E V A L U A T I O N OF P L A S M A A N D P L A S M A - A L G I N A T E FIBRES FOR USE IN S A U S A G E S

OLAVO RUSlG~"

Food Science Laboratories, Department of Applied Biochemistry and Nutrition, University of Nottingham, School of Agriculture, Sutton Bonington, Loughborough,

Leics. LEI2 5RD, Great Britain

(Received: 3 November, 1978)

S UMMA R Y

Fresh beef sausages were made in which 0, 20 or 40 ~ o f the meat protein was replaced b)' proteh7 f rom bovine blood plasma in order to determine the effect this had on stability, shrinkage, texture, juiciness, flavour, colour and general acceptability. Both the plasma proteins as isolated, and after spbming into fibres, were examined.

Sausages in which 20 or 4 0 ~ of the meat protein had been replaced by plasma-alginate f ibres were preferred less than those made at the same levels o f replacement using plasma protein as isolated, taste panel members disliking their flavour and colour.

On the other hand, sausages incorporating plasma-alginate f ibres were drier than those containing corresponding replacement levels o f plasma protein as isolated, and their texture was preJerred.

INTRODUCTION

There is presently great interest in protein fibres because of possible technological applications, one promising application being their use in preparing synthetic or simulated foods.

Fibres from vegetable proteins have been subject to intensive research. Balmaceda & Rha (1974) investigated the relationship between some of the spinning variables which may apply to such products, e.g. dope composition, bath temperature and diameter of spun fibres. Jaynes & Asan (1976) studied the spinnability of protein

~f Present address: Faculdade Engenharia de Alimentos e Agricola (FEAA), UNICAMP, CP 1170, 13.100, Campinas, Sb.o Paulo, Brazil.

295 Meat Science 0309-1740/79/0003-0295/$02.25 © Applied Science Publishers Ltd, England, 1979 Printed in Great Britain

296 OLAVO RUS1G

from cottage cheese whey; Kelley & Pressey (1966) considered the mechanisms involved in fibre formation from soy protein, using alkali, urea and mercaptoethanol and Huang & Rha (1971) assessed the possibility of fibre formation from single-cell protein.

According to Tolstoguzov et al. (1974) products resembling minced meat, which were made from non-meat protein (casein), had a low heat-resistance and thus could not be cooked satisfactorily. This problem could be overcome when a protein-polysaccharide complex was used. Bromstein (1974) has used polysac- charide complexes to produce fibres which were incorporated into luncheon meat emulsions as a texturising agent. Ishler et al. (1963) developed a method to obtain fibres by the addition of sodium alginate to a protein solution which was spun into a calcium acetate or calcium acetate and acetic acid bath. Imeson et al. (1979) made fibres by spinning blood plasma and sodium alginate into a calcium chloride coagulating bath solution. Methods of extraction and properties of spun fibres made of proteins from meat industry by-products have been studied by Young & Lawrie (1974, 1975) and Swingler & Lawrie (1977).

Although there have been some technical advances in meat analogues, at present these products have so far not been a success due to texture, flavour, technical, commercial and legal problems. It was thought that the use of plasma proteins in meat products could alleviate the waste problems of the meat industry by-products by finding new methods of application of those proteins which are currently under- utilised.

The present work was designed to study the effect of replacing meat proteins in fresh beef sausages at the 0, 20 and 40 ~ levels by blood plasma protein, both as isolated and after texturisation by spinning, in order to determine the effect on the final characteristics of the product.

