Walnuts

详情

Walnut specifications focus on quality, size, and color, while packaging is designed to prevent rancidity due to the nut's high oil content.

1. Quality Grades

Commercial walnuts are generally categorized into three classes:



* Extra Class: Superior quality; kernels are uniform in color and shape with virtually no defects.

* Class I: Good quality; allows for slight defects in color or shape.

* Class II: Standard quality; allows for more noticeable surface defects, provided the kernel remains edible and sound.



2. Physical & Technical Specifications



* Color Classification: Categorized from most to least valuable as Extra Light, Light, Light Amber, and Amber.

* Kernel Styles:

* Halves: At least 7/8 of the kernel is intact.

   * Quarters: Lengthwise pieces roughly 1/4 of the kernel size.

   * Large/Medium/Small Pieces: Broken portions categorized by their ability to pass through specific mesh screen sizes.

* Moisture Content: Strictly controlled to prevent mold. Maximum moisture is typically 5% for kernels and 8% for in-shell walnuts.

* Tolerance for Defects: Strict limits are placed on "rancidity," "shriveled kernels," "shell fragments," and "foreign material."

* Chemical Safety: Must meet low limits for Aflatoxins (typically $leq$ 4 ppb) and peroxide values to ensure freshness.



3. Packaging Details

Packaging must provide a barrier against oxygen, moisture, and light.



* Bulk Shelled Kernels: Typically packed in *0kg or *1.*4kg (*5 lb) corrugated fiberboard boxes. These always include a food-grade polyethylene (PE) liner.

* In-Shell Walnuts: Usually shipped in *5kg or *0 lb polypropylene (PP) woven sacks or jute bags to allow for some breathability.

* Preservation Methods: High-quality exports often use Vacuum Packaging or Nitrogen Flushing (Modified Atmosphere Packaging) to extend shelf life by displacing oxygen.

* Retail Packaging: Stand-up pouches made of multi-layer laminates (often plastic/foil) with resealable zippers are the industry standard.



4. Storage & Handling



* Temperature: Best maintained at 0°C to 5°C (*2°F*1°F). High temperatures cause the oils to oxidize (turn rancid) quickly.

* Humidity: Relative humidity should stay between *0% and *0%.

* Odors: Walnuts are highly "hygroscopic" and absorb smells; they must be stored away from pungent items like spices or chemicals