December 2016 | Issue 17
Welcome to the seventeenth edition of our Insights for Cultured Dairy newsletter! The purpose of this newsletter is to share
information within the dairy industry about stabilizers, cultures, antimicrobials, probiotics, fiber addition, processing, and
specific ingredients used in cultured product and cheese applications. We will always add a recipe utilizing cottage cheese
and discuss troubleshooting issues from the field! We hope you enjoy it and look forward to your feedback! If you would like
to see specific subjects covered in this publication or if you want added to the electronic mailing list, please contact the
editor, Doug Vargo, at [email protected].
FROM THE FIELD – BY DOUG VARGO
How Long Can You Let Sour Cream
Set (or sit) Before You Package It?
Having worked in a production environment previously, I know how equipment breaks
down from time to time. With sour cream incubation taking such a long time, the question
came up, “How long can you let it sit there before it has to be packaged”?
Recent FDA regulations say that sour cream needs to be packaged and down to a core temperature of 45F or
less after 72 hours. That gives you basically 3 days from the time the sour cream is ready to be broken and
packaged (if you break it at all) until it needs to reach a core temperature of 45F or less. Core temperature
depends upon package size, and how long the product is in the cooler before it is shipped out. It also depends
upon how well the cold air circulates in your refrigerated cooler and the temperature of the cooler itself.
In this example let’s assume the biggest retail package you are filling is a 16 oz. package size. You know from
experience that when your sour cream is packaged at an incubation temperature of 76F it takes approximately
36 hours to cool the core of the pallet of 16 oz. retail cups to 45F or less. And this probably depends upon
cases placed on the pallet (pallet configuration) and where those pallets are stored in your refrigerated
warehouse. One trick to cool down the sour cream faster would be to place the pallets in the cooler with fans
blowing the cold air on the pallet or to place the pallets right in front of the air circulation fans in the cooler. In
this example, you would have 36 hours to package the sour cream and get it into the cooler to cool it down
within the 72 hour requirement. That means if you have filler or casing issues, you can let your sour cream sit in
the incubation tank at set temperature for 1 ½ days.
You may ask yourself what does this do to the product? The answer is that the sour cream culture continues
to grow until the pH gets down to about a pH of 4.30. Usually some wheying off will occur on the top of the
coagulum or perhaps between the outside wall of the setting tank and the sour cream coagulum itself. However,
this whey can be mixed into the sour cream when it is “broken” or stirred with the vat agitator right before
packaging begins. Stirring sour cream for 3-5 minutes right before it is packaged is usually enough time to
remix in any whey separation and get the product homogeneous for packaging.
Taste-wise, sour cream is already sour and pH 4.30 sour cream will not taste that much different than pH 4.55
sour cream. Granted it might have a higher acid taste or bite to it, but isn’t sour cream supposed to be “sour”?
In some cases, more of an acid bite might be a desirable trait. In today’s production environment where time is
December 2016
|
Page 1
money, a lot of times we get anxious waiting on a tank of sour cream to come down to the break pH.
Frequently, the flavor has not sufficiently developed yet. Letting sour cream sit there longer before packaging
will assure you have developed the diacetyl flavor to the highest degree. The flavor producing strains in sour
cream, namely the Streptococcus diacetylactis and the Leuconostoc strains will have had the chance to have
complete fermentation of the inherent citrate in milk and convert it to the flavor compound, diacetyl and with
subsequent CO2 production. This happens in the last hour or so of a typical sour cream fermentation when the
lactic acid bacteria (Streptococcus lactis) have lowered the pH to 4.6 or lower. Letting the pH drop to 4.30
assures complete flavor development.
One production procedure that worked quite well at one dairy was to have a cleanup man come in on a
Saturday and heat up the pasteurized cooled sour cream mixture run into the incubation tank on a Friday to the
set temperature of 74F. He would put the culture in, agitate the mixture for half of an hour, and then let the sour
cream sit quiescently for 14-18 hours until the pH came down to the break pH of 4.5 on Sunday morning.
Nothing would happen for 24 hours and then the sour cream was packaged first thing Monday morning when
the filler crew would start at 6 a.m. In this case, it was perfect “production timing” to have sour cream ready to
be packaged first thing Monday morning by setting it 36 hours previously. Although this dairy had “given up” 24
hours by not packaging on a Sunday, they always felt they would have the retail cups down to 45F or less as
they still had 48 hours to get it there, and knew it would get there in 36 hours. Timing is everything!
