For growers, packing houses, and distributors, sorting isn’t just about appearance; it’s crucial for determining product value, reducing waste, and ensuring customer satisfaction.
In this blog, we’ll explore various fruit and vegetable grading methods, from traditional to high-tech.
Manual Sorting: Relies on the Human Eye and Experience
- How it Works: Trained workers, working on sorting tables or conveyor belts, visually inspect and manually sort individual fruits and vegetables.
- Sorting Criteria: Size, shape, color, and external defects (such as scars, scratches, bruises, and insect holes).
- Advantages: Low initial investment, suitable for small-scale operations. The human brain can flexibly detect complex and irregular defects.
- Disadvantages: Standards may be inconsistent. Low efficiency and labor intensity. Error-prone: High long-term labor costs, and human error can lead to misjudgments and lost revenue.
Mechanical Sorting: Classified by Physical Properties
- How it Works: Primarily utilizes simple mechanical structures. Drum/Screen Sorter: Utilizes a rotating drum or screen bed with holes that gradually increase in size. Small fruit is screened out first, while larger fruit falls out later.
- Weight Sorter: Utilizes a precision scale to weigh and sort individual products (such as eggs and citrus).
- Roller Sorter: Utilizes rollers with gradually increasing spacing, with fruit falling into the gaps corresponding to their diameter.
- Sorting Criteria: Primarily based on size (diameter) or weight.
- Advantages: Very effective in achieving uniform packaging specifications. Simple, durable, and cost-effective for single-parameter sorting.
- Disadvantages: Completely incapable of determining color, ripeness, internal quality, or external defects.
Automated Photoelectric Sorting:
Machine Vision (Camera-Based) System
- Working Principle: High-speed cameras capture images of fruit and vegetables from multiple angles as they pass along a conveyor belt.
- Sorting Criteria: External quality: color, shape, and surface defects. Advanced software can be trained to identify specific defect types.
- Advantages: High speed, objective, and stable. Completely eliminates human subjectivity in visual judgment.
Near-Infrared Spectroscopy
How it works: A sensor emits near-infrared light at fruits and vegetables and measures the absorbed and reflected light. The resulting spectrum acts like a “chemical fingerprint” for the product.
- Sorting Criteria:Internal Quality: Brix, acidity, dry matter, and internal defects (e.g., hollow potatoes, browning inside apples).
- Advantages: Measure internal eating quality without damaging the product, which is impossible to detect with the naked eye. This is crucial for ensuring consistent taste and flavor.
Comparison of Grading Methods
| Method | Primary Criteria | Pros | Cons | Best For |
| Manual | Visual & Subjective | Low startup cost | Slow, inconsistent, costly labor | Small farms, local markets |
| Size/Mechanical | Size, Weight | Simple, effective for size | Ignores quality defects | Initial rough sorting, specific crops |
| Electronic (Vision/NIR) | External & Internal Quality | Fast, objective, comprehensive | High initial investment | Commercial packers, quality-focused operations |
Summary: How to choose the right sorting method?
The sorting method you choose depends entirely on the size of your operation, target market, and budget.
- For small farms selling at farmers’ markets, manual sorting may be sufficient.
- For packinghouses that need to provide uniform product to retail chains, machine vision systems are essential.
- For producers of high-value products where internal sweetness and quality are key selling points (such as high-end honeydew melons and mangoes), investing in a system that integrates NIR and vision is the best option.
Looking to improve sorting efficiency and accuracy?
Contact us today for a customized fruit and vegetable sorting solution!