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    freeze roasted beans will lose flavor

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I bought some roasted SO beans and some green SO beans for experimenting with coffee blends. At the roasters. these roasted beans came out from a cool-room freezer. So when I got home, I put them in the freezer too. The roasted SO beans i bought tasted great, I tried indonesian sulu wesi, indonesian mandheling, brazil, ethopian . I tried them like 1-2 days gap, with condense milk. I am not a regular coffee drinker, so I had to stretch the coffee drinking a bit, to sink in the taste,flavor,aroma,etc. The next stage, I mix these SO roasted beans and play around the proportions - tasted aweful. Something seem wrong, so I went back to test the SO manhedling, the flavor was not the same as I 1st bought it. I think frozen roasted coffeebean may have spoil the flavor, or time gap (3wks from 1st taste) have been too long a shelf life for the coffee. I pound the coffee beans before every brew. My next stage is to roast the green beans and compare my roast with the ones I bought. But since my purchase roasted beans have gone off flavour, I think I am stuck with 250gmX4(variety) of flavor expired beans, can I re-roast them to lifen them up? Can anyone shed some light pls, thanks in advance. Also - I bought these beans and had these plans before knowing about this coffeesnobs site, then I spent many weeks going over the blend section and was a great help in getting me educated on the do's dont and trials and errors of other experts or hobbyists in this blending game. Thank you

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    Member Tony_Barista's Avatar
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    The first place you went wrong was putting them in the freezer! Once coffee is roasted it needs to be placed in a sealed bag to age between 5 and 14 days to get the best results. Coffee is very delicate, It hates the cold/heat and sunlight. Keep then in a airtight container in the cupboard and only grind as you need. As ground coffee will go stale after 10-15 minutes after grinding and whole beans will go stale within 24 hours out of the bag.

    Re roasting beans will not get them back to life. Best thing to do is toss them in the bin and start again. Blending coffee is an art form and takes many years of practise and kg too. start off with a nice base coffee like a brasil or a colombia and add 20% here and 10% there of other beans to get the flavour you want.

    Hope this helps

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    Senior Member Vinitasse's Avatar
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    Quote Originally Posted by otahotah View Post
    I pound the coffee beans before every brew.
    Yikes!!! I hope you meant to say "I grind the coffee beans..." or do you really pound them?????!!!!!! If you do it is definitely time to buy a proper coffee grinder as this will make all the difference in the world.
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    Understand your reaction re pounding.

    Bear in mind the fact that a large part of the coffee drinking word do in fact grind their beans using a mortar and pestle or similar ASMR Kitchen - Mortar Pestle 02 Grinding Coffee - YouTube looks like the bloke in the clip did a pretty good job, not sure I would have the patience to spend 7 mins grinding a few grams of coffee in a M&P.

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    Senior Member Vinitasse's Avatar
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    Quote Originally Posted by Yelta View Post
    Understand your reaction re pounding.

    Bear in mind the fact that a large part of the coffee drinking word do in fact grind their beans using a mortar and pestle or similar ASMR Kitchen - Mortar Pestle 02 Grinding Coffee - YouTube looks like the bloke in the clip did a pretty good job, not sure I would have the patience to spend 7 mins grinding a few grams of coffee in a M&P.
    I'm well aware of that and I am pretty sure that somewhere in the world there are people who still rub sticks together to get a fire going as well. What surprises me is that it is possible to find someone on Coffee Snobs who "pounds their coffee" and then expresses shock that the results in the cup are inconsistent and disappointing

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    Senior Member Barry O'Speedwagon's Avatar
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    Welcome Otahotah,

    Where are you located? Singapore/Malaysia (just guessing from the username)? I'm also guessing that your roaster had been keeping the beans in the freezer because their shop has no air con. As the others have said, freezing the beans isn't a great idea, and certainly don't try roasting them twice (save that for duck ) I'd consider the frozen roasted beans as a learning experience, and concentrate on getting the best out of your green beans. Try to find somewhere dark and cool, but not freezing.

