3
Jordan, Animal rennets s von CPA beim Gefrieren wahrend der Herstellung bei Verwendung kontaminierter Milch und anschlief3ender 4 Lagerung der gefrorenen Milchprodukte wie Speiseeis berichtet. Ziel dieser Untersuchung war es, die Stabilitat von CPA bei Gefriertemperaturen wahrend der Zuberei- tung des Speiseeises und der Lagerung iiber 3 Monate bei Verwendung kiinstlich kontaminierter Rohvollmilch (1 pg CPA . g-1) festzustellen. Heif3- und Kaltbehandlung wahrend der Speiseeisher- stellung beeinfluOte die CPA-Level in der Mischung nicht wesentlich. Die Reduktion betrug von der Mischung bis zum Altem insgesamt fast 12%. Jedoch hatte nach der Pasteurisierungdas Altem bei 4°C iiber Nacht eine geringe Wirkung auf die CPA-Level (2% Abnahme). Die Lagerung von 9 Wochen bei -20°C begrenzt den Verlust an CPA angemessen, aber die CPA-Level sanken in Speiseeis signifikant nach 4 (5%) bzw. 9 Wochen (12%) Lagerung. Es ist offensichtlich, daf3 bei Milch, die "Carry over-CPA" enthielt, durch Herstellung und Lagerung des mit kontami- nierter Milch hergestellten Speiseeises die Stabilitat die- ses neurotoxischen Mykotoxins im Produkt nicht sehr be- einfluOt wird. Die Moglichkeit, daf3 CPA den Konsumenten erreicht, ist somit hoch, wenn Speiseeis aus hochgradig mit CPA kontaminierter Milch hergestelltwird. Characterization and comparative study of animal rennets from different ruminants applied to goat milk By M.J. JORDAN, P. HELLIN, M. CASTILLO, J. LAENCINA and M.B. LOPEZ Food Technology Department, Faculty of veterinary, Campus de Espinardo, Aptdo. 4021,30071 Murcia, Spain 1. Introduction 2.4 Cheese yield Currently there are various different proteases on the Three fresh cheese productions were carried out in a market capable of producing milk coagulation (1). How- pilot plant and in the laboratory under the conditions ever, some of them present a high rate of non-specific normally used by cheesemakers in the Region of Murcia, proteolytic activity, which causes a reduction in cheese Spain (Fig. 1). yield as well as rheological and sensorial differences in the final product. For this reason it is necessary to char- acterize and at the same time establish the technologi- cal suitability of each of the enzymes on the substrate of application, using calf rennet as a reference (2). The objective of this study is to compare rennets from the abomasum of different types of ruminant ani- mals (calf, lamb and kid goat) through a characteriza- tion based on enzymatic and coagulant activity, and its yield in the production of fresh goat cheese in the Re- gion of Murcia. 2. Materials and methods 2.1 Enzymes Commercial rennets of different origin were studied: calf, lamb and kid goat rennets from the Caglio Star Espaiia S.A. company. Samples of rennet with the same activity due to chymosin are represented by their mean value. Goat milk 1 Filtering 1 Pasteurization (65°C 30 min) 1 Cooling to 35-36 "C 1 Rennet -+ Renneting t F.O.P. 1 Cutting (grain of 2-3 cm) 1 Stirring 1 Pressing (1 h) 1 Salting 1 h (12-13" Be, 14-15°C) 5 Storage at 4°C 5 Fresh cheese 2.2 Enzymatic activity In order to determine this activity IDF Norm 110 B:1997 (3) and high performance liquid chromatogra- phy were used. High performance liquid chromatogra- phy (HPLC) is carried out following the method defined by RAMPILLI etal. (4). The HPLC used was a Kontron model equipped with two 422 pumps and a 280 nm ultra-violet detector. The chromatographic column was a non-porous anionic MA7Q (Bio-Rad). 2.3 Coagulant activity In order to determine this activity IDF Norm 157:1992 (5) was used. Fig. 1: Flow diagram of fresh goat cheese production In both cases the cheese yield was expressed as the ratio between milk employed and cheese produced, adjusted to 60% humidity (6). 3. Results and discussion 3.1 Enzymatic activiiy The use of the ionic strength gradients defined in the IDF Norm of 1997 led to an insufficient level of enzyme separation, since the coagulation time of those eluant fractions considered to be intermediate in the change of gradient are capable of coagulating milk in less than 3600 s, a value above which this method considers any enzyme activity to be invalid. Milchwissenschaft 54 (3) 1999

