Cooking food destroys some disease-germs but not always all. It cannot be relied upon to purify impure food or freshen unsound food. Care alone, guided by science in production, preservation, transportation, manufacture, preparation, furnishes humankind with food that promotes human well-being.

Pure food, pure water, pure air, are needed for wholesome living. All are possible when it is known what makes these pure and that their purity is as important to human life as their plentifulness. It is only as these are pure for all of a community that they can assuredly be for any one in it. Disease anywhere easily passes to food, and through food takes health from those to whom such food goes.

Clean-appearing food may not always be pure food, as clear water may not be pure water. Pure food is clean food, so kept as to be sound without introducing non-food substances to preserve the food or improve its appearance without improving its quality, as does coating rice with glucose and talcum or using benzoate of soda in factory foods, such as canned tomatoes.

Storage of food may preserve freshness of appearance without preventing deterioration in quality. Low temperatures may delay development of bacteria, yet not destroy them. Bacteria are then left to grow when the food comes from storage. Temperatures even so low as probably to free food from such danger still may not have made inactive soluble ferments natural in foods themselves. Such ferments can cause fermentation at the lowered temperatures of cold storage or refrigerated freight. Food that has been stored long or traveled far is often decayed by such ferments. Food may become so in the home refrigerator when not used promptly.

Germ-life (bacteria and molds) abounds in refuse, vitiated air, contaminated water. These are disease-sources.