wine making exam questions Flashcards
Why would you conduct Malolactice fermentation?
- Deacidification
- Reduce risk of bacterial growth inbottle (is it stable?)
- Removal of nutrients
- Sensory effects
Two major physiochemical factors that affect the growth of lactic acid bacteria (LAB) in wine are pH and the concentration of sulfur dioxide (SO2).
A. Describe how these two factors they influence growth of LAB. (6 marks)
B. With the aid of a diagram discuss the interaction of pH and SO2 on the growth of LAB in wine. (4 marks)
Q4. 2013, 2014 (Worth 10 marks; recommended time to answer question is 10 minutes)
Part A)
PH
- Related to intracellular pH (pHi ) limit, Growth stops below this limit
- Malo activity tipically faster at high pH
- O. oeni can manitain a higher pHi (hence greater proton motive force) at low extracellular pH, relative to other LAB
Sulfur dioxide
- Molecular SO2 is antimicrobial
- Concentration of molecular SO2 is pH dependant
- Inhibits both growth & malolactic enzyme
- Bound SO2 is toxic
LAB can metabolise acetaldehyde bound to SO2
Bound is 5-10x less active than free
A. List the major physiochemical factors that affect the growth of lactic acid bacteria (LAB) in wine? (4 marks)
B. Describe how these factors could be used to explain why a malolactic could become stuck or sluggish. (4 marks)
C. In the context of these factors, what steps could you take to restart this affected malolactic fermentation? (5 marks)
Q4. 2015 (Worth 15 marks; recommended time to answer question is 15 minutes)
A. pH, Temperature, Alcohol concerntration, SO2 concerntration.
B. See image
C.
- Look&listen,smell&taste
- Check & maintain temperature 15-20°C.
- Paperorthinlayerchromatography,teststrips, enzyme analysis, FTIR, HPLC.
- L-malicacidanalysis(idealrate:0.1-0.2g/L/day).
- Microscopic observations ➔ chain formation in O. oeni
A. LIST the various options for inoculation of malolactic fermentation available to winemakers. (Worth 4 marks)
B. Describe the advantages and disadvantages of two of these options. (Worth 6 marks)
Qu. 2016 10 marks
1) Uninoculated/indigenous LAB
102-104 cfu/mL at crushing, from vineyard & winery equipment
High pH favours Pediococcus & Lactobacillus (>3.7)
Low pH favours Oenococcus oeni (<3.6)
Advantages
Cheeper, will happen over time
Disadvantages
No selection of stran, wine conditions may kill the natural MLF
2) Inoculated/selected LAB
Agar slant, liquid & freeze dried (concentrates) cultures of Lactobacillus plantarum or Oenococcus oeni that require propagation prior to inoculation
– Highly concentrated freeze dried, or frozen preadapted Lactobacillus plantarum and/or Oenococcus oeni for direct inoculation
Advantages
Previous experience
Timing of inoculation
Direct inoculation, no or limited reactivation
Commercially available since 1993
Strains selected on basis of physiochemical tolerance
Preparation of cultures via progressive adaptation
‘Rip & tip’
Disadvantages
– Financial constraints (between $100-$120 for 25 hL pack)
With the aid of graphs and diagrams explain what the “cap hot spot” is. Show how and where they occur in three types of red fermenter. For each fermenter type show how the negative effects can be minimised.
Q2. 2013, 2014, 2015 (Worth 20 marks; recommended time to answer question is 20 minutes)
Open Fermenter, cap ot submurged
Cap mamagement, plunge, pump over, rack and return and heading-down boards
Often Premium styles
Limited colour extraction, cap mamange ments is pumping over and plunging causing poor maseration.
The cap sits above the juice causing it to get hot quicker and limits temperature control.
Potter Fermenter closed tank, cap not submerged
Less suseptibility to oxidation and spoilage due to the closed top
Submerged cap system
Vinomatic, roto tanks, heder down boards
Increased rate of colour extraction
Juice circulated through the Cap providing excellent temperature control
Cap is held static, more masseration of skins
Spoilage is minimised as the cap is kept anaerobic
Outline the methods that could be used to produce 500L of the following juice style in the wine science laboratory at Waite.