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Page 1: Characterization and comparative study of animal rennets

Jordan, Animal rennets

s von CPA beim Gefrieren wahrend der Herstellung bei Verwendung kontaminierter Milch und anschlief3ender

4 Lagerung der gefrorenen Milchprodukte wie Speiseeis berichtet. Ziel dieser Untersuchung war es, die Stabilitat von CPA bei Gefriertemperaturen wahrend der Zuberei- tung des Speiseeises und der Lagerung iiber 3 Monate bei Verwendung kiinstlich kontaminierter Rohvollmilch (1 pg CPA . g-1) festzustellen.

Heif3- und Kaltbehandlung wahrend der Speiseeisher- stellung beeinfluOte die CPA-Level in der Mischung nicht wesentlich. Die Reduktion betrug von der Mischung bis zum Altem insgesamt fast 12%. Jedoch hatte nach der

Pasteurisierung das Altem bei 4°C iiber Nacht eine geringe Wirkung auf die CPA-Level (2% Abnahme). Die Lagerung von 9 Wochen bei -20°C begrenzt den Verlust an CPA angemessen, aber die CPA-Level sanken in Speiseeis signifikant nach 4 (5%) bzw. 9 Wochen (12%) Lagerung. Es ist offensichtlich, daf3 bei Milch, die "Carry over-CPA" enthielt, durch Herstellung und Lagerung des mit kontami- nierter Milch hergestellten Speiseeises die Stabilitat die- ses neurotoxischen Mykotoxins im Produkt nicht sehr be- einfluOt wird. Die Moglichkeit, daf3 CPA den Konsumenten erreicht, ist somit hoch, wenn Speiseeis aus hochgradig mit CPA kontaminierter Milch hergestellt wird.

Characterization and comparative study of animal rennets from different ruminants applied to goat milk

By M.J. JORDAN, P. HELLIN, M. CASTILLO, J. LAENCINA and M.B. LOPEZ

Food Technology Department, Faculty of veterinary, Campus de Espinardo, Aptdo. 4021,30071 Murcia, Spain

1. Introduction 2.4 Cheese yield Currently there are various different proteases on the Three fresh cheese productions were carried out in a

market capable of producing milk coagulation (1). How- pilot plant and in the laboratory under the conditions ever, some of them present a high rate of non-specific normally used by cheesemakers in the Region of Murcia, proteolytic activity, which causes a reduction in cheese Spain (Fig. 1). yield as well as rheological and sensorial differences in the final product. For this reason it is necessary to char- acterize and at the same time establish the technologi- cal suitability of each of the enzymes on the substrate of application, using calf rennet as a reference (2).

The objective of this study is to compare rennets from the abomasum of different types of ruminant ani- mals (calf, lamb and kid goat) through a characteriza- tion based on enzymatic and coagulant activity, and its yield in the production of fresh goat cheese in the Re- gion of Murcia.

2. Materials and methods 2.1 Enzymes

Commercial rennets of different origin were studied: calf, lamb and kid goat rennets from the Caglio Star Espaiia S.A. company. Samples of rennet with the same activity due to chymosin are represented by their mean value.

