workshop 1 Flashcards
causes of deterioration of food (3)
microbial growth
enzyme action
insect damage
what canning involve
heating jars of food to temperature high enough to destroy microorganisms and enzymes and is referred to as processing. Processing also drive air out of the jars (airtight vacuum seals forms)
role of the airtight seal
kep air and microorganisms from re-entering the jars
what is clostridium botulinum
one spoilage organism that should chause concern among home canners. It is destroyed at boiling temperatures, nut not its hardy spores that produce a deadly toxin
- gro well in low acid envrironment
2 methods to destroy clostridum botulinum
- processing in a pressure canner at 240F (116C) which a pressure canner can attain (it has a tight seal and at high pressure this temperature can be attained)
- being in the presence of of acid
example of high acid foods (6)
jams jellies marmalades fruit fruit preserves pickles
examples of low acid food (7)
meat polutry game seafood vegetables soups stews
what do we have to do with low acid food and food in oil like pesto, garlic in oil or flavored oils
they must processed at a minimum of 116C to destroy the Clostridium botulinum
role of pectin
acts as a cementing substance holding the cell walls of fruit together and giving them shape
place very concentrated in pectin
in the skin and cores of fruit
why fruits with more pectin are suitable for jam and jelly
because they rely on naturally occuring pectin to gel the product
3 tests to know that the gel stage is reached when you do some jam and jelly with fruit high in pectin (generally takes 10-45 minutes)
- the temperature test: using a jelly or candy thermometer, the product is ready when it reaches 4C above boiling temperature (take temperatire of boiling water first)
- the Plate Test: it is really when a small amount placed on a cold plate in the freezer gels
- The Spoon Test: it is ready when a cold metal spoon is dipped into the jelly and the drops join and drop as a sheet
commercial pectin is used for what (2)
to make jam with fruit that is low in pectin
to avoid boiling the mixture until the gel stage is reached
how is the commercial pectin made
by extracting pectin from apple pomace (residue once the juice is extracted) or citrus products
how is the commercial pectin available
in powder or liquid form
- used with enough sugar so that the final sugar concentration of the jelly average is 60%
what is special about the special pectin
- it forms gel without sugar in the presence of divalent ions, such as calcium
- its structure is slightly different from regular pectin
what special pectin contains
bean gum and xanthan gum
special pectin is used for what and what other ingredient may be used
- used in manufacture of low-calories jam (spread) and jellies
- artifical sweetener may be used (may be added after cooking if heat affects it)
what is carrageenan
it is a linear sulfated polysaccharide extracted from red edible seaweef from the North Atlantic Ocean
- it is a powerful gelling agent and may be used for gelling jams
difference between carrageenan and regular pectin
it does not require as much sugar as regular pectin and sets very quickly (less than 30 minutes) without cooking and results in a softer, more spreadable jam than cooked jam
carrageenan are sold as a jam gelling powder. What are its ingredients (4)
sugar
carrageenan
ascorbic acid
sodium benzoate
in food industry, carrageenan is used as a common additive for what (7)
ice cream sherbets condensed milk instant soup cakes cookies candies
role of carrageenan in food industry
serves to stabilize, thicken or gel these foods
instructions with Carrageenan
- combine 1L of finely chopped fruit with 375 ml of sugar. Let stand for 15 minutes
- Gently stir in one package of No Cook Freezer Jam gelling powder and let stand for 5 minutes
- Stir again for 1 minute
- Poor jam into clean jars, leaving 1-inch (2.5 cm) headspace
- Close jars and freeze
why freezer jams do not require processing
because freezing (-18C) halts bacterial growth
freezer jams may be made with what and why
since freezer jams are not exposed to high temperature, they may be made with artificial sweeteners (often unstable when heated)
freezer jams are appropriate for who
for individuals who wish to restrict their intake of carbohydrates/calories (ex: diabetes or on weight loss diets)
concentrated fruit juices and artificial sweeteners can be used for what
reduce and/or modify carbohydrate content of product
what can perk up flavor in concentrated fruit juices..
spices, herbs or flavorings
spices and herbs may be tied in ________ for easy removal after cooking
cheesecloth
how do we do color preservation
light color fruit shoul be placed in color protection solution prior to canning and 5-7 ml lemon juice may be added per 250 ml canning liquid to help prevent discoloration
how freezing preserves food
by halting growth of surface microorganisms and slowing enzyme activity
best temperature of freezing
-18 degree celsius
what happens when it is frozen slowly
most of the water content forms large ice crystals that puncture the cell walls, so there is loss of juices
what do rapid freezing
formation of small ice crystals and therefore reducing leakage of juices
3 ways to achieve rapid freezing
- cooling food before freezing in small portions
- placing food near freezer wall with space around package for air circulation
- limiting the amount of food placed in the freezer at once so as not to raise the freezer temperature
what should we do to prevent freezer burn due to the dry (cold air)
packaging should be airtight
thawing is safest where
in the refrigerator, allowing 10 hours per kg of food
6 general instructions for successful freezing
- SELECT fresh food of high quality
- PREPARE food quickly but with great care, using color-preserving solutions for food that undergo non-enzymatic browning
- BLANCHING: blanched foods should be cooled before packaging, they may be cooled with cold water which also stops the cooking process
- PACKAGE in odorless, tasteless, vapor-proof and moisture proof freezer bags or containers. It prevents drying out of foods + protects them from freezer odors. Any air in the bag should be removed priori to freezing. A straw may be helpful to suck out any remaining air
- FREEZE foods at -18C or lower immediately after packaging. However, if a delay is unavoidable, place each package in the refrigerator as soons as it is sealed
- THAW foods carefully and use immediately after thawing
what BLANCHING helps (in general instructionsfor successful freezing) (3)
helps preserve color
inactivates surface enzymes of fruits and vegetables
enabls easy removal of skins
drying is an ideal means of….
preservation, which reduces the volume and weight of foods
what is important for the reproducibility of results in drying (3)
a record of methods, quantities and time required
drying- by use of heat, water will evaporate from the food (what is the advantage)
lack of moisture = limits of microorganism growth
% of moisture remains in food after drying
6-10%
drying- treatments solutions and methods (3)
- sodium bisulphate solution (using food grade from drug store)
- salt solution
- citric acid or ascorbic acid solution
used of dried foods - what should we do with vegetables before cooking
- they should be soaked for several hours in the refrigerator to rehydrate
- added salt near the end of cooking
storing of dry food
cool thoroughly before packaging in small package that can keep at room temperature in a cool, dark, dry place
what indicates the appareance of molds during storing
that too much mositure were left
general guidelines of drying (8)
- obtain good quality, fresh, fully ripe produce
- wash well and remoce any bad spots
- slice food thinly (.5 cm) or less
- treat by blanching or applying solution to prevent discoloriation if desired - slows enzymes activity. Blanching also helps to break skin to permit moisture to escape
- spread in a single layer
- if using an oven, monitor foodto prevent over drying at edge of pans
- if using a dehydrator with multiple trays, trays should be rotated and switched for even drying.
- Seeds may be easier to remove once partially dried to avoid loss of juices
- 6-10% moisture may remain in food
