Fruit size, color, texture, purity, and flawlessness of the fruit from wastage such as burns, worms, sourness and spoilage microorganisms are the indices of good appearance of dates. Another index is the amount of sweetness.
Sourness: microbial fermentation results in the dates that contain a higher moisture content to become sour.
Sugar Crystallization:The crystallization of date sugar is seen under its skin and in its flesh in its soft varieties. Although crystallization does not have an impact on the taste of dates, it does change their texture and appearance. In order to prevent crystallization, dates should be kept at the right temperature.
Note: Sugar crystallization does not mean that the date is rotten, and by exposing the date to temperature, it will be removed and the date will be restored to its previous form.
Microbial Spoilage: It occurs as a result of becoming contaminated with yeasts, molds or bacteria. Microorganisms cause the vinegar smell by converting the date sugar into acetic acid. To prevent this spoilage, the dates should be stored at an appropriate humidity (below 35%) and at a cool temperature (below 20 °C), and their hygiene should be observed at various stages from planting, holding, and harvesting to packaging.
Dates may be contaminated with the larvae of some insects at different stages of harvest or during storage. To prevent this contamination, dates should be fumigated in packaging companies with substances such as nitrogen, methyl bromide, carbon dioxide, phosphine gas, or ozone, and stored in anti-insect packages.