Goat milk 1

Filtering 1

Pasteurization (65°C 30 min) 1

Cooling to 35-36 "C 1

Rennet -+ Renneting t F.O.P. 1

Cutting (grain of 2-3 cm) 1

Stirring 1

Pressing (1 h) 1

Salting 1 h (12-13" Be, 14-15°C) 5

Storage at 4°C 5

Fresh cheese

2.2 Enzymatic activity In order to determine this activity IDF Norm 110

B:1997 (3) and high performance liquid chromatogra- phy were used. High performance liquid chromatogra- phy (HPLC) is carried out following the method defined by RAMPILLI etal. (4).

The HPLC used was a Kontron model equipped with two 422 pumps and a 280 nm ultra-violet detector. The chromatographic column was a non-porous anionic MA7Q (Bio-Rad).

2.3 Coagulant activity In order to determine this activity IDF Norm 157: 1992

(5) was used.

Fig. 1: Flow diagram of fresh goat cheese production

In both cases the cheese yield was expressed as the ratio between milk employed and cheese produced, adjusted to 60% humidity (6).

3. Results and discussion 3.1 Enzymatic activiiy

The use of the ionic strength gradients defined in the IDF Norm of 1997 led to an insufficient level of enzyme separation, since the coagulation time of those eluant fractions considered to be intermediate in the change of gradient are capable of coagulating milk in less than 3600 s, a value above which this method considers any enzyme activity to be invalid.

Milchwissenschaft 54 (3) 1999

Page 2: Characterization and comparative study of animal rennets

1

I Jordan, Animal rennets

Table 1: Modification of the chromatographic method of ionic exchange

Milk clotting time (s) - IDF method Milk clotting time (s) - modified IDF method Rennet IS' F IS' I.F. 2nd F 2"d I.F. Chym. IS' F 1S'I.F. 2"d F 2nd I.F. Chym.

(0.25 N) (0.5 N) v') (0.3 N) (0.6 N) (Yo)

1 185 300 1059 >3600 75 409.5 >3600 761.5 >3600 64.5 2 370 1080 770 1620 68 351.33 >3600 628.5 >3600 64.14 3 367 840 553 >3600 60 360 >3600 614.6 >3600 63.03

I.F.: Intermediate fraction of the eluant; F: Fraction of the eluant;; % enzymatic activity due to chymosin

in an attempt to improve the enzyme separation the higher level of coagulant activity in calf rennet, followed buffer concentrations were modified to 0.3 N and 0.6 N. by lamb, and the lowest level of activity corresponds to The results obtained are shown in Table 1. kid goat rennet.

The triplicate analysis of a rennet of bovine origin with the modified method applied confirms that the in- termediate fractions analyzed present coagulation times of over 3600 s. With this increase of the strength of the eluant, 18 commercial rennets of different origin were analyzed. Each sample was repeated 3 tityes, the mean values being shown in Table 2. The commercial classi- fication of the samples studied corresponds to the chy- mosin content determined in each of them.

Table 2: Determination of enzymatic activity in sam- ples of commercial rennets

Samples IDFl HPLC Classification

1 98 98 Calf rennet extract 2 90 90 Calf rennet extract 3 64 65 Calf rennet 4 42 45 Calf rennet 5 21 20 Bovine rennet 6 75 75 Lamb extract 7 70 - Lamb rennet 8 80 - Kid goat extract 9 57 60 Kid goat rennet

Percentage of enzymatic activity due to chymosin

These results have been confirmed by the use of high performance liquid chromatography. The milk clot- ting time measurement of the fractions coming out of the detector leads us to determine enzymatic activitiy values which are close to those obtained through the use of the modifed IDF method.

3.2 Coagulant activity Another parameter to be considered in the characteri-

zation of a rennet is the determination of the coagulant activity, defined in IMCU (International Milkclotting Units).

The strength of the different samples is calculated according to their enzymatic activity (Table 3). In gen- eral we observed that rennet with high chymosin con- tent does not imply a higher coagulant activity; in ;jur results rennet with 21 O h chymosin has higher coagulant activity than 90, 64 and 42% chymosin rennets. This may be due to the action of pepsin, which has a high level of coagulant activity.