MATERIALS AND METHODS

Collection and separation o f beef blood plasma Blood from beef animals was obtained in a local slaughterhouse. A 10 ~o (w/v)

sodium citrate solution was added to the blood, at a concentration of i 0 ~ (v/v), to prevent coagulation. The blood was maintained at 4 °C and separated within 2 h of collection into serum and red blood cell fractions by centrifugation at 1000g for 15min. The red cells were discarded and the plasma frozen at - 2 5 ° C . When concentrated plasma was needed, it was defrosted to - 2 °C, crushed to an icy pulp, added to the basket of a laboratory basket centrifuge in 400 g lots and centrifuged at 3000 g for 2 min. A layer of muslin cloth prevented the smaller ice crystals being forced through the basket mesh with the protein solution. The protein content of the concentrated plasma was estimated by the AOAC method (AOAC, 1975). When needed, the plasma was concentrated one- or twofold. The concentration of blood

PLASMA AND PLASMA-ALGINATE FIBRES FOR USE IN SAUSAGES 297

plasma centrifuged was about 7 ~o protein. This could be increased to 12 ~ in the first concentration and to 17 ~ in the second.

Spinning of protein fibres (Fig. 1) The basic equipment as described by Young & Lawrie (1974) was employed. The

procedure used was as described previously by Imeson et al. (1979). The plasma protein concentrat ion was adjusted to 100 mg/ml by dilution with distilled water and a viscous solution suitable for spinning was prepared in a Sitverson homogeniser by

: . . L. , ? .

(A) (B)

Fibres used to replace meat in the sausage formulations. (A) Plasma-alginate fibres. (B) AIginate fibres.

Fig. 1.

mixing the solution for 2min in the presence of 2 ~ Manucol DM (Alginate Industries Ltd). After dissolving the alginate, the solution was centrifuged at 2000 g for 5 min in order to separate the bubbles from the solution which formed when dissolving the alginate.

The spinning dope was extruded through a stainless steel spinneret (40 holes, each 0-008 cm diameter) into a coagulating bath which contained a solution of 5 calcium chloride in water (pH 10.3). The extrusion rate and take-up speed were kept constant during the spinning process at 0-19 m min - t and 7.2 m m i n - t, respectively. The fibres were removed from the Godet wheel, drained of excess fluid, washed in water, centrifuged at 3000 g for 2 rain in a basket centrifuge and kept at 2 °C. Fibres of Manucol DM were prepared similarly, in the absence of plasma protein.

298 O I . A V O R L I S I G

TABLE 1 PROXIMATE CHEMICAL COMPOSIIlON OF SAMPLES (AS °/o WET WEIGHT)

Constituent Chuck beeJ Pork back./at (%) (%)

Protein 21-4 4.2 Water 70.0 11-0 Fat 6.5 86.0

Meat and Jat preparation C h u c k beef and pork back fat were ob t a ined f rom the local s l augh te rhouse . The

chuck beef was freed f rom excess fat and connec t ive tissue. The c leaned muscles and po rk back fat were minced in a H o b a r t Mincer , using a 5 m m mincer phtte.

Samples were taken for chemical ana lyses and the minced beef and fat was divided into lots o f 500 g each, p laced in m o i s t u r e - p r o o f p las t ic bags and s tored at - 25 °C. Pro te in , fat and mois tu re con ten t o f the lean and pork fat were de t e rmined by the A O A C p rocedure s ( A O A C , 1975) and are shown in Tab le 1.

Sausage preparation Two series o f sausages were m a d e and ana lysed . Series I was in tended to s tudy the

effect o f r ep lacement o f 0, 20 and 40 o/~o of the mea t p ro te in by p l a sma as isola ted or p l a s m a - a l g i n a t e fibres. In Series 1I the effects o f a lg ina te and p la sma , a lg ina te fibres and p l a s m a and p l a s m a - a l g i n a t e fibres were c o m p a r e d at the 40','~ r ep lacement level.

A re la t ively low to ta l p ro te in concen t r a t i on (7 ~o) was de l ibe ra te ly chosen to c o m p l y with the legal r equ i rements for m i n i m u m mea t con ten t . The c o m p o s i t i o n s o f sausages , ca lcu la ted by s imul t aneous equa t ions , are shown in Tables 2 and 3.