    Cheers
    BOSW

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    thanks to everybody who commented on my thread. yes I pound them, this way i can see the and feel and examine the roasted beans that i bought, for example the ethopian had heaps of peals (silver something cant think of the jargon). One of the SO had beans that are crunchy brown, others the feel and texture is a bit different. One could slowly smell the aroma, and guess what - after I brewed them I even kept the sediments/coarse bits in a small port glass for 5days - and coming back for a sniff. From pounding the beans to brew to drink to after-sniff, I noticed some beans still have the power-in-the aroma whilst others faded. In particular, the brazilian and manhedaling but less so the sulawesi and ethopian. I am located in sydney, I bought those beans from a reputed local roaster, my aim is to recreated the typical southeast asian coffee which they drink with condensed milk. So it may seem odd me being a newbie, not a coffee addict, doing things may seem out of the ordinary. But hopefully I can create the blend recepes of say indonesian aroma kopi etc. Their mix would be some robusta, liberica, arabica roasted with sugar margarine sesame salt corn(maybe) . Try this in your roaster or grind these in your grinder and you will spend hrs cleaning the equipment. I will plod along with this experiment and see what i encounter. Thanks again for all your input.

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    Freezing works fine if you freeze it in an airtight container (so it doesn't absorb the freezer smells) then don't open the container until fully thawed (so condensation doesn't form on the beans).

    I've got a bag thawing at the moment that I'll crack open tomorrow morn. Went a bit overboard testing out a new roaster a few weeks back

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    Quote Originally Posted by Hamburglar View Post
    Freezing works fine if you freeze it in an airtight container (so it doesn't absorb the freezer smells) then don't open the container until fully thawed (so condensation doesn't form on the beans). I've got a bag thawing at the moment that I'll crack open tomorrow morn. Went a bit overboard testing out a new roaster a few weeks back
    my coffee beans comes in those special coffee heavy duty clear plastic bags with zips and with a 1-way purge value.

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    Quote Originally Posted by Yelta View Post
    Understand your reaction re pounding. Bear in mind the fact that a large part of the coffee drinking word do in fact grind their beans using a mortar and pestle or similar ASMR Kitchen - Mortar Pestle 02 Grinding Coffee - YouTube looks like the bloke in the clip did a pretty good job, not sure I would have the patience to spend 7 mins grinding a few grams of coffee in a M&P.
    I saw the youtube video, this chap is using force to crush the beans. Its strenous and time consuming. A better approach is just put the mortar pestel into a large plastic bag and pound away, instead of crushing the beans. pound away means - the distance of at least 20mm to 40mm distance between pestal and motar base. Initially when the beans are whole, then reduce this distance, Once there is less chances of spill 40.60mm distance is OK. - The spills are trapped in the bag. The pestal must not be flat but oblong, The motar must also be eclipse-shape instead of round. Then pounding is easy relax and fun.

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    Senior Member Vinitasse's Avatar
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    Quote Originally Posted by Hamburglar View Post
    Freezing works fine if you freeze it in an airtight container (so it doesn't absorb the freezer smells) then don't open the container until fully thawed (so condensation doesn't form on the beans).

    I've got a bag thawing at the moment that I'll crack open tomorrow morn. Went a bit overboard testing out a new roaster a few weeks back
    I can't say that I agree with this... at all. Airtight or not, there is some water present in the beans and this water will freeze, cell walls will rupture and there will be effects at both the molecular and macro levels. Other changes also occur to the oils within the beans so please never assume that freezing is benign... because it ain't.
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    Quote Originally Posted by Vinitasse View Post
    I can't say that I agree with this... at all.
    Well have you actually tried it?

    Cell walls rupturing? Other changes occurring to the oils? Please cite evidence.

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    Quote Originally Posted by Hamburglar View Post
    Well have you actually tried it?

    Cell walls rupturing? Other changes occurring to the oils? Please cite evidence.
    I'll cite my palate as evidence. Nevertheless, should your palate be in disagreement, you should do whatever suits it best
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    Serious question -will it really be possible to tell if the coffee isnt at its best, after adding sweetened condensed milk, margarine, sugar, sesame (!) and corn (syrup?)?

