Enzymes in dairy product manufacture - Enzymes in Food Technology - page 100

Single use
lactase in
solution

Lactase at
35-40°C

15% TS

Hydrolyzed
whey syrup

ion
exchange

evaporation

Whey
permeate

concentration

20% TS

Immobilized
lactase
bioreactor

Immobilized
lactase
column at
35-50°C

Fig. 5.3 Flow diagram of lactase-based lactose hydrolysis process using batch solution method and
immobilized enzyme method.

and diarrhoea due to the accumulation of lactose in the gut lumen. Lactaid R tablets deliver
active lactase to the gut to break down the ingested lactose and alleviate the intolerance
symptoms.
Hydrolyzed whey syrup is produced from whey, the by-product of cheese making and
casein production. The hydrolysis step can be on the whey itself, or on the permeate from
ultrafiltration (UF) plant used to make WPC. The UF permeate still contains some whey pro-
tein but is enriched in lactose. It is concentrated to 15-20% total solids (TS), demineralized,
usually by ion exchange, though electrodialysis or nanofiltration can be used for this, then
heated according to the type of lactase treatment to be used. The hydrolysis step can be by
batch treatment with yeast lactase, though the use of immobilized enzyme reactor columns
is more efficient, using Aspergillus lactase. Immobilized lactase reactors can achieve up to
90% lactose hydrolysis in whey permeate, whereas the batch process converts only about
70%. However, both processes produce sufficient free glucose and galactose to make the
product sweet, and this property is enhanced by evaporation of the hydrolyate to 60% TS to
make the final syrup. A typical flow diagram for the process is shown in Fig. 5.3.
The whey syrup is made sticky by the high concentration of glucose and galactose, so it is
not dried, but sold and used in that form. It is used in food manufacture to replace sweetened
condensed milk, sugar and skim milk in many products such as ice cream, milk desserts
and sauces. The syrup is also an excellent caramel ingredient and as a sweetener/binder in
cereal bars.

REFERENCES

1. Harboe, M. and Budtz, P. (1999) The production, action and application of rennet and coagulants. In:

Technology of Cheesemaking (ed. B.A. Law). Sheffield Academic Press, Sheffield, pp. 33-65.

2. Lomholt, S.B. and Qvist, K.B. (1999) The formation of cheese curd. In: Technology of Cheesemaking

(ed. B.A. Law). Sheffield Academic Press, Sheffield, pp. 66-98.

3. Foltmann, B.F. (1992) Chymosin: a short review on foetal and neonatal gastric proteases. Scandinavian

Journal of Clinical and Laboratory Investigation 52 , 65-79.

4. Fernandez-Salguero, J., Tejada, L. and Gomez, R. (2002) Use of powdered vegetable coagulant in the

manufacture of ewe's milk cheese. Journal of the Science of Food and Agriculture 82 , 464-468.