How to choose the right starch? Methods of starch selection

Unfortunately, many suppliers are not aware of how their ingredients, which are utilized within product formulations and/or processing parameters, they have studied may not be relevant to your system. To illustrate various conditions that are important and should be asked, I’ll use the following.

What Is the Desired Function of the Starch You Are Adding?

Having identified the food product, will the starch be expected to provide only one function or act as a multifunctional ingredient? Your answer to this question could help you identify whether you require one starch, a blend of starches, or an ingredient system approach. If it is a blend that is required, then the ratio between starches becomes critical as related to the physical properties ultimately desired. Answering just this one question directs many of your choices regarding starch selection or what other ingredients (hydrocolloids) may be worth considering.

What Is the Method of Processing You Anticipate Using?

Your answer to this question will determine whether you are going to cook the starch or not. If your process is a dry mix or a noncooking preparation, we have now identified the potential to consider instant starches; maybe not entirely, but we should consider them. If you had stated cooking, use of thermal processing is required: from a cost and functional standpoint, a cook-up starch would be suggested as the first choice. For foods that are dry mixes, we will have to consider what happens postblending or when the consumer interacts with the product.

What Is the Food System’s pH?

The acidity of the food is extremely important. Foods can be hot filled at a pH of less than 4.6, but are temperature dependent. So, knowing the finished food pH is important not only related to processing but for food safety. Acids possess different “pk” values (titratable acidity) and therefore food technologists should consider the total acidity of the food system. Using titration to calculate the total acidity is more accurate. The pH considered neutral for starch is not 7. Those foods having a measurable pH of at least 4.6 or higher (up to 7.5) are considered neutral. A pH value above 7.5 is generally selfregulating due to off-flavors being developed. Neutral foods expected to retain long shelf-life require sterilization. The sterilization process requires temperatures above atmospheric and thus dictate starch selection. Foods having extreme or high acidity, less than pH 3.5, possess the potential to hydrolyze starch and therefore starch selection will be determined by the degree of cross-linking and finished textural properties. The food systems that range between 3.5 and 4.6 offer several starches for selection. The texture, process, and other handling parameters will determine the starch or starches of choice. Many times container size and cooling are critical for these products and starch selection.

Does the Process Contribute High Shear?

The answer to this question assists the food scientist in determining how to maintain granule integrity during and postprocessing. If this is not important, an instant starch may be acceptable. However, if water management is critical, granule stabilization is also important. Shear is similar to heat and acidity, in that it can damage the starch granules. Simple milling can fracture granules; consider what high shear such as homogenization or vacuum cooling could do to starch under stress conditions (low pH and/or high heat). Improper handling or the incorrect starch choice could lead to granule damage, free water, and instability during storage.

What Percent of Water-Soluble Materials Will Be Present?

Ingredients that hydrate water limit the available water for starch granule hydration, swelling, and the generating of viscosity. Starch requires minimum levels of water to be fully functional. When other soluble material is present and elevates the total soluble solids to greater than 45%, the starch has a tendency to be limited in hydration under atmospheric conditions. At soluble solids less than 20%, the water phase is in such excess compared to the percentage of starch used that it is typically incapable of managing the water compared to food systems with soluble solids greater than 20% but less than 45%. Therefore, to stabilize the water phase, the technologist must increase the percentage of added starch or other total soluble solids to greater than the desired amount as originally identified.

Is One or More of the Following Used: Fat(s), Salt(s), and Gums?

As within the term soluble solids, two of the aforementioned ingredients hydrate water and can significantly alter the hydration and functional potential of any incorporated starch. Gums, like starches, contribute to viscosity and texture. They can also influence mouth-feel and/or eating quality. Because they compete for water, they can cause latent starch hydration, or not allow it to hydrate at all. Without proper hydration a starchy flavor (off-taste) could result. Salts too hydrate water, but more importantly can be thermally active (eutectic). In other words they may retain or store heat, thus potentially causing starch to overcook as well as altering flavors. Lipids or fats and oils obviously do not hydrate the water but can alter the hydration rate of added starches. This can be accomplished by coating the starch with the lipid or using the lipid to coat other ingredients; therefore knowing the type of lipid is important. If it is a hard fat, knowing the melting point is important. All of these are critical, if you are preparing a dry mix. Identifying the correct order of ingredient addition cannot just change the hydration rates but contribute and control the final product characteristics and stability.