    Ive had the coffee in Malaysia, which is commonly served with sweetened condensed milk; I dont think much origin character is getting through that.

    The OP states he isnt a regular coffee drinker; are you just getting into coffee, or are you hoping to make this for groups of friends?

    If its the former, I'd like to suggest trying a coffee with less additives
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    Quote Originally Posted by Talk_Coffee View Post
    I'll cite my palate as evidence. Nevertheless, should your palate be in disagreement, you should do whatever suits it best
    Comparing frozen for a few weeks/months vs sitting on the shelf for the same length of time? Or comparing frozen for a few weeks/months vs freshly roasted?

    I'd pick frozen over 'aged on the shelf' any day of the week..... but definitely not over freshly roasted stuff.

    This is the 2nd pour of the day. Just thawed out last night. It's a Rwandan, just over 3weeks old, and still has slightly harsh acidity and uberfizz crema of freshly roasted stuff. If I hadn't frozen it, by now it'd be a spotchy oily mess which would be almost ready to bin.
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    Last edited by Hamburglar; 6th May 2013 at 09:32 AM.
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    Senior Member Dragunov21's Avatar
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    Quote Originally Posted by Hamburglar View Post
    Well have you actually tried it?

    Cell walls rupturing? Please cite evidence.
    Flash freezing - Wikipedia, the free encyclopedia

    It's kinda common knowledge, and I'm talking scientific, not old-wives' tales. Can't comment on the rest of it. I would be very surprised were there any chemical changes to the oils themselves.

    Quote Originally Posted by Hamburglar View Post
    I'd pick frozen over 'aged on the shelf' any day of the week..... but definitely not over freshly roasted stuff.


    Perhaps, but if you come on a specialty watch forum arguing that your Casio is awesome because it beats the heck out of the knock-off watches you buy for $2 weekend markets, you may be right in the comparison but people are still going to tell you that your watch sucks in the greater context.

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    What does a coffee cell membrane even taste like?

    If your google-fu is good enough to find that wiki article then surely you can find plenty of info on freezing roasted coffee.

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    Senior Member Dragunov21's Avatar
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    Quote Originally Posted by Hamburglar View Post
    What does a coffee cell membrane even taste like?

    If your google-fu is good enough to find that wiki article then surely you can find plenty of info on freezing roasted coffee.
    Surely, but I'm not in the business of doing someone else's research for them if I'm not interested myself.

    The idea stems from the fact that the cell-damage caused by slow-freezing negatively affects texture and (I believe) allows accelerated degradation (reactions like oxidation) upon thawing. Freeze a mushroom and let it thaw if you want to see it in action for yourself.

    Whether or not this is applicable to coffee or not is up for [s]debate[/s] research, but as someone who feels that constant access to freshly-roasted coffee is a cakewalk, I'll leave that research to those who insist on storing coffee for extended periods.

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    Quote Originally Posted by Dragunov21 View Post
    Whether or not this is applicable to coffee
    Yes exactly!

    Mushrooms, cell membranes, oil degradation, molecular damage, casio watches. Trying to apply it to frozen roasted coffee is just psuedoscience in action.

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    Quote Originally Posted by MrJack View Post
    Serious question -will it really be possible to tell if the coffee isnt at its best, after adding sweetened condensed milk, margarine, sugar, sesame (!) and corn (syrup?)? Ive had the coffee in Malaysia, which is commonly served with sweetened condensed milk; I dont think much origin character is getting through that.
    coffee shop coffee is usually so-so, wholesale supply of the powder ranges from A$2.70/500gm to A$3.50/500gm. Glass of coffee at coffee shops cost around A$0.50c market stalls coffee is around A$4 A$5 per 500gm. 1 particular stall/supplier dominates the sales, this is in east malaysia. The beans are roasted with the mix recepes I mentioned earlier. The aroma, taste and body feel is awesome, I have grind them before and even left the beans for about 2months and the aroma is still intense but a little less perfume 'if you know what I mean', the body feel still very good. If I have another opportunity I will go through the roasted beans with a mag glass to seperate out all the bits to investigate further. The "speciality blend secret recepe " in this type of coffee is heavily sort after, and they monopolise the market. "the body" in the coffee, simply look on the milo tin recepe, they have wheat, corn, comprising a large percentage in the drink like 35%, this feel in good coffee is really satisfying. I am just giving a shot at trying to create this blend.