TABLE 2 FORMULATION FOR EXPERIMENTAL SAUSAGES (PERCENTAGE) SERIES 1

Constituent 1 I1 111 IV V

Meat protein 7.0 5.6 4.2 5-6 4-2 Plasma-alginate fibres 0 1.4 2.8 0 0 Plasma 0 0 0 1-4 2.8 *Alginate 0 0.7 1-4 0.7 1.4 Fat 25.0 25-0 25-0 25.0 25.0 Water 55-0 55.0 55.0 55.0 55.0 Rusk 10-0 10-0 10-0 10-0 10.0 "lSeasonings 3.0 3.0 3.0 3.0 3.0

I~Control (0 ~ replacement). ll--Plasma-alginate fibres (20 ~ replacement). llI--Plasma-alginate fibres (40 ~ replacement). IV--Plasma (20 ~ replacement). V--Plasma (40 ~ replacement). * Alginate not computed in formulation. t See Fischer (1956).

PLASMA AND PLASMA-ALGINATE FIBRES FOR USE IN SAUSAGES

TABLE 3 FORMULATION FOR EXPERIMENTAL SAUSAGES (PERCENTAGE) SERIES 11

299

Constituent 1 I1 111 IV

Meat protein 7.0 4.2 4.2 4-2 Plasma-alginate fibres 0 2.8 0 0 Plasma 0 0 2-8 2.8 *Alginate 0 1.4 1.4 1-4 Fat 25-0 25.0 25.0 25-0 Water 55.0 55.0 55.0 55.0 Rusk 10.0 10-0 10-0 I 0-0 tSeasonings 3.0 3.0 3.0 3-0

l---Control (0 ~o replacement). li--Plasma-alginate fibres (40 ~o replacement). Ill--Plasma and alginate (40 ~o replacement). IV--Plasma and alginate fibres (40 ~ replacement). * Alginate not computed in formulation. ~- Amasal Gold Beef seasoning with preservative and polyphosphate (Amasal Ltd).

The frozen samples o f mea t and fat were thawed for 48 h at 2 °C and sausages were p repa red in a H o b a r t C h o p p e r (mode l 84142) using chuck beef, p o r k back fat, wate r , rusk ( R H M - f i n e grade) , p l a s m a and fibres when desi rable , and seasoning. A fine mix was ob t a ined by emuls i f ica t ion for 3 min. Rusk was a d d e d and the mix tu re emulsif ied l o t 1 min more . Samples o f the mass were taken for a s tab i l i ty test and the r ema inde r was filled in to 2 2 m m d i a m e t e r synthe t ic Viskase casings. Sausage samples for object ive tests o f ju ic iness and tex ture were c o o k e d in a water ba th at 70°C for 30 min; and for subject ive tests (panel) and shr inkage , hea ted for 3 -4 min (to coagula te a skin o f prote in over the sausages). All sausages were cooled in t ap water and left overn ight a t 2 °C before r emov ing the casings to test for shr inkage , ju ic iness and texture (objective). Sausages for subject ive eva lua t ion (panel) were kep t a t - 2 5 ° C .

Fibre analysis Fibres were ana lysed tor p ro te in , wate r and ash con ten t by the A O A C p rocedure s

( A O A C , 1975). A lg ina t e con t en t o f fibres was found by difference ( ~ a lg ina te = 100~o - ~ p ro te in - ~o wa te r - ~o ash). The p H was measu red as for sausages (below).

Sausage analysis pH." The p H o f sausages (not c o o k e d ) was de t e rmined by homoge n i s i ng a 5 g

sample with 50 ml o f dis t i l led wa te r for 1 min in a M S E homogen i se r a t m a x i m u m speed. The so lu t ion was f l t e r e d t h r o u g h glass wool and p H was de t e rmined us ing a Pye U n i c a m po ten t iome te r .

Stability: The s tabi l i ty o f the sausages was measu red jus t af ter emuls i f ica t ion o r mixing, by hea t ing samples o f sausages in p las t ic centr i fuge tubes in a wate r ba th at 80°C for 1 h. S tab i l i ty was r e p o r t e d in re la t ion to the vo lume o f fat o r wa te r separa ted du r ing hea t t r e a tmen t , by ca lcu la t ing the ra t io o f vo lume o f fat or wa te r

300 OLAVO RUSIG

which separated from the cooked sausage samples to the uncooked sausage and multiplying by 100. Thus, decreased stability was reflected by increased volume of fat and water separation. These tests were performed in quadruplicate.

