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Vegetable Fermentation (II)

Vegetable Fermentation (II). Key points for vegetable fermentation. Benefits Enhanced preservation Desirable flavor and texture property Antimicrobial activity High conc. of thiocyanates and other sulfur-containing comp. Nutritional property

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Vegetable Fermentation (II)

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  1. Vegetable Fermentation (II)

  2. Key points for vegetable fermentation • Benefits • Enhanced preservation • Desirable flavor and texture property • Antimicrobial activity • High conc. of thiocyanates and other sulfur-containing comp. • Nutritional property • Sauerkraut has anti-scurvy properties (high vitamin C) • Koreans consume ~43Kg per year (120 g/day) of kimchi

  3. Key points for vegetable fermentation • Natural fermentation • No heat process to inactive other flora • Natural lactic acid bacteria to carry out fermentation • LAB minor population, but dominant in successful product fermentation • Succession: the fermentation depends not on any single organism, but a consortium of bacteria representing several different genera and species. A given organism (or group of organisms) initiates growth and becomes established for a period of time. Due to accumulation of inhibitory compounds, growth slows down and gives way to other species that are less sensitive to those factors. (Fig. 7.3) • Bacteriophage may also have a role

  4. Sauerkraut • Leuconostoc mesenteroides • Has relatively short lag phase and high growth rate at low temp (15-18C) • Heterofermentative pathway (lactic acid, acidic acid, CO2, ethanol) • Acidic environment (0.6%-0.8%, as lactic acid) inhibit non-lactic competitor and favors other LAB • Acid approaches 1.0%, inhibit L. mensenteroides (4-6 days) • Other homolactic bacteria • Acidity 1.6%, pH below 4.0, only L. plantarum can grow • Final acidity 1.7%, pH 3.4-3.6 (Fig 7-2)

  5. Kimchi • Most popular of all fermented foods • More than 100 varieties with various raw materials and processes • 360 million Kg produced annually, 100 grams daily consumption, 12% of the total food intake • Multiple ingredients, flavor and texture properties • Nutrition • Vitamin C, B, calcium, iron, potassium, dietary fiber, antioxidants, live microflora • Functional food • Producing antimicrobial compounds

  6. Pickle Production • Any vegetable or fruit preserved by salt or acid • Most important: cucumber • 1 billion Kg in the US used for pickles (half of the crop) • Now more than half of the pickles are not fermented (direct add acetic acid) • Types • Fresh-packed (non-fermented) • Refrigerated (non-fermented) • Fermented (processed) • Distinctive flavor and texture

  7. Manufacture of fermented pickles • Rely on salt, oxygen exclusion, anaerobiosis to select for growth of • instead of dry salt • Salt conc. higher than that for sauerkraut • Less diverse microflora • Brine at least 5% salt, some 7%-8%, up to 12% • Up to 2 months, end pH ~3.5, acidity 0.6%-1.2% (as lactic) • L. mensenteroides cannot grow • Initiated by L. plantarum and Pediococcus sp. • Brine condition inhibitory to coliforms and other non-LAB • De-salted after fermentation for further consumption • Can use starters (controlled fermentation) (Fig 7-5)

  8. Defects • Pickles • Bloaters and floaters (Table 7-4) • Excessive gas pressure, internal cavity formation • LAB (heterolactic, malolactic fermentation), coliforms, yeasts • Control: remove dissolved CO2 by flushing or purging with nitrogen gas • Some can still be used • Destruction and softening • Slippery, loses crispness and crunch • Cannot be used • Pectinolytic enzymes by microorganisms • Fungi • Penicillium, fusarium, Alternaria, Aschyta, Cladosporium • Control: acidity

  9. Olives • 90% of the world production used to make olive oil • Only 7%-10% consumes as table olives • From middle East • Italy, Spain, Greece, Turkey: 75% of worldwide production, US less than 1%, but 90%-95% from California used to make table olives • More than 70% on the US market are brined and canned (California-style olives)

  10. Composition • Phenol and polyphenol compounds common to olives • Color, antimicrobial activity • Antioxidant • oleuropein • Bitter flavor • Glucosidic phenols and oleropein

  11. Fermented olives • Spanish-style (green Spanish-style) • Treated with sodium hydroxide (lye) and fermented (natural microflora) • Greek-style (natually black, ripe-style) • Not treated with lye, but fermented (natural microflora) • Ripe black- or green-style • Lye-treated, not fermented • Going through a special aeration treatment, promote oxidation of pigments and conversion of green to black (California-style)

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