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    Quote Originally Posted by Hamburglar View Post
    Yes exactly!

    Mushrooms, cell membranes, oil degradation, molecular damage, casio watches. Trying to apply it to frozen roasted coffee is just psuedoscience in action.
    Er, no, it's just a lack of information that may or may not be out there (do coffee beans not have molecules or something?)

    Look, based on the information that's readily available, if you freeze beans (that contain moisture) then thaw them, we can reasonably infer that they will degrade/stale faster than fresh beans.

    I roast my own beans in a popper weekly; staling is not an issue that affects me. If you care whether or not freezing affects bean quality, do some subjective experiments yourself or do some research to see if someone else has done objective research.

    If you just care that you have the best coffee you easily can then get a popper/coretto and forget the whole debate.

    If you don't care about it if finding the answer is harder than asking someone to spoon-feed you, then just enjoy your defrosted coffee.

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    Quote Originally Posted by Dragunov21 View Post
    Look, based on the information that's readily available, if you freeze beans (that contain moisture) then thaw them, we can reasonably infer that they will degrade/stale faster than fresh beans.
    *Facepalm*

    You're just putting 2 and 2 together and getting 5.

    Where is this info you're talking about that relates directly to roasted coffee beans? Fresh mushrooms and the like are a helluva lot different to roasted coffee beans.

    I have messed around with freezing roasted coffee and haven't had any problems with it degrading prematurely. It certainly doesn't degrade as quickly as stuff that sits on the shelf at room temp for the same amount of time. My conclusion is that it seems like an effective way to store roasted coffee if you're stuck with a whole bunch of it that you can't possibly use within a few weeks time.

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    If you refuse to get it I'm not gonna spell it out for you; feel free to consider it nonsense.

    Your conclusion is probably correct, but it doesn't mean that freezing beans doesn't cause problems and it's not too hard to avoid a situation in which you'd have to freeze them anyway.

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    Freezing coffee beans for storage is a much debated topic.
    Do a search over on HB for a few days worth of reading and be sure to find the article "To freeze or not to freeze" .
    They did some rigorous testing and concluded that there was no detectable difference.
    Further searching will also reveal that it is also not unusual to grind the beans direct from the freezer whilst still frozen !
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    I don't place too much trust in a lot of stuff HB or what anyone else writes for that matter. Fudged results and hidden agendas will generally deliver the required results.

    Roast some beans and freeze some and store the others (properly). Give 'em time and taste them. As I previously suggested it's your coffee and you do what suits you.

    Bottom line is if you think freezing is best, no amount of text here, on HB nor from the mouths of sirens for that matter is likely to convince you otherwise. Live and let live, but please don't force feed!
    Last edited by TC; 6th May 2013 at 05:36 PM.
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    What about the fridge?

    When I roast some Decaf WOW, if I was leave the entire batch in the one way valve bag for say 3 days to de gas a bit. Then put half the beans in a vac sealed bag and put them in the fridge.

    Surely they would have to keep better than sitting in the normal bag at room temp continuously exposed to air?
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    Yes! Finally some sense rather than unfounded 'science'.

    I don't think anyone here thinks freezing is best. I certainly don't. Even if they did taste identical it's still just making life more complicated.

