Gelation and Melting of a Mixed Carrageenan-Gelatin Gel

J. Home Econ. J pn. Vol. 44 No. 12 999-1005 (1993)

Reiko SHIMADA, Keiko KUMENO,* Hiro AKABANE * * and Nobuko NAKAHAMA *

Junior College at Mishima, Nihon University, Mishima, Shizuoka 411, Japan * Japan Women's University, Bunkyo-ku, Tokyo 112, Japan * * Kantogakuin Women's Junior College, Kanazawa-ku, Yokohama 236, Japan

The rheological changes in a mixture of two different gelling agents were studied. A 0.9%

(w/v) ƒÈ-carrageenan solution (C(1)), a 4% (w/v) gelatin solution (G(1)) and mixed samples in three proportions were prepared. The gelling temperature and melting temperature were mea-

sured. Changes in the dynamic viscoelasticity when the state of the gel changed were determined with a Rheolograph-Sol instrument, and the endothermic reaction during melting was also examined by DSC. The gelling and melting temperatures for C(1) were the highest among all

the samples. These values for the mixed samples were reduced according to the decreasing ratio of carrageenan. Gelling and melting of the samples were observed when the storage modulus

was in the range of 6-8 N/m2.

This suggests that the change point for state exists in this range. The DSC result revealed that the peak heights of the mixed gelatin-carrageenan samples were lower and their shapes were broader than those of the pure samples. The peak temperature of the endothermic reaction and

the melting temperature corresponded well. (Received February 2, 1993)

Keywords: carrageenan/gelatin mixed gel, gelation, melting, DSC, dynamic viscoelasticity.

bean gum, in different ratios, and have also reported INTRODUCTION rheological changes during gelling of pure samples.4) Both gelatin and carrageenan are widely used However, there is no information available about as gelling agents for cookery and food applications global changes in the gelling properties, including since both form a highly transparent gel. The both gelling and melting. gelling properties of these agents are, however, Thus, a Reolograph-Sol instrument equipped very different. Gelatin is often used for home with a computer-controlled temperature stabilizer cookery as it melts quickly in the mouth due to its was utilized to clarify changes in the viscoelasticity low melting point, but this property is trouble- (which is assumed to quantify the texture in the some when handling. While not melting very mouth) of the mixed gels during their gelling and well in the mouth, carrageenan is frequently used melting transitions. The gelling temperature, us- in commercial products because of its stability ing the laid-down test tube method, melting during transportation. Thus, it would be advan- temperature, using the upside-down test tube tageous to determine the optimal ratio of these method, and endothermic reaction during melting two gelling agents so as to obtain a gel with proper- were also measured to examine their relationships ties of good melting in the mouth and ease of to viscoelasticity. handling. To approach this goal, we investigated EXPERIMENTAL METHOD in this study the gelling properties of various gelatin-carrageenan mixtures in terms of melting Sample preparation in the mouth. κ-carrageenan CS-88 (San-ei Chemicals), alkali- Several studies have reported the different gel- treated gelatin A-U (Miyagi Chemicals) and su- ling properties obtained by mixing four gelling crose (Kanto Chemicals) were used. Their con- agents,1)-3) carrageenan, gelatin, agar and locust centrations were adjusted to 0.9% (w/v) for carra-

( 999 ) 1 J. Home Econ. Jpn. Vol. 44 No. 12 (1993)

