Download New perspectives on starch and starch derivatives for snack

New Perspectives on Starch
and Starch Derivatives
for Snack Applications
D. P. Huang
National Starch and Chemical Company
Bridgewater, New Jersey
In nature, starch is available in an abundance, surpassed only by cellulose as a naturally
occurring organic compound. Starch is located in many parts of green leafed plants, such as
roots, stems, seeds, and fruits. Starch serves as food for energy during dormancy and germination
in plants and functions similarly for humans and animals. However, uses for starch extend far
beyond its original function as a source of biological energy. Today, many industries use starch
or its derivatives in one form or another in various applications. In foods, starch is traditionally
used at moderately low levels as ingredients that have nutritive value while also imparting
functional properties to food systems. Starches play an important role in controlling the aesthetic
and organoleptic characteristics of a number of processed foods (Fig. 1). Depending on the type,
starch and its derivatives may be used to facilitate processing, provide texture, thicken, suspend
solids, yield a desired appearance, and control moisture, consistency, and shelf stability.
Starches and starch derivatives have a long history of use in snack foods, especially as functional
ingredients to help snacks achieve various textural attributes. For example, in expanded or puffed
snacks, the target texture can be obtained by changing the amylose/ amylopectin ratio by
manipulating combinations of high-amylose and high-amylopectin starches according to the
properties desired. High-amylose corn starches, derived from genetic hybrids of regular corn, can
be used when increased crunchiness and strength are required. An effective way to increase the
expansion of a snack is to add waxy corn starch, which is essentially 100% amylopectin. One
problem with high-amylopectin starch is the breakdown of amylopectin molecules by the hightemperature/high-shear processing conditions experienced during cooker extrusion and frying.
To increase the resistance of starch molecules to break down under excessive heat and shear,
specialty starch suppliers use “crosslinking” agents to chemically modify the waxy corn starch.
A crosslinked waxy corn starch exhibits controlled expansion capabilities in the puffed snacks
due to the improved resistance of amylopectin to breakdown.
For snacks that expand by baking, a different modification of waxy corn starch is required. In
baking, where internal temperatures of snacks increase more slowly than in extrusion or frying,
pregelatinized waxy corn starches are recommended. Pregelatinized starches have been
precooked in water and then dried; they require no further cooking before baking to contribute to
texture development. This is an important feature because conditions in baked expanded snacks
do not allow adequate gelatinization of regular waxy starch. Pregelatinized waxy corn starch
allows the expansion process to begin earlier. In addition, high-amylose starches are used to
reduce oil absorption in fried snacks, due to their strong film-forming properties.
Snack foods include a broad range of products that can take many forms, and definitions of
snacks are being modified to include sandwiches, yogurt, and even ice cream. These items now
compete with traditional savory, bagged snacks and confectioneries. It would be impossible to
cover the whole range of what could be termed snack foods. One of the reasons is that because of
geographical and cultural differences, a product that is considered a snack by one population
may not be considered one by another population. In this article, snacks include only savory
products, such as chips, extruded snacks, nuts, popcorn, etc., as defined by the Snack Food
Association.
Fig. 1. Typical Foods with Starches
Baby foods
Barbecue sauces
Beverages
Brown gravy mix
Canned soup
Coated nuts
Confectioner’s sugar
Custard filling
Encapsulated food flavors
Fruit snacks
Hot dog/bologna/frankfurter
Instant pudding
Instant soup
Jelly gum candies
Low-/No-fat mayonnaise
Low-fat ice cream
Low-fat yogurt
Meat pie/chicken loaf
Pie filling/fruit filling
Salad dressing
Snack dips
Spaghetti sauces
In 1993, the U.S. retail dollar sales for snack foods totaled $14.7 billion, up 6.2% from 1992. The
volume increased 6.6% to 5.5 billion lb. Based on dollar sales, the major 1993 snack market
shares were potato chips (31.3%), tortilla chips (19.9%), snack nuts (10.0%), pretzels (7.5%),
microwave popcorn (5.4%), extruded snacks (5.2%), corn chips (4.3%), meat snacks (3.7%),
ready-to-eat popcorn (3.2%), and all other snacks (9.5%). Among all snacks, pretzels, “the snack
of the ‘90s,” had the highest growth, climbing a remarkable 24.7% in dollar sales and reached
the $1 billion mark in 19931 . The projected growth for pretzels for the next few years is expected
to continue at double-digit rates. The growth is attributed to their excellent reputation as a
healthy (low-fat) snack.