Shrinkage: The shrinkage of the sausages was measured by frying the samples at 170 ___ 5°C for 5min. The weight of fat and water cooked out during frying was expressed as an index of shrinkage, by dividing the difference of weight of sausage before and after frying by the weight of sausage before frying and multiplying by 100. These tests were performed with five samples.

Texture: The samples were analysed using tensile strength and compressive strength and ten replicate measurements were made for each test. Tensile strength was analysed by a modified method of Swift & Ellis (1957). The apparatus employed was attached to an Instron Universal Machine Model 1140 fitted with a 5-50 N capacity compression load cell. The crosshead speed was 20 mm/min and the chart speed 200 mm/min. The tests were performed using sausages 4 cm long and 2 cm in diameter.

Compressive strength was measured using sausage cores 2 cm long and 2 cm in diameter. A strict cylindrical geometry was used on all samples in order to allow correct uniaxial compression. A compression anvil assembly was attached to the Instron and the conditions of running were those described above for tensile strength measurement. Compressive strength and tensile strength were expressed in ki logrammes to break down the sausage.

Juiciness." Juiciness was measured by a method modified f rom Baker et al. (1968). The percentage fluid expressed (as an indication of juiciness) was determined by weighing 0-50 _+ 0.05 g of sausage with skin removed and pressing at 28 kg/cm 2 for two minutes in two filter papers (Whatman No. 3, 11 cm diameter) between two plexiglass plates using a Labora tory Model Press. The filter papers were kept in a desiccator over anhydrous CaCI z prior to use. The sample was reweighed and the percent of fluid expressed was determined, dividing the difference of weight of samples before and after pressing by the weight of sample before pressing, multiplied by 100. This test was performed in ten samples.

Sensory tests Before sensory tests the frozen sausages were thawed for 48 h at 2 °C and deep-

fried at 170 + 5 °C for 5 min. The sausages were assessed by a panel of fourteen tasters for five characteristics using the following scoring system, as described by Thomas et al. (1973):

Texture Juiciness Colour Flavour General acceptability

1 sof t - -5 ideal- -9 hard I wet - -5 ideal - -9 dry 1 pale - -5 ideal- -9 dark 1 inedible--9 ideal 1 dislike ext remely--9 like extremely

The sensory tests were performed in duplicate.

PLASMA A N D P L A S M A - - A L G I N A T E FIBRES FOR USE IN SAUSAGES 301

Statistical procedure The data obtained were statistically analysed by analysis of variance using an ICL

1906 A computer .

RESULTS

pH of meat and o f sausages containing various amounts o f meat replacement The pH ot" sausages with 20 and 40 ~o plasma protein replacement was higher than

the control sausage (0 ~o replacement), due to the high pH of blood plasma. The results are given in Table 4.

TABLE 4 pH OF MEAT AND SAUSAGES

pH

Meat Control (0 % replacement) Plasma-alginate fibres (20 ~ replacement) Plasma-alginate fibres (40 ~ replacement) Plasma (20 % replacement) Plasma (40 ~ replacement) Plasma and alginate (40% replacement) Alginate fibres and plasma (40 ~ replacement)

6.20 6.45 6.60 7.00 6.75 7.15 7.00 6.90

Fibre analysis The results of analysis of the prepared spun fibres are given in Table 5. Although

the plasma protein solution was adjusted to 10% for spinning, the final protein concentration of the fibres was 8 %. The plasma solution was separated from the fibres during washing to remove the spinning bath solution and centrifuged to extract excess water from the fibres. The alginate concentration was lower in the fibres made by spinning plasma and alginate solution than in those made f rom alginate only. Washing and centrifuging could have contributed to this difference. Fibres made by the method of Young & Lawrie (1974), using 10 % plasma protein

TABLE 5 FIBRE ANALYSIS

Parameters A B

pH 8.2 8.0 Protein 8-0 0 Water 85-0 88.7 Ash 2.7 1.8 Alginate 4-0 9-5

A--Plasma-alginate fibres. B--Alginate fibres.