Table 1. Volumetric proportions of the mixed samples

geenan, 4% (w/v) for gelatin and 40% (w/v) for were injected into test tubes with a diameter of 1.2 sucrose. cm, and maintained at 50°C for 30 min in a pro- Although too high for a table jelly, the sucrose grammed hot bath (Taiyo Chemicals). The tem- concentration of 40% was selected for our study perature was then decreased at a rate of 0.5°C per in order to make the result clearer.5' Five-hun- minute. One test tube was removed every minute, dred-milliliter samples were prepared by the laid down as shown in Fig. 1-a, and the distance method of Isozaki et al.,6) carrageenan being soaked migrated after 3 sec was measured. in distilled water for 1 h, and heated for 1 h at As the temperature fell, the sol became more 75°C and then for 30 min at 98°C (carrageenan. viscous, and the migration finally became zero. sample). Gelatin was soaked in distilled water for This happened when the sol in the very center 1 h and then heated for 30 min at 65°C (gelatin (0.6 cm away from the test tube wall) gelled, sample). The carrageenan and gelatin samples indicating a difference between the temperature of prepared in this way were mixed in the volume the water bath and the gelling temperature. To ratios shown in Table 1, these being 3:1, 1 :1 and produce the most realistic value possible, we 1:3 (mixed samples). decided to take the temperature of the water bath Both pure carrageenan and gelatin samples were when the length of migration was 2 mm and to use also prepared with sucrose by using the method already stated, but the volume of water for each sample was decreased beforehand so that the subsequent sugar addition would give the same final volume. Sugar was added, and each sample was then heated for a further 30 min. The carrageenan-sucrose and gelatin-sucrose sols were mixed in the volume ratio of 1 :1 (mixed sample with sucrose). The abbreviations shown in Table 1 will be used throughout the remainder of the paper. Measurement The laid-down test tube method and the upside- down test tube method are illustrated in Fig. 1. (a) (b) 1. Gelling temperature Fig. 1. Measurement of gelling temperature by the The method of Takebayashi et al." with some laid-down test tube method (a) and of melting modifications was employed to measure the gelling temperature by the upside-down test tube temperature. Aliquots of the sample sol (5 ml) method (b)

2 ( 1000) Gelation and Melting of a Mixed Carrageenan-Gelatin Gel this as the gelling temperature ( TO for the laid- down test tube method.

2. Melting temperature

The melting temperature was measured by the upside-down test tube method (Tanii et al.8)).

First, 5-ml aliquots of the sample sols were injected into test tubes with a diameter of 1.2 cm. The test tubes were maintained at 10•Ž for 3 h until the contents had gelled, and were then placed upside-down in a water bath at 20•Ž (Fig. 1-b).

The temperature of the water bath was then Fig. 2. Gelling temperatures of the samples increased by 0.5•Žper minute. The temperature of the water bath at which the gel collapsed was taken as the melting temperature ( Tm).

3. Viscoelasticity

A Rheolograph-Sol instrument (Toyo Seiki; 3

Hz, + / -50 ƒÊm) was utilized to measure the

dynamic viscoelasticity. A sample (1.5 ml) was

cooled at a rate of 0.5•Ž per minute to 5•Ž, and

the gelled sample obtained was then heated until

it melted. Changes in the viscoelasticity during

gelling and melting were consecutively measured. 4. Endothermic reaction

The endothermic reaction of the samples with-

out sucrose was measured during melting by DSC

(Rigaku DSC 8240). A sample (25 mg) was

prepared in a sealed aluminium cup, and water Fig. 3. Melting temperatures of the samples was used as a reference. Measurements were

conducted while increasing the temperature at a

rate of 2•Ž per minute from 5•Ž to 78•Ž.

RESULTS AND DISCUSSION by carrageenan, which started gelling more quickly

Temperature for gelling and melting than gelatin. The gelling temperatures of the

To gelling temperatures from the laid-down test samples with sucrose were 4•Ž to 12•Ž higher than

tube method are shown in Fig. 2, those of samples those of the samples without sucrose. Since the

C(1) and G(1) without sucrose being around 30•Ž two lines in Fig. 2 (SC(1) to SC-G(1:1) and C(1)

and 18•Ž, respectively. The mixed gels had an to C-G(1 :3)) are nearly parallel, the gelling tem- intermediate gelling temperature. The higher perature for the samples with sucrose is also as- the carrageenan concentration, the higher the gel- sumed to have been affected by the carrageenan

ling temperature for the mixed gel samples (C(1), concentration.

