Tuesday, June 2, 2015

Low Carb Whole Milk Replacement for Ice Cream - Part 1

Chefs that make regular sugar-based ice creams use ingredients like corn syrup, nonfat milk powder, and cream cheese because they contain simple sugars like glucose and/or milk proteins that improve aspects of the finished product. I’m going to concentrate on the milk proteins for obvious reasons.

Home ice cream recipes generally use a 2:1 ratio of heavy cream to whole milk yielding a product that’s a little over 20% milk fat. (The legal minimum milk fat required for ice cream in the USA is 10%.) Heavy cream is great for low carb dieting since it has very little sugar and is high in fat. Whole milk is relatively low in fat and higher in sugars like lactose that are not only a poor source of nutrition, they’re undesirable for making hard ice cream. The parts of whole milk that are useful are the proteins. Whey protein provides a lot of benefits such as water binding, viscosity (thickness), and emulsification. Casein adds body (chew), texture (smoothness), and resistance to heat shock. Substituting whole milk for almond milk means we’re missing out on these important milk proteins. The solution is simple: add them back in...and then some!

Of all the companies that sell protein supplements, Optimum Nutrition usually comes out on top whenever these kinds of products are tested independently. They no longer make unflavored whey and casein products. If they did, I would use them in a heartbeat.
Whey protein isolate and casein are used by body builders as easily digestible sources of protein, so getting a hold of them is easy. Health supplements aren’t regulated by the FDA, so there’s really not a lot of testing whether or not the products contain what the manufacturers’ claim. I’m experimenting with NOW brand because they sell whey isolate and casein without any added flavoring, they’re the cheapest ones I’ve found, and the company has a relatively good reputation.

You might be wondering why I’m going through all this trouble when Lactaid whole milk is so easy to find. Lactose-free milk does not mean the lactose is removed. They don’t take the lactose out; they add lactase enzyme in. People whose bodies don’t make enough lactase can’t fully digest lactose, so lactase is used to break the disaccharide lactose into the simple sugars glucose and galactose prior to packaging. If the lactose was removed, why is the amount of carbohydrates and sugars the same in the nutritional information? The only foolproof way I know around this problem is to avoid whole milk entirely and instead add the desired dairy components into non-dairy “milk.”

Note: I am not a chemist or food scientist. What I’m about to present is based mostly on information published by the U.S. Dairy Export Council for the food industry. There may be critical flaws in my interpretation and implementation of these concepts. For example, ice cream manufacturers usually add whey prior to pasteurization of the ice cream mix. Because the ice cream manufacturer is concerned about milk proteins binding with water molecules, they probably use the minimum amount of heat needed to ensure pasteurization (161 °F). Perhaps the whey isolate sold in the big containers to bodybuilders is pasteurized at a very high temperature and may limit its utility for our application. I have no way of knowing. A lot of the source documentation is written using technical terms. A sentence like, “Dry whey should be added under high shear to the totality of liquid ingredients (water, milk, skim milk, cream, liquid sugar, sweeteners) to prevent lumping and pre-gelation,” translates to, “Put the whey protein with the rest of the ice cream mix in a blender and blend for a few minutes at high speed,” for the home ice cream chef. If I’ve misinterpreted then the results will suffer and I apologize in advance. That’s the risk of listening to an autodidact.

Denatured proteins


Proteins become denatured when exposed to an external stressor. The structure of the amino acids unwind and change shape. Heat is the fastest way to denature proteins. The coils of the protein molecule unwind when heat is applied and rewind themselves when cooled. However, there is a point-of-no-return where the protein molecule is irrecoverably changed. Cooking an egg (white) is a good example of this phenomenon.

Diagram of denatured proteins.

We want the proteins to unfold because doing so creates additional water binding sites. Heating the ice cream mix will increase the viscosity of the liquid after it’s cooled and helps prevent large ice crystals from forming when frozen. The critical temperature for whey protein is approximately 170 °F / 77 °C. This is the temperature where whey protein will begin to coagulate (precipitate) and is probably why most ice cream cookbooks tell you to not exceed that temperature when making a custard. (That and so the egg yolks won’t overcook.) If heated too high (90-100 °C) for too long, the proteins will turn irreversibly into a gel.

Low PH conditions can affect whey protein and casein solubility. Casein is most affected by low PH. Generally, this isn’t a concern for us since ice cream mixes will be only slightly acidic and close to neutral. However, keep this in mind when using very acidic ingredients like fruit juices, vinegars, and sour cream. I suspect those ingredients should be added right before churning.

