effect of starch characteristics on the physical
TRANSCRIPT
J. Home Econ. Jpn. Vol. 42 No. 8 711-717 (1991)
Effect of Starch Characteristics on the
Physical Properties of Cookies
Yoshiko WADA, Taeko KURAGANO* and Hiroki KIMURA* *
Kanto-Gakuin Women's Junior College, Kanazawa-ku, Yokohama 236, Japan * Konan Women's University, Higashinada-ku, Kobe 658, Japan
** Showa Sangyo Co. Ltd., Research and Development Center, Funabaski, Chiba 273, Japan
Simplified model cookie doughs containing two kinds of starches with different gelatinization characteristics, waxy corn starch (WCS) and high-amylose corn starch (HACS), were baked and evaluated by physical test methods and a sensory panel to study the effect of starch characteristics on the cookie quality.
WCS cookies showed a larger expansion in the vertical direction and smaller spread than HACS cookies. Both the physical and sensory evaluation revealed the hard texture of WCS cookies and significant shortness of HACS cookies. A continuous structure was observed in the defatted WCS cookies by SEM, which is considered to have been responsible for the expansion and the hard texture. Although the degree of gelatinization in both cookies was very low, that of the WCS cookies was slightly higher than that of the HACS cookies. DSC thermograms and scan-ning electron micrographs suggest the possible gelatinization of WCS granules in the cookie.
It is assumed that a continuous structure due to starch gelatinization led to expansion of the cookie during baking and a hard texture for the finished product, so that interruption of starch
gelatinization might be essential to produce cookies with a short texture. (Received November 21, 1990)
Keywords cookie, shortness, starch, gelatinization, compression fracture test.
INTRODUCTION
Shortness is a term relating to the soft texture of baked products such as biscuits and cookies in a masticated form.1) The authors have studied which parameters affect the physical and textural characteristics of cookies, especially shortness as an important textural parameter for consumer accept-ance.
In our previous studies,2)3) it was suggested that shortness judged organoleptically might be com-
prehensible as a complex texture relating intimately to softness, brittleness and easiness of disintegration when masticated and wetted with saliva in mouth, and could be quantified by a low fracture stress and small fracture energy by physical test methods. Our present interest in this matter is learning what is important in producing cookies with a short texture.
In cookie baking, no gluten or very little gluten is required,4) because the use of gluten leads to
tougher products without shortness.53 Some au-
thors have described that the use of fat produced
a short cookie, since fat coats the flour and inter-
rupts hydration and the development of gluten.4)6)
Hoseney5) stated that the interruption of gluten
development was due to the high level of sugar
existing in most cookie formulas and the relatively
high pH created by sodium bicarbonate.
Wada and Hashimoto7) prepared two model
cookies from simplified recipes without sugar, one
of which contained cysteine and the other iodine.
Each reagent affected the gluten structure and
starch swelling, respectively. Although the addi-
tion of cysteine, which destroyed the gluten net-
work, produced hard and not short cookies, the
addition of iodine, by interrupting the swelling
and gelatinization of starch as a fat does, resulted
in short and palatable cookies.
These results were considered to suggest that
interference with the swelling and gelatniization
of the starch granules in flour by fat played an
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J. Home Econ. Jpn. Vol. 42 No. 8 (1991)
important role in producing short cookies as well as interrupting the gluten network; in other words, shortness could be understood as a characteristic texture caused by disturbing the development of a continuous phase formed by gelatinized starch.7) From this point of view, we are interested in the
gelatinization of starch in the presence of a high proportion of fat, as is used in cookies.
The objective of the study reported in this paper was to examine the effect of starch characterisctis in gelatinization on the physical and textural pro-
perties, and especially the shortness, of cookies.
MATERIALS AND METHODS
Materials Waxy corn starch (WCS) and high-amylose corn
starch (HACS) were obtained from Honen Corpo-ration, Tokyo. The gluten used was a special-
grade reagent (Nakarai Chemicals Co. Ltd., Kyo-to). Baking powder, containing 10% potassium hydrogen tartarate, 34% sodium phosphate, 27% sodium hydrogen carbonate and 29% starch, was supplied by Meijiya Co. Ltd., Tokyo. The fat used was hydrogenated fish oil obtained from Nippon Oil & Fat Co. Ltd., Tokyo.
Determination of the amylose/amylopectin ratio of starches The amylose and amylopectin ratio of the starch
samples solubilized with an alkaline was deter-mined by iodine colorimetry.8)9)
Cookie preparation Table 1 shows the recipes of simplified model
cookie doughs used in this study. Starch, gluten and baking powder were mixed thoroughly in a weight ratio of 96:4:2 prior to dough mixing. Fat was mixed for two minutes by a domestic cake mixer (Cakemaster MK-710 from Matsushita Elec-
tric Industrial Co. Ltd., Osaka), and the other
ingredients were then added to the creamed fat
and mixed together for an additional 2 min.