C-G(3:1), C-G(1:1), C-G(1:3)). Although data The melting temperatures by the upside-down

are not presented, the gelling temperature for test tube method are shown in Fig. 3, those for

sample C-G(1 :1) and that of the pure 0.45% samples C(1) and G(1) being 50•Ž and 30•Ž,

(w/v) carrageenan sample (which had the same respectively. The melting temperature tended to

carrageenan concentration as that of the C-G(1 :1) increase as the concentration of carrageenan

sample) were the same. This shows that gelatin increased, as was the case with the gelling tempera-

had no influence on the gelling temperature of the ture. This suggests that the gel fell from the test

mixed samples, probably because carrageenan has tube wall only when the carrageenan started to

a higher gelling temperature than gelatin. The melt, and that the effect of gelatin on the melting

gelling of the mixed sample was therefore controlled temperature was small. The melting temperature

( 1001) 3 J. Home Econ. Jpn. Vol. 44 No. 12 (1993)

(a) (b)

Fig. 4. Storage moduli and temperatures of the samples without sucrose

for each sample was higher than the gelling tem- the gel from the blade of the Rheolograph-Sol,

because a carrageenan gel did not adhere well to perature by 12•Ž to 20•Ž. The melting temperature for each sample with the metallic blades. Although it is possible that sucrose was higher than that for each sample the data after this point are not realistic because of without sucrose by up to 14•Ž. this assumption, the main concerns of this study

Viscoelasticity are the increase and rapid decrease of G', which

The Rheolograph-Sol instrument is character- were not affected by this slower increase. ized by its ability to measure viscoelasticity both Although the graph is not shown, the curve for during the phase transition from a sol to gel, the loss tangent (tan 3) of C(1) was clearly different and within the gel phase. This method is useful from the others. That of C-G(3 :1) also showed a when continuous rheological changes from a sol to different trend at around 20•Ž. Since tan 3 is the gel and from a gel to sol are of interest. ratio of loss modulus G" to storage modulus G', Changes in the viscoelasticity of the samples instability of G' is thought to have been the cause. without sucrose are shown in Fig. 4, Fig. 4-a Tg (gelling temperature by the laid-down test showing the process of cooling and Fig. 4-b show- tube method) and Tm (melting temperature by ing the process of heating. The hysteresis curve the upside-down test tube method) are indicated for storage modulus G' is very different between by arrows (•© •©respectively). Except for the

C(1) and G(1). When cooled, the storage modulus melting temperatures of C-G(1 :3) and G(1), all of C(1) increases steeply from about 32•Ž, but the gelling and melting temperatures were at then drops at around 29•Ž and slowly increases around 6 to 8 N/m2 for G', which suggests that again (Fig. 4-a). In contrast, that of G(1) in- the sol-gel transition point was within this range. creases rapidly from about 18°C when cooled The temperatures for C-G(1 :3) and G(1) at this

(Fig. 4-a), and drops steeply when heated from point were 27_2•Ž and 27.0•Ž, which are lower 29•Ž (Fig. 4-b). C-G(1 :1) and C-G(1 :3) show the than T. (30.3•Ž and 29.9•Ž, respectively). same behavior as that of G(1), while C-G(3 :1) and Since the melting temperature in this study (Tm)

C(1) show a slower increase in storage modulus was the temperature at which the gel sample when cooled (Fig. 4-a). This slower increase is collapsed in the test tube, the viscosity of the assumed to have been caused by detachment of sample might have caused these differences. C-G

4 ( 1002 ) Gelation and Melting of a Mixed Carrageenan-Gelatin Gel

(1 :3) and G(1) were samples with a high gelatin concentration, and this tended to adhere strongly

to the container material, for example, glass.