302 OLAVO RUSIG

TABLE 6 T H E EFFECT OF REPLACEMENT O F MEAT PROTEINS BY PLASMA PROTEINS O N V A R I O U S S A U S A G E P A R A M E T E R S ~

SERIES I

Type of sausage Stability Shrinkage Tensile Compressive Juiciness A B strength strength

Control (0 ~o replacement) 2.0 3-8 35.8 0-24 1.03 73-4 Plasma (20 ~ replacement) 0 0 31-2 0.37 1.42 76.4 Plasma (40 ~ replacement) 0.6 0.6 30-8 0-38 1-62 72.6 Plasma-alginate fibres

( 2 0 ~ replacement) 1.5 3-9 30-7 0.41 1.19 74.7 Plasma-alginate fibres

( 4 0 ~ replacement) 2-0 6.5 28.8 0.57 1.92 76.0 Significant differences * * * * * ns

* Significant differences (P < 0-05). ns = Not significant. A = Millilitres of water cooked out per 100 g sample. B = Millilitres of fat cooked out per 100 g sample.

s o l u t i o n , h a d a n i n c r e a s e d p r o t e i n c o n t e n t (17 ~o) d u e to t h e d e g r e e o f d e n a t u r a t i o n

a n d a g g r e g a t i o n o f t h e p r o t e i n d u r i n g s p i n n i n g ( b y t h e u s e o f l ow p H a n d h i g h sa l t

c o n t e n t in t h e s p i n n i n g b a t h s o l u t i o n ) .

Stability, shrinkage, tensile and compressive strength and juiciness T h e r e s u l t s f o r t h e a b o v e p a r a m e t e r s a r e s u m m a r i s e d in T a b l e 6 f o r Se r i e s I a n d

T a b l e 7 f o r Se r i e s II .

T h e t o t a l p r o t e i n q u a n t i t y is ve ry i m p o r t a n t in m e a t p r o d u c t s as i t is t h e a g e n t

r e s p o n s i b l e f o r e m u l s i f y i n g a n d b i n d i n g fa t a n d w a t e r to g ive d e s i r a b l e t e x t u r e to t he

p r o d u c t . D e s p i t e t h e l ow p r o t e i n c o n c e n t r a t i o n u s e d , n o fa t o r w a t e r w e r e c o o k e d

TABLE 7 THE EFFECT OF R E P L A C E M E N T OF MEAT PRO T E IN S BY PLASMA PROTEINS ON V A R I O U S S A U S A G E P A R A M E T E R S - -

SERIES 11

Type of sausage Stability Shrinkage Tensile Compressive Juiciness A B strength strength

Control (0 ~ replacement) 1.2 0.3 18-3 0.79 2.05 77.4 Plasma-alginate fibres

(40 ~ replacement) 1.2 2.7 23-7 0.55 1.52 74.3 Plasma and alginate

( 4 0 ~ replacement) 0 0 17.7 0.32 ND 80.7 Plasma and alginate fibres I-0 1-5 20.6 0-70 2-00 73.0

(40 ~ replacement) Significant differences * * * * * *

* Significant differences (P < 0-05). ND = The compressive strength could not be determined as the sample was very soft, having no strength. A = Millilitres of water cooked out per 100 g sample. B = Millilitres of fat cooked out per 100g sample.

PLASMA AND PLASMA-ALGINATE FIBRES FOR USE IN SAUSAGES 303

out during the heat treatment or the stability test from sausage in which 20 ~ of the meat protein had been replaced by isolated plasma proteins. The same results were obtained for sausage made using plasma and unspun alginate, at the 40~o replacement level, in Series II (Table 7), but very poor texture was obtained. The stability in relation to fat and water separated during heat treatment for sausages in Series I and II (Tables 6 and 7) was significantly different (P < 0.05).