Is the Finished Product Subjected to Postprocessing?

The knowledge of what is going to happen to the finished food is also very critical to the food technologist. If, for example, the consumer is going to bake, microwave, or subject it to steam heating, for prolonged periods, the developing food scientist’s choice for a starch and processing will be very important. The food scientist should ensure the product supplied to the consumer is capable of meeting the requirements anticipated; therefore process specifications related to the consumer market are necessary before formulating and choosing ingredients. In many cases for food systems that are to be post-processed, the food scientist will utilize a starch blend and/or a hydrocolloid system approach.

How Will the Product Be Stored?

Storage of the food product is sometimes as important as the processing or preparation. Knowledge of how it is to be stored, time of storage, and the conditions of storage are critical. Without this information, the food scientist formulating the food product may not know the best process to ensure stability during storage. An example is a food that is to be frozen at (-20 to -40°C) and kept in the freezer at (-20°C) for greater than a year. The food scientist should know what the storage conditions are for that period of time. This will aid with the decision as to should the finished product be slow or fast frozen. If that is not an option then it will still aid with starch (system) selection.

Starches that offer good to excellent freeze-thaw stability, do not always guarantee extended freezer shelf-life of up to a year or more. However, those starches that can give a 1 year or more freezer life will always provide adequate freeze-thaw stability. Refrigeration is a simple shelf profile to meet. Extended freezer life at -20 to -40°C is very difficult to achieve. Starch alone is not the best answer. This is one of those times when mixed hydrocolloids are advantageous. A properly modified starch (cross-linked/mono-substituted) with a small percentage of a gum (xanthan) can provide the needed stability. Similar stability can be achieved with other starch/gum or gum-only systems, but texture and economics must be profiled. These are many of the important questions that should be asked before formulating with starch. For additional information, see Table below.

1. What is the desired function for the added starch?
a. thickenere. binder
b. stabilizerf. bulking agent
c. texturizerg. several
d. emulsifier
2. What is the processing method?
a. cooking (liquid)c. dry mix
b. noncook (liquid)d. several
3. What is the pH of the food system?
a. >4.5c. <3.5
b. <4.5d. unknown
4. What is the percent soluble solids?
(ingredients that hydrate water)
a. >45%d. <20%
b. <45%e. varies
c. >55%
5. What is the shelf-life expectancy?
a. <30 daysc. >1 year
b. 1-6 monthsd. unknown
6. How will the finished product be stored?
a. ambient temperature
b. frozen
c. combinations
7. What is the desired product texture?
a. smooth
b. nonsmooth
c. grainy
d. other
8. What is the desired eating quality (mouth-feel)?
a. creamyd. jelly
b. fudgee. unknown
c. pasty
9. What is the desired surface appearance?
a. sheend. translucent
b. opaquee. unknown
c. dull
10. How will you measure or determine viscosity? And when?
a. Visco-Amylo-Graphd. Fluidity (funnel)
b. Brookfielde. Rapid-Visco-Analyzer
c. Bostwickf. unknown
11. Is high or excessive shear introduced?
a. homogenizationd. direct steam injection
b. millinge. pumping > 25 ft. hot
c. vacuumf. several
12. Will the process involve one or more of the following?
a. hot fillinge. blast or quick freezing
b. ambient fillingf. reheating (reconstitution)
c. refrigerationg. steam tables
d. slow freezingh. yours
13. If fat is used, what type?
a. liquidd. lard
b. solide. blend
c. shortening
14. Are salts utilized?
a. what type
b. percent
c. blends
d. other
15. Are other hydrocolloids used?
a. what type
b. blends
c. unknown
16. Is the final product a dry mix?
17. If yes to 16, what does the process involve?
a. blendingc. extruding
b. agglomeratingd. combinations
18. Is moisture content of the added starch critical?
19. If yes to 18, what is the anticipated packaging?
20. If not a dry mix, what is the anticipated packaging?
a. glasse. paper
b. canf. plastic
c. pouchg. tote
d. drumsh. severa
21. Is the added starch to be used in more than one product?
If yes, consider similar events for the other products and identify the critical functions
contributed by the starch.
22. How important is ingredient economics?
a. veryc. quality dependent
b. not veryd. unknown
TABLE 1. Questions to Ask Before Selecting a Starch

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