Acidified Foods

The Food Processing Center Author

03/27/2018 Added

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This lecture discusses the principles of acidified foods. In general, it covers definitions, regulations, and exemptions related to acidified foods, pH and acidity in foods, acidification procedures, thermal processing for acidified foods, and some processing considerations.

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[00:00:05.060]Okay.
[00:00:06.330]So this lecture will be covering acidified foods.
[00:00:10.360]And this is for our Science of Safe Food:
[00:00:13.430]Food Safety for Farmer's Markets series.
[00:00:17.425]And principles of acidified foods.
[00:00:19.090]Again, we're going to have a similar outline
[00:00:21.580]covering a little bit of the history
[00:00:22.970]and then working through our definitions
[00:00:24.850]and some of our regulations.
[00:00:27.490]So I'm starting out with a question.
[00:00:30.220]Why do we need to preserve food?
[00:00:32.780]Well that kind of brings us back to an even deeper question
[00:00:36.730]of what are the eight life processes?
[00:00:39.640]So anything that is alive, that would include an animal,
[00:00:43.770]a plant, or a bacteria, we need nutrition.
[00:00:47.830]We need to be able to transport things
[00:00:50.170]like waste and nutrients and oxygen.
[00:00:53.160]We need to synthesize,
[00:00:55.210]we need to make complex substances, we need to grow.
[00:00:59.280]Perhaps if we're a bacteria, growing means dividing.
[00:01:02.220]If we're a human, maybe that means
[00:01:03.600]just getting larger and larger.
[00:01:06.290]We need to excrete things.
[00:01:08.190]We have respiration, regulation, and reproduction.
[00:01:11.210]So these are all part of the life processes
[00:01:13.450]but that's not unique to humans, okay?
[00:01:16.890]So that means that we're in competition
[00:01:18.720]with everything else out there for our food.
[00:01:22.200]So if we have this basket of food in here, we have bacteria.
[00:01:26.430]They want to try to obtain nutrients.
[00:01:29.580]Mold, birds, rats,
[00:01:32.320]we're even in competition with each other.
[00:01:34.030]I don't know about anybody here,
[00:01:35.550]but I grew up in a family of seven
[00:01:38.680]and we were always competing for food at the table.
[00:01:42.760]Sometimes my brother always seemed to win though.
[00:01:47.020]So this is what we're looking at
[00:01:48.270]when we're talking about food preservation.
[00:01:50.250]We want to be able to save our food
[00:01:52.340]because we don't want certain things to happen to it.
[00:01:56.890]So with life, we have living healthy plants and animals.
[00:02:01.920]And they can automatically control
[00:02:03.815]the organisms in the environment.
[00:02:06.780]When plants and animals are killed,
[00:02:09.020]organisms will immediately start to
[00:02:13.050]take over that particular piece of food.
[00:02:16.050]We have decay.
[00:02:17.060]Decay happens very, very quickly.
[00:02:19.280]You would look at this moldy piece of fruit.
[00:02:21.810]In addition to microorganisms, we have enzymes.
[00:02:25.000]You know, enzymes occur in all raw food products.
[00:02:28.220]We have oxygen reactions.
[00:02:30.570]So we need to preserve food not only from bacteria
[00:02:34.020]but to avoid these other processes that are going on
[00:02:37.520]that's gonna decay our food.
[00:02:41.190]So how do we keep this from happening?
[00:02:42.840]How do we keep our tomato from becoming moldy?
[00:02:46.470]We can do lots of different things.
[00:02:48.040]We can dry it, we can add acid to it,
[00:02:51.020]and can it under low temperature,
[00:02:52.900]we can use high temperature, high pressure to can it,
[00:02:55.810]or we can freeze dry it into a powder.
[00:02:59.350]So what we're going to be focusing on in this lecture
[00:03:01.840]and the next one is acidity and canning processes.
[00:03:07.440]So what are some of the foods that you might be making?
[00:03:10.130]You might be making pickles, salsa, sauces, and dressings.