1 2 3 4 5

Fig. 2. Sausages made with replacement of meat proteins by plasma proteins (after frying at 170 °C for 5min)---Series I. I. Control (0% replacement). 2. Plasma (20~ replacement). 3. Plasma (40% replacement). 4. Plasma-alginate fibres (20~ replacement). 5. Plasma-alginate fibres (40~

replacement).

Shrinkage was greater in the controls than in any sausages having plasma protein, whether spun or not, in Series I (Table 6). Although the shrinkage of sausages was not very different, great differences in the appearance of sausages could be seen after frying (Figs. 2 and 3). In Series II (Table 7) it could be seen that incorporation of phosphate (in the commercial seasoning--Table 3) improved the stability, shrinkage and tensile strength of the sausages. Sausages of different composition were statistically different (P < 0-05) in respect of shrinkage. Increasing the replacement of meat by plasma protein from 20 to 40 ~o did not noticeably change the tensile strength, but this parameter was very different for sausages in which the meat had been replaced by plasma-alginate fibres (Table 6). Tensile and

1 2 3 4

Fig. 3. Sausages made with replacement of meat proteins by plasma proteins (after frying at 170 °C for 5 min)--Series II. 1. Control (0 % replacement). 2. Plasma-alginate fibres (40 ~ replacement). 3. Plasma

and alginate (40 ~ replacement). 4. Plasma and alginate fibres (40 % replacement).

304 O L A V O R U S I G

compressive strength were very low for sausages made with plasma and alginate but high when alginate fibres were used (Table 7).

An increase in replacement of meat by plasma protein from 20 to 40 ~ produced an increase in the cohesiveness of the sausages, as shown by values for compressive strength in Series I (Table 6).

Sensory tests The results for sensory tests of sausages are summarised in Table 8 for Series I and

in Table 9 for Series II. Texture, as analysed by the taste panel (Table 8), indicated that the sausage

preferred was that made with 20% replacement by plasma protein or

TABLE 8 THE EFFECT OF REPLACEMENT OF MEAT PROTEINS BY PLASMA PROTEINS ON SENSORY EVALUATION OF

SAUSAGES----SERIES 1

Type of sausage Texture Ju ich~ess Colour Flavour General acceptability

Control (0 ~ replacement) 2-9 3-I 4.6 5-0 5.0 Plasma (20 ~ replacement) 5.2 4.4 4.9 5.3 5.8 Plasma (40 ~ replacement) 3-8 3.9 4.3 4.8 4.4 Plasma-alginate fibres

(20 ~ replacement) 4.8 5-5 4.2 3-9 4-5 Plasma-alginate fibres

(40 ~ replacement) 5.6 6.7 3-9 3-9 4-3 Significant differences * * ns * *

*Significant differences (P < 0-05). ns = Not significant.

plasma-alginate fibres. The score for the control sausage was the lowest in Series I but in Series II the texture of control sausages was found to be virtually the same as that incorporating plasma-alginate fibres at 40 ~/o replacement (Table 9). The worst texture was found in sausages in which 40 o / o f the total meat protein had been replaced by plasma and unspun alginate. In Series II the texture preferred was that which had incorporated plasma protein and spun alginate; this was statistically different (P < 0.05).

Juiciness values for all sausages tested by pressing (Table 6) were not significantly different (P > 0.05). Juiciness, as analysed by the panel (Table 8), showed that control sausages were wetter than those made with plasma or plasma-alginate fibres. Sausages made with 20 and 40 ~o plasma-alginate fibres were judged slightly dry by the panel. This is an important parameter for the final characteristic of sausages and further studies are needed to judge the effect of different percentages of fat and water on the formulation in relation to juiciness. The colour of the sausages