The dough was rolled to a thickness of 5 mm
and cut to a diameter of 3.3 cm, before baking at
200•Ž for 15 min.
Measurements of thickness, spread factor,
expansion ratio and weight decrease from
cookies
The thickness of a cookie was determined as the
average of the maximum and minimum values of
the measured thickness.
Spread factor was calculated by dividing the
diameter by the thickness of a baked round cookie.
Expansion ratio was calculated as the ratio of
the cookie volume after baking to that before
baking, both of which were determined by multi-
plying the area of the top of the cookie by its thick-
ness. The area of the top of the cookie was meas-
ured by a planimeter.
Roughness was obtained by dividing maximum
thickness by the minimum thickness of a cookie.
Weight decrease was measured as a percentage
of the cookie weight after baking to that before
baking.
Forty-eight replications were made for all the
measurements.
Determination of the degree of gelatiniza.
tion
Cookie samples were defatted with hexane,
ethanol and acetone, using the procedure of Ichi-
kawa et al.10) The degree of gelatinization of each
sample was determined as described by Fujii et
al.11)
Differential scanning calorimetry (DSC)
About 30 mg of dough was exactly weighed and
sealed in a silver pan of 70 ƒÊ1 in volume. The
sample was heated at 1•Ž/min from 0 to 130•Ž
in a DSC-100 differential scanning calorimeter
equipped with an SSC-5020 system for tempera-
ture control and data handling (Seiko Instruments
Inc., Tokyo). Thirty-five mg of distilled water
was used as a reference.
Scanning electron microscopy (SEM) of the
starches and cookies
A small amount of raw starch was put on to
adhesive tape. A piece of a cookie was cut and
defatted with diethyl ether and acetone, before
drying with hot air to remove the solvents. These
samples were mounted on aluminum specimen
Table 1. Recipes for the simplified model cookies
36 ( 712 )
Effect of Starch Characteristics on the Physical Properties of Cookies
stubs and sputter-coated by a Hitachi E-101 ion sputter with gold and palladium. Scanning elec-tron micrographs were obtained, using a Hitachi S-510 scanning electron microscope operated at 15 kV.
Determination of the physical properties The physical properties, i.e. breaking or fracture
characteristics, of the cookies were measured with a Dynagraph (Iio Denki Co. Lrd.) at a constant rate of deformation. A cookie sample was com-
pressed with a tooth-like plunger of 1 cm diameter at 5 cm/min from its original height to 3 mm. The apparent fracture stress and energy were cal-culated from the force-deformation curve of the cookie sample as described by Kuragano et al.12) These values have been reported to have good correlation with the cookie hardness and brittleness determined by a sensory evaluation (the term "apparent" means measured "as is" in this paper) .
Sensory evaluation Hardness, brittleness, easiness of disintegration
in mouth and shortness of the cookies were eval-uated by 28 panelists of students and researchers from Kanto-Gakuin Women's College, Konan Women's College, and Showa Sangyo Co. Ltd. Each panelist was asked which was harder, shorter, more brittle and easier to disintegrate when mas-ticated in the mouth from a comparable pair of cookies.
RESULTS AND DISCUSSION
Size and appearance of the cookies The characteristics relating to the dimensions
and appearance of the cookies are shown in
Table 2. Because of expansion in the vertical direction,
the mean thickness of WCS cookies was about 36%
greater than that of HACS cookies, which gave a relatively greater spread. The diameter and area of the top of both cookies were almost the same. The expansion ratio of WCS cookies was 115% due to the increased thickness, and that of HACS cookies was 83%. Sugimoto et al.13) have reported that WCS gave a larger expansion volume when heated after gelatinization compared to HACS in "Ebi -senbei" (a typical Japanese snack) production,
The results obtained in this study were consistent with the report by Sugimoto et al.,13) although the
Table 2. Characteristics relating to the dimensions
and appearance of the cookies
Each value was obtained from 48 replications for all
the measurements.
Fig. 1. Change of cookie appearance during baking
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J. Home Econ. Jpn. Vol. 42 No. 8 (1991)
amount of water available for starch swelling was limited, and fat, which interrupted swelling and
gelatinization of the starch, existed in the recipe. WCS cookies showed slightly larger value of
roughness than HACS cookies. It was observed that the surface of the WCS cookie was became rough during baking, whereas the HACS cookie remained smooth (Fig. 1).