[00:03:15.250]Probably for those of you maybe in the farmers market now,
[00:03:18.490]you might be interested in moving on to pickles and salsas.
[00:03:21.590]And these are all going to be processed for shelf stability.
[00:03:26.440]So here's our definition of an acidified food.
[00:03:29.410]Again, and we really point it out,
[00:03:30.890]it has a pH of 4.6 or less,
[00:03:33.720]water activity greater than 0.85.
[00:03:36.975]21 CFR part 114 covers all of those regulations.
[00:03:43.180]Certain foods are exempt.
[00:03:45.070]Carbonated drinks, certain condiments
[00:03:48.056]with the standard of identity.
[00:03:49.400]Again, we kind of get back to those regulations there.
[00:03:52.330]And some foods have an acid formulation.
[00:03:55.550]And I'll discuss that acid formulation
[00:03:58.010]in another slide about how you can do that.
[00:04:00.550]And that would make you an exempt product.
[00:04:05.510]Again, we talked about the jams and jellies.
[00:04:07.330]Those are exempt based on their acidity
[00:04:10.560]and their water activity.
[00:04:14.540]Refrigerated foods, naturally fermented foods.
[00:04:18.090]These are typically exempt products as well.
[00:04:25.483]Now we're getting into the guys
[00:04:26.907]that are going to have to be regulated.
[00:04:28.750]And you're going to have to go a little bit further
[00:04:32.370]to make sure that these are going to be safe
[00:04:34.470]and they're going to follow the regulations to be sold.
[00:04:38.120]So these would be pickles, relish, salsa,
[00:04:41.260]anything that has a low acid food
[00:04:43.510]that's been acidified using vinegar
[00:04:46.030]or some type of an acid food like tomato sauce.
[00:04:52.610]So the basis of all of this is pH and acidity.
[00:04:56.760]And since this is called the Science of Safe Food Workshop,
[00:05:00.120]that means we have to throw some science in here.
[00:05:03.100]So pH itself, this is a symbol that's used to designate
[00:05:07.890]the degree of acidity or alkalinity.
[00:05:12.070]It's a measure of the free hydrogen ion concentration.
[00:05:17.470]So the lower the pH, the higher the acidity.
[00:05:21.410]And if we look at our little chart here,
[00:05:25.070]zero to four, zero to five, these are all in the acid range
[00:05:30.420]in terms of acid foods.
[00:05:32.870]For acid foods, the cutoff is 4.6.
[00:05:35.730]Everything below here would be
[00:05:37.710]considered an acid or acidified food.
[00:05:40.070]All of our low acid foods would be above that level.
[00:05:43.860]So it's a hard and fast cutoff.
[00:05:48.640]With this particular chart, it shows a little bit more
[00:05:51.340]in-depth about how the pH and hydrogen ion
[00:05:54.410]concentration are related to one another.
[00:05:57.200]And the main thing I want you to take away from this slide
[00:06:00.960]is that the pH scale is based on a logarithmic scale.
[00:06:07.470]So if you look at these numbers,
[00:06:10.370]as you get higher and higher,
[00:06:12.430]you see that number gets lower and lower.
[00:06:15.740]The main point behind this is in this next slide,
[00:06:19.620]is when you're moving from one pH to the other,
[00:06:22.690]for example, moving from a pH of six to a pH of five,
[00:06:28.870]you're going to be moving by a factor of 10
[00:06:32.460]in terms of the increase in acidity.
[00:06:36.970]If you're moving from a pH of five to a pH of four,
[00:06:41.800]again, you're 10 times more acidic than pH of five
[00:06:46.030]but you're 100 times more acidic than a pH of six.
[00:06:50.060]So by a factor of 10, you're going to be increasing
[00:06:52.610]or decreasing as you move through that pH scale.
[00:06:59.420]Most of your low acid foods that are below 4.6
[00:07:03.107]are going to be your fruit products,
[00:07:05.460]obviously because of their acid content.