PLASMA AND PLASMA--ALGINATE FIBRES FOR USE IN SAUSAGES 305

TABLE 9 THE EFFECT OF REPLACEMENT OF MEAT PROTEINS BY PLASMA PROTEINS ON SENSORY EVALUATION OF

SAUSAGES---SERIES ii

Type o f sausage Texture Juiciness Colour Flavour General acceptability

Control (0 ~ replacement) 3-4 3. I 4-5 6.1 5.9 Plasma-alginate fibres

(40 % replacement) 3-2 4.6 4-2 5.8 5-3 Plasma and alginate

(40 % replacement) 2-6 3.6 4-6 5.1 3.9 Plasma and alginate fibres

(40 % replacement) 5.0 6-1 4.6 5-2 5-3 Significant differences * * ns * *

* Significant differences (P < 0-05). ns = Not significant.

studied was not statistically different (P > 0.05). The flavour of control sausages was preferred for both Series I and Series II, although all sausages studied were considered edible by the members of the panel. The 20 % replacement level was quite satisfactory from the point of view of flavour and general acceptability. The sausages were statistically different (P < 0-05) for flavour and general acceptability.

DISCUSSION

The final quality characteristics of meat products are greatly dependent on the amount and type of protein (Simon et al . , 1965; Smith et al. , 1973). Beef protein is primarily composed of fibrous actin and myosin. Blood plasma, on the other hand, contains a high concentration of albumin (Halliday, 1973). Although blood plasma proteins have a different chemical composition from meat proteins, they have the ability to form a stable three-dimensional network (gel) which can bind water and fat in meat products when heat treated (Hermansson & Tornberg, 1976). Thomas et al. (1973) found that the use of protein additives to replace meat protein in sausages had deleterious effects on sensory qualities, the texture being softer than that of the control.

In the present work it was thought initially that sausage texture would be improved by replacement of part of the meat content by synthetic fibres made from polysaccharide (alginate) incorporating plasma as a protein source.

The literature presents many methods of preparation of fibres. From the economical point of view the type of fibres developed by Young & Lawrie (1974) could be used as there is no need to use alginate to make them; however, the drastic conditions of pH and ionic strength used induce changes in the plasma proteins to the point where their use in sausage products could be undesirable due to the high

306 OLAVO RUSIG

degree ofdenaturation. Carpenter (1964) found that any factor which influences the shape and net charge of protein molecules will influence the ability of the protein to form a meat emulsion and soiower the ability to hold fat and water in the sausage mixture.

The method of Imeson et al. (1978) for making fibres was used preferentially since it employs mild spinning conditions. It was hoped that in this way fibres with useful characteristics for improving texture and stabilising fat and water in sausage mixtures would be obtained. The results of the present work indicated that fibres could improve the texture of sausages made using mixtures of plasma-alginate fibres or alginate fibres with the plasma added in liquid form to the mixture (Figs. 2 and 3). The formulation used to make those sausages was based on plasma-alginate concentrations; in future studies it would be interesting to study the effect of fibres in relation to the formulation components, i.e. water, fat and total protein.

Swift et al. (1954) made bologna sausage with variations in the fat and moisture content and found by taste panel evaluation that juiciness and tenderness were considerably more dependent on water than on fat. In the present work there was no great difference in juiciness (analysed by pressing) mainly due to the use of constant values of fat and water in the formulation. According to Baker et al. (1968) the method of measuring juiciness of sausages by pressing has been shown to have little correlation with taste panel juiciness scores. It should be pointed out that the sensory method did not measure amounts of juiciness but only preference for juiciness (Goltry et aL, 1976).

The texture measured by tensile and compressive strength could not be compared with the texture measured by the taste panel as both tests were made in different conditions (for the taste panel the sausages were fried and served hot but for the tensile and compressive strength tests the sausages were heated in a water bath and analysed cold). Swift & Ellis (1957) have used tensile strength as a measure of cohesiveness and moisture losses produced during cooking operations of sausages. As would have been anticipated, the incorporation of commercial seasoning, including phosphate in sausage mixes (Series II), increased the capacity to bind water and fat and improve the tensile and compressive strength measurements (Table 7).

The flavour of meat is a complicated matter and it is one of the great problems in the manufacture of meat analogues. The present work showed (Tables 8 and 9) that, due to the nature of the mix composition of sausage products, fibres resembling meat could be used to improve texture without creating problems of flavour.

