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Biosci 106 (part 2)

Plant biochemistry, food biochemistry and microbial biochemistry

Limit of classical methods (plant extraction) Low yield. Unreliable quality supply (locations, seasons, diseases and politics). High costs (long time required for production, extensive downstream recovery)
Limits of classical methods (chemical synthesis) Most consumer prefer natural food additives. Undesirable racemic mixture (low substrate selectivity, reduced process efficiency) Increased downstream costs
Alkalisation of cocoa beans An additional process gives darker colours of the powder through interactions among phenolic compounds. Before roasting. pH goes from 5.3 to 6.8-7.5 Over treatment results in off-flavours from breakdown of fats but a bit of tartaric acid can prevent it
Fermentation of cocoa beans (aerobic bit) Acid + alcohol penetrate the bean (destroys cellular integrity; the bean dies). Loss of integrity (compartmentalisation) allows mixing of polyphenol oxidase + phenolic substrates. In aerated environment it results in formation of brown coloured pigments
The drying of cocoa beans Either occurs in the open air or they are fan dried. Traditionally seeds and mucilage are lef tin a heap on the ground and convered in banana leaves or are placed in boxdes - more control and more hygenic
Maillard Reactions Proteins in the bean interact with sugars present to form brown coloured pigments. Continues during roastin + is important for final colour and flavour. Reaction occurs between glucose, amino acids and proteins
Roasting of Cocoa Beans relatively low temperature (<120 degrees C). Must have good control of the temperature as burning them results in crappy flavours. Resulting cocoa contributes flavour and colour to foods, both are dependant on the type of bean + the process carried out
Cocoa and Spain The explorer Cortez brought cocoa back home to spain from cnetral and south america where the THEOBROME CACAO tree originates. It was a jealously guarded national secret. But it eventually spread (duh) and is now grown in the equitorial regions
Harvesting Cocoa Beans Usually by hand. Pods are broken apart. Beans and mucilage are scooped out and subjected to fermentation.
Uses of Enzymatic browning Beneficial for developing - flavour in tea - colour and flavour in dried fruits eg. figs, raisins and cocoa. However it is detrimental to fruits and vegetables, particularly apples and potatoes
Developing food in New Zealand A healthy population reduces health costs. Food is important for the NZ economy as we are such large exporters. Currently incorporating bioactive components found in native foods is being developed to provide additional health benefits
Fermentation of Cocoa Benas (anaerobic bit) Fermentation is largely an anaerobic process. Temperature = 45-50. Carbohydrates in the pulp are broken down by yeasts + lactic acid into acids and alcohol. The pulp liquifies + drains away spaces from around the bean allowing air air to penetrate
Studying Food Food that we eat has many components that interact positively + negatively with our physiology + hence our genes. We're interested in those with bioactive or antioxidant abilities (usually highly coloureded + provide protection against serious diseases)
Food It's a source of energy. Influences mood (eg milky foods are soothing, chocolate is good for stress). Most of the food we eat is either living or derived from living materials.
Describe the nutritional function of Plant sterols Reduces the absorption of cholesterol
Describe the nutritional function of Lycopene Implicated in preventing prostate cancer
Describe the nutritional function of Iondine Prevents goitre (an enlarged thyriod gland)
Describe the nutritional function of Anthocyanins Removes free radicals (its an antioxidant)
Describe the nutritional function of Dietary Fibre Reduces the risk of colo-rectal disease, cardiovascular disease and lowers serum cholesterol
Describe the nutritional function of Calcium Helps bone develop and prevent osteoporosis
Describe prebiotics Ingredients added to promote the growth of specific bacteria in the gut
Describe Probiotics Live microbes
Describe lycopene A plant pigment in tomatoes. It accumulates as the cell wall breaks down (chlorophyll has broken down and pH decreases)
Describe Nutrigenomics The concept of nutrition based on an individual's genome
Describe Sclerid Tissue The more gritty, woody and compacted tissue
Describe anthocyanins The blue pigment in blueberries
Describe Parenchyma The soft main tissue of fruits etc which forms a large part of dietary fibre for humans
Describe natural Pigments Plants are flippin slow. Microbial takes 2-3 days - its expensive to regulate as it has to be proven that it wont FSU. E.G. B-carotene; we already eat it, it can be roed, orange or yellow 9blakeslea Trispona
What are some popular microbial products? Food, AA, antibiotics, specialitly compounds, biopolymers. But the ones we are concentrating on are BIOFLAVOURS, ORGANIC ACIDS and NATURAL PIGMENTS
It's from slucose oxidation. Aspergillus Niger. It's used in formation of food, pharmaceuticals + hygenic products.
Because it makes apples less desirable to people which causes problems in marketing them, particularly when apples need to be processed e.g. canning and drying.
Why does enzymic browning occur? When apple is bruised or cut or bitten, several components previously kept separate by compartmentalisation (in vesicles often associated with thylakoids + in vacuoles) are brought together + exposed to oxygen (Ox is required for the reaction to proceed)
What are the components of enzymic browning? Polyphenol oxidase which has a prosthetic group with copper which catalyses the oxidation of phenolic substrates such as chlorogenic acid in apples.
What are the factors that influence the extent of the browning reaction? Different cultivars, different tissues, chlorogenic acid concentration e.g. in greater amounts near the core compared to under the skin.
Describe some of the controls of enzymic browning: temp of 0-4 slows process. NaCl: Cl complexes wit Cu. Dunkd in H2O dilutes reactnts. Vit C red 0-benzoquinones 2 dihydroxy phenols. Citric A: low pH: PPO no longer functns. Na metabisulfate + SO2 complexs wit quinones: form S quinones: maybs anaphylactic.
At what pH do most platn enzymes function at? most plant enzymes function optimally at a pH of 6.5-7.2
Created by: fbk0371



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