Full bodied whites Pinot Gris, Chardonnay from the Adelaide Hills. Chardonnay Sauvignon Blanc Chenin Blanc Semillon Marsanne Verdelho Muscadelle
In your answer show all significant stages including harvest criteria, as well as the type and size of equipment you would use, as well as pressing cuts.
(Worth 20 marks; recommended time to answer question is 20 minutes)
Harvest Criteria
- Wide variation in style
- High alcohol levels 13-14% v /v
- Lower acidity 6-7 gL-1 H2T
- Low pH 3.3-3.5
- MLF and oak flavours
Methods Juice preperation
Press cycle
- Free run 1 x 0.5 bar
- medium 1 x 0.5 and 2 x 1 bar
- Hard 2 x 1.5 bar
Start with 1000L
free run 450-550 L
pressings 100-150 L
main objective recover full and flavoursome juice without excess phenolic extraction
- Add low-moderate SO2 at picking OR none (MLF, Oxidative handling)
- Crush and destem
- Must chill to prevent spontaneous ferment
- Possibly maintain inert gas cover and inert gas sparge all juice transfers
- Draining/Pressing operations should aim to provide low phenolic
extraction - Skin contact at low to moderate temperature can yield higher
levels of flavour but with the compromise of increased phenolics - Acid adjust if necessary
- Clarify juice to various degrees
- Inclusion of pressings with free run
Methods Juice Clarification
- Add inert solids(eg bentonite), propagate yeast aerobically to build up yeast sterol levels, add vitamin mixes and DAP
Yeaste selection
- Strong fermenter at high alcohol
- Low H2S producer especially in higher solids juices
- Efficient converter of CHO to ethanol
- Flocculates well/low foaming for barrel ferments
- Usually a less aromatic yeast
- Compatible with chosen LAB
Management Fermentation
- While maintaining desired rate of fermentation (higher than Floral) chill ferment to as cool as possible 15-18o C
- Ferment in tank until 6-7 o Be
- Racked from very gross lees to barrel
- Baume, temperature and sensory evaluation as often as required (1-4 times/24hr day)
- As foaming dies down barrels are gradually topped up
- Barrels may require cool room storage
- Bentonite additions should be light
- Early or mid fermentation production of H2S should be treated with 100-200 mgL-1 DAP - late production more difficult
- Raise temperature near the end of ferment to complete primary fermentation
Management Post ferment
- Option of ageing on yeast lees in barrel
- Stirring of lees in barrel
- Yeast autolysis - complex process, builds flavour and mouthfeel
- Yeast lees reductive, scavenge oxygen
- SO2 additions only after MLF is complete
- Wood maturation - rack to tank, for fining and stabilising
- Blending should proceed any final stability checks
- Protect wine against oxidation with each movement, treatment
- Bottle using high quality low oxygen pick-up filler/corker
Medhods use of MLF
- Natural process to lower acidity (Burgundy)
- Desired in Australia for flavour complexity
- Enhanced butter like flavour, flavour persistence and mouthfeel
- LAB can cause elevated levels of VA if allowed to grow unchecked, growth should be arrested with SO2 when malic acid falls below 0.1 gL
Type and size of equipment
Pressing Cuts
Outline the methods that could be used to produce 500L of the following juice style in the wine science laboratory at Waite.
A light bodied Pinot Grigio from the Adelaide Hills.
A crisp early harvest Riesling from the Adelaide Hills.
In your answer show all significant stages including harvest criteria, as well as the type and size of equipment you would use, as well as pressing cuts.
