Shelf life of concentrate?

[Woodsrover]

So I'm getting myself a 600-gallon refrigerated milk tank that I will store sap in behind my sugar shack. Plans are to bring raw sap up 550 gallons at a time and transfer to this cold tank. From there I'll reduce it through my RO (which takes a lot of time with my little RO) until I'm ready to boil. I'm assuming this tank will keep my sap between 35-40 degrees for as long as I need to. Will 6%-8% sap keep for a few days at that temperature?

[Galena]

PM Dr Tim. He's the expert here on all things maple.

[wiam]

I had about 250 gallons of 8% Friday evening when I had an RO issue. Could not find an oring. I usually second pass to 18%. I ended up boiling that sap early Sunday morning with out a second pass. I don't believe the sap was over 40'degrees. There was a smell to the steam and a little off flavor.

[eagle lake sugar]

The bacteria will eat the sugar in your concentrate, lowering the brix. It will also spoil much faster than raw sap.

[Thompson's Tree Farm]

Does the tank work as a cooling unit?

[DrTimPerkins]

There is no way to know for certain. It depends upon the microbial load in the sap and concentrate, how clean you're keeping everything, the sugar content of the concentrate, and the time and temperature it comes in at and what you're holding it at.

The simplest way to think of sap is like milk. If milk would spoil during that time, so would sap. With concentrate everything becomes accelerated. It will spoil faster. The colder you can keep it the better (and sometimes it can come out of the RO rather warm). So 6-8% for a few days at 35-38 deg F is likely possible....probably not a week or more though. It is likely you could lose some sugar during that time, and you may find it going ropey if you leave it too long. Only way to know for sure is to give it a try.

[Woodsrover]

Thanks, Doc. Plans are to get this milk tank operational again and be able to keep this sap at 35-40 as long as I need. Most of the time it will hold raw sap but with my little 100gph RO I'd most likely have to start concentrating the day before I want to boil. The longest I'd need to keep concentrated sap is 24 hours. Like you say, we'll give it a go next year and see what happens.

Thanks for the input.

[Woodsrover]

Does the tank work as a cooling unit?

The evaporator is in the tank. It didn't come with a condensing unit but plans are to get one and make this tank operational again.

[DrTimPerkins]

When recirculating sap through an RO, it will warm up slightly each pass through the machine. So unless your bulk tank can keep up with the heat input, it may warm up the concentrate over that time.

[maple flats]

The last year before I got my RO, I had to sell sap to another producer. Over a 4 day period from Friday thru Monday I sold a total of just under 1200 gal of sap. That producer concentrated it to 8% and pumped it into a refrigerated tank held at 30 F. He then boiled it at an open house the following Saturday and he made Medium Amber. While there is no way to know , it might have made Light Amber had he boiled right away, but after storing it for 5-8 days and still making Medium Amber says that holding concentrate of 8% in that case worked for him.
The Medium Amber was good flavor, I know, because I got a 30 gal barrel back as my share.
This in no way says that holding concentrate at 35-40 for a few days will be OK but it points out that the specific batch he concentrated to 8% and stored at 30 degrees F worked in that case.
There may well be a huge difference in 30 F vs. 35-40 F in stored concentrate. All of the sap I took him was fresh and perfectly clear when he got it, and he concentrated it immediately upon delivery and the concentrate was immediately pumped to the cold storage tank and held at 30 F. His RO took the sap to 8% in one step, which may also be a factor, he did not have to make multiple passes.
I'm a believer in this enough that I'm going to get my newest milk tank operational if it tests good and I'll get a control that can go down to 30 F, I don't think a standard milk tank controller will get that cold, however, I may be wrong.

[markcasper]

It depends on the tank and model, I have one non working tank that goes down to 0 on the dial. Our former milkhouse tank that is still in the milkhouse can go down to 37, but I bent the dial to get it down to 30 degrees.

I had first hand experience this year of storing concentrate. If you go back and read some of my posts from 3 weeks ago its all there. In short, we had a huge, huge run and I was not ready to cook yet. The weather turned very cold a few days after this big 2 1/2 day run. I got all the sap brought in and had to start concentrating on a Thursday in order to get 1200 more gallons that would have turned to an ice cube in the woods tanks if I wouldn't have. Now this cold spell lasted a week getting down to near zero several nights. There was ice in all of my tanks. I had about 6000 gallons of sap on hand. I concentrated 3000 gallons on Thursday, another 1200 on Friday, and the rest on the following Monday or Tuesday. I had to work in town during that time frame so that put me even more behind. I finally got cooking by Wednesday night and ran the concentrate through the RO a second time headed for the evap.

The concentrate was coming into the RO for the second pass at 34-36 degrees. The concentrate tanks had lots of ice in them. The first barrel was close to light amber and the second barrel got darker, either a high dark or medium. (I didn't have my grader at the time) It had a darker smell to it when it was drawing off, but not too strong. Keep in mind....500 gallons of this sap was 16 days old by that time. The rest of the sap would have been 4-5 days old before that Thursday start of concentraing. The cold was so intense that it was a mere chore to have to deal through, everything I wanted to do took way longer because of stuff freezing up and having to spend extra time dealing with all of this.

