Research project funded by the National Honey Board and conducted at Kansas
State University by Dr. Paul E. Neumann, research associate and project
coordinator, Extrusion Research Center, Department of Grain Science and
Industry, and Dr. Edgar Chambers, professor and director, Sensory Analysis
Center, Department of Foods and Nutrition
The importance of breakfast is well-recognized; therefore, many people start their day with a bowl of their favorite ready-to-eat (RTE) cereal.
Breakfast eaters often choose all-natural RTE cereals to satisfy their morning appetites. These cereals appease both the health- and flavor-related concerns of cereal lovers by being free of preservatives, additives and added sugar.1 To maintain sweetness, many cereal manufacturers use pure and natural honey, which imparts a sweet flavor and golden color that many consumers prefer and recognize.2
According to research findings, honey is an ingredient that works well in RTE cereals.
Extrusion is a commonly used processing method in food manufacturing, so it is no surprise that many breakfast cereals are produced in this manner. Yet, little data is available on the use of different honey types and levels in extruded cereals.
Because honey is usually not the primary flavoring agent, nor does it completely replace refined sugars in a formula, this study was initiated to gain a better understanding of honey’s functionality and usage levels in extruded RTE cereal products.
In high-sugar cereals, the key processing considerations are the sugar, starch and water interactions to allow for optimal characteristics in the end product.
The sugar often competes with starch for available water, which may prevent optimal expansion of the product. If extra water is added to compensate for the high sugar concentration, the starch properties are changed so the end product may have an undesirable hard and glossy texture.
What is extrusion?
Simply defined, extrusion is a continuous process in which a preformed
food product is cooked, shaped, and puffed by a combination of mechanical
and thermal energy inputs. A wide range of mechanical hardware configurations
and process conditions are possible with the extruding equipment. This
versatility enables product developers to experiment to achieve the desired
flavor and
texture characteristics in the finished product.
The objectives of the study were to determine the effects of formula and processing variables on the acceptability of extruded, RTE honey-graham cereals. Four variables were examined:
Three colors of honey were used in the study: white (17% moisture), light amber (17.8% moisture) and dark amber (18.0% moisture).
Researchers developed a base formula for the cereal and defined the parameters for a controlled study of the experimental variables (Table 1).
Relative proportions of base formula ingredients were held constant as the levels of honey and lecithin were varied. In the controlled study, five levels of honey concentration (4.6, 6.0, 10.0, 1.0 and 15.4% dry weight basis), lecithin concentration (0, 0.25, 1.0, 1.75 and 2% dry weight basis) and extruder screw speed (282, 300, 350, 400 and 418 rpm) were evaluated.
The variables were studied in various combinations, yielding a total of 17 extrusion runs. Each of the honey colors was subjected to the various treatments, so a total of 51 treatments were produced.
Investigators used a corotating twin-screw extruder (model TX-52, Wenger Manufacturing, Inc.) to process the treatments.
Honey was diluted with one part tap water to two parts honey and added to the extruder barrel’s feed inlet head with a variable stroke length piston pump (Bran-Lubbe). Moisture content was held constant at 19% for all treatments.
In general, as the amount of honey was increased, the specific mechanical energy input from extrusion decreased, especially at lower screw speeds.
Higher honey levels increased the bulk density and radial expansion (piece
diameter) of cereals but lowered the piece thickness and relative numbers
of broken pieces in a given bulk sample. Piece diameter was increased when
screw speeds were decreased, but bulk density, piece thickness and relative
level of broken pieces decreased.
The decrease in specific mechanical energy input during extrusion was attributed
to the apparent concentration-dependent viscosity lowering effect imparted
by the honey. Thus, low-honey cereals produced at high screw speeds tended
to “explode” as they discharged from the die, which resulted in
more broken pieces.
Moisture adsorption, one of the primary concerns with higher levels of honey, was marginally related to honey levels in the sample; it was only slightly higher in cereal samples with higher levels of honey compared to those with low levels. Extrusion conditions were evidently sufficient to disperse the honey and protect it from adsorbing moisture from a humid environment. Lecithin level did not affect the protective effect imparted by the extrusion process.
Ten trained sensory panelists evaluated the samples for appearance, flavor and texture in milk. Eight flavor descriptors were chosen to represent the cereals: graham, honey, spice, sweet aroma, sweet taste, burnt, animal-like and off-flavor. Seven appearance/ texture attributes were selected: amount of broken pieces, brightness, crispness, fracturability, hardness, thickness and cohesiveness. Intensities for each descriptor were rated on a scale from 0 to 15 (none to extreme).
Following is a brief summary of the trained sensory panel results:
Based on the results of the trained panel testing, optimal honey colors and levels for texture and flavor were determined. These data were in turn used to develop samples for consumer study.
The consumer panel consisted of 101 males and females of varying ages and socioeconomic backgrounds who had no training in sensory evaluation. Each panelist had to have eaten RTE cereal at least once in the preceding two weeks. They evaluated six cereal samples, one at a time, and rated sweetness, texture and honey-like note. They also rated the cereals for overall acceptability (see Tables 2-6).
To develop the desired appearance, flavor and texture attributes noted by the sensory panelists, honey and lecithin were incorporated in the six samples at 10% and 0.85% levels, respectively. The cereal was extruded at a screw speed of 350 rpm.
Following is a summary of the consumer test results:
Based on the results of this study, several conclusions may be made:
In addition to these conclusions, the qualitative observations in this study suggest that higher levels of honey may help delay rancidity development, thus reducing the need for the use of chemical antioxidants with these products.
©2007 National Honey Board
www.honey.com | www.honeylocator.com