[00:07:08.140]Above 4.6 is going to be your vegetable-type products.
[00:07:16.610]And one comment about buffering capacity.
[00:07:20.290]So this is the ability of a food to resist a change in pH.
[00:07:25.280]So this is where you have to understand
[00:07:26.990]about the nature of your product.
[00:07:28.660]If you're pickling vegetables, they're much more easy
[00:07:31.630]to acidify than say a meat product.
[00:07:34.620]So you might have to add more acid
[00:07:36.680]to make sure that that entire product becomes acidified.
[00:07:42.920]So determining pH can be done by two different ways.
[00:07:46.370]And we have some demonstrations down in the lab.
[00:07:48.560]We'll kind of let you walk through
[00:07:50.320]after the seminar is done.
[00:07:53.100]You can use colorimetric methods or electrometric methods.
[00:07:58.090]We have these little pH strips.
[00:08:00.240]Does everybody remember those from high school?
[00:08:02.870]My high school, well I won't say when I went to high school.
[00:08:05.170]But we used those in high school.
[00:08:07.860]Kind of fun to play with.
[00:08:09.510]These are actually allowable under the law
[00:08:12.120]but only for products that are under a pH of four.
[00:08:17.360]When you have solid product, is anybody here doing pickles?
[00:08:22.606]When you have a solid product like that,
[00:08:24.730]you have to measure both the liquid portion
[00:08:27.400]and the solid portion.
[00:08:28.960]And the way you do that is you can measure
[00:08:31.330]the liquid pretty easy but you take that solid portion
[00:08:34.610]and you'll have to blend it up and then you can measure
[00:08:37.540]that pH of that particular portion as well.
[00:08:44.180]Large price range for these devices,
[00:08:46.710]anywhere from $80 to $1000.
[00:08:50.020]A little handheld one, a nice bench top one.
[00:08:53.920]If this is going to be part of your critical control points
[00:08:56.240]that you're going to be measuring,
[00:08:57.340]I'd probably get something middle of the road.
[00:09:01.050]You know, don't get the cheapie one
[00:09:03.640]but you probably don't need the high end one either.
[00:09:05.690]You know, a few hundred dollars,
[00:09:07.950]good investment for producing these types of products.
[00:09:13.240]Acidification procedures.
[00:09:15.910]Number three up here that I have
[00:09:18.010]is probably the most common one.
[00:09:20.690]Or excuse me, number two.
[00:09:22.850]Direct batch acidification.
[00:09:24.980]So this is where you have a big vat
[00:09:27.120]and you're acidifying the entire product together
[00:09:30.420]and then dispensing it out and bottling it later.
[00:09:34.510]There's other ways to acidify, but that's probably
[00:09:36.500]the most common for people producing these products.
[00:09:41.570]So I touched on formulation a little bit.
[00:09:44.620]How is a product considered exempt from these regulations?
[00:09:49.800]The basic rule of thumb that the FDA looks at
[00:09:52.570]is the 10%, I call it the 10% rule.
[00:09:56.440]If you have less than 10% low acid foods in that product,
[00:10:01.090]then it can be considered an acid food and exempt.
[00:10:07.080]The other thing that it looks at is the pH.
[00:10:10.170]So if that resultant equilibrium pH doesn't differ that much
[00:10:14.520]from the final product, then it can really be considered
[00:10:19.060]excluded from the regulations.
[00:10:21.860]And I'll show how this works in the next couple of slides.
[00:10:26.530]So if we have a product, we're making an applesauce
[00:10:29.920]made from fresh apples and fresh dates.
[00:10:34.140]Our apples have a pH of 3.4, our dates have a pH of 4.7.
[00:10:41.050]That's our low acid ingredient.
[00:10:42.700]It's above 4.6.
[00:10:45.180]Our finished product equilibrium is 3.5.
[00:10:49.260]So our final product is below that 4.6
[00:10:51.740]so we know it's probably an acid or an acidified food.
[00:10:56.000]So we've answered all of these questions.