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    We use a wine fridge set to 18 degrees C

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    As the frozen bean banter has missed the very 'discussable', and far more black and white post by the OP...
    Quote Originally Posted by otahotah View Post
    coffee shop coffee is usually so-so, wholesale supply of the powder ranges from A$2.70/500gm to A$3.50/500gm. Glass of coffee at coffee shops cost around A$0.50c market stalls coffee is around A$4 A$5 per 500gm. 1 particular stall/supplier dominates the sales, this is in east malaysia. The beans are roasted with the mix recepes I mentioned earlier. The aroma, taste and body feel is awesome, I have grind them before and even left the beans for about 2months and the aroma is still intense but a little less perfume 'if you know what I mean', the body feel still very good. If I have another opportunity I will go through the roasted beans with a mag glass to seperate out all the bits to investigate further. The "speciality blend secret recepe " in this type of coffee is heavily sort after, and they monopolise the market. "the body" in the coffee, simply look on the milo tin recepe, they have wheat, corn, comprising a large percentage in the drink like 35%, this feel in good coffee is really satisfying. I am just giving a shot at trying to create this blend.
    It sounds like you are trying to replicate a form of 'instant' coffee?

    If you are impresses by the aroma of 2 month old grinds, perhaps you should have a smell of some really fresh grinds. No comparison (regardless of origin/blend). The body is probably the result of the cornstarch/syrup, not the stale coffee.

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    Quote Originally Posted by Hamburglar View Post
    Well have you actually tried it?

    Cell walls rupturing? Other changes occurring to the oils? Please cite evidence.
    Refrigeration and/or freezing is regarded as a failure as it causes the moisture and lipids to emulsify, accelerating oxidation and observably rendering the coffee somewhat gummy. And... if you really need citable evidence to reinforce logic... The Technical Standards Committee of the SCAA does not recommend freezing because testing indicates that freezing diminishes flavor. Please feel free to look into this further if you must.

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    Thanks. That's what I was looking for.

    But why delete the "probably?" And leave out the sentence "Some have found freezing to be adequate (reportedly most successful with dark roasts, with low moisture content)?"
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    Quote Originally Posted by MrJack View Post
    As the frozen bean banter has missed the very 'discussable', and far more black and white post by the OP...

    It sounds like you are trying to replicate a form of 'instant' coffee?

    If you are impresses by the aroma of 2 month old grinds, perhaps you should have a smell of some really fresh grinds. No comparison (regardless of origin/blend). The body is probably the result of the cornstarch/syrup, not the stale coffee.
    I bought the roasted coffee beans then I ground a handful, then left some beans for 2months in plastic bag stored in proper conditions, ground this lot, and the coffee is still as impressive only slight loss of aroma.

    some experiment needs to be done here, but i guess the sugar marjarine mix must have caramalized and seal the roasted bean to maintain freshness and balanced the bitterness. The wheat corn component strengthen the body-ness in the mouth feel.
    Its the 1st gulp impression and satisfaction that 1 gets.

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    Senior Member Vinitasse's Avatar
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    Quote Originally Posted by Hamburglar View Post
    Thanks. That's what I was looking for.

    But why delete the "probably?" And leave out the sentence "Some have found freezing to be adequate (reportedly most successful with dark roasts, with low moisture content)?"
    Easy answer... because "probably" is a scientifically useless word and means absolutely nothing and.. secondly... just because "some" have found freezing to be "adequate" does not mean much to me either. "Some" believe in the man in the moon too... and the findings of the very few do not rule out the findings of the many... I think the conclusions drawn were clear... keep your coffee out of the fridge and/or freezer... period.

    And.. if you're into "dark roasts, with low mositure content" it really doesn't matter one way or the other as the coffee was already killed in the roaster to start with.

    Of course... wine fridges/cabinets are the exception as they approximate ideal storage conditions at 14-16 degrees.

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    So you've manipulated the article quote to suit your point of view. What's the point of even discussing this stuff if you can't be open, honest, and objective?

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    Great thread guys! Are you sure this OP isn't just pulling your leg? I personally think that anyone who adds margarine to coffee and then super-heats it can stick the result anywhere they like, including the freezer!

