How to Optimize Peanut Roasting and Cleaning Systems
Abstract: In-shell peanut processing is an important link in the peanut industry chain, and the advanced nature of its processing technology directly determines product quality and market competitiveness. This article systematically describes the complete processing workflow for in-shell peanuts, from raw material handling to finished product packaging, including key procedures such as cleaning, bleaching, flavoring, roasting, and grading, and lists the equipment required for each process. By combining the technical characteristics of traditional techniques with modern automated production lines, it analyzes the process differences among product types (salted dried, brine-flavored, roasted), providing a comprehensive technical reference for peanut processing enterprises on equipment selection and process optimization.
Keywords: in-shell peanut; processing technology; equipment list; cleaning machine; roasting machine
I. Introduction
Peanuts are known as the “longevity nut”, and their rich nutritional value offers good medicinal and health benefits. In-shell peanut processed products (such as salted dried peanuts, brine-flavored peanuts, and roasted peanuts) are deeply loved by consumers. However, traditional manual processing methods are inefficient and unstable in quality, making it difficult to meet the demands of industrial production. Modern in-shell peanut processing has developed into a complete production line integrating mechanization, automation, and intelligence.
A complete set of in-shell peanut processing technology usually includes core links such as raw material cleaning, washing, flavoring, roasting, grading, and packaging. Starting from the process flow, this article will explain in detail the technical points of each procedure and provide a supporting equipment list to help enterprises build a scientific and efficient production system.
II. In-shell peanut processing workflow
2.1 Overall process flow
The standard process flow of in-shell peanut processing is as follows:
Raw material inspection → Cleaning & impurity removal → Washing → Soaking/flavoring → Draining → Roasting/drying → Cooling → Screening & grading → Packaging → Finished product
Depending on the product type, special procedures such as bleaching, sulfur fumigation, and vacuum flavoring may be added.
2.2 Technical points of each process
Table 1: Technical points of each process
| Process | Technical points |
| Raw material inspection | Remove surface mud and microorganisms, usually with a brush roller or high-pressure spray |
| Cleaning & impurity removal | Remove stones, metal, light impurities, defective peanuts |
| Washing | Remove stones, metal, light impurities, and defective peanuts |
| Soaking/flavoring | Prepare seasoning liquid, normal temperature or vacuum infiltration, time control |
| Draining | Remove surface moisture to shorten roasting time |
| Roasting/drying | Key process to form crispness and aroma, multi-stage temperature control |
| Cooling | Rapid cooling to avoid overcooking and restore crispness |
| Screening & grading | Size grading (drum screener) and optical color sorting |
| Packaging | Vacuum or gas-flush packaging to extend shelf life |
III. Detailed equipment list for each process
3.1 Raw material cleaning system
The cleaning system removes various impurities from raw materials and serves as the first line of defense to ensure the quality of subsequent processing.
Table 2 Raw material cleaning equipment list
| Equipment name | Function description |
| Vibrating screen cleaner | Remove large and small impurities (soil, branches, leaves) by vibration |
| Remove stones of a similar size by specific gravity | Remove light impurities (husks, dust) by airflow |
| Destoner | Magnetic separator/iron remover |
| Remove incomplete or moldy peanuts based on the density difference | Remove metal impurities to protect subsequent equipment |
| Specific gravity separator | Remove incomplete or moldy peanuts based on density difference |
Technical points: The cleaning system usually adopts a combination of “vibrating screening + air separation + destoning”. The peanut cleaning system includes a first feeding device, an air separation device, and a vibrating screening device arranged in sequence. As the material slides down to the vibrating screening device under gravity, the air separation device performs negative-pressure adsorption of light impurities in the material.
3.2 Washing system
Washing is a key process to remove mud and microorganisms from the peanut surface. Various types of cleaning equipment can be selected based on production scale and product requirements.
Table 3 Cleaning equipment list
| Equipment name | Features & applicable scope |
| Brush roller cleaning machine | Roller brush friction, suitable for peanuts with heavy soil, low breakage |
| High-pressure spray cleaning machine | Water jet impact, suitable for lightly soiled peanuts |
| Ultrasonic cleaning machine | Deep cleaning removes microscopic impurities and is used for high-end products |
| Bubble cleaning machine | Using bubble turbulence to clean gently, suitable for easily damaged materials |
| Peanut soaking machine | Pre-soak before cleaning to loosen mud (commonly used for brine peanuts) |
Technical points: The peanut cleaning machine can use a brush-roller design. The motor drives the stirring rod, causing the water to flow and clean the peanuts. At the same time, the brush device causes peanuts to rub against the bristles during rotation, improving the cleaning effect. For brine-flavored peanuts, a peanut soaking machine is usually used first for preliminary soaking to loosen mud on the shell surface, and then the peanuts enter the cleaning machine for washing.