However, we highlight that a firmer curd can be ob- tained with the use of rennets which had a higher level of chymosin coagulant activity, this being a conse- quence of a higher level of proteolytic pepsin activi!y, an observation which coincides with that found by LOPEZ et al. (7).

From a comparative study of rennet with the same enzymatic activity but different sources, we observed a

Table 3: Coagulant activity

Source Enzymatic activity Coagulant activity (% chymosin) (IMCU)

Calf 98. 2129 90 198.69 64 187.93 42 203.72 21 214.9

Lamb 75 107.73 70 121.196

Kid goat 80 92.23 57 11.15

3.3 Cheese yield To obtain a better characterization of the rennets

analyzed, this parameter was determined on a common substrate, namely Murciano-granadina goat milk.

In order for the results to be comparable, only those rennets of similar enzyme composition were consid- ered. The average values of the different experiments are shown in Fig. 2.

Fig. 2: Comparative study of cheese yield obtained with dif- ferent animals rennet. A: lamb rennet 75%; B: kid goat 80%; C: calf rennet 90%. z Pilot plant, m laboratory

In the laboratory the highest yield found was in calf rennet, with 90% activity due to chymosin; no significant differences were found between the yields of the other rennets.

In the pilot plant the highest cheese yield corre- sponded to lamb rennet, followed by calf rennet, and finally the kid goat rennet. These results confirm that a higher coagulant and enzymatic activity is not always associated with higher yield.

Goat rennet has a low cheese yield, which can be ex- plained by the fact that the high milk clotting time pro- duces a softer curd, and this is associated with the presence of fine curd particles, and a higher fat content in the whey (8).

Milchwissenschaft 54 (3) 1999

Page 3: Characterization and comparative study of animal rennets

146 I

r In conclusion, it can be highlighted that in the pro- 6 duction of fresh Murciano-Granadina goat cheese, the

I use of rennets of different origin, with similar but differ- ing enzymatic activity, does not cause significant differ- ences in the cheese yield, except in the case of kid goat extract; in this case a lower yield was observed as a re- sult of its higher level of proteolytic activity, which im- plies a greater loss of minuscule particles of casein in the whey.

Acknowledgement To Caglio Star Espafia S.A. company for the rennet

samples provided and to Marlowe Center and Bente Han- sen for the translation of this paper.

Carrera, Milk coagulant

study of rennet with the same enzymatic activity but from different sources with the application of IDF Norm 157:1992, we can deduce a higher coagulant activity in calf rennet followed by lamb. The lowest activity corre- sponded to kid goat rennet.

A comparative study of cheese yield was carried out in goats milk using rennets with similar enzymatic activity but different origin. Three batches of fresh cheese were pro- duced at 2 levels, one in the pilot plant and another in the laboratory. In the laboratory the highest yield found was in calf rennet with 90% activity due to chymosin. However, in the pilot plant the highest cheese yield corresponded to lamb rennet, followed by calf and finally the kid goat rennet. These results confirm that higher coagulant and enzymatic activity is not alw'hys associated with higher yield.

4. References JORDAN, M.J., HELLIN, P., CASTILLO, M., LAENCINA,

(1) HA;~BOE, M.K.: E ~ ~ . Dairy Magazine 6 6-1 5 (1 992) J., LOPEZ, M.B.: Charakterisierung und Vergleich von

(2) BIRKKJAER, H. JHONK, p.: IDF ~ ~ l l . 1 9 4 8-1 0 (1 985) Lab verschiedener Wiederkauer bei Ziegenmilch. Milch-

(3) IDF Standard 1 108 (1 997) wissenschaft 54 (3) 144-146 (1 999). (4) RAMPILLI, M., BARZAGHI, P., MOLINARI, P. TENA- 86 Tierisches Lab (Charakterisierunq)

