Newsletter #7: SHELF LIFE! 🍏👄🍏👄🍏 Greetings from your local food scientist! 🍏👄🍏👄🍏

Folks often ask me, "what is food science?" I've met young people at the farmers market with an interest in studying food science! Well, how about I provide some food science 101, methods of food preservation? Here’s a list off the top of my head of ways to extend the shelf life of food! Maybe you’ll find it interesting!

“Shelf life extension”: both for preventing microbial spoilage, and some prevention oxidation / “rancidity” of pleasant flavors, unsaturated fats, and loss of pleasant textures (eg staling of bread, aka “moisture migration” which relates to water acivity (#2 below), however texture is really a whole other topic!)
1. pH (acidic or alkaline) pH below 4.6 to prevent botulism (plus having oxygen keeps away Clostridium botulinum which is anaerobic, although oxygen feeds other microbes, in particular molds; you can really spend a lifetime categorizing all the microorganisms, but basically there are anaerobic, aerobic, and "facultative anaerboes" meaning they can get by on no-oxygen but do better with oxygen. Evolution is an amazing thang!) So pH... acidic or alkaline food environments: eg olives are typically alkaline brines; fermentation is a natural preservation process (if controlled) typically producing acetic acid or lactic acid, as well as alcohol! Alcohol is food preservative (since alcochol doesn't affect pH much.) There are so many natural edible acids: citric, malic (apples), phosphoric (in cola, but today is not so "natural" and should arguable be avoided), tartaric (grapes and wine), acetic (vinegar, sour-dough bread), and lactic (yogurt and cheese.)
2. Water Activity: big topic: sugar binds water; glycerin is a “humectant” (binds water); salt lower water activity; Dehydration! (My favorite process) lower water activity. Water activity ranges from 0 (no water available for microbes) to 1.0 (all water available for microbes.) Water Activity is the ratio of the food's "vapor pressure of water" (the evaporative pressure) is the numerator, the denominator is pure water. If water in the food can evaporate, the reasoning is that evaporating water in the food can also be used by microbes to multiply. Example of a food-liquid loaded with fermentable sugar but with a low water activity: HONEY!
3. Salt... Not only lowers water activity, but also causes microorganisms to swell and pop!
4. Heat sterilization (eg pasteurization of milk, “canning”, or “asceptic processing”)
5. Antimicrobial/antifungal perservatives (eg sorbates and benzoates)
6. MAP: modified atmospheric packaging (eg no oxygen: replace with nitrogen such as during wine bottling) or vacuum packaging (helps to a degree especially for flavor preservation)
7. Alcohol is a preservative! (but not really good for your liver.) You could say it fits into category #5 above, but you could say the same about salt. It may even lower water activity a bit. Preservatives have varying "mechanisms of action" on microbes that make all preservatives quite unique.
8. Smoking (very slight extension of shelf life but may also be carcinogenic)
9. Antioxidants (for preserving flavors and unsaturated fats) eg vitamin E / tocopherols. Would you like some black garlic antioxidants with your olive oil? :-)

10. COMBINATIONS OF THE ABOVE!

I might have left some methods out... If you have any questions, see me during “office hours” at the market! (Disclaimer, I am no professor and was NOT the best student… by far!)