(Worth 20 marks; recommended time to answer question is 20 minutes)
Fruity aromatic still white table wine
Harvest Criteria
- Low to moderate alcohol 9-12% v /v
- High acidity > 7.5 gL-1 H2T
- Low pH < 3.3
- Absence of MLF and oak flavours
- Dry wines < 7.5 gL-1 residual sugar
- Med-dry wines 10-30 gL-1 residual sugar
- Terpenes are major flavour contributors
Press cycle
- Free run 1 x 0.5 bar
- medium 1 x 0.5 and 2 x 1 bar
- Hard 2 x 1.5 bar
Start with 1000L
- free run 450-550 L
- pressings 100-150 L
Methods Juice preperation
- low in solids and phenolics
- protection from Oxidation
- Add SO<strong>2</strong> and ascorbic acid as early as possible OR If hand picked (whole bunch press)
- Maintian inert gas cover
- All juice transfers (inert gas sparge)
- Draining pressing produce low phenolic free run juice
- Skin contact increase terpenes but will increase phenolics
- Adjust acid below 3.6pH
- Clarify Juice to minimum 0.5% solids - enzyme setteling/earth filtration
- Add bentonite to propergate yeast aerobically to build up yeast sterols levels
- Add vitimins and DAP
- Yeast selection- Strong fermenter, Low production H2S and VA, Flocculates well, Produces fruity esters
Fermentation Management
- Baume 0.5 per 24 hours
- Temperature 10-15C
- Cool ferments to produce and retain fruity esters
- Add bentonite
- Test Baume, Temp and sensory 1-4 times a day
- Production of H2S add 100-200 mg/L DAP
- Maintain adequate fermentation rate
Management post fermentation management
- Minimise movements
- Rack off gross lees ASAFIC
- Maintain free SO2 at > 25 mgL-1
- Ascorbic acid
- Store cold < 5 C (cold stabilise)
- Keep tanks full and gas covered
Management Post ferment
- Blending should precede any final stability checks
- Protect wine against oxidation with each movement, treatment
- Sterile filter at bottling especially if sussreserve is used to adjust
- RS
- Bottle using high quality low oxygen pick-up filler/corker
Describe the production methods used in white juice to produce both a full bodied and a lighter bodied Pinot Gris. Detail the juice sensory characteristics in both styles.
Q3 2015 (Worth 25 marks; recommended time to answer question is 25 minutes)
Press cycle
- Free run 1 x 0.5 bar
- medium 1 x 0.5 and 2 x 1 bar
- Hard 2 x 1.5 bar
Start with 1000L
free run 450-550 L
pressings 100-150 L
Describe the processes you would use to produce both a full bodied Merlot and a medium bodied Merlot from the Barossa Valley. In your answer detail the type of fermenter and cap management regime.
Q8. 2015 (Worth 15 marks; recommended time to answer question is 15 minutes)
- medium to full bodies
- Baume 14
- minimal acid
- yeast, enhances varetal characters
- Open fermenter, Gentle plunging fo subtle extraction , rack and return for oxygenation
- Cooler fermentation to retain fruit
- 2 year old oak vs new oak
- destem and crush
- adjust acid if needed
- pump into 1000L open fermenter
- innoculate with desired yeast strain
- Dap addition if needed
- temp between 15 to 25 C t get 2 baume per day
- plunging twice a day, rack and return once a day
- at 3 baume innoculate with MLF
- ferment to 1 Be
- press the furit and combine pressings and free run
- transfer to 2 year old french barrells if finish primary ferment
- Rack off gross lees
- Keep at 15-18C for MLF
- Complete MLF then rack off gross lees
- Add SO2 (50ppm free)
- Mature for 12 months at 15-18C
- racking 2 times and topping
- fining with egg whites
- Filtration
- botteling
Press cycle
- Free run and 1 x 1 bar
- 2 x 1 bar medium
- 2 x 2 bar hard pressings
List 15 factors in the production of red wine.
Pick the five most important of these factors, for the following wine styles, which may be different for each style, and explain why these five are more relevant options than the others for this style.