The weight decrease of each type of cookie was similar.
Determination of the amylosefamylopectin ratio of starches Amylose/amylopectin ratios of WCS and HACS
cookies were 1 :99 and 76:24 respectively. Takahashi et al.14) has reported that expansion
of "Arare-Okaki" (a Japanese snack made from rice) was caused by the high extensibility of amylo-
pectin. Sugimoto et al.13) also confirmed that amylopectin prepared from rice starch gave a
greater expansion than the original rice starch. In this study on cookie baking, amylopectin-rich.
WCS gave a higher expansion ratio than amylose- rich HACS. Amylopectin might also have played a pronounced role in the expansion of the cookies.
Determination of the physical properties and the sensory evaluation A typical force-deformation curve for HACS
cookies obtained from the compression test con-sisted of a sharp peak and rapid drop in force after fracture, which has been reported to be charac-teristic of crisp, brittle or snappy foods15) (Table 3). That of WCS cookies had a saw-toothed line with multiple peaks.
The apparent fracture stress and energy of HACS
cookies were smaller than those of WCS cookies,
suggesting that HAGS cookies were less hard and
easier to break.
The difference in textural properties of the
cookies was also confirmed by the sensory evalua-
tion (Table 4). The panelists discerned a signif-
icant difference (P•„0.01) between the two cookies
in all characteristics evaluated in the test. WCS
cookies were evaluated as being harder, less brittle,
difficult to disintegrate in the mouth and less short,
while HACS cookies were judged softer, more
brittle, easier to disintegrate when masticated and
shorter.
Scanning electron microscopy of the
starches and cookies
WCS granules were polygonal with a dimpled
surface and larger than those of HACS. Most
HAGS granules were spherical or with a budded
shape, but some of them were elongated. Every
Fig. 2. DSC thermograms of a WCS cookie dough (A) and an HACS cookie dough (B)
Table 3. Physical properties of the cookies
n=30. Values in parentheses are coefficients of varia-tion (%). Low apparent fracture stress and low ener-
gy correspond to cookie softness and shortness judged. orgaoleptically.2)3)*,**Significantat 5 and 1% pro- bability, respectively.
Table 4. Result of a sensory evaluation of the
cookies
38 ( 714 )
Effect of Starch Characteristics on the Physical Properties of Cookies
granule of HACS had a smooth surface (Fig. 3). It is known that, compared to bread, pie and
other bakery products, starch granules remain in-tact in a baked cookie.16)17) After baking, how-ever, some of the starch granules were deformed, and a smooth and continuous structure, which appeared as if "covered with resin," was observed in the WCS cookies, but not in the HACS cookies
(Fig. 4). Every granule remained intact in the HACS cookies, as is normal in cookies containing sugar.
The continuous microstructure with a smooth surface observed in the WCS cookies is presumed to have acted as a membrane capable of retaining
gases such as air, carbon dioxide and water vapor, and giving rigidity to the total mass. Retained
gas, expanding with heat, would increase the dough. volume. Sugimoto et al.13) observed a thin mem-brane in baked products from rice-amylopectin
and WCS by SEM, whereas the heterogeneous gel remained without expanding in those from HACS, which gave the least volume. Lack of a continu- ous structure in the HACS cookies presumably caused less rigidity and ability for gas retention.
Neither a fibriller nor thin membrane structure due to developed gluten was found in either cookie, so that no gluten was assumed to have developed under the mixing conditions used in this study. Fat acted as a barrier between water and gluten in both of the simplified cookies, as in normal cookies.
Degree of gelatinization and DSC thermo-
grams The degree of gelatinization of the WCS and
HACS cookies was 2.0% and 0.8%, respectively
(Table 2). Although both values are quite low,
Fig. 3. Scanning electron micrographs
of raw starches
A, Waxy corn starch.
B, High-amylose corn starch.
Fig. 4. Scanning electron micrographs of the defatted
cookie structure
A, a WCS cookie. B, a HACS cookie.
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J. Home Econ. Jpn. Vol. 42 No. 8 (1991)
that for WCS cookies was slightly higher than that for HACS cookies.
A distinct endotherm of fat melting at about 36•Ž was observed in the DSC thermogram of
each cookie dough (Fig. 2). No thermal event was found over 36•Ž in the thermogram of the HACS cookie dough, whereas the WCS cookie dough gave a broad endotherm at about 114•Ž, starting at about 88•Ž.
Hoseney5) had assumed that the endotherm at about 115•Ž that was observed in a sugar-snap cookie dough was due to starch gelatinization, but confirmed that starch was not gelatinized during cookie baking because the cookie dough did not reach the transition temperature mentioned above during baking.
