuring high efficiency, stable performance, and easy installation and use.
Advantages of Vacuum-Fried Foods
Color Preservation: Vacuum frying significantly reduces the frying temperature and greatly lowers the oxygen concentration in the frying chamber. The fried products are less prone to fading, discoloration, or browning, preserving the natural color of the raw materials. For example, kiwis are highly susceptible to heat-induced browning, but vacuum frying can maintain their green color.
Flavor Preservation: In vacuum frying, raw materials are heated in a sealed vacuum state. Most flavor components in the raw materials are water-soluble and do not dissolve in oil. As the raw materials dehydrate, these flavor components become more concentrated. Thus, vacuum frying technology effectively preserves the natural aroma of the raw materials.
Reduced Oil Deterioration: The deterioration of frying oil includes oxidation, polymerization, and thermal decomposition, with hydrolysis occurring mainly when water or steam comes into contact with the oil. During vacuum frying, the oil is in a negative pressure state, gases dissolved in the oil quickly escape, the steam pressure generated is low, and the frying temperature is reduced. As a result, the degree of oil deterioration is significantly minimized.
Process Characteristics
Vacuum frying involves frying and dehydrating food at low temperatures (80–120°C), effectively reducing the destruction of nutritional components caused by high temperatures.
Vacuum frying and de-oiling have unique effects. They are mainly used for:
① Fruits: apples, kiwis, grapes, persimmons, strawberries, grapes, peaches, pears, etc.;
② Vegetables: tomatoes, sweet potatoes, potatoes, green beans, shiitake mushrooms, mushrooms, garlic, carrots, bell peppers, pumpkins, onions, etc.;
③ Nuts: jujubes, peanuts, etc.;
④ Aquatic products and livestock meat, etc.
Low-temperature vacuum frying can prevent the deterioration of edible oils, eliminating the need for additional antioxidants, improving oil reuse rates, and reducing costs. Conventional fried foods have an oil content of 40%–50%, while vacuum-fried foods have an oil content of 10%–20%, saving 30%–40% of oil, with significant oil-saving effects. The products are crispy but not greasy and have good storage stability.
In a vacuum state, the moisture in the intercellular spaces of fruits and vegetables rapidly vaporizes and expands, enlarging the spaces, resulting in excellent puffing效果. The products are crispy and palatable, with good rehydration properties.
Industry Status
In the face of ongoing food safety trust crises, more consumers are leaning toward natural foods. Nutrition, convenience, safety, and green practices are current trends in food production. Moreover, many consumers are wary of fried foods. To alleviate these concerns and produce healthy, safe products, vacuum frying technology is employed, allowing fried foods to be both healthy and natural.
With rising consumption levels, consumers’ pursuit of food flavor and safety continues to increase. Whether in terms of raw materials, production processes, or equipment, food processing should strive to make products natural, nutritious, and convenient. Vacuum-fried products, with their unique flavors, variety, and healthy components, are highly favored by people worldwide and are hailed as the “green revolution” in fried snack foods for the 21st century. Vacuum frying technology combines frying and dehydration organically, placing the sample in a negative pressure state where the absolute pressure is lower than atmospheric pressure. Processing food under such relatively oxygen-deficient conditions can reduce or even avoid the hazards of oxidation (e.g., fatty acid rancidity, enzymatic browning, and other oxidative spoilage), while also preserving the color and flavor of the food. It is suitable for fruits, vegetables, meat products, and more. Welcome to inquire.