Fermented Dairy Ingredients 347Bitter Taste of Quark
Bitter taste arising from proteolysis is
another concern. This is particularly true if
rennet is used in the preparation. During
wheying out, most of the rennet added to
the skim milk is discarded with the whey.
However, traces of rennet may remain in the
curd. Rennet is known to cause bitterness,
especially in quark that is produced using
ultrafi ltrated milk before fermentation due to
high calcium content in the retentate (Jelen
and Renz - Scauen 1989 ). Rennet retention in
quark increases with low pH at draining,
and its activity is high in low - pH products
(Guinee and Wilkinson 1992 ). Reducing the
rennet is one way to eliminate the bitter
taste, though this may reduce the yield of the
cheese. The use of 388 units of rennet/1,000 kg
of milk has been shown to produce accept-
able quark with reduced bitterness, good
yield, and extended shelf life (Sohal et al.
1988 ).Use of Quark
Quark is a suitable ingredient in several
dishes due to its neutral fl avor, no added salt,
and its consistency (smooth, can be blended)
(Walstra et al. 2006 ). It can be used as an
ingredient in cakes such as the German
cheesecake k ä sekuchen and Dutch kwarkta-
art, in sandwiches as a fi lling or spread, and
in salad.
Quark also has been used in the prep-
aration of shrikhand, although strained yogurt
is more commonly used. Several spices
such as nutmeg and saffron are also used to
fl avor the product (Tamime and Robinson
2007 ).
Quark can be used to prepare foods such
as healthy tiramisu; sweet quark pasta cas-
serole; rhubarb vanilla tart; pinwheels with
poppy seed, cherry, and raisin; the German
poppyseed cake mohnstrietzel; vanilla plaits
with raisin; and many other delicacies (www.
recipezaar.com/recipe.php).resulting in a non - homogeneous product
(Walstra et al. 2006 ). Traditionally, whey is
separated is by cutting the curd and allowing
it to drain in a linen cloth. This is time con-
suming, laborious, and unsuitable for large -
scale production. The keeping quality of the
cheese is also limited due to possible con-
tamination. In a modern production plant, a
centrifugal quark separator is used to sepa-
rate the coagulated skim milk. The drained
quark can then be cooled at 5 ° C (41 ° F) or
lower, packed, and stored at a refrigerated
temperature (Winwood 1983 ). This method
enables the adjustment of the quark ’ s water
content by varying the fl ow rate of the whey,
but it does not work well if the quark is
produced from whole milk (Walstra et al.
2006 ).
The whey can also be separated by fi ltra-
tion followed by homogenization to produce
smooth quark. Ultrafi ltration and diafi ltration
of quark made from skim milk are alterna-
tives to centrifugation technique; however,
the latter is of little use. Ultrafi ltration
increases the total solids of the fi nal quark to
17% to 19%. The quark produced from ultra-
fi ltration of sour skim milk is rated as close
to the conventional quark, with no bitter
taste. High heat treatment of milk before
acidifi cation by lactic acid bacteria followed
by ultrafi ltration results in quark with smooth
texture (Patel et al. 1986 ) and higher yield
(Walstra et al. 2006