[Bucket Head]

I have kept 10% concentrate in a working dairy bulk tank (at 36 degrees) this year for up to five days with good results. The sap prior to ROing looked good due to the cold so that helped I'm sure. The sap I've collected this week doesn't look the greatest, but I'm trying it. We will boil the concentrate this Sat. and we'll see how that turns out.
Overall, I'm happy I got this tank going and it has been a big help seeing my father and I can not boil every day.

[Woodsrover]

When recirculating sap through an RO, it will warm up slightly each pass through the machine. So unless your bulk tank can keep up with the heat input, it may warm up the concentrate over that time.

These tanks are meant to take 101.5 degree milk down to 40 degrees fairly quickly so I'm assuming it will handle any temperature rise from the RO easily.

[DrTimPerkins]

These tanks are meant to take 101.5 degree milk down to 40 degrees fairly quickly so I'm assuming it will handle any temperature rise from the RO easily.

Yes, with the correct compressor. It was unclear whether the bulk tank was operational and the original compressor worked or something different was being used to cool the sap.

[Bucket Head]

After reviewing my entries on the calendar as to what we collected and when we boiled, I did hold some 10% concentrate for six days at 36 degrees. It made some nice Amber syrup.

I don't know how low my temperature setting will go on the tank. I know 35 is the last number on the scale but there are a few more lines past the 35.

[Bucket Head]

And Woodsrover is right. These tanks don't have to work very hard to keep sap cold. They don't run long trying to bring 45-50 degree sap down to thirty something. And they hold it there for quite a long time also. They don't run as frequently as you would think. They can handle cool sap in March a lot easier than warm milk on a 90 degree day in July!

[Woodsrover]

Thanks, Bucket. I got this new tank home last night and though I haven't opened it up yet, plans are to get a condenser unit for it and get it operational. I may not need to keep concentrate longer than overnight but I'd like that option if I need it. With the weather this past year keeping raw sap was difficult at times. It would be nice to have a place to dump 600 gallons of sap and not have to worry about it if we get two or three 65 degree days like we did this past February.

Will keep you posted on what it takes to make this thing chill!

[Buddy 58]

Question for you guys that do have tanks with ( working ) cooling systems , Are you using the agitator to slowly turn the contents of the tank ? For those of you who don't know the agitator motors are geared down to slowly mix what is in the tank .

[Bucket Head]

Yes. Having the ability to keep sap or concentrate cool has been a huge benefit to us. I always wanted to do it but I never had a chance to get a bulk tank with a compressor until I bought this last one. The others I have did not have any cooling parts with them.

My agitator is operational. It comes on automatically when the compressor comes on. It needs to operate or you get ice build up on the bottom of the tank where the cooling plates are. The agitator ensures the sap is cooled evenly and completely, and as quickly as it can. I would imagine it would take quite a while to cool a tank full without it and you would always have cooler sap on the bottom and warmer sap at the top due to warmer things rising.

[Bucket Head]

Just an update on what I mentioned earlier.

Took a closer look at the dial/scale on the temperature setting on my tank. It's minimum setting is 33 degrees.

So I turned it down to 33. We collected sap Sun. the 2nd and Mon. the 3rd. We ROed Sundays sap to 7 or 8% and then collected such a small amount of sap on Monday that we didn't bother ROing it and just added it to the concentrate from Sun. That diluted the concentrate down to a little over 6%. The sap wasn't the best looking stuff, but we figured we'd try it and see. We then kept that at 33 degrees until yesterday (Sat. the 8th) and boiled it. It ended up making some very nice dark syrup. And I'm not talking real dark- it wasn't very far off from amber when we graded it. I was surprised that it graded out so well! I figured it would have been pretty dark stuff.

So there is a definite benefit to keeping sap cold and a myth that you can not keep concentrate for any length of time. As long as it's held at a safe temperature I see no reason why it can not be boiled.

I know a working dairy tank isn't usually on anyone's maple wish list, but you might want to consider the investment someday if given the opportunity. Even if you don't concentrate, keeping raw sap cold is better than dumping spoiled sap because you couldn't get to it quick enough. We've been there too and didn't like it.

Steve

[DrTimPerkins]

So there is a definite benefit to keeping sap cold and a myth that you can not keep concentrate for any length of time.

There never was a question that keeping sap or concentrate cold would prolong the time you can hold it. There are a bunch of articles written about it if you look around. It is essentially like milk -- keep it cold and it'll stay ok longer. Concentrate is like "super milk." It'll spoil faster than sap, but keeping it cold will retard spoilage and prolong shelf life.

[Bucket Head]

That statement was for the folks who, for whatever reason, were still doubting that concentrate could be held. A lot of folks told me it couldn't be stored at all while I was trying to get my tank up and running.
I have not seen any of the articles you mention but I did speak with a representative from H2O Inovations a couple of years ago. He said, "they stored high-brix concentration for over a week with no degradation". I forget the exact percentage now but it was much, much higher than I was ever going to concentrate to, and probably higher than most of the forum users here would concentrate to.
I already knew that refrigeration would be a benefit but that statement about the high-brix was what sped up my plans for the bulk tank. If they could hold that than I could hold mine until we could boil it.

Steve