3.3 Soaking & flavoring system
The flavoring process determines the product’s flavor quality. Depending on the product type, either normal-temperature soaking or a vacuum-flavoring process can be used.
Table 4: Soaking & flavoring equipment list
| Equipment name | Function description |
| Stainless steel soaking tank | Normal temperature or heating soaking, simple process, low cost |
| Vacuum flavoring machine | Vacuum infiltration, fast入味, low moisture absorption, good taste |
| Cooking pot (steam jacketed kettle) | Normal temperature or heating soaking, a simple process, low cost |
| Seasoning liquid preparation system | Boiling flavoring for brine peanuts can be batch or continuous |
Technical points: The fully automatic vacuum feeding machine includes a processing furnace, a vacuum pump, and a seasoning cylinder, which quickly flavors peanuts through vacuum high-temperature treatment. Compared with traditional cooking, this process has a shorter flavoring time and allows control of peanut moisture content, resulting in better taste.
3.4 Roasting & drying system
Roasting is the core process in in-shell peanut processing, directly affecting the product’s crispness and aroma.
Table 5: Roasting equipment list
| Equipment name | Features & applicable scope |
| Heat conduction oil roaster | Uniform heating, large capacity, suitable for medium and large enterprises |
| Electric heating drum roaster | Remove part of the moisture before roasting to shorten formal roasting time |
| Continuous chain plate dryer/roaster | Suitable for large-scale continuous production, even temperature |
| Microwave drying equipment | Fast drying, crispy inside and outside, but high equipment cost |
| Far infrared crisping machine | Combined with low-temperature drying to improve crispness |
| Peanut pre-dryer | Remove part of the moisture before roasting to shorten the formal roasting time |
Technical points: The roasting process recorded in the patent technology includes steps such as pre-drying, steam heating for flavoring, low-temperature drying, and far-infrared crisping. The supporting equipment includes a pre-dryer, ingredient flavoring equipment, a low-temperature dryer, and a far-infrared crisping machine. The roasting machine produced by Anqiu Zhengda Peanut Machinery Factory can roast both peanut pods and red-skinned and white peanuts, making it an ideal replacement for electric and oil furnaces.
3.5 Screening & grading system
Grading and screening ensure uniform size and consistent appearance of the product.
Table 6 Screening & grading equipment list
| Equipment name | Function description |
| Vibrating grading screen | Classify by particle size, multi-layer screen design |
| Rotary drum grader | Smooth grading, low damage, suitable for in-shell peanuts |
| Color sorter | Optical sorting to remove discolored, moldy, or defective peanuts |
| Specific gravity grader | Separate full and shriveled peanuts by density |
3.6 Special process equipment
For specific product types, the following equipment may be required:
Table 7: Special process equipment
| Equipment name | Application scenario |
| Bleaching tank / whitening pool | Shell whitening treatment (export bright type) |
| Sulfur fumigation room | Shell bleaching & preservation (export type, strictly controlled) |
| Vacuum packaging machine | Extended shelf life, maintain flavor |
| Gas flushing (MAP) packaging machine | Replace oxygen with nitrogen or CO₂ to prevent oxidation |
| Pasteurization line (tunnel) | Cooling tower/cooling conveyor |
| Cooling tower / cooling conveyor | Rapid cooling after roasting |
3.7 Special production line equipment for brine-flavored peanuts
For brine-flavored peanut products, complete sets of equipment are available:
Table 8 Special equipment for brine-flavored peanuts
| Equipment name | Steam-heated, continuous |
| Peanut soaking machine | Used for soaking and cleaning |
| Brine peanut cooking machine | Steam heated, continuous |
| Spreading & cooling machine | Cool after cooking before packaging |
| Vacuum packaging machine | Automatic or semi-automatic |
| High-temperature sterilization pot | Retort sterilization |
| Pasteurization line (with leak detector) | Can detect bulging/leaking bags |
| Drying machine (air knife) | Dry packaging bags after sterilization |
This production line uses SUS304 food-grade stainless steel and can be customized to suit output.