[00:10:59.090]We know we need to determine whether this can be excluded.
[00:11:03.290]Well let's take a look.
[00:11:04.710]In our recipe, our low acid ingredient,
[00:11:07.840]the dates, that's 2%.
[00:11:09.770]So number one, that's less than 10%.
[00:11:13.230]So we're good there.
[00:11:15.290]Now we look at our pH.
[00:11:18.860]So we take the pH of our apples, and that's 3.4,
[00:11:23.940]we put all of our dates in, we mix it up, pH is 3.5.
[00:11:30.070]That shift is 0.1.
[00:11:32.300]So according to some of the rules
[00:11:35.400]and some of the documents out there, it's not significant.
[00:11:38.800]So that satisfies our criteria number two.
[00:11:42.730]So it's excluded.
[00:11:43.820]So it's not going to be covered.
[00:11:45.080]We can make this product without
[00:11:46.660]filing a process with the FDA.
[00:11:52.110]We heard a little bit about spores this morning.
[00:11:55.570]The main reason that we acidify these products
[00:11:58.660]is we want to prevent those spores
[00:12:00.840]from germinating and producing toxin.
[00:12:04.550]So we use acid to prevent that spore from germinating
[00:12:09.630]but we also use a mild heat treatment
[00:12:11.630]to kill any growing or vegetative cells as well.
[00:12:17.080]This shows it in a little bit similar fashion.
[00:12:22.230]Over here, we have our high acid foods and fruits.
[00:12:25.830]Only a mild heat is needed plus the acid.
[00:12:28.850]Low acid foods, we need a high heat
[00:12:31.950]to kill off those spores and the vegetative cells.
[00:12:36.980]When you're working with acidified foods, the lower the pH,
[00:12:40.360]the less heat is needed to preserve that product.
[00:12:44.840]So depending on your pH,
[00:12:48.120]you may need less heat or less time.
[00:12:52.910]For the higher pH products, you might need more heat
[00:12:55.990]and more time to make a shelf stable product.
[00:13:01.530]There's two basic methods for producing acidified foods.
[00:13:05.200]The first one is a Hot-Fill-Hold
[00:13:07.420]where you're taking the product,
[00:13:09.410]you're thermally processing it like in that batch
[00:13:12.610]that we talked about, putting that into containers,
[00:13:16.560]here I have a little barbecue sauce container,
[00:13:19.090]closing it, and doing a jar inversion.
[00:13:21.860]So what's going to happen is that jar inversion
[00:13:23.830]is going to sanitize that head space and lid
[00:13:26.570]with that hot liquid that you've used.
[00:13:31.630]Processing method two is a pasteurization method.
[00:13:35.140]And so this is where you are filling product into
[00:13:37.670]containers, sealing it, and then thermal processing.
[00:13:40.880]So this is your water bath method essentially.
[00:13:45.180]Adding the product into the container, closing it,
[00:13:48.670]and then processing it by hand.
[00:13:50.410]So that's going to sterilize both
[00:13:52.080]your container plus your product together.
[00:13:55.850]So if you're covered under FDA regulations,
[00:13:58.790]things get a little bit more stringent.
[00:14:00.870]You're going to have to be filing a process
[00:14:03.450]that includes your heat processing conditions, pH,
[00:14:06.400]salt, sugar, preservative level for each container size.
[00:14:11.030]And this is known as filing a scheduled process.
[00:14:15.090]And this is one of those products
[00:14:17.090]that needs to have process authority review.
[00:14:19.320]And then they will send you back information
[00:14:21.430]on the important parameters that are needed
[00:14:24.500]to file that process with the FDA.
[00:14:29.260]So here's two resources.
[00:14:31.150]Two NebGuides.
[00:14:32.170]One on acidified foods, one on selecting a pH meter
[00:14:35.570]if you're just getting started.
[00:14:37.190]So a couple of different resources there
[00:14:38.910]in the same location as the fruit jelly NebGuide.

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