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21 Cards in this Set
- Front
- Back
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Definition of Food Fermentation
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Bio-processes that change food properties,
bacteria generate energy from carbohydrates in the absence of oxygen. |
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Final electron acceptor during fermentation |
Sugar |
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Name some results of fermentation that can add value to foods |
Flavor compounds, carbonation, texture changes (thickening of dairy), increased nutrient bioavailability |
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Describe Lactic Acid Bacteria: gram, motility, oxygen requirements, nutritional requirements |
Gram positive, non-motile (no flagella), facultatively anaerobic, catalase negative (do not respire), somewhat fastidious, require amino acids, vitamins, purines, pyrimidines |
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What effect does homofermentative LAB have? |
Contributes acidity: produces mainly (homo) lactic acid from glucose, >90% |
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What effect does heterofermentative LAB have? |
Contributes flavor: many (hetero) end products from glucose metabolism (lactic acid, propionic acid, acetic acid, ethanol, carbon dioxide) |
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Name the main genera of cocci LAB and associated type of fermentation |
Homoferms: Streptococcus (mostly homo), Lactococcus, Pediococcus Heteroferm: Leuconostoc |
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Name the main genera of rod LAB and associated type of fermentation |
Lactobacillus (hetero & homo) Carnobacterium (hetero) |
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Why are starter cultures used in dairy products? What are the advantages? |
Pasteurization temps kill natural bacteria. Starter cultures are used for fermented products & do not have natural competition. Time & consistency can be controlled, desired flavor (heteroferms) and pH can be targeted. |
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List the uses of fermentation in food products |
Develop sensory prop (flavor, aroma, texture, create new products) Increase dietary value (improve digestibility, enrich products with desired micro metabolites) Food safety (destroy natural toxins, improve shelf life, preservation) |
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What are the benefits of combining hetero and homoferm LABs? |
Impart flavor and characteristic texture of particular cheeses (holes in Swiss). In some cases, combos will acidify faster than a single culture. |
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What dictates fermentation speed in vegetables? What type of environment is needed? |
Specific natural flora of the field crop results in unique processing and can cause variations from lot to lot and plant to plant. Anaerobic conditions are required. |
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Describe salt's role in vegetable fermentation |
Enhances fluid release, promotes anaerobiosis Higher salt selects LAB and inhibits undesirable bact and fungi Consumers expect salty flavor |
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What is the salt concentration that favors heterofermentative LAB? What level inhibits them? |
Low salt concentrations of approximately 1%
3% greatly inhibit heteroferms |
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What is the salt concentration that favors homofermentative LAB? |
High salt concentrations favor homoferms, accelerate fermentation and causes rapid acidification. |
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What are the attributes of natural microbiota associated with meat? How are they controlled? |
Gram negative, aerobic, putrefying, spoilage LAB fermentation prevents spoilage (acid lowers spoilage micros). |
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What are the most common types of fermented meats? |
Dry and semi-dry sausage |
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What are regulated requirements of shelf-stable sausages? |
Curing agents (nitrite) pH <5 MPR =/< 3.1 : 1.0 |
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Why are nitrites used in cured meats? |
Inhibits C botulinum (FSIS) Imparts flavor myoglobin -> nitrosomyoglobin (pink color) |
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Why are fermentable sugars added to shelf stable sausages? |
There is little glucose in meat so the addition of ferm sugars is needed for LAB to product lactic acid and acetic acid. |
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Why are starter cultures used in shelf stable sausages? |
The use of native flora can result in putrefying and spoilage and can cause difficulties in process control. |