IV. Summary of complete equipment list
Table 9: Summary list of in-shell peanut processing equipment
| Process section | Main equipment |
| Raw material cleaning | Vibrating screen, air separator, destoner, magnetic separator, specific gravity separator |
| Washing section | Brush cleaning machine, spray cleaning machine, soaking machine, ultrasonic cleaner |
| Flavoring section | Soaking tank, vacuum flavoring machine, cooking pot, seasoning preparation system |
| Roasting & drying | Heat conduction oil roaster, drum roaster, chain plate dryer, microwave, far infrared crisper, pre-dryer |
| Screening & grading | Vibrating grader, drum grader, color sorter, specific gravity grader |
| Packaging & auxiliary | Vacuum packaging machine, MAP machine, sterilization line (Pasteurization/retort), cooling tower, air knife dryer |
| Special optional | Bleaching tank, sulfur fumigation room, halved nut separating machine, etc. |
V. Process differences among different product types and equipment selection suggestions
5.1 Salted dried peanuts
Process characteristics: Soaked in salt water, then roasted, a relatively simple process.
Core equipment: Cleaning machine, soaking tank, roasting furnace, screening machine.
Selection suggestion: Roasting equipment is the key. It is recommended to choose a heat-conduction oil roaster or a drum roaster to ensure uniform roasting.
5.2 Brine-flavored peanuts
Process characteristics: Need brine cooking, sterilization after packaging, and a complex process.
Core equipment: Soaking machine, cleaning machine, cooking machine, spreading cooling machine, vacuum packaging machine, and pasteurization line.
Selection suggestion: It is recommended to choose a complete brine peanut production line to ensure that each process is matched. The pasteurization line can simultaneously detect bulging/leaking bags.
5.3 Roasted original peanuts
Process characteristics: No seasoning or only salt, highlighting the original aroma.
Core equipment: Cleaning machine, roasting furnace, screening machine.
Selection suggestion: For cleaning equipment, choose a drum type with a low breakage rate; for roasting, adopt a low-temperature, long-time process (e.g., 90°C for 16 hours) to improve quality.
5.4 Export bright type peanuts
Process characteristics: Need bleaching treatment to achieve a bright white shell color.
Core equipment: Bleaching tank, cleaning separator, pre-dryer, sulfur fumigation room, low-temperature dryer, far-infrared crisping machine.
Selection suggestion: The bleaching process requires attention to environmental protection requirements; it is recommended to equip wastewater treatment facilities.
VI. Equipment investment and production line configuration suggestions
6.1 Small-scale production (daily processing 1-2 tons)
- Equipment configuration: Cleaning machine, jacketed kettle, small roaster, vibrating screen, vacuum packaging machine
- Equipment investment: about 100,000 – 200,000 RMB
- Factory area: 100-200 m²
- Applicable objects: Family workshops, small food factories
6.2 Medium-scale production (daily processing 5-10 tons)
- Equipment configuration: Cleaning unit, cleaning machine, soaking tank, cooking machine, heat conduction oil roaster, screening machine, automatic packaging machine
- Equipment investment: about 300,000 – 600,000 RMB
- Factory area: 300-500 m²
- Applicable objects: Regional food enterprises
6.3 Large-scale production (daily processing over 20 tons)
- Equipment configuration: Fully automatic cleaning line, continuous cleaning machine, vacuum flavoring machine, chain plate dryer, color sorter, fully automatic packaging line
- Equipment investment: 1 – 3 million RMB
- Factory area: over 1000 m²
- Applicable objects: Large food processing enterprises
VII. Conclusion
In-shell peanut processing technology has evolved from traditional manual operations to mechanized and automated complete production lines. From raw material cleaning to finished product packaging, each process has corresponding professional equipment to choose from. Enterprises should reasonably configure equipment based on product positioning, production scale, and investment budget, to build a scientific and efficient production system.
As consumers’ requirements for food safety and quality continue to increase, in-shell peanut processing technology is also advancing toward “more hygienic, more precise, and more efficient”. Adopting food-grade stainless steel equipment, introducing automatic control systems, and establishing a comprehensive quality management system will become the industry’s mainstream trend.
For enterprises intending to enter the field of in-shell peanut processing, it is recommended to carefully consider product positioning and future development opportunities when selecting equipment, and to choose equipment suppliers with strong technical capabilities and comprehensive after-sales service to lay the foundation for long-term, stable production.