The present work has also shown that satisfactory sausages, containing only 7 ~ total protein, could be made when the meat protein was replaced by plasma at the 20 ~o level but not at 40 ~ since, when frying the latter, holes form inside the mass due to a lack of binding (Fig. 2). Sausages containing plasma-alginate fibres, or plasma and alginate fibres, could be made with up to 40 ~o protein replacement and still have good texture.

PLASMA AND PLASMA--ALGINATE FIBRES FOR USE IN SAUSAGES 307

O b v i o u s l y , s o m e r e s e a r c h c o n c e r n i n g the use o f i so la t ed p l a s m a o r its f ibres in

d i f fe ren t m e a t p r o d u c t s r e m a i n s to be d o n e . H o w e v e r , the use o f a h igh n u t r i t i o n a l s o u r c e o f p r o t e i n as b l o o d p l a s m a has d i s t inc t mer i t , e spec ia l ly if i ts u t i l i s a t i on

c o n t r i b u t e s to t he so lv ing o f w o r l d f o o d p r o b l e m s .

ACKNOWLEDGEMENT

T h e in te res t o f P r o ~ s s o r R. A. L a w r i e in th is i n v e s t i g a t i o n is a c k n o w l e d g e d w i t h

t h a n k s .

REFERENCES

A OAC (1975). Offich~l Methods o f Analysis. Association of Official Agricultural Chemists, Washington, DC.

BAKER, R. C., DARLFER, J. M. & BOURNE, M. C. (1968). Poultry Sci., 47, 1989. B^LMACEDA, E. & RHA, C. K. (1974). J. FdSci., 39, 226. BROMSTEIN, R. A. H. (1974). US Pat. No. 3,833,744. CARPElCrER, J. A. (1964). A study o f some o f the physical and chemical characteristics o f a sausage emulsion

using a model system, University of Georgia, USA. FISCHER, J. (1956). Beef and pork sausage. In: Pork andpork products, Practical Press Ltd, London, 57. GOLTRY, S. J., STRINGER, W. C. & BALDWIN, R. E. (1976). d. Fd. Sci., 41,973. HALUDAY, D. A. (1973). Process Biochem., 12, 15. HERMANSSON, A. M. & TORNBERG, E. (1976). Proc. 22rid European Meeting o f Meat Research Workers,

Malmd, p. I, 1.1. HUANG, F. & RH^, C. K. (1971). J. Fd. Sci., 36, 1131. IMESON, A. P., LEDWARt), D. A. & MITCHELL, J. R. (1979). Meat Sci., 3, 287. ISHLER, N. H. et aL (1963). US Pat. No. 3,093,483. JAYNES, H. O. & ^.SAW, T. (1976). J. Fd. Sci., 41,787. KELLEY, J. J. & PR~SSEY, P. (1966). Cereal Chem., 43, 195. StMON, S., FIELD, J. C., KRAMLICH, W. E. & TAUBER, F. W. (1965). Food Technol., 19, 410. SMITH, G. C., JOHN, H., CARPENTER, Z. L., MAl-rm, K. F. & CATER, C. M. (1973). J. Fd. Sci., 38, 849. SWIFT, C. E., WEIR, C. E. & HANKINS, O. G. (1954). Food Technol., 8, 339. SwxFT, C. E. & ELLIS, R. (1957). Food Technol., 8, 450. SWINGLER, G. R. & LAWRIE, R. A. (1977). Meat Sci., 1, 161. THOMAS, M. A., BAtJMGARTNER, P. A., BOARD, P. W. & GtPPS, P. G. (1973). J. Fd. Technol., 8, 175. TOLSXOGOZOV et al. (1974). US Pat. No. 3,829,587. YOUNG, R. H. & LAWRm, R. A. (1974). d. Fd. Technol., 9, 171. YotJN,3, R. H. & LAWRm, R. A. (1975). J. Fd. Technol., 10, 453.