Seed Saving Basics
Saving seeds from your garden favorites isn't always as simple as cutting open the fruits or vegetables. Seeds of pulpy vegetables and fruits, such as tomatoes (Lycopersicon esculentum) and cucumbers (Cucumis sativus), require a fermentation process that mimics the natural rotting that occurs in nature. As the seeds ferment, the pulp separates, leaving behind clean seeds that are suitable for saving. Harvest, ferment and save seeds only from open-pollinated or non-hybrid vegetables and fruits. Hybrid varieties don't produce seeds true to their parent plant, which means they may not share disease resistance, fruit quality or other beneficial qualities with the original plan.
Why Ferment Some Seeds?
Fermenting some wet seeds can dramatically improve their ability to sprout. Fermentation removes germination-inhibiting substances from seed coats, makes them more permeable to water, and also helps reduce or control seed-borne diseases (for healthier seedlings).

Purposely fermenting wet seeds mimics the natural process of fermentation that occurs when ripe fruits are eaten by animals or drop to the ground and rot. When we intervene to keep seeds from fermenting naturally, it becomes necessary to ferment them artificially so they can complete their natural ripening cycle.

Fermentation is needed for tomato seeds (in order to remove a germination-inhibiting gel), and can also benefit Squash Family and eggplant seeds, though more care must be taken with these to avoid premature sprouting. Ferment Squash Family seeds for only a day-and-a-half or so, eggplants a little longer.

Harvesting and Cleaning Seeds
Seed harvesting and cleaning techniques fall into two main categories according to whether the fruits and seeds are dry or wet when mature
#1. Dry Seeds
'Dry' seeds include beans, okra, peppers, basil and members of the Onion and Carrot Families. Cleaning dry seeds usually involves simply drying and crumbling the pods or husks, then screening or 'winnowing' the seeds to separate them from the chaff
#2.Wet Seeds
'Wet' seeds are found in such plants as tomatoes, eggplants and many squashes. Cleaning wet seeds requires washing to clean the seeds and to separate them from the surrounding pulp.

In addition, in some cases wet seeds (such as tomatoes) are best fermented for several days to remove germination-inhibiting substances from the seed coats . Fermenting can also help such seeds as members of the Squash family by killing molds, mildews and other disease organisms that may be present on the seeds after growing.

Some families (such as the Cucumber family) include some plants that produce wet seeds (e.g., squashes and melons) and others that produce dry seeds (e.g., luffa and hard gourds)