Rose light coloured and fruity
Medium bodied fruit forward red wine
Full bodied red wine for aging
Q7. 2016 (Worth 15 marks; recommended time to answer question is 15 minutes )
- Baume
- Acid
- Temperature
- T.A
- Flavour/tannin
- Cap Management
- Harvested machine/hand
- Fermenter choice
- Oxidative choices
- SO2
- Tannin addition
- Time on skins
- Cap mamagement
- Pressing cycle
- Desteming/ not desteming
- Crushing
- Yeast selection / methods
- milf selection and innoculation time
*
You are the winemaker in charge of acid additions at the crusher. You are required to process 10T of the following fruit.
A Cabernet Sauvignon at 14Be, pH 3.9 and TA 7.0. This wine is destined for a full bodied red style.
Indicate how much acid and the type of acid you will add and indicate the problems that the acid will have on future winemaking procedures. What solutions to these problems, do you suggest?
5 Marks
An appropriate yeast rehydration protocol is a critical step in avoiding stuck or sluggish alcoholic fermentation. Using a flow chart describe what are the key steps in rehydration and highlight which steps will limit stuck or sluggish alcoholic fermentation.
5 Marks
Critical factors: inoculation
• Temperature of water or use of juice at rehydration can be detrimental to yeast viability
• Yeast physiological restrictions & nutritional requirements must be respected
• Addition of complex nutrients (is this beneficial?)
• Inoculation rates/procedures must be technically qualified (i.e. manufacturer recommendations, trial & error)
• Winery hygiene, microbiological/chemical control
• Forward planning essential
Explain the evolution of total acid in a red wine from crushing to bottling. In your answer show the relationship of pH and total acid at the different stages.
Q9. 2014, 2015 (Worth 15 marks; recommended time to answer question is 15 minutes)
In all exams so far
Total acidity – a measure of the total organic acids present in a juice or wine
An analytical measure of the total organic acid species in a solution, viz H2T, HT-, T2-, H2M, HM-, M2- etc
Cannot be determined by titration (dianions have no titratable protons… T2-, M2-)
The juice pH
- at pH levels approaching 4.0, the risk of microbial spoilage is high and must be adjusted
- pH levels below 3.0 become marginal for both yeast and bacterial growth
Under conditions of high pH and high TA, aim for pH values
near 3.65 so that bitartrate precipitation results in pH
decreases.
Acid additions to red must should always be approached with
caution as acid associated with grape solids is generally
evenly distributed throughout the must volume only after
about a third of the way through fermentation.
Tartaric versus malic addition can only be considered where
MLF is not to take place. (Due to D/L mix)
Sensory advantages of one acid to the other is debatable,
with some winemakers attracted to malic acid because they
believe it provides for a more integrated sensory outcome.
A further risk, is the potential for succinic acid production
during the yeast fermentation. In 1998, up to 2.4 g/L
increases in TA were observed following alcoholic
fermentation, mainly due to succinate.
A. Define yeast assimilable nitrogen (YAN). (2 marks)
B. Outline the consequences of YAN limitation during alcoholic fermentation by yeast? (6 marks)
C. If a nitrogen addition is made to an alcoholic fermentation discuss the implications around the timing of this addition. (4 marks)
A. Definitions
- 2nd most important macronutrient after carbon
- Required for amino acids synthesis, therefore proteins (cellular structure, enzymes etc….)
- Minimum N to complete or maintain
- Maximum N or Total N used when present in excess
B. Consequences of nitrogen limitation
• H2S liberated ➔ no action, mercaptan
• Sugar transport slows or ceases
– Hexose permeases irreversiblely inactivated – Delayed additions may be slow to help
• Biomass formation limited
– Fermentation rate is a function of
• Fermentation stops !!!
C. Implications
- If added early it will speed up fermentation
- Increased yeast cell numbers
- Later addition leads to reduced cell numbers, reduced fermentation rate.
- Can not add belwo 4 baume, too much excess
The success of alcoholic fermentation can be strongly influenced by the choice of the strain of active dried wine yeast.
Describe what are the key characteristics of the yeast strain that is required to undertake fermentation of the following musts.
a. Grenache, 13.5° Baumé at harvest, yeast assimilable nitrogen (YAN) 75 mg/L
b. Shiraz, 16° Baumé at harvest, YAN 300 mg/L Include in your answer recommendations for nitrogen management strategies to undertake these two fermentations.