New generation snacks fall into the following categories: 1) lower fat, 2) baked, not fried, and 3)
high-fiber products. Their sales are on the rise, and projected retail sales will reach an estimated
$2 billion by 19982 . These snack foods are triumphing because they promote a healthy image.
Starches are playing a very important role as functional ingredients to help snack foods achieve
the healthy image. The following products contribute to the development of these new generation
snacks.
Starch-Based Adhesive Coating
Fat and oil have traditionally been used for adhering seasonings and flavorings to the surface of
cereal-based snack foods. However, as a result of recent market demand for low-fat and fat-free
snack foods, many companies have introduced or intend to introduce low-fat and fat-free baked
chips, crackers, and extruded snacks. Adhering seasoning or flavorings to the snacks is a
challenge when oil or fat is reduced or eliminated. Many manufacturers have evaluated gumbased solutions to replace fat or oil to adhere seasonings. However, there can be drawbacks with
some gum systems.
These include: 1) too viscous at high solids concentration resulting in difficulty in spraying, 2)
the spray solution sets to a gel when cooled and plugs the spray nozzle, and 3) a post-drying step
is required.
A starch-based-coating system with a high degree of tackiness has been introduced into the
market and is intended to replace fat or oil as a tackifier for cereal based snack foods. It exhibits
significantly better tensile strength when compared with various tackifiers as measured by
Instron equipment at 30% solid concentration (Fig. 2). The product is available as a powder.
However, it is easy to dissolve in water or can be mixed with glycerin and water. The starchbased-coating is used in solution and sprayed onto snacks to adhere both seasonings and
particulates. It develops a very tacky texture and dries quickly. The solution is easy to spray at a
high solids concentration (30-40%) due to its low viscosity characteristics (Table I). One
advantage of this coating is that it can be applied cold or hot. For example, at the temperature
ranges shown in Figure 3, the solution remains stable (i.e., liquid), thus minimizing any chances
of plugging the spray nozzle during application.
The starch-based adhesive coating has shown many benefits in snack and cereal applications. Its
low use level makes it cost effective, and it does not mask applied flavors. This coating system
offers the flexibility and compatibility to be used in many snack applications including RTE
cereals, tortilla chips and corn chips, pretzels, baked chips, nut products, crackers, and granola
bars. It even seals the ends of egg rolls and burritos, resulting in more visually appealing
products.
Functional Fiber-Resistant Starch
Dietary fiber, which was front-page news in the 1980s and lauded for reducing the risk of colon
cancer to heart disease through cholesterol lowering, has taken a back seat to other food issues,
especially fat. Recent data from the National Cancer Institute (NCI) confirm that Americans’
fiber intake is still well below the recommended levels 3 . As the nation continues to focus on
weight control and healthy type foods, fiber’s important role is still recognized by many
consumers and food companies. However; many consumers do not like the high-fiber snacks
currently on the market. The reason is quite simple. The existing snacks are not high in quality.
Taste and texture are not very good and do not meet consumers’ expectations.
