Outline Good Growing Practices Good Harvesting Practices Food Preservation and Food Microbiology Food Safety: Growing, Harvesting, and Using Olives Curing Olives Basic Principles Water, brine Dry Salt Lye History Linda J. Harris, Department of Food Science and Technology University of California, C Davis Growing and Harvesting Microbiology 101 Good Growing Practices Water Inputs Wildlife People Microorganisms Spoilage Pathogens Beneficial Good Harvest Practices Equipment Food preservation is based on techniques that Food grade Clean Reduce, control, or eliminate (spoilage and pathogens) Control (beneficial) Hygiene Preservation techniques Goal REDUCE CONTAMINATION Food (modification), Process, Package, Storage Conditions SEM images Dennis Kunkel, www.pbrc.hawaii.edu/kunkel/gallery The Food System What is ph? Storage Conditions Extrinsic - temperature, atmosphere, relative humidity ph is a measure of acidity Food Available water Acidity Available oxygen Nutrients Natural inhibitors Package Extrinsic - atmosphere, RH ph = -log [H+ ions] Scale ranges from 0 to 14 1 Processing Physical - Heat Chemical - acid, fermentation, preservatives 2 Low ph: Acidic 3 4 5 6 7 Neutral 8 9 10 11 12 13 14 High ph: Basic/ Alkaline 1
Growth Factors - Water Activity (aw) ph Examples of Some Foods ph 3 ph 7 ph 4.6 Neutral ph Scale High acid foods Low acid foods Olives are low- acid. Lye- cured olives are above ph 7. Lye (sodium hydroxide) is alkaline ph 12 to 13. 15 molecules total Add Sugar/ Salt OR Remove Water 15 molecules available 15 molecules total 8 molecules available A Measure of Available Water Determining Water Activity aw Clostridium botulinum Electric hygrometer measures equilibrium Contained in soil and water worldwide relative humidity Spore- former (heat resistant) Water activity results between 0 and 1 Produces a deadly toxin E.g., 0.98, 0.65, 0.47 Needs When growing in food Moisture, low acidity, anaerobic conditions Tests take 5 to 10 minutes warmth (in most cases) Botulism Effect of ph on C. botulinum Symptoms Spores of C. botulinum will not germinate and Muscular weakness double vision difficulty swallowing respiratory paralysis - stop breathing grow below ph 4.8 ph 4.6 (safety factor built in) is the legal dividing line between commercial foods canned by pressure canning and those by water bath or steam The same applies for home canning but methods are more conservative because controls are variable 2
Water Activity (aw) Salt and aw Most foods greater than 0.95 allow microorganisms to grow C. botulinum prevented from growing ü aw less than 0.93 10% salt is a water activity of about 0.93. All pathogens inhibited ü aw less than or equal to 0.85 Microbiology 101 olive oil Environment (ambient or refrigerated)" Oils, in general a low risks for microbial food safety Refined oils (canola, sunflower, peanut, etc.) have no water, no place for microorganisms to hang out Olive oils, especially extra virgin do carry small numbers of microorganisms within tiny water droplets Yeasts may be involved in some flavor development Minimal water Reduced ph Antimicrobials Extra virgin olive oils also carry broad range of antimicrobials Extraction" Levels vary in composition and amount Variety, production practices, maturity extraction method, storage condition, time UC Davis Olive Center Report, Microbiological Food Safety of Olive Oil: A review of the literature.2011 Package (excludes light, air)" Flavored olive oil Curing Olives Botulism risk Preservation principles Garlic- in- oil mixtures Stored at room temperature Preventing microbial growth Increasing acidity, decreasing available water or water activity (increasing salt or drying) Prevention Flavor with dry herbs and spices Low water activity Killing microorganisms Thermal processing (canning) If moist ingredients are added Store refrigerated short time (7 days) Freeze 3
Water- Cured Olives Curing Environment (cool or cold, dark)" A method to remove oleuropein Water- cured olives (salt/vinegar brine) ph lower water activity lower Water cured Brine cured Natural fermentation ph lowered Dry salt cured Reduced water activity Water cure" Olive Lye cured Brine- Cured Olives Brine- cured olives fermentation reduced nutrients lower ph salt/vinegar brine ph lower water activity lower Lye- cured Olives Environment (cool, dark)" Environment (cool or cold, dark)" Lye- cured olives High water activity ph Olive Fermentation" Canning Lye- cured Olives Olives and botulism Lye- cured and unfermented olives Canned lye- cured olives were Low- acid (ph 7 or 8) Water activity high Temperature/time of storage Depends upon brine salt concentration Light and medium salt brine need to refrigerate Concentrated brine (10%) Room temperature storage Lye " Canning" marketed across the US Scientific understanding of thermal processing was limited Several outbreaks occurred in 1919, CANNING MUST BE DONE IN A PRESSURE CANNER Follow times and pressures indicated in instructions for your local elevation 1921, 1924 Lead to National Canners Association and significant research in this area Some done at UC Davis Initial canning- inspection program 4
9/24/11 Olive Spoilage www.ucfoodsafety.ucdavis.edu Preservation is also designed to prevent spoilage Often spoilage microorganisms are more ph and water activity tolerant than the pathogens Softening Multiple causes - breakdown of pectin Microbial causes Molds and bacteria that produce pectin- degrading enzymes Keep covered, appropriate brine concentration, refrigeration Chemical causes Lye too strong or too hot Olives Variety, too ripe, overly large Gas Pockets Bacterial growth and gas formation Frequent water changes during the lye washing phase 5