1 / 14

Chemical factors that shorten the shelf-life of food

Chemical factors that shorten the shelf-life of food. James McCoy. Background . What is Shelf-Life It is defined as the time during which the food product will Remain safe Be certain to retain desired sensory, chemical, physical and micro-biological characteristic

etenia
Download Presentation

Chemical factors that shorten the shelf-life of food

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chemical factors that shorten the shelf-life of food James McCoy

  2. Background • What is Shelf-Life • It is defined as the time during which the food product will • Remain safe • Be certain to retain desired sensory, chemical, physical and micro-biological characteristic • Comply with any label declaration of nutritional data

  3. Background • Factors Effecting Shelf-Life • Microbiological • Chemical • Physical • Temperature Related • Intrinsic Factors- properties of the final product • Water Activity • pH and Total Acidity • Redox Potential • Available Oxygen • Nutrients • Natural Microbes • Natural Biochemistry • Use of Preservatives • Extrinsic Factors- factors that the final product encounters as it moves through the chain • Temperature • Relative Humidity • Exposure to light • Consumer handling • Atmosphere • Environmental microbes

  4. Background • Some Chemical Factor Examples • Oxidation • Enzymatic Processes • Chemical Hydrolysis • Browning Reaction (non-enzymatic, enzymatic)

  5. Oxidation • The Reaction is driven by • Temperature • Water activity • Presence of metal ions • Exposure to light • Reactive Oxygen Species (ROS) • Enzymes • Causes • Rapid determination of beer flavor • Rancidity development in fat containing foods

  6. Oxidation • Photo- Oxidation • The oxidative rancidity reaction catalyzed by UV light • In milk the UV light activates riboflavin(Vit. B2) and catalyzes the oxidation of the amino acid methionine present in milk protein to methanal • Produces a burnt or medicinal like flavor • Oxidative Rancidity • Oxygen reacts with metal ions (copper, iron) to produce a reactive oxygen species (ROS) • The ROS reacts with unsaturated fatty acids replacing a hydrogen with an oxygen • Produces off flavors and aromas

  7. Oxidation • Mechanism

  8. Enzymatic Browning • A redox reaction that occurs in foods such as fruits and vegetables that contain polyphenoloxidase(PPO) • PPO is a copper containing enzyme that catalyzes of causes the oxidation of phenol compounds contained in plant tissues • Occurs rapidly at warm temperatures with a pH between 5.0 and 7.0 • Is responsible for up to 50%of the losses during production

  9. Enzymatic Browning

  10. Non-Enzymatic Browning • Two main types • Millard reaction and Caramelization • Driven by • Temperature • pH • Presence of sugars • Presence of metal ions ( Cu(I), Cu(II), Fe(II), Fe(III) )

  11. Non-Enzymatic browning

  12. Hydrolytic Rancidity • Occurs in food contain saturated fatty acids • Produces off flavors and aromas • Driven by • Water activity • Temperature • Presence of the enzyme lipase • Mechanism • The fat molecule is hydrolyzed back to a glycerol and 3 fatty acid molecules

  13. References • Kilcast, David; Subramaniam, persis (2000) Stablility and Shelf-Life of Food : Woodhead Publishing • Eskin, N. A; Robinson, David S. (2001) Food Shelf Life Stability. New York, New York; CRC Press

More Related