    I'm not convinced of the water and ruptured cell wall argument, that's pretty much what happens during roasting - most obviously during 1st crack. Perhaps you can freeze roasted coffee, if you have to. I'm personally in the don't freeze camp, mostly based on experience with other aromatics that go into the freezer, only to emerge missing the desired vitality. I suspect it's a bit like freezing your cat, it's still a cat when it's thawed, there's just something missing.
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    Quote Originally Posted by Hamburglar View Post
    So you've manipulated the article quote to suit your point of view. What's the point of even discussing this stuff if you can't be open, honest, and objective?
    Open... I told you where the article was so you could read it yourself
    Honest... I told you what I edited and why
    Objective... I have experimented with freezing, and therefore have visited both sides of the coin... objectively... and very quickly concluded it was a crap storage medium

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    Quote Originally Posted by habahabanero View Post
    Great thread guys! Are you sure this OP isn't just pulling your leg? I personally think that anyone who adds margarine to coffee and then super-heats it can stick the result anywhere they like, including the freezer!
    It's all real I'm afraid... it's a commonplace coffee-like-beverage prevalent throughout SE Asia

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    Quote Originally Posted by Vinitasse View Post
    Open... I told you where the article was so you could read it yourself
    Honest... I told you what I edited and why
    Objective... I have experimented with freezing, and therefore have visited both sides of the coin... objectively... and very quickly concluded it was a crap storage medium
    Only after the fact when you were called out on it...

    I'll be honest, I don't think much of Hamburglar's ability to reason or hold a logical train of argument, but editing the wording of cited resources to apparently strengthen your point isn't a good look...

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    I was in the middle of roasting at the time and didn't have much time for mucking about.

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    With regard to the modified quote, I emphatically disagree that "probably" is an unscientific word- it pertains to the level of certainty of the conclusions, and there is a world of scientific difference between "probably does" and "does". But in any case, the science is lacking. This particular quote is from the SCAA's newsletter. The things that jump out at me are that the people supporting freezing are "some" anonymous people, and that the argument against freezing is based on an uncited conclusion from the SCAA Technical Standards Committee based on uncited 'limited testing', the nature and results of which are unknown. Neither conclusion is particularly strong. The statement about moisture and lipids emulsifying lacks detail and is uncited, and there is also no evidence provided to justify the statement that the effect of this is "probably accelerating oxidation". Some have argued that temperature does make a difference, but that oxygen and moisture are the most important factors (as expected) Predicting Algorithms for Oxygen Uptake and Shelf Life of Dry Foods and the Application to Coffee. These authors only went down to 4 degrees though, not freezing, and the results are based on ground coffee so they are not directly applicable here either. I also don't believe this was peer-reviewed.

    Confirmation bias is likely to play a significant role when tasting as well. Vinitasse has experimented 'objectively' with freezing, and finds freezing to significantly degrade the coffee, but the details of the experiments are not provided. I would suggest that unless it was at the very least a blind test, the results do not generalize. Of everything I have seen, HB's 'To freeze or not to freeze' is the most rigorously justified viewpoint, regardless of the possibility of "fudged results and hidden agendas" - at least there *were* results for a change, and the results were even provided for all to see! There is always the possibility of hidden agendas- so in the absence of substantive claims I'm not convinced that this is an adequate criticism of the HB article.

    I don't think anyone is disputing that fresh is preferable to frozen, but it *is* a valid question to ask how long coffee needs to be kept before storing in the freezer is preferable. Is 3 weeks in the freezer better than 3 weeks on the shelf? 4 weeks? 6 weeks? Pretty much everyone agrees that you need to store coffee in an airtight container, ideally with a one-way valve, with minimal moisture, and away from sunlight. The fact that there is this level of uncertainty about freezing suggests to me that the effect of freezing is not likely to be on par with these other factors, and would be much more minimal (which is the same conclusion as the linked article). As with most others here, I don't see any need to freeze my coffee any time soon. Incidentally, I think Hamburgler had a Behmor roaster, and would likely know just as much about fresh coffee as anyone else here.
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  41. #41
    Senior Member Vinitasse's Avatar
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    Quote Originally Posted by papagoose View Post
    Incidentally, I think Hamburgler had a Behmor roaster, and would likely know just as much about fresh coffee as anyone else here.
    I wasn't aware that the ownership of a Behmor was recognized as proof of such knowledge. Has that credential been peer reviewed?
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  42. #42
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    Quote Originally Posted by Vinitasse View Post
    I have experimented with freezing, and therefore have visited both sides of the coin... objectively... and very quickly concluded it was a crap storage medium
    Yes! Now that's the kind of stuff that's useful. Why not just say it at the beginning? Rather than talking at us like you're Illy reincarnated and inventing "facts" about physical/chemical changes happening inside the bean during freezing. There would be no reason to misquote then try to spin "some" clever english to justify it.