Know Your Meter: pH Meters are one of the most
important tools in a Cultured Products Plant
BY DOUG VARGO
In today’s production plant environment, it is critical to measure and record pHs accurately. After all, the
controlled production of lactic acid is what we are measuring when we check the pH during fermentation of our
cultured product. Having an accurate and reliable pH meter is imperative for achieving the correct break pHs
and cutting pH (in the case of cottage cheese). All too often pH meters are not taken care of, or even
standardized regularly. Many employees do not understand them or how to take care of them. In my opinion, a
pH meter is a plant’s best friend and should be treated as such. I will address what pH is, which pH meters
might be best for measuring pH in fermented dairy foods, how to take care of that pH meter, and which probes
might be the best choice for use near a cheese room.
What is pH?
A pH meter is an instrument that displays a value that is converted to pH units from an attached electrode that
is sensitive to H+ (hydrogen ions) in the solution you are measuring. As you know, pH is a measurement in a
numerical value from 0-14 that tells how acidic (low pH from 0-7) or basic (high pH from 7-14) a solution is. The
electrode is usually made of pH sensitive glass; although there are now gel electrodes and even ion specific
field effect transistors (ISFET) that have a chip instead of the typical glass or gel electrode to measure pH.
Therefore, pH is a way to compare the relative acidity or alkalinity of a solution (or product) at any given
December 2016
|
Page 2
temperature. At pH 7, the pH is considered neutral (neither acidic nor alkaline) since the solution (or product)
would contain the same amounts of hydrogen ions (H+) and hydroxide (OH-) ions, which in effect neutralize one
another. Sour cream and yogurt have pHs near 4.0 - 4.5, so it is important to have a pH meter that measures
acidic conditions accurately.
A change of 1 tenth of a pH unit; say from a pH of 4.6 to a pH of 4.5 is a dramatic change in the amount of acid
in your cultured product. Missing a cottage cheese cut pH of say, 4.7 and cutting cottage cheese coagulum at
pH of 4.6 rather than at pH of 4.70 equals 25.9% more acid in your cultured product as when the pH was at
4.70. You know what acid does to cottage cheese curd…. (it makes it softer if cooked to the same cookout
temperature) so it is important to accurately measure pH!
Choosing a pH meter:
Most pH meters in today’s marketplace are accurate to +/- 0.01 (one hundredth) pH unit and some up to 0.002
(two thousandths) pH units. Those old needle type pH meters with a line scale that were graduated to 0.10 (a
tenth) of a pH unit are (or should be) a thing of the past. If you are still using one of those old needle pH meters,
I suggest you upgrade and come into the modern digital age! I do not promote or endorse any kind of pH meter,
but see many of the Orion brand of meters in use out in the plants.
If I were to choose an accurate ATC (automatic temperature control) pH meter, I might consider Thermo
Scientific Orion Star A211 for a lower cost meter, or an Orion Dual Star Mutiparameter meter as a better choice,
or even the Orion Versa Star Electrochemistry meter for auto recording into a database as maybe the best
choice if you like to review data and have a record of the pH recordings.
Which Probes or pH Meters Might Be Best
for Measuring Fermented Dairy Foods?
Selecting the right pH meter with the right electrode is imperative. An electrode compares the pH reading in a
sample with that of known buffers (usually pH 7.0 buffer and pH 4.0 buffer, when measuring acidic solutions).
The most common cause for error in pH measurement is temperature of the sample! Temperature affects the
slope and this can change with variations in temperature. It is critical to get a pH meter that adjusts the pH
reading to the temperature of the sample (one with an automatic temperature compensation or ATC probe).
Selecting a pH meter that is accurate to a hundredth or two hundreths of a pH unit should be accurate enough.
There are so many pH probes to choose from, I can’t possibly cover them all here. Several types would be
more conducive to a production environment rather than in a lab, but don’t sacrifice accuracy for the need to
keep the pH meter in a protected cabinet (or even out in another room) to save the cheesemakers a few steps.
A flat serviced tip is a probe that I see a lot out in the plants and even one with a “rugged” glass bulb might be
better for using in a cheese room. Epoxy bulbs are more durable than glass bulb electrodes.
