effect of starch characteristics on the physical

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

( 711 ) 35

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

( 713 ) 37


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 )


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 continuous 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.

( 715 ) 39


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.

REFERENCES

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2) Wada, Y., Kuragano, T. and Hasegawa, M.: Nihon Kasei Gakkaishi ( J. Home Econ. Jpn.), 34, 609 (1983)

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.

Technology, Production & Management, Mag-azines for Industry Inc., New York, 197 (1972)

5) Hoseney, R.C.: Principles of Cereal: Science and Technology, Am. Assoc. Cereal Chem., St. Paul, MN, 257 (1986)

6) Manley, D. J.R.: Technology of Buiscuits, Crackers and Cookies, Ellis Horwood Limited, West Sussex, 62 (1983)

7) Wada, Y. and Hashimoto, K.: Nippon Eiyo Shoku-ryo Gakkaishi (J. Jpn. Soc. Nutr. Food Sci.), 40, 505

(1987) 8) Maeda, I.: Denpun Kagaku Jikkenhou, Asakura-

40 ( 716 )


shoten, Tokyo, 32 (1984) 9) Fukuba, H. and Kainuma, K.: Denpun Kagaku

Handbook, Asakurashoten, Tokyo, 174 (1985) 10) Ichikawa, A. and Sasaki, I.: Nihon Kasei Gakkaishi

(J. Home Econ. Jpn.), 37, 865 (1986) 11) Fujii, T. and Danno, G.: Nihon Kasei Gakkaishi (J.

Home Econ. Jpn.), 37, 341 (1986) 12) Kuragano, T., Hasegawa, M. and Wada, Y.:

Nihon Kasei Gakkaishi ( J. Home Econ. Jpn.), 35, 307 (1984)

13) Sugimoto, K., Takagi, M. and Goto, F.: Denpun-kagaku ( J. Jpn. Soc. Starch Sci.), 26, 241 (1979)

14) Takahashi, T., Oohashi, H. and Hasegawa, T.:

Denpun Kogyo Gakkaishi ( J. Starch Ind. Jpn.), 6, 46 (1959)

15) Bruns, A. J. and Bourne, M.C. : J. Texture Stud., 6, 445 (1975)

16) Hoseney, R.C., Lineback, D.R. and Seib, P.A.: Bakers Digest, 52 (4), 11 (1978)

17) Derby, R.L., Miller, B.S. and Trimbo, H.B.: Cereal Chem., 52, 702 (1975)

18) Lineback, D.R. and Wongsrikasem, E.: J. Food Sci., 45, 70 (1980)

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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.

(717) 41

effect of starch characteristics on the physical

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