Vegetables
Properties of vegetables:
*Principle components- Water, fibre, starch, certain vitamins, minerals, & lipids
Protective property: Vegetables are protected from spoilage microbes & pathogens when in prime condition due to presence of intact cell wall that serves as a protective barrier. When cell integrity is lost (due to wilting, ageing & injury like chopping, shredding, bruising & juicing), there is loss of protection.
Origin of natural biota: Soil, water, air, insects & animals
Primary processing of Vegetables:
1) Transportation, where there is physical damage due to pressure
2) Precessing like washing & s
3) Storage
WASHING
As for introduction of spoilage bacteria, washing is a hydro cooling action that involves water. Water quality & internalize of organisms if water is colder than produce, results in pressure differential. Pseudomonas might be introduced & the main problem is soft rot.
Whereas for pathogens, it involves washing with chlorinated water. Pathogens are introduced by agricultural practices. Survival of pathogens depends on 3 factors: Moisture, Temp, time.
Solution: Tumble-dry vegetables to prevent re-contamination (remove water)
FROZEN VEGETABLES
Divided into spoilage of microbes & pathogens.
For former, predominant is LAB. Microbial spoilage is rare, however main concern is spoilage of thawed pdt, which is temp dependent.
For latter, it is rare. Main concern is spore forming bacterium (Clostridium botulinum). 2 types of pathogens are non-spore forming pathogen which is killed during blanching & most contaminating pathogen that cannot grow at frozen temp.
CANNED VEGETABLES (Thermal process)
-Main concern: spore-forming mesophile (C.botulinum)
- Contamination during cooling due to contaminated water.
3 sources of contamination:
1. Insufficient thermal process- Inaccurate thermometers/timers & inadequate steam supply
2. Container leakage- Faulty seam cans, punctures & spoilage microbes & pathogens in cooling water
3. High temp storage
DRIED & FERMENTED VEGETABLES
Main concern: spoilage by yeast & fungi
3 causes of spoilage:
1. Control of water activity
2. Humidity of storage environment
3. Temp fluctuations
EGG & EGG PDTS
Properties:
-High water content of 73%74%
-Proteins 13%
-Lipids 12%
*Curtice on surface prevents entry of water
2 primary sources of Initial microflora:
1. Trans-ovarian transmission
-Via oviduct of infected poultry
-main concern: S.typhimurium
2. Trans-shell infection
-poultry contamination in production environment
4 Primary Processing of Shell egg:
1. Washing-
Spoilage & pathogens: egg washed with natural water containing 4.8ppm iron, in which 6.2% of spoilage caused by Psedomonas spp. pH 9 increases re-contamination of Salmonella spp & Listeria monocytogens
2. Post-washing & drying: Drying must be immediate to reduce risk of remaining bacteria on surface from penetrating egg.
3. Shell coatings: minerals like paraffin pil can be used to prevent water loss & retard penetration of Pseudomonas & salmonella spp.
4. In-pasteurization of intact shell eggs: Reduces spoilage microbes & pathogens but it is costly.
LIQUID EGGS
4 sources of contamination:
-egg contaminated with fecal contaminant
-processing equipments like broken utensils, pipes, pumps, pails, churns & holding tanks
-food handlers
-contaminated egg content
DAIRY PRODUCTS & ALCOHOLIC BEVERAGES
Cheese pdtion flow chart: (9 steps)
Preliminary milk treatment, heat treatment, addition of starter cultures, coagulation, cutting, cooking, whey removal; handling of curd, moulding & maturation
*Coagulation-cooking: Vat stage
Initial Microflora of cheese maturation
Divided into 2 parts: Starter cultures & secondary flora.