Recently, the first commercially developed concentrated source of resistant starch was
introduced to the market. The resistant starch, billed as a functional fiber, contributes
approximately 30% total dietary fiber as analyzed by the approved AOAC method for fiber
analysis. It is well suited for snack applications because the resistant starch may allow snacks to
display a highly marketable “good source” or “high fiber” nutritional claim without
compromising quality. Unlike traditional sources of dietary fiber that hold significant moisture
and can impart a gritty mouthfeel and characteristic fiber taste, the commercially developed
resistant starch has low water-holding capacity (Fig. 4), small particle size, and bland flavor. As
the photomicrograph comparison demonstrates, the commercially developed resistant starch
crystallites are much smaller than those in traditional sources of fiber and therefore do not
adversely affect texture (Fig. 5A- D).
Resistant starch has a long history of safe consumption in humans. It has been found in both
unprocessed foods such as bananas and lentils and processed foods such as bread and cereal. For
nutritional purposes, starch in foods can be classified into three categories: rapidly digestible
(RDS), slowly digestible (SDS), and resistant (RS). Resistant starch can be further divided into
three categories according to the type found in foods4 . RS1 refers to physically trapped starch
and can be assumed to pass through the body unchanged, such as that found in partially milled
grains and seeds. RS2 starch is raw β-type starch granule and is typically found in bananas and
raw potatoes. RS3 starch is retrograded, like the starch found in cooked and cooled potatoes,
bread and cereal. The commercially developed resistant starch is technically classified as an RS3
starch.
Resistant starch is not digested or absorbed in the small intestine. This non-digested starch is
subsequently passed to the large intestine and, like many soluble fibers, it is broken down in the
colon by fermentation to short-chain fatty acids, carbon dioxide, hydrogen gas, and methane.
Like other fibers, resistant starch plays an important role in normal digestive physiology.
The commercially developed resistant starch is not simply a high amylose starch. It is the result
of special corn hybrid breeding program in combination with biochemical and physical
processing that optimizes the retrogradation profile of the starch to maximize its total dietary
fiber contribution. Because the snack market is lacking good fiber sources as ingredients for use
in snack products, the new commercially developed resistant starch can help snack processors
open up new categories and deliver good quality fiber-fortified snacks to demanding customers.
Conclusions
Specialty starches can provide a number of functional benefits to snacks – increased expansion,
improved crispness, reduced oil pick-up, and better overall eating quality. The use of starchbased coating to replace fat or oil in snack foods is likely to increase due to the market demand
for tasty and appealing reduced-fat products. The starch-based coating provides many benefits,
including cost effectiveness due to low use level, good flavor release, compatibility with a range
of processes, and friendly labeling as corn syrup solid.
Commercially developed resistant starch opens up new opportunities for snack manufacturers to
develop high-quality, fiber-fortified snack products. It can be classified as a functional fiber. In
snack applications, resistant starch improves fiber-fortified product quality, increases expansion
of fiber-fortified and high-fiber extruded and baked snacks, reduces oil pick-up in fried snacks,
provides light, crispy texture, and can be used alone as a fiber source or as a functional
complement to other types of fiber.
References
1. Anonymous. 1994 Snack Food Association state-of-the-industry report. Snack World, 94.
2. Levy, B. Snaxpo 95 offers a new tack for the future. Snack World, April 1995.
3. Sloan, A. E. Not just another oat bran Consumer/product trends. Food Technol. 49:32, 1995.
4. Englyst, N. H., Kingman, S. M., and Cummings, J. H., Classification and measurement of
nutritionally important starch fractions. Eur. J. Clin. Nutr. 46:S33, 1992. D. P Huang.
Author
David P. Huang is cereal and snack strategic business unit manager at National Starch and
Chemical Company in Bridgewater, NJ. He received his M.S. and A.D. degrees in food science
from Michigan State UniveRS1ty in 1979 and 1982, respectively, and an M.B.A. degree from
Fairleigh Dickinson UniveRS1ty in 1990. Before joining National Starch and Chemical, he was
general manager for H.J. Heinz.
Reprinted with permission from the August 1995 issue of CEREAL FOODS WORLD