BIOTECHNOLOGY AND BIOENGINEERING VOL. XIV (3972)

Fiber Formation from Single-Cell Protein

One of the interesting approaches for improving the acceptability of nonmeat proteins is to convert the protein material into fibrous form, which can be further fabricated into masticatory foods. HBden et a1.l reported their preliminary experiments on the spinning of a cell material from organisms called “methane or methanol oxidizers”. They found capillary tubes with diameters of 0.1-0.6 mm yielded better fibers than various spinnerets.

MATERIALS AND EQUIPMENT

In our laboratory, the alkali-extracted single-cell protein (SCP) concentrate from Torula dried yeast (N. F. XI1 Type B, S t . Regis Paper Co., Rhinelander,

TABLE I Fiber Formation of SCP under Various Conditions

SCP Con- Driving Shear Plunging centration Speed Ratea Force Fiber

(%) pH (in./min) (sec-l) (Ibs) Formation

25 8 1 .0 0 . 3 0. I

25 9 3 . 0 1.0 0 . 3 0 . 1

20 8 1 .o 0 . 3 0 . 1

20 9 3 . 0 1 . o 0 . 3 0 . 1

3 . 0 1 . 0

15 9 3 . 0 1 . o 0 . 3

15 8 10

2,340 700 234

7,000 2,340

700 234

2,340 700 234

7,000 2,340

700 234

23,400 7,000 2,340 7,000 2,340

700

16 12 10 19 14 11 9

28 23 20 12 I1 10 9 8 5 3 5 3 2

good excellent, good good good excellent good good excellent good good excellent excellent good good poor/none poor/none good good Door h o n e

a Shear rates at the capillary wall are calculated by the equation, i. = (2/15) (VD2/d3), where V = driving speed in in./min, D = plunger diameter (0.375 in.), and d = capillary diam in inches.

1047 @ 1972 by John Wiley & Sons, Inc.

1048 BIOTECHNOLOGY AND BIOENGINEERING VOL. XIV (1972)

Wis.) was made into dope of various concentrations and pH, as described by Huang and Rha.2 For the preliminary experimental spinning of the SCP dope, an Instron capillary rheometer (model 3211) was used. The capillary used was 0.020 in. in diameter and 0.396 in. long.

EXPERIMENTAL

The dope sample in the extruder barrel at 60°C was extruded with various driving speeds. Where fiber formation was possible (Table I), a spun filament could be stretched upon coming out of the capillary. As the filament was extruded into the open air a t 2 5 T , the filament cooled down rather rapidly while being drawn away from the capillary. Once the filament was cooled, it became fragile, and no further stretching could be applied. Nevertheless, both the stretched and the unstretched filaments exhibited considerable tensile strength when they were partially dried under room conditions, t.hough they lacked elasticity and resistance to shear.

As shown in Table I, shear rates around 700 sec-l seemed to be optimal for the fiber-formation of the dope. Under these spinning conditions, dope with 20% SCP concentrate gave the most desirable stretching and spinning char- acteristics, while samples of pH 9 appeared to be better than those of pH 8 in this respect.

The authors thank Dr. S. Middleman for his advice.

References

1. C . 4 . HQden, N. Molin, U. Olsson, and A. Rupprecht, Biolechnol. Bioeng.,

2. F. Huang and C. K. Rha, J . Food Sci., 36, 1131 (1971). 13, 147 (1971).

FRANK HUANG CHOKYUN RHA

Dept. of Food and Agricultural Engineering University of Massachusetts Amherst, Massachusetts 01002

Accepted for Publication July 25, 1972