Electrode fill types
1. Refillable electrodes require periodic filling and draining. They have a long expected life span and are
accurate to +/- .01 to .02 pH units. They have the best response time (fastest pH reading).
December 2016
|
Page 3
2. Polymer filled electrodes are low maintenance and no filling solution is needed. They are sealed,
accurate to +/- .02 pH units and have a good response time.
3. Gel filled electrodes are easy to use, but are less accurate from +/- .05 to 0.10 pH units and don’t have
as good a response time as the others.
I guess if I were to choose one for a cottage cheese room, I would pick a pH meter accurate to +/- .02 pH units
with automatic temperature compensation with a flat surfaced tip, perhaps an epoxy body rather than glass,
with an open junction for less clogging, and be refillable or even polymer sealed. I would stay away from ISFET
meters, as I would think they would not have the accuracy necessary for measurement of cut pH in a cottage
cheese plant.
Taking Care of the pH Meter (the electrode):
Taking care of the pH meter involves just a few simple things. Foremost, it should be standardized at least daily
by the same person at the same time, or preferably standardized perhaps 3 times daily at the beginning of
each shift, so that the cheesemakers will have confidence in the readings. If each cheesemaker standardizes
the meter themselves, then they will know it is accurate. That means making sure all operators have training in
how to standardize the pH meter, what solution to soak the electrode in between measurements, and how to
take an accurate reading (rinsing off the soaking solution and sample after each measurement). After training is
accomplished and everyone feels comfortable, taking care of the pH meter is about taking care of the electrode.
This entails inspecting it at the end of the week of use for cracks, salt crystal buildup, and membrane/junction
deposits (the little measurement area on the tip). If it is cracked replace it ASAP. If it has salt crystal buildup
rinse or soak it in distilled water. If it has deposits on the tip soak the electrode in 0.1 molar HCl or 0.1 molar
HNO3 solution for 15 minutes.
If a refillable electrode is used, make sure the liquid level is ¾ to 9/10 full up to the filling hole at the top of the
electrode. Keep your electrode problem free for accurate and consistent pH readings from week to week.
Electrodes are not good forever! Did you know they have a “shelf-life” on them, if you will! Most of them have a
shelf-life or recommended use life of 6-12 months. After that, buy a new one to maintain accuracy.
Also, be careful of mixing rinse water into the storage solutions and buffers. It is best to dab the tip of the probe
off with a non-abrasive Kimwipe towelette before storing the probe. And if your buffer has expired (there is a
good till date printed right on the bottle), or it gets contaminated during the day, change it before your next
standardization to keep the reference buffers reading accurately.
Dairy Chemistry – Part III of IV: Lactose
BY JON HOPKINSON, PHD.
Milk, the lacteal secretion of the mammalian mammary gland is a mixture of substances that
are intended for the nutrition of infant mammals. Milk is composed of protein to provide amino
acids for the growing infant and energy sources which are fat and sugar. For most mammals,
this mixture is adequate for the complete nutrition of the infant.
The primary sugar in milk is lactose. There are two exceptions, in nature, the milk of monotremes (platypus and
echidna) and some pacific pinnipeds (fur seals, sea lions and walruses) that produce no lactose in their milk at
all. As far as it has been studied all other mammals produce lactose in their milk.
Lactose is separated from milk and, more commonly, whey by crystallization. Pure lactose is used in foods and
pharmaceuticals (as a filling material in nearly all pills). It is also used in the production of industrial derivatives
ranging from the sugar alcohol lactitol, used in many laxatives to some plastics
Lactose is a disaccharide composed of glucose and galactose connected with
aβ-1→4 glycosidic linkage. Its chemical name is β-D-galactopyranosyl-(1→4)D-glucose
December 2016
|
Page 4
The galactose can only have the β-pyranose form and the glucose can be in either the α-pyranose form or the
β-pyranose form: hence α-lactose and β-lactose refer to the anomeric form of glucose moiety alone. Both the
alpha and beta forms of lactose are poorly soluble in water. The ratio of alpha to beta forms and the solubility of
the two forms are dependent on the initial ratio, the temperature, and other components in the dairy product and
the process the lactose is involved in. On rapid cooling or rapid dehydration lactose remains in solution forms
an amorphous solution or glass. These conditions exist during drying and freezing, as with nonfat dry milk and
frozen desserts. Lactose is one of the least soluble sugars with a solubility of
only 21.6 gm/100 ml water (sucrose – 200gm/100 ml). It is this property of
lactose (ease of glass formation and low solubility) that causes sandy texture in
ice cream. Sandiness can also result from lactose crystallization in condensed
milk. One property of Lactose crystallization is that due to the equilibrium
properties of α&β lactose the sugar can persist in a supersaturated form for a
long time. This is problematic because a product can persist in the super
saturated state for long periods without getting sandy and then turn sandy
unpredictably during shelf life. Lactose crystals are easily identified under the
microscope, they are hatchet shaped, see picture on right.
Like most reducing sugars, on heating lactose, with amino acids present, will participate in the Maillard reaction.
This leads, through a very complex series of rearrangements to brown colors and (cooked) flavors. Heating milk
also results in the formation of Lactulose (4-0-β-D-galactopyranosyl-D-fructose). Lactulose is slightly sweeter
than lactose and considerably more soluble. Up to 1% of this compound can be found in condensed milk. This
is an interesting molecule that has been alleged to promote the growth of Bifido bacteria and is thus thought of
as a prebiotic.
Lactose is less sweet than other common sugars. It is roughly around 16% as sweet as sucrose, but it is
sweeter at higher concentrations than it is at lower ones. Protein can cover the lactose sweetness somewhat,
and this explains why whey seems just a bit sweeter than milk. In many formulations with dairy products the
minimal sweetness from lactose can be ignored especially when it is at low concentrations. Hydrolyzed lactose,
containing glucose and galactose, is considerably sweeter than lactose.
Lactose is difficult to hydrolyze into glucose and galactose. Treatments like heating a solution of lactose to
150⁰C with 0.1M hydrochloric acid that will easily hydrolyze sucrose will hydrolyze lactose only slowly. There
are a set of enzymes that can enable the hydrolysis they are collectively called β-galactosidase or simply
lactase. These enzymes are widely distributed in nature; in plants, animals, bacteria and fungi. They act on the
β-1,4 linkage between the glucose and galactose in lactose. They also can act to link the galactose units to
various other hydroxyl-containing compounds such as glycerol. Under the right conditions lactase can link
galactose units to form oligosaccharides containing glucose and multiple galactose sugars linked in various
ways. Galactooligosaccharides (GOS) are known to occur naturally in milk (especially human milk) and are
important in stimulating the growth of Bifido bacteria in the gut (especially in infants).
Lactose is the energy supplying material in dairy fermentations. In homofermentative organisms such as
Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus lactose is fermented into galactose
and lactic acid, one mole of lactose yields either two or four moles of lactic acid depending on if the bacteria can
ferment galactose. Heterofermentative organisms such as Leuconostoc and some lactobacillus organisms
follow different pathways to lactic acid production and produce other compounds like ethanol and acidic acid.
The relative amounts of these products and by -products depend on the organism. Propionobacterium can
ferment lactic acid into propionic acid, acetic acid CO2 and water. This fermentation is important to Swiss type
cheeses. Lactic acid can be further fermented to butyric acid and CO2 by certain clostridium bacteria this can
be undesirable because of the off flavor and gas produced. There are of course, many fermentative pathways
that start with lactose; and this is a separate study in and of itself.
December 2016
|
Page 5
Cottage Cheese – The Forgotten High Protein Food?
BY DOUG VARGO
Here is another delicious recipe using cottage cheese as one of the ingredients. With winter approaching and
people having the desire to fire up the oven a bit more, here is one comfort food everyone likes to eat. If you
love macaroni and cheese, you are going to love this recipe. Enjoy!
Macaroni & Cottage Cheese Casserole
INGREDIENTS
•
1 ea. (8 oz.) package of dry elbow macaroni
•
1 ea. (8 oz.) package of sharp cheddar cheese (sharper the better)
•
1 ea. (12 oz.) container of small curd cottage cheese
•
1 ea. (8 oz.) container of sour cream
•
½ cup milk
•
¼ cup grated Parmesan cheese
•
½ tsp. salt and ¼ tsp. pepper (or to taste)
•
2/3 cup of dry bread crumbs
•
¼ cup butter
BAKE TIME:35 minutes
PREP TIME:20 minutes
YIELD:4-6 servings DIRECTIONS:
Preheat oven to 375F. Bring a pot of lightly salted water to a boil. Add macaroni noodles and cook until done.
Drain water.
In a 9x13 inch baking dish add the cooked macaroni, cheddar cheese, cottage cheese, milk, sour cream,
Parmesan cheese, salt and pepper. Stir. Separately in a small bowl melt the butter and mix in the bread
crumbs. Sprinkle this topping over the entire surface of the mixture in the baking dish.
Bake in a 375 degree oven for 35-40 minutes until the top is golden brown and bubbling. Remove from the oven
and serve hot!
December 2016
|
Page 6
Discussion Threads – Questions from the Field
BY DOUG VARGO
QUESTION:
In conversations concerning extending shelf-life, I have heard a food professional refer to the term, “competitive
exclusion”. What were they talking about, and how does that help in shelf-life extension?
ANSWER:
Competitive exclusion is a term that refers to the situation where favorable bacteria are present in large
numbers in a food and “compete” with spoilage bacteria for the same food source. Since the favorable bacteria
are present in such a large number already and the microflora population is already established, they effectively
“exclude” the spoilage bacteria to some degree. Consider the fact that if many millions of cells of favorable nonspoilage bacteria, such as lactic acid bacteria are already present in a dairy product, it makes it extremely
difficult for spoilage bacteria to gain a foothold in the dairy product and spoil it.
One prime example is cottage cheese dressing. Cottage cheese dressing cultures are available that “seed” the
dressing with many millions of lactic acid bacteria per gram of dressing. Because of their presence, it makes it
difficult for other spoilage microorganisms to thrive and grow in the finished cottage cheese since the lactic acid
bacteria population is already so high in the dressing. The spoilage bacteria compete with the lactic acid
bacteria so they can grow and multiply. Since one competes with the other, we refer this type of method to
extend shelf-life with the use of another culture as “competitive exclusion”.
The favorable bacteria culture effectively excludes the other based on competition for the same nutrients
(lactose) that the bacteria need to thrive on. This type of food preservation in cottage cheese is considered just
one of many tools or hurdles that you can use to extend shelf-life. As I discussed in a previous issue, if you
combine a dressing culture with a chemical preservative or a natural one such as DuPont’s Microgard 100, 200
or 430, and with CO2 gas sparged right into the dressing, you have the most protection against spoilage
microorganisms as you possibly can. This assures your dairy of the longest shelf-life possible for a cold
packaged cottage cheese. In the past a 28-30 day shelf-life was the norm. Adding the “hurdles” described
above can lengthen the shelf-life to 50-54 days or more. The preservation methods described above combine to
create “growth hurdles” for the spoilage bacteria to overcome, and many times are referred to as “hurdle
technology”.
Fig. 1
Fig. 2
Fig. 3
Fig. 1 – Photo of CO2 gas spargers
Fig. 2 – Photo of CO2 being sparged into water
Fig. 3 and below – DuPont antimicrobial ingredients that can be used as part of hurdle technology (note –
nisaplin is not approved for use in cottage cheese)
December 2016
|
Page 7
PRODUCT
BENEFIT
APPLICATION
®
Anti-Gram-negative bacteria
Anti-yeasts and molds
Cultured skim milk-based
Yogurts, cottage cheese, sour cream, dairy
desserts, fresh cheese (quark), filled
chocolate confections
®
Anti-Gram-negative bacteria
Anti-yeasts and molds
Sauces, dressings, pasta, side dishes, baked
goods incl. fruit applications
®
Anti-Gram-positive bacteria
Cultured skim milk-based
Cottage cheese, flavored dairy
drinks, custards and dairy desserts
®
Anti-Gram-positive bacteria
Cottage cheese and other food products
Anti-Gram-negative bacteria
Anti-yeasts and molds
Cultured skim milk-maltodextrin
based
MicroGARD 100
MicroGARD 200
MicroGARD 300
MicroGARD 430
We hope you have enjoyed the latest issue of
“DuPont Insights for Cultured Dairy.” See you next issue!
®
DuPont™ Danisco ingredients, backed by the knowledge of DuPont scientists, help manufacturers of food and beverages, dietary
supplements and pet food innovate for the future.
®
The DuPont Oval Logo, DuPont™, Danisco and all products denoted with ® or ™ are registered trademarks or trademarks of E.I. du Pont
de Nemours and Company or its affiliated companies.
December 2016
|
Page 8