This adhesiveness might have prevented the sample from collapsing even after the region of the sample

that was adhering to the glass had melted. This

could have resulted in a slightly higher apparent

melting temperature. The adhesiveness of the

sample to the container would need to be studied

further in order to confirm this theory.

The range of 6 to 8 N/m2 obtained for G' with

the Reolograph-Sol were the limits for the ap-

pearance and disappearance of the modulus, and it is possible to obtain the gelling and melting

temperatures from these results. Tg and Tm for

both the laid-down test tube method and the

upside-down test tube method correspond well to

those obtained with the Reolograph-Sol, apart

from the melting temperatures for C-G(1 :3) and

G(1). These methods may therefore be con-

sidered effective for determining the gelling and

melting temperatures of samples, apart from those

with high viscosity. Fig. 5. Endothermic curves for the samples without Akabane et al.9) have reported that starch sam- sucrose ples were in the gel state when tana was below Sample, 25 mg; heating speed, 2C•‹/min; reference, 0.45 and in the sol state when tanƒÂ was above 0.45. water. In our study, Tg of C(1), C-G(3 :1) and G(1) and

Tm of C(1), C-G(3 :1) and C-G(1 :1) gave similar

results. peak for carrageenan seemed to reduce with in-

Endothermic reaction creasing gelatin concentration. From the two

The use of DSC has recently become popular peaks for the C-G(3 :1) sample, it could be assumed for following the thermal changes during the melt- that melting of the mixed sample started with the

ing and gelling of a gel.10) In this study, DSC melting of gelatin and then of carrageenan. As

was utilized to clarify the endothermic changes Nishinari et al.11) have suggested for a mixed agar-

during melting (which was used as a model for gelatin gel, this gelatin-carrageenan gel could also

melting in the mouth) of the samples without be considered as a phase-separation gel.

sucrose. The results are shown in Fig. 5. The The endothermic peak and the melting tem-

peaks for pure samples C(1) and G(1) are steeper perature measured by the upside-down test tube than those for the mixed samples. The lower and method ( Tm) correspond well with each other,

wider peaks for the mixed samples would have been with only small differences of between 3.5 and

caused by the different endothermic peaks of the -2℃. An endothermic reaction Was observed

carrageenan and gelatin samples. For the C-G when the unified network structure of the gel broke down, and a peak was observed when this (3:1) sample, these two peaks were far apart,

giving this sample a two-peak curve, while the process was at its most active. The melting tem- C-G(1 :1) and C-G(1 :3) samples showed gently perature by the upside-down test tube method sloping curves, probably due to the two peaks corresponds to the temperature at which break

being closer together. The peak at around 31•Ž down of the gel structure reaches the point at

corresponds to the melting temperature of gelatin, which it can no longer hold itself together. Thus,

which was not affected by carrageenan or the it follows that these two temperatures would be

gelatin concentration. On the other hand, the quite similar.

( 1003) 5 J. Home Econ. Jpn. Vol. 44 No. 12 (1993)

The small differences may be explained by the were lower and the shape was broader than those different sample quantities and heating conditions; of the pure samples. The peak temperatures for that is, 5 ml at 0.5•Ž per minute for the upside- the endothermic reaction and the melting tem- down test tube method, and 25 mg at 2•Ž per peratures by the upside-down test tube method minute for DSC. These differences need further correspond well.

investigation. We thank Rigaku Corporation for the DSC CONCLUSIONS experiments, and San-ei Chemicals Corporation A 0.9% (w/v) ƒÈ-carrageenan solution (C(1)) and for the materials. This work was supported by a a 4% (w/v) gelatin solution (G(1)) were mixed in grant for category B scientific research (No. the following ratios of C(1) :G(1), 3:1 (C-G(3:1)), 01480518) from the Ministry of Education, Science 1:1 (C-G(1:1)), and 1:3 (C-G(1:3)). The influ- and Culture of Japan.