We also measured the temperature rise in the cookie dough. Under the conditions of our ex-
perimental baking, 200•Ž for 15 min in an oven, the temperature in the center of the dough reached 107•Ž at the most. This result suggests that most of the WCS granules were not gelatinized during baking with our simplified cookie recipe, but the
possibility that very few granules of WCS were gelatinized remains because the endotherm started at about 88•Ž in the cookie dough.
Lineback et al.18) have reported that, due to the low water content, the starch granules in cookies were difficult to gelatinize compared to those in such bakery products as bread, angel-cake, and doughnut.
We confirmed that the gelatinization degree of the cookies tested was very low, suggesting difficulty in starch gelatinization. However, the DSC thermograms and the scanning electron micro-
graphs of our simplified cookies appear to give evidence for possible gelatinization of very few of the WCS granules. The slight difference between. the WCS and HACS cookies in the degree of ge-latinization could also be considered to support this assumption.
Hoseney5) has pointed out the possibility of starch gelatinization in cookies low in sugar. The formula used in this study contained no sugar, so that it is probable that a small portion of WCS
granules in the cookie dough gelatinized to form a continuous phase, which resulted in expansion and the hard texture.
WCS is known to swell and gelatinize at a lower temperature than normal corn starch, whereas
HACS showed restricted swelling and gelatiniza-tion in the amylograph condition,19) in which more
excess water was available than in the cookie dough.
These observations lead to the assumption that WCS granules bound water and gelatinized at a
relatively low temperature in the simplified cookie dough, so that setting of the cookie had been
finished earlier than water was completely lost by drying. In the HACS cookies, on the contrary,
free water was lost without contributing to the
formation of a continuous structure during baking, as in normal cookies, because HACS granules do
not bind as much water as WCS.19) The absence of the continuous structure is presumed to have
caused little resistance to force application or de-formation, resulting in the short texture of the
product. In conclusion, it has been suggested in this study
that unless gluten developed, very little of the waxy corn starch could be gelatinized in the sim-
plified cookie dough without sugar in spite of the existence of a high ratio of fat, forming a continuous
structure resulting in expanded and hard cookies without shortness. These results are considered to
support the importance of disturbed gelatinization of starch suggested in the previous paper.7) The
interruption of starch gelatinization might be essen-tial to produce short cookies.
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3) Wada, Y., Kuragano, T. and Takimoto, M.: Nihon Kasei Gakkaishi (J. Home Econ. Jpn.), 36, 87
(1985) 4) Smith, W.H.: Biscuits, Crackers & Cookies, Vol. 1.
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Effect of Starch Characteristics on the Physical Properties of Cookies
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ク ッキ ー の 物 性 に及 ぼ す 澱 粉 特 性 の 影 響
和田淑子,倉 賀野妙子*,木 村宏樹**
(関東学 院女子短期大学, *甲 南女子大学, **昭 和 産業(株)総合研究所)
平成2年11月21日 受理
澱粉特性 が クッキーの品質 に及 ぼす影響 を調べ るため,ワ キシー コーンスターチ(WCS)と ハイ
ア ミロース コーンスターチ(HACS)と い う,糊 化特性 の異 なる二種類 の澱粉を用 いて単純化 した
配合 のモデル クッキーを調製 し,こ れを物性 測定 と官能検査 に より評価 した.WCSク ッキ ーはHACSク ッキ ーと くらべ,垂 直方 向に大 き く膨化 し,ス プ レッ ド(焼 き広が
り)は 小 さ くな った.物 性測定 と官能 検査 のいず れにおいて も,WCSク ッキ ーは硬 く,HACSク
ッキ ーは顕著な ショー トネスを示 した.走 査電子顕 微鏡で観察 してみ ると,脱 脂 したWCSクッ キーには連続的 な構 造が認め られ,こ れが膨化や硬 い物性の原因 と考え られた。 両 クッキ ーともに糊
化度は 非常 に低か ったが,WCSの ほ うがHACSク ッキー よりわずか に 糊化度 が高か った.示 差
熱分析 と電子顕微鏡 観察か ら,WCSの 粒子が クッキー中で 一部 糊化 してい ることが示 唆 された.
澱粉 の糊化に よる連続構造は ク ッキ ーを膨化 させ,最 終製品を 硬い ものに して しま うことが推察
された.し たが って,シ ョー トなもろい食感 のクッキ ーを作 る うえで,澱 粉糊化 の阻害は重要であ
る と考 えられ る.
キー ワー ド: クッキ ー,シ ョー トネス,デ ンプン,糊 化,圧 縮破断試験.
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