BAEN-625 Advances in Food Engineering
Induced activityHeating effects of radiationBiochemical effectsOganoleptic changes
Radiation may also affect the food itself by inducing radioactivityHeavy particles (protons, deuterons, alphas, neutrons, etc) cannot be used Above certain threshold energy, γ radiation can also induce activity
The products from γ radiation of most elements found in foods have short-livesException is iodine-126 (12 d) from iodine-127For food containing iodine – minimum storage time
Induced activity from electrons is well bellow the maximum concentration permitted in foodsExcept with carbon and chlorine, the half-lives are short (20-33 min)
10 kGy is equivalent to 10 kJ/kg of irradiated materialThe rise in temperature being inversely proportional to the specific heatPossibility that certain foods of low Cp may be damaged by heating effects Cp
DoseT
TmQCp
mED
=Δ
Δ=
Δ=
Biological or nutritive value and the digestibility of food may be concluded to be unaffected by radiationOr slightly lowered if compared with other treatment methodsMore studies are neededUndesirable by-products of radiation action make the food unacceptable
SugarsStarchesMonosaccharide
GlucoseFructose
DisaccharidesSucroseLactoseMaltose
PolysaccharidesStarchfiber
Complex carbos break down into simpler sugarsMonosaccharide break down into sugar acids and ketonesA general reaction is oxidation of alcoholic to carbonyl groups
Responsible for the development of brown color in milk
Polysaccharides are depolymerized and oxidized leading to softening of the food
Large compounds that contain nitrogenSome contain iron, phosphorus, and sulfurThey consist of long chains of amino acids connected by peptide bonds
Most are affected by high doses
LeucineValineLysineArginine
Possible source of objectionable odors and flavors after radiation
Lucine yields isovaleraldehyde which has a strong ‘goaty’ odors, and tryptophan yields indole or related compoundsThese and the sulphur compounds from radiation of methionine and cytine also smell unpleasant
Fast and oils composed of the same element as carbohydrates (C, H, O)Triglycerides -glycerol plus fatty acids
Undergo peroxidation
And carbonyl groups formation (in the presence of O2)Ingestion of carbonyl compounds can produce toxic effects but not proved
OH
O
OCCOOH −−−→−||
All seen susceptible to break down by radiationParticularly vitamins C and EMore sensitive when in pure state than when incorporated in food
Radiation often indices undesirable changes in taste and/or appearance in foodsSome foods are nor suitable for radiationMeat – limiting factor is the development of rancidity in its fat, and the development of bitter, metallic, or burnt flavors
Fish in general appears to be less sensitive to changes than meatsRefrigeration shelf-life of all fishes can be extended by up to 1 to 2 months by dose of 5 kGy(pasteurization)Higher dose levels cause burnt flavors and discoloration
Fruits are very prone to spoilage by radiationSoftening is the most difficult problemGood results obtained with apple juice and strawberries
5 kGy will destroy mould on strawberries and double their shelf-life
Causes mushroom caps to remain closed longer and kills microorganisms that cause spoilage; Thus irradiated fruits and vegetables have longer shelf lives
Milk gives very disappointing resultsQuickly development of unpleasant taste, odor, and color
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