STARTER CULTURES
divided into 3 parts:
1. Natural starter cultures- reproduced daily by back-slopping & selective pressure. Little control when used.
Advantages: Phage resistance, pdtion of antimicrobials, aroma pdtion
Disadvantages: Variable performance
2. Mixed-strain cultures-undefined mixture of strains selected from natural starters, maintained & propagated.
Adv: Phage resistance
Disadv: Can harbour their own phages
3. Defined-strain starters- Defined strain & species ratio, reproducible technological performance, susceptible to phage attack
SECONDARY FLORA
divided into 4 parts:
1. Non starter lactic acid bacteria (NSLAB)
3 grps: Obligatory homofermentative, facultatively heterofermentative, obligatory heterofermentative
6 Factors affecting growth & survival:
-ripening temp
-moisture
-salt
-pH & organic acids
-redox potential
-nitrates
2 Significance:
-Gives more intensed flavour with improved gastronomy quality
-involved in proteolytic & lipolytic activities
Sources: raw & pasteurized milk
2. Non lactic acid bacteria (Micrococcus)
3 significance:
-accelerates cheese ripening
-contributes to cheese quality through proteolytic & lipolytic activities
-possess a range of hydrolytic enzymes
Factors affecting growth:
-ripening temp
-absence of oxygen
Sources: Raw milk, cheese made from raw milk & pasteurized milk
3. Yeasts
4 significance:
-produce volatile compounds from metabolism of fats, proteins, lactose & lactic acid.
-Autolysis of yeast cells release cellular content that produces savour flavours, umami effects & serve as flavour precursors.
-Generate carbon dioxide which in limited amount helps to open Blue-veined cheese curd and assist spread of P.roqueforti.
-Together with moulds, increase pH at cheese surface which stimulates bacterial growth & enzymatic activities.
Sources: Milk, brines & rennet
4. Moulds
5 significance:
-Gives cheese different appearances
-Production of important aroma & flavour compounds
-possess intra & extra-cellular proteinases, peptidases & acid/alkaline lipases that are important for protein & fat metabolism.
-Neutralises pH, allowing acid sensitive organisms to grow.
-Antimicrobial activity
WINE
Outline of wine fermentation (12 steps)
1.Grapes
2.Crushing; addition of sulfur dioxide
3.Juice & skins
4.Inoculation with yeast (optional)
5.Maceration & partial fermentation (Colour & tannin extraction)
6.Pressing-removal of skins
7.Completion of alcoholic fermentation, followed by racking off yeast lees
8.Wine
9.Malolactic fermentation (optional)
10.Ageing in oak barrels/other vessels
11.Fining, clarification & packaging
12.FINAL PRODUCT
Origin of wine microorganisms:
Grapes, winery equipment & environment, starter cultures (controlled inoculation)
7 Factors affecting yeast ecology:
1.Addition of sulphur dioxide
2.Extent of juice clarification
3.Particulate matter;skins
4.Temperature
5.Microbial contamination of grapes (LAB, AAB)
6.Chemical composition of grape juice
-Amino nitrogen
-pH 3.0-4.0
7.Fungicides/pesticide residues
*LAB in wine: Conducts malolactic fermentation, causing wine spoilage
*AAB in bulk wines: Converts ethanol to acetaldehyde, causing vinegary spoilage
MALOLACTIC FERMENTATION
Advantages:
1.Deacidifies & enhances quality of high acid wine
2.Contributes additional flavour notes
3.Enhances microbiological stability of wine by:
-decreasing available nutrients
-bacteriocin production
Disadvantages:
1.Depreciates quality of low acid wine
2.Can occur in bottled wine (spoilage)
3.Increases wine pH, allowing other bacteria to grow.
TATS ALL!!! I STILL HAVE 3 MORE FREAKING CHAPTERS TO MEMORIZE!!! omggggggggggggggggggggggggggggggggggg....I WANNA DIE! I really feel like giving up BUT I WUN!!!! :'(
Hope the paper is EASY! Alright I'm off to bed now..because the weather isn't helping me! Thanks yea...of ALL days, it must rain today & seduce me to bed! Grrrrr...
Goodnight all...OOPS...hehe, GOOD MORNING!
Zzzzzzzzzz..... <3
P.S: SCREW those people who came up with SCIENCE! :P