. GLIA, L.: Sci. Tec. Latt.-Cas. 43 387401 (1 992) (5) IDF Standard1 57 (1 992) (6) MAUBOIS, J.L., MOCQUOT, G., BLANC-PATIN, E.:

Ann. Tech. Agric. 16 (4) 287-299 (1 967) (7) LOPEZ, M.B., JORDAN, M.J., HELLIN, P. LAEN-

CINA, J.: Milchwissenschafl52 (7) 370-373 (1 997) (8) CASTILLO, M., JORDAN, M.J., BARON, S., GARRI-

DO, M.D., LAENCINA, J., LOPEZ, M.B.: Arch. Zoo- techn. (1 997)

5. Summary JORDAN, M.J., HELLIN, P., CASTILLO, M., LAENCINA,

J., LOPEZ, M.B.: Characterization and comparative study of animal rennets from different ruminants ap- plied to goat milk. Milchwissenschaft 54 (3) 144-146 (1 999). 86 Animal rennets (characterization)

The characterization of rennets of different origin (calf, lamb and kid goat) was studied in goat milk in terms of their enzymaticand coagulant activity as well as the cheese yield.

The determination of enzyme activity according to a modified IDF Norm 1 10:1997 led to the conclusion that the application of ionic strength gradients between 0.3-0.6 N in NaCl implies a complete separation of the enzymes and a greater reproducibility of the method. From a comparative

-. Die Eigenschaflen von Lab unterschiedlichen Ur-

sprungs (Kalb, Lamm und Zickel) wurden in Ziegenmilch auf ihre Enzym- und Gerinnungsaktivitat sowie die Kase- ausbeute untersucht.

Die Bestimmung der Enzymaktivitat nach der modifi- zierten IDF-Norm 110:1997 fuhrte zu dem SchluB, daR die Anwendung von lonenstarkegradienten zwischen 0,3- 0,6N bei NaCl eine vollstandige Trennung der Enzyme und eine gronere Reproduzierbarkeit des Verfahrens be- inhaltet. &s einer ~er~leichsstudie mit Lab gleicher En- zymaktivitat aber unterschiedlichen Ursprungs kann bei Anwendung der IDF-Norm 157:1992 eine hohere Gerin- nungsaktivitat bei Kalberlab, gefolgt von Lamrnlab, abge- leitet werden.

Eine Vergleichsstudie iiber die Kaseausbeute aus Zie- genmilch bei Verwendung von Labsorten mit ahnlicher En- zymaktivitat und unterschiedlichem Ursprung wurde durchgefuhrt. 3 Chargen Frischkase wurden hergestellt, jeweils 1 in einer Pilotanlage und 1 weitere im Labor. Im Labormanstab wurde die hochste Ausbeute bei Kalberlab mit 90% Chymosinaktivitat festgestellt. Jedoch wurde in der Pilotanlage die hochste Kaseausbeute mit Lammlab, gefolgt von Kalberlab und dann Zickellab, erreicht. Diese Ergebnisse bestatigen, daO eine hohere Gerinnungs- und Enzymaktivitat nicht immer mit einer hoheren Ausbeute verbunden ist.

Effect of milk coagulant on the formation of hydrophobic and hydrophilic peptides during the manufacture of cows' milk Hispanic0 cheese

By E. CARRERA, P. GAYA, M. MEDlNA and M. NUNEZ

Departamento de Tecnologia de Alimentos, INIA, Carretera de La Coruiia Km 7, Madrid, 28040 Spain

1. Introduction

Milk coagulation in rennet cheeses is accomplished Coagulant enzymes retained in the curd have a major by the cleavage of the Phe,,,-Met,,, bond of K-casein, impact on flavour and texture development during the with the subsequent destabilisation of the casein micelle. complex process of cheese ripening (2).

Milchwissenschaft 54 (3) 1999