Class I preservative is

Preservatives are added to foods for preventing rancidity, mould growth and spoilage. There are natural and synthetic preventives, which are widely used for preventing foods from getting spoilt.
Class I preservative belongs to natural sources which also exhibit preservative effects in foods. Examples of Class I preservatives are sugar, salt, vinegar, honey, spices, edible oils, etc. Class 1 preservatives are not dangerous to health.
Class I preservatives are Sugar, Salt and Spices.