- Chop all vegetables in food processor. Transfer to a large bowl, cover with coarse salt, and let sit at room temperature for 12 hours, covered with plastic wrap.
- Rinse the vegetable mixture and drain well.
- In a large saucepan, combine sugar, vinegar, celery seed, mustard seed, and turmeric. Bring to a boil, add vegetables, and boil for 15 minutes, stirring from time to time.
- When relish is cooked, add cornstarch diluted in a little cold water, and stir well.
- Place relish in sterilized Mason jars.
Commercial relish is always bright green. To obtain this colour, manufacturers add food colouring, which is why homemade relish does not have the same hue.
- Sterilize jars by immersing in boiling water for about 5 minutes. The lids must be new to ensure a proper seal. Soak lids in hot water before using.
- Fill jars, leaving a headspace of about 1 cm (½-in.).
- Place lids and screw bands on jars but do not overtighten.
- Immerse jars in boiling water and boil for at least 15 minutes.
- Remove jars from water and let rest for 24 hours. The lid will be depressed and make a sudden popping noise when the seal is tight.
- The jars can be stored for one year in a dark, dry, cool place.