I'll Drink to That
Nowadays, more choices in healthful, great-tasting dairy and soy drinks are appearing in the refrigerated dairy case than ever before. Manufacturers are hoping that new product concepts will enlighten consumers.
“The mainstream consumer doesn't know about the benefits of protein. That is something we are working to change,” says K.J. Burrington, dairy ingredients applications program director in the Wisconsin Center for Dairy Research at the University of Wisconsin (Madison).
For example, a clear mango-flavored isotonic sports drink, created by Dairy Management Inc. (Rosemont, Ill.) and exhibited at the 2005 Institute of Food Technologists (IFT, Chicago) conference in New Orleans, carries 10g of whey protein in 8oz. “That is a significant amount. It would qualify as an excellent source of protein,” says Burrington. Aside from drinks for endurance athletes, protein is not often added to isotonic beverages, or those products that have added sodium and potassium to help with hydration and muscle recovery.
“Whey proteins are isolated by physical processes and not chemical processes,” says Burrington. The addition of whey protein isolates (WPI) at a low pH (below 3.2) can influence clarity. With increased pH, clarity is lost. Fat and lactose also cause a creamier appearance and turbidity. WPIs achieve a higher clarity because these protein ingredients have less than 1% lactose and less than 1% fat in WPI. The lactose and fat is removed with ash and other minerals as part of the filtration process.
Soy protein has a growing reputation as a heart-healthy ingredient that may also reduce the risk to several types of cancers. Soy that undergoes ultrafiltration processing tends to produce products with fewer off-flavors. One conventional method precipitates protein by lowering the pH. At its isoelectric point, a protein loses solubility and is collected. In both methods (i.e., ultrafiltration and precipitation), the soy oil is removed before the soy liquid is filtered. Some companies press the soy oil out. The majority of companies use a hexane or ethanol wash to remove soy lipids. When the oil (a valuable commodity in itself) is removed, soy protein isolates (SPI), concentrates (SPC) and soy flour are produced.
Protein precipitation or filtration is used to concentrate soy protein into flakes or soy flour, which has 50% or less protein. SPI has more than 85% protein. Various SPIs and SPCs have varying amounts of protein.
“The ideal soymilk is developed to be nutritious, with a good flavor, and sufficient protein so that it can be a comparable alternative to cow's milk in protein content,” says Karl Weingartner, director of the International Soybean Program at the University of Illinois (Urbana-Champaign).
Spiked Punch“Minerals [in beverages] cause a lot of challenges when interacting with proteins because of their sheer bulk,” says Ram Chaudhari, chief scientific officer at a vitamin/mineral pre-mix formulation and manufacturing company. Magnesium, iron, copper and potassium cause problems with texture, but calcium is the most challenging to add to beverages. “If fortification is desired, there are many different calcium sources at different levels of solubility and absorption,” says Burrington.
Whey mineral concentrate (WMC) provides calcium, magnesium, phosphorus and potassium, contributes to bone health development, aids in blood pressure regulation, assists in colon cancer prevention and enhances many metabolic functions. In general, B complex vitamins help increase energy levels and vitamins A (beta carotene), C and E work as antioxidant nutrients. They do not react with proteins either, says Chaudhari. These vitamins, specifically B vitamins, are co-factors that are very important for protein utilization and other metabolic requirements.
Certain minerals and nutrients, such as magnesium, potassium and zinc, are intrinsic in dairy products. However, calcium is filtered out of WPI. In a beverage where WPIs are used, fortification is required if calcium is desired as a healthful ingredient. This step is not necessary for whey protein concentrate (WPC) in that the calcium remains with the protein.
Calcium causes destabilization and precipitation, depending on the pH level. If pH is low, added calcium can react, causing sedimentation or flocculation. “Precipitation also depends on the amount of minerals added to get the label claim,” states Chaudhari. Adding a small amount does not cause as significant a reaction as when adding more than 35% of the RDA value for protein. The latter would result in nothing but sedimentation or flocculation.
“Usually, suspension is the main complaint about calcium,” agrees Burrington. Adding stabilizers like hydrocolloids can help prevent such precipitation. Carrageenan, xanthan, locust bean gum, guar gum, gum acacia, or simple food starch will work well as a stabilizing agent. A pectin stabilizer works exceptionally well to stabilize milk calcium. Thinner beverages are more difficult to fortify because of the viscosity of the drink. Adding up to 20% of the Daily Value (DV) of milk calcium is not that difficult; adding above 20% becomes more difficult.