  43. #43
    Senior Member Dragunov21's Avatar
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    Dude. Seriously.

  44. #44
    Senior Member smokey's Avatar
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    I love this thread so much that I am going to bump it!

    The thread title, "Freeze roasted beans will lose flavour", deserves argument because there is no evidence besides hearsay on this thread one way or another.

    OK, I want to argue the science behind staleness. Its all about exposure to Oxygen - O2. O2 is a very unstable and very reactive molecule, as an atom it has 2 electrons orbiting the nucleus, instead of orbiting in opposite directions they orbit in the same direction, this creates instability. When O2 approaches another molecule it grabs that molecules electrons which in turn destabilises them as well.

    This process is called Oxidation and is the foundation of disease and inflammation. We can use antioxidants like Vitamin C which replaces the stolen electron back to the damaged molecule to cure illness.

    Oxidation plays a huge role in food spoilage, we cook, salt, tincture, smoke and dry foods to prevent oxidation aka food spoilage. We have even developed specific chemicals that will prevent and or slow the oxidation process in our foods, problems arise when we then ingest these chemical along with our food, but thats another thread.

    Oxidation occurs only in the presence of O2, there are other biochemical pathways but lets stick to Oxygen and its oxidation process for simplicity's sake. Thus removal of O2 and we prevent oxidation.

    Oxidation needs temperatures above freezing (although below 0 C oxidation events do occur but this is very very slow). So freezing your food (steaks, bananas, cakes, beans, etc) will slow the oxidation aka staling process.

    Oxygen is part of water, H2O, so any moisture present will seep into the bean causing an avalanche of oxidation.

    The question I am arguing is, "does freezing harm the roasted coffee bean's flavour?"

    The answer should become obvious as we look at the fresh roasted bean. The roasted bean has its natural cell structure changed beyond recognition, temperatures of above 200 C will sure denature cell membranes, proteins denature and carbohydrates take on precarbon forms ready to burst into flame, the ultimate oxidation expression. All water and moisture is driven off during the roasting process, there is minimal to no water present in the bean at the time roasting stops.

    Once the bean begins to cool it begins to oxidise in the presence of air forming flavour compounds and eventually rancidity and staleness. There is no way to stop oxidation at this stage of the now warm and dry bean. The roasted and therefore very dried beans, are now extremely hydroscopic, they are now active water seekers, the bean cells are as dry as a dead dingo's donga and will absorb massive amounts of O2 rich moisture if allowed to. If water is allowed to seep into the bean at this stage oxidation will occur at a rapid pace. It is difficult to prevent if you roast on a humid day, but air contains moisture anyway so leaving them out uncovered for too long is not good.

    If there is high humidity present then the pulled roasted beans will immediately soak up this moisture.

    Once the beans have been cooled they are put into a plastic bag or container and placed in a cool place. But this too presents its own problems because there will be a small amount of moisture and there will be air in and around the beans regardless of how careful you have been. Thus we have the window of 3 to 8 weeks while the beans slowly go stale/oxidise.

    So now we need to see how temperature affects oxidation/staleness. Anything above freezing will oxidise faster than below freezing. If you can freeze your beans with minimal air/O2 and with minimal humidity then you are going to reduce the rate of oxidation inside the bean. In other words freezing your fresh-roasted coffee beans WILL slow the staling process, its basic chemistry, drop the temperature and oxidation slows.

    An example, leave one of your t-bone steaks out in the sun and the leave the other frozen and see which one oxidises/goes rancid the fastest.

    Does freezing affect the flavour of the bean? Not in the short term, but yes in the long term, oxidation continues while frozen, but at a much reduced pace. The quality of flavour should remain much longer than beans not frozen for the same length of time. For example, beans frozen and thawed at around 2 months should initially taste awesome compared to a pack of beans stored in the cupboard for 2 months.

