Lecture - Fruits, Vegetables, and Grains

Lecture - Fruits, Vegetables, and Grains - Fruits...

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Click to edit Master subtitle style Fruits, Vegetables, and Grains
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Microbiological Spoilage Fruits : seed-bearing organs (e.g. apples, tomatoes) Vegetables : all other edible portions Spoilage related to plant pathogens Varies with type of food True pathogens: actively infect plants Opportunistic pathogens: infect only when external protective layer is damage by insects or processing Pathogens target cellulose (glucose polymer) and pectin (galacturonic acid polymer), which provide structural integrity of plants
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Structure of Cellulose
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Spoilage Types : 1. Active spoilage : pathogens microorganisms initiating infection of healthy products 2. Passive or wound : opportunists infect via damage to epidermal tissue (usually during processing or from insects) 3. Portal induced : opportunists infect via lesions caused by pathogens or by natural openings
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Plant Defense Mechanisms Intact healthy plant cells resist invasion and disease Both external and internal mechanism Roots make hydrogen peroxide Phytoalexins : antibiotics produced by plants in response to breakdown of cell wall Protease inhibitors
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Epidermal layer Cutin (Skin, peel, or testa): protective barrier Cell wall: cellulose, pectates and glycoproteins Pre-harvest compromise by insects, sand, or rubbing Post-harvest damage by processing equipment Molds can penetrate external tissues of plants Opportunists use nutrients present in damaged tissue Cutin Cell Wall
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Interior Defense Mechanisms Middle lamella Holds Plant tissues together Pectin, pectinic acid Degradation results in detachment of cells from one another Middle Lamella
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Influence of Physiological State Wounds causes
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