15 marks
What a wine maker wants from a yeast =
• Survive, adapt and grow under
- – Anaerobic
- – High sugar (10-15oBé)
- – pH below 4.0
- – Temperature range 8-35oC
Basic features
- Tolerance to sugar, alcohol, SO2
- Predicable & controllable
- Desirable fermentation by-product
- profile
- Nitrogen demand
Special features
- Low temperature fermentation
- ß-glucosidase, fermentation aromatics – Mouthfeel & phenolic extraction
- Colour enhancement
- Compatibility with Lactic Acid Bacteria
A number of factors influence microbial control in winemaking, in-particular relation to winery hygiene. Describe how winery design and effectiveness of cleaning and sanitation are important for microbial control.
10 Marks
Cleaning of hoses and pumps
- run caustic thought the hose
- then citric acid
- then water
- clean before each use as you dont know what the person before did
Cleaning is the removal of extraneous or unwanted material or any matter, solid or liquid, that is foreign to a particular surface
Sanitation is the maintenance of unwanted matter or microorganisms at a level that prevents potential negative effects on quality
Sterilisation is the complete elimination of microorganism.You can’t be half pregnant!
Objective = minamize numbers or completely iliminate, more effective when there are fewer numbers, Bacteria, yeaste, mould, phage and viruses.
Control of microorganisms
- Control access of microorganisms to grapes & wine
- Physical removal of microorganisms
- Prevent or reduce growth
- Kill cells or spores present
Factors to conider in cleaning and sanitisation
- Winery design
- Equipment
- Training of staff
- Effectivness of cleaning and sanitation
Aspects of winery design
▪ Inside & outside must be considered
▪ Equipment must be positioned to allow easy
access for cleaning
▪ Winery floor should be sloped and resistant to sanitising chemicals
▪ Equipment should be graded as potential sources of contamination: incorporated into quality management programs
Basic sanitation principles
- Winery kept free of refuse inside & out
- Equipment arranged in orderly way, work areas free of clutter
- Entire winery cleaned on regular scheduled basis
- Winery protected against; bacteria, yeast, moulds, insects, and rodents
- Premises, equipment & cooperage inspected monthly
Explain the evolution of Sulphur Dioxide in both red and white wines from crushing to bottling. In your answer show the relationship of both free and bound forms at the different stages. Use a diagram
Worth 20 marks; recommended time to answer question is 20 minutes
White wine
- SO2 during crushing and/or at the Press are likely to be predominately reflected.
- It cannot be assumed that SO2 levels are maintained after additions/measurement.
- approximately 30% of added SO2 remains in the free form, while approximately 70% becomes bound.
Red wine
- SO2 additions (if any) to reds should be minimal
- to avoid the bleaching of red colour.
- Importance of SO2 in its antimicrobial action must not be underestimated.
- It is difficult to collect representative samples from grape must, therefore in the case of red musts following crushing and destemming, rates of SO2 addition should take account of the fruit condition, the ease to which the fruit was picked (i.e. without damage) and the must temperature.
- SO2 additions to red wine are best made as small increments.Free SO2 cannot be equated for both red and white must, juice and wine.
- pH values are generally lower in whites, favouring more Free SO2.
- most of added SO2 in reds is in the bound form.This bound form in reds can be sub-divided into loosely bound SO2 (e.g. anthocyanin- SO2) and firmly bound SO2 (e.g acetaldehyde-SO2 complex).
- During SO2 determination by aspiration the loosely bound SO2 is continually released and sparged out of the red must/juice/wine.
- As a general rule, 15ppm Free SO2 in reds is equivalent to about 5ppm Molecular SO2, this being considered adequate protection.
- If MLF is to take place, Total SO2 levels must be maintained as low as possible (less than 50ppm and preferably less than 30ppm) to avoid problems associated with the growth of the Oenococcus.