    However, once thawed, the beans will begin to oxidise in earnest, so they will not last as long once thawed, so don't expect them to last the usual 3 to 4 weeks. I would recommend using them up to 2 weeks max.

    A long winded lecture I know, I hope it explains oxidation and staling, I studied food technology and chemistry many years ago and worked in the food industry for some years so know a little about this topic

    I welcome comments on this fascinating topic.
    Last edited by smokey; 3rd December 2013 at 03:12 PM.
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    Senior Member Journeyman's Avatar
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    On another thread there are some comments about outgassing of CO2 from new beans. Do you think this would be something to wait for before freezing beans or might it be better to vac-pack and freeze immediately to slow the outgassing as well?

    I don't have a roaster myself so can't test it - unless I can get my local guy to release beans direct from the roaster...?

  46. #46
    Senior Member Dragunov21's Avatar
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    Quote Originally Posted by smokey View Post
    OK, I want to argue the science behind staleness. Its all about exposure to Oxygen
    I can't claim much knowledge of food chemistry, but I'll ask the question; when we talk about degradation of coffee beans, part of it is oxidation, but I get the impression that it is also a function of the loss of aromatic compounds, some of which evaporate (possibly not the correct term so go ahead and correct me) faster than others.

    Is that true, to the best of your knowledge, or no?

  47. #47
    Senior Member smokey's Avatar
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    Quote Originally Posted by Journeyman View Post
    On another thread there are some comments about outgassing of CO2 from new beans. Do you think this would be something to wait for before freezing beans or might it be better to vac-pack and freeze immediately to slow the outgassing as well?

    I don't have a roaster myself so can't test it - unless I can get my local guy to release beans direct from the roaster...?
    Hmm, good question Journeyman, I think outgassing is part of the flavour development and therefore necessary, so I think it needs to happen before you freeze. But this is still an educated guess, hopefully someone will do a live experiment and let us know the outcome.

    Just quickly, talking about flavour development, oxidation helps produce the flavours we enjoy, but it is a two edged sword.

  48. #48
    Senior Member smokey's Avatar
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    Quote Originally Posted by Dragunov21 View Post
    I can't claim much knowledge of food chemistry, but I'll ask the question; when we talk about degradation of coffee beans, part of it is oxidation, but I get the impression that it is also a function of the loss of aromatic compounds, some of which evaporate (possibly not the correct term so go ahead and correct me) faster than others.

    Is that true, to the best of your knowledge, or no?
    Dragunov21, thats a really good question, I haven't mentioned the essential oils / aromatic compounds and flavours. These have a lower boiling point than water, so warm temperatures will evaporate them, yes correct word

    Part of what happens to the oils is they go rancid in the presence of oxygen and free radicals. When a cell breaks down or is injured oxidation starts up with a vengence, free radicals are formed and act as a second line of offense to further degrade the oils and proteins etc.

    So yes, you are correct, once the roasted beans are exposed to air and temperature (and moisture), they will start to degrade due to these processes, - aromatic oils evaporate and they go rancid. In short they go stale

  49. #49
    Senior Member Vinitasse's Avatar
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    Or better yet... don't freeze the beans... EVER!

    Rather than compare meat left out in the sun vs meat that has been frozen... why not compare frozen vs fresh? Frozen will ALWAYS be second rate!

  50. #50
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    Quote Originally Posted by smokey View Post
    I love this thread so much that I am going to bump it!

    The thread title, "Freeze roasted beans will lose flavour", deserves argument because there is no evidence besides hearsay on this thread one way or another.

    OK, I want to argue the science behind staleness. Its all about exposure to Oxygen - O2. O2 is a very unstable and very reactive molecule, as an atom it has 2 electrons orbiting the nucleus, instead of orbiting in opposite directions they orbit in the same direction, this creates instability. When O2 approaches another molecule it grabs that molecules electrons which in turn destabilises them as well.

    ...

    I welcome comments on this fascinating topic.
    Smokey, there is so much nonsense in this post I don't know where to begin. For starters, electons don't orbit (queue quantum physics).



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