Interestingly, calcium phosphate and milk calcium derived from whey works very well in acidic beverages. When making low-pH beverages with whey protein, a stabilizer is not needed below pH 3.5. Between pH 2.8-3.5, whey proteins have the greatest heat stability and the highest clarity, because the net charges on the protein are highly positive; there is a lot of repulsion occurring, inhibiting protein aggregation. Whey protein stabilization is necessary between pH 3.5-4.5. Pectin stabilizers work well in this range. There are very few beverages with pH levels between 4.5-6.0. Kappa carrageenan or locust bean gum are designed for either a neutral pH or a pH above 6. Carrageenan is the common ingredient for most of the canned shake meal replacements products like Mead Johnson Nutritionals' Boost (Evansville, Ind.), which typically has a pH at 6.5-7.
A homogenization step, which is recommended before heat treatment, typically accompanies the addition of stabilizers. Homogenization is recommended to disperse/activate the stabilizer and provides better interaction between proteins and gums.
“Whey proteins need to be hydrated (for a half hour, minimum) before they are added into a drink,” warns Burrington. Adequate hydration will give the whey protein a better heat stability so that problems with sedimentation or flocculation are reduced or alleviated.
“If you are looking for more heat stability, the products available now are designed better than five years ago,” says Burrington. Today's whey processors know more about how processing effects the functionality of whey, resulting in better-quality whey ingredients and better heat stability. Manufacturers also can make modifications to their whey ingredients to improve heat stability. Hydrolyzing some of the whey protein is one way to increase heat stability for whey ingredients used in retort products or UHT-processed treatments that previously resulted in flocullation and sedimentation.
In general, insoluble minerals often are considered less bioavailable, notes Chaudhari. Thus begins the tug-of-war between solubility and bioavailability. “If you want both, you have to have a balanced approach as to the stability and bioavailability by selecting appropriate sources of nutrients,” says Chaudhari.
Powdered beverages are mixed right before consumption and so are liberated from most solubility problems. “Compared to powdered beverages, beverage formulation is much more important for ready-to-drink beverages,” says Chaudhari. Still, consumers have certain expectations when they reconstitute a beverage. Minimizing the particle size will enhance the mouthfeel or texture of powdered drinks. Instantizing whey protein helps the powdered beverage to dry in a way that increases the particle area surface, allowing it to dissolve more quickly in water.
A micropulverizer can create particles finer than 10 microns, so the end-user does not detect grittiness in the mouth. This is especially useful for minerals.
Dry blends often first combine proteins with certain other ingredients such as emulsifiers before co-drying them. Typically, lecithin and flavors are added to protein to help with the wettability of the product. The lecithin helps reduce lumps upon reconstitution. “The consumer wants to put it in water, not use a blender and expects a smooth drink,” says Burrington.
Also, antioxidants such as ascorbyl palmitate, vitamin E or alpha tocopherol can be added to decrease discoloration.
Taste Tests“Of course it has to taste good, too,” notes Chaudhari. “If taste, texture and stability are not in good form, then customers won't repeat the purchase.”
Depending on isoelectric pH, soluble proteins are more susceptible to reacting with other minerals and other components of the beverages. The 100% bioavailable form of ferrous sulfate, an iron enrichment, will cause some metallic taste or discoloration when reacting with protein. Calcium can cause similar problems.
To overcome the challenges mentioned above, microencapsulation and chelation with amino acids can block the reactive sites of minerals so that they will not react with other ingredients. “That will minimize aftertaste or other reactions that could occur at given processing temperatures,” says Chaudhari.
Vitamin B1 has sulfur-containing molecules that, when combined with protein, give off a sulfurous note resembling a rotten egg odor. Removing the vitamin B1 or decreasing the amount added can eliminate the odor. However, if adding vitamin B1 is necessary, a flavor-masking agent, such as nucleotide adenosine monophosphate (AMP), will mask that objectionable odor and metallic taste. “Unfortunately, AMP is not a popular alternative because it can be costly,” says Chaudhari.
“It is generally said that there is a flavor problem with soybeans and products such as soymilk. That is incorrect,” opines Karl Weingartner, director of the International Soybean Program at the University of Illinois (Urbana-Champaign). “It is possible to make an excellent, tasty soymilk but, to some extent, it depends on the starting material and process that you use. That is, some processes will give flavor that is milder than others,” says Weingartner. For example, when the whole soybean is ground into soy flour the possibility of rancid taste is much greater.
