Fruit and Vegetables part 2 Flashcards
Production of fruits and vegetables
affected by many factors up to harvesting point:
- soil will vary for different types of F & V (diff region)
- watering & fertiliser requirements vary (type/variety dependant)
- actual days available for plant to grow and ripen is critical (seasonal change)
- some F & V don’t have adequate time at appropriate temperature to grow to maturity (we need to keep up with consumer demand)
Harvesting Fruits & Vegetables
at specific time of peak quality in terms of colour, texture & flavour, in order to market
- by hand or machine = affects quality and quantity of F & V
- mechanical harvesting = exert more impact & damage = new cultivars & varieties developed to offset greater handling forces (firmer; higher in solids; different flavours
- changes post-harvest are important = influence safety & quality
- farmers harvest at a particular maturation point, then supplying chain looks after, timed for consumer purchase, or stored in cold chain to not ripen
Respiration of Fruit & Vegetables
= the produce take in oxygen & give off carbon dioxide, moisture & heat
- respiration continues after harvest
- influences storage, packaging & refrigeration requirements
- resulting moisture and heat = cause growth of moulds, damage produce (heat alone)
Ripeness VS Maturity
- NOT the same
- Ripeness: optimum or peak condition of flavour, colour & texture
- Maturity: the condition of a F/V when picked
- some F/V picked when mature but not ripe
- some F continue to ripen after picked = become overripe if picked at peak ripeness
- affected by many factors and interactions (temperature, time, added gasses) different for each F & V
Ripening
- Ethylene (C2H4) acts like a signal, orchestrates/helps growth stage of F & V, activates ripening process
- climacteric fruits produce ethylene gas during ripening (non-climacteric don’t, therefore don’t ripen after harvesting, are ethylene sensitive)
- sometimes don’t have enough ethylene to fully ripen
Flavour/texture quality attributes affected by changes occurring post-harvest in:
- Carbohydrates (starch, sugars. one decreases and other increases?)
- pectins: decrease in water-insoluble & increase in water-soluble, contributes to gradual softening of F & V, further decrease in water-soluble pectin by pectin methyl esterases (long term)
- organic acids: generally decrease during storage and ripening = affects juice quality
Senescence
Quality decline in stored respiring F & V after harvesting
- results form continues enzymatic activity
- affected by temperature & storage atmosphere
Storage
most important factor during storage influencing quality = temperature reduction & maintenance
- reduces metabilic activity of produce and spoilage microorganisms
- general rule: for every 10 degree temp rise from optimum = metabolic rate increases 2 to 3 fold
Use commercially of natural or synthetic chemicals:
- to maintain quality through prolonged storage life
- overcome effects of water vapour/humidity, co2 & ethylene on F & V
- edible coatings - lipid-based waxes; polysaccharide/protein-based materials; chitosan, cellulose; aloe vera gels
- chemicals = chlorine-based solutions; peroxyacetic acid (PAA); organic acids; hydrogen peroxide (h2o2)
- gases = nitric ocide; sulphur dioxide fumigation
Modified atmosphere:
- done for intact or processed F & V
- controlled-atmospheric storage (CAS) procedures used
- attempt to control level of those gases influencing respiration of F/V
- dynamic relationship between ethylene gas & storage life
Processing of fruits
- varietal differences need to be considered when selecting for use in various products
- differ in: tolerance to weather, insects & disease; maturity time & yield; flesh firmness when cooked; amount of juice; acidity; storage stability
Canning or freezing of fruit
- need to harvest fruit at proper ripeness stage for good texture & flavour preservation
- processing done by automated equipment with minimal handling by plant workers
- assured of wholesome, sanitary products with good flavour & quality
initial preparation similar for both:
- sorted into size by machine
- washed continuously circulating water or under sprays of water
- mechanical peeling or coring if needed by automatic equipment & prepared in various styles (halves, slices, pieces)
- plant workers remove undesirable portions.
Canning of fruits:
cans/glass filled with fruit by machine -> moved to machines that fill with correct amount of juice/syrup -> moved to machine that automatically seals them -> sealed cans are cooked under carefully controlled temperature and time conditions -> after cooling, containers stored in cool, dry, well-ventilated warehouses until shipped to market
Frozen fruits:
- often packed with dry sugar or syrup
- after initial preparations, semiautomatic equipment fill packages with fruit
- sugar or syrup then added
- packages automatically sealed
- then packaged fruits quickly prozen in special low-temperature chambers & stored at -18 degrees or lower
- flash and cryogenec freezing currently providing the best results
Fruit juice processes:
not all juices go through all processes = desired end product determines if the juice will be concentrated & frozen
main steps in production for most juice:
- extraction
- clarification (clearing)
- deaeration (removal of air)
- pasturization/high pressure processing
(HPP)
- concentration
- essence add-back (flavours)
- canning or bottling
- freezing