ence of mixing on the gelling and melting processes REFERENCES was studied. Samples with 40% sucrose were also 1) Fiszman, S.M. and Duran, L.: FoodHydrocolloids, 3, prepared to examine the influence of sucrose addition. 209-216 (1989)

The following results were obtained: 2) Kobayashi, M. and Nakahama, N.: J. Texture Stud., 17, 161-174 (1986) 1) The gelling temperature of C(1) was 30.3•Ž, 3) Kawamura, F. and Takayanagi, S.: Sci. Cookery, which is the highest of all the samples. The gel- 22, 299-304 (1989) ling temperature of the mixed samples was reduced 4) Murayama, A. and Kawabata, A.: KaseigakuZasshi as the proportion of the carrageenan solution was ( J. HomeEcon. Jpn.), 31, 475-480 (1980) decreased. The gelling temperature of the sam- 5) Nagasaka, K., Kumeno, K. and Nakahama, N.:

ples with sucrose was higher than that of the Nihon Kasei Gakkaishi ( J. Home Econ. Jpn.), 42, samples without sucrose, and this was most obvious 621-627 (1991)

for SC(1). 6) Isozaki, H., Akabane, H. and Nakahama, N.:

2) The melting temperature of C(1) was the NougeiKagaku, 50, 265-272 (1976)

highest (48.4•Ž), as was the case with the gelling 7) Takebayashi, Y. and Haba, R.: KaseigakuZasshi

temperature. These temperatures for the mixed ( J. HomeEcon. Jpn.), 12, 107-110 (1961) 8) Tanii, K.: Nihon Suisan Gakkaishi, 13, 245-247 samples were reduced with decreasing C(1) con- (1948) centration. The addition of sucrose raised the 9) Akabane, H., Harada, S. and Nakahama, N.: melting temperature of the samples, and this was KaseigakuZasshi ( J. HomeEcon. Jpn.), 36, 484-491 most obvious for SC(1). (1985) 3) Gelling and melting of the samples without 10) Watase, M., Nishinari, K., Williams, P.A. and sucrose (except for the melting of C-G(1 :3) and Phillips, G.O.: J. Agric. Food Chem.,38, 1181-1187

G(1))were observed when the storage modulus was (1990) 11) Nishinari, K., Koide, S., Williams, P.A. and between 6 and 8 N/m2. This suggests that the Phillips, G.O.: J. Plys. France, 51: 1759-1768 sol-gel transition point existed at around this value.

4) The DSC result reveals that the peak (1990) heights of the mixed gelatin-carrageenan samples

カラギーナンーゼラチン混合ゲルの凝固と融解

島田玲子, 粂野恵子 *, 赤羽ひろ * *, 中濱信子 *

(日本大学短期大学部,*日本女子大学,* *関東学院女子短期大学)

平成5年2月2日受理

性質の異なる2種のゲル化剤を混合することによるレオロジー特性の変化について検討した.κ- カラギーナン0.9W/v%溶液(C(1)),ゼラチン4w/v%溶液(G(1))およびその3種の混合溶液を試料とした.まず,凝固温度・融解温度を測定し,同時にレオログラフゾルにより試料のゾルーゲル変化時の動的粘弾性の変化を調べ,その関係について検討した.またDSCにより融解時の

6 ( 1004 ) Gelation and Melting of a Mixed Carrageenan-Gelatin Gel

吸熱反応も調べた,結果は次のようになった.(1)凝固温度・融解温度のどちらもC(1)が最も高く,混合試料ではC(1)の割合が減少するに比例して,温度も低下した.(2)融解および凝固は, 貯蔵弾性率の6～8N/m2の範囲で起こった.このあたりにゾル・ゲル転移点が存在すると考えられる.(3)混合により,吸熱のピークの高さは低くなり,なだらかで幅の広い山になった.吸熱のピークの温度は融解温度とほば等しかった.

キーワード:カラギーナン/ゼラチン混合ゲル,凝固,融解,DSC,動的粘弾性.

(1005 ) 7