However, one process allows manufacturers to use the whole soybean in a formulation, with a reduced chance of rancid flavor. Whole soy powder includes protein and oil, which is spray-dried and then high-heat treated to extract water. Whole soybean products are dairy-like in that the texture made from the whole soy water extraction technology is creamy because it has never been made into a powder, says Ted Nordquist, founder and CEO of WholeSoy (San Francisco), the first company to launch a dairy-like, cultured soy smoothie in 1996. This process uses a chemically free process of heat, grinding and vacuuming to deactivate the development of the enzyme lipogenase (which creates a beany taste).
“Arriving at the best process, and acquiring the best soybeans to make soy cream (similar to full-fat milk) is often more challenging than formulation, says Nordquist. Once a soy base is created--without a beany taste--the flavor of the soy product cannot resemble dairy drinks without the help of flavoring ingredients.
Flavoring soy beverages depends on what the public becomes accustomed to. The best example would involve a comparison of Chinese soymilk with White Wave's (Boulder, Colo.) Silk soymilk. “Soymilk does not--no matter what you do to it--really ever taste like dairy milk, primarily because they come from two entirely different sources,” explains Nordquist. Nevertheless, he believes it is possible to produce soymilk that can get very close to dairy milk. Most importantly, formula refinements that are specific to soy can be learned over time to create a soy drink that may not taste like dairy milk, but tastes great nonetheless, says Nordquist.
“Soy isolates are very much controlled and provide better quality than using whole soybeans,” says Soo-Yeun Lee, PhD, an assistant professor in the department of Food Science and Human Nutrition at the University of Illinois. There is more variation with the whole soybean and a greater tendency towards oxidation because of soy oil. 8th Continent's (Minneapolis) soymilk is reconstituted from soy protein isolates. “This may be why some people believe the taste of 8th Continent is less objectionable,” says Lee.
“There are thousands of commercial masking agents, but most are not good at masking bitterness and astringency,” opines Lee. Some masking agents basically add different flavors so that they override the soy flavor. Other flavors are good at binding soy flavor compounds without adding a significant amount of their own flavor. A general consensus says that brown flavors like chocolate, cinnamon or peanut butter are good at hiding the beany flavor of soy.
“We've encountered products with only a hint of coconut added that rid a product of soy's grassy flavor but, at the same time, didn't convey an obvious coconut flavor,” observes Brown, who still believes that brown flavors are not masking agents, but just flavoring agents.
“Soybeans are astringent, but the astringency is not instant,” says Lee. “It is a lingering perception that builds up with consecutive consumption. Soy astringency compounds produce a “mouthcoating”--a thin layer of protein, saliva and physical compounds--also experienced when drinking red wine or tea. Bitterness is perceived right away.
Lee, a sensory scientist, has conducted constructive analysis to study whether objectionable flavors (like rancid or beany) have an impact on bitterness and astringency.
Theoretically, bitterness and astringency are not supposed to be perceived by smell. However, Lee wanted to know if blocking smell had an impact on bitterness. She found that it increased perception of bitterness and astringency.
Her assumption is that soy-based products have a “halo effect,” or the tendency of a sensory attribute to be rated as more intense or more hedonically negative due to other logically unrelated sensory attributes in a product. For example, when the level of a cherry flavor is increased, most people perceive an elevation in sweetness, despite the fact that no additional sweeteners have been added. Similarly, Lee's research has found that increasing rancid flavor in a food will increase the perception of bitterness, even if no alteration was made in the level of bitterness.
Therefore, objectionable flavors such as rancid or “cardboard,” typically used to describe soy beverages, are the result of a halo effect (i.e., an increase in bitterness or astringency). She also investigated masking agents and found they may not decrease bitterness or astringency.
Both usually are related as an objectionable perception in dairy-like products, because American consumers compare soy beverages to dairy beverages, which do not have astringency. Asian consumers, on the other hand, expect astringency and bitterness in a product. “If they don't taste that, they don't regard it as good,” says Lee. Therefore, formulating a product depends on the demographics developers are targeting. She determines, “There isn't a gold standard of a good-tasting beverage. It is really in the eyes--or tastes--of the consumer.”