Ice cream formulation


As discussed in my earlier write-ups on ice cream science, the magnitude of other ingredients depend on the fat content. More nonfat milk solids, stabilizer and emulsifier are need as the fat content is lowered. The minimum (legal) fat content for ice cream is 10%, which means nonfat milk solids would be 11%, 14% sucrose, 0.15% stabilizer, 0.25% emulsifier, etc. Ice cream factories generally mix the ingredients, pasteurize, then homogenize. Temperatures around 75-85 °C cause the whey proteins to denature and interact with the caseins. The mix should be cooled and held (i.e., aged) for at least 4 hours (preferably overnight) at approximately 2-5 °C. This allows time for the fat to cool down and crystallize, and for the proteins and polysaccharides to fully hydrate.

Homogenization should occur at the pasteurizing temperature. Professional homogenizing machines work at high pressures. We can’t reproduce this exactly at home, but the “high shear” aspect can be accomplished by a household blender or mixer.

Interaction with other stabilizers and emulsifiers


Whey protein may add or detract emulsification or stabilization of an ice cream mix. It may be necessary to reduce or eliminate the gums used in the ice cream base otherwise the result will be sticky and/or gummy. Too much whey will give the ice cream a “dry” texture.

Percentage of whey and casein


Mature cow’s milk contains an average 32 g of protein per liter with 26 g being casein and 6 g of whey. However, this does not mean ice cream manufacturers are forced to abide by this ~4:1 ratio.
If total milk protein (total of casein and whey proteins) is used as a regulatory standard, then it is recommended that at least 50% of the total milk protein be as naturally occurring casein. Thus, the amount of any given whey ingredient can be simply calculated based on this target and the percent protein in the specific whey ingredient. This retains the functionality of casein in the conditioning of the fat globule during aging of ice cream mix in preparation for fat agglomeration during freezing and whipping but allows significant use of whey protein for function, quality and cost savings opportunities. Fat agglomeration is necessary to build air cell strength and subsequent resistance to heat shock.
The FDA says proteins ought to account for at most 3% of the ice cream mix by weight. That’s approximately what it would be for a french custard ice cream base using 2 cups heavy cream, 1 cup whole milk, 4 egg yolks, and ¾ cup sugar. Quite frankly, I don’t give a damn since I’m not bound by any government regulations for ice cream I make in my own kitchen for myself.

Tip: We want whey protein isolate, not concentrate. Whey protein concentrate contains trace amounts of lactose and milk fat. We’re just interested in the protein, so stick with the isolate.
Considering that almond milk, the base of my low carb whole milk replacement, contains zero milk proteins, it’s easy to control the formula. Our initial goal is to replace the 8 g of protein missing from the lack of whole milk. However, we will end up using more whey to achieve an overall ratio of 1:1 to counterbalance the milk proteins in the heavy cream. The instructions on the container of whey protein isolate tell us to combine a 28 g scoop of powder with 1 cup of liquid yielding 25 g of protein. A scoop of casein is 24 g of powder yielding 19 g of protein. This should shift the balance of whey/casein to better than 50/50. Heavy cream has 5 g of protein. Assume this means 4 g casein and 1 g whey, so the net 6 g difference from the powders put the combined whey protein at slightly over 50% by 3 g. Our quart of ice cream will have a lot more protein from the powders and almond milk than the whole milk it’s replacing. (44 g vs. 8 g not counting the small amounts of protein from the almond milk itself.) This also means that our mix will be approximately 5.5% protein by weight, which exceeds the 3% minimum target.

Fun fact: Human milk contains almost three times the amount of whey proteins as caseins.

Impact on ice cream added flavorings


Ice cream flavorings usually come with instructions that prescribe how much to use. The rule of thumb for LorAnn Oils Fountain Flavors, for example, is to use more flavoring if the mix is higher in fat. However, whey and casein proteins may blunt the flavoring, too, requiring more than the recommended dose:
High molecular weight proteins such as whey proteins can absorb various chemical components of added flavors such as vanilla extract and reduce perceived vanilla flavor. The higher the whey protein content, the more impact on added flavorings. This effect can occur with other proteins and formulators need to optimize their formulations in terms of protein/flavorings addition.
Bottom line: Taste test and use your own judgement.

Conclusion


I’ve used LC Foods Milk Powder with almond milk in the past to replace some of the heavy cream in my low carb ice cream base. The results were good when combined with other techniques like rapid freezing. However, my goal is to develop an ice cream mix that does not rely on proprietary ingredients, has an improved texture, and can be recreated consistently and easily. In part two, I will provide a step-by-step method to create a low carb ice cream base that’s, lower fat, lower calorie, and higher protein than the ones I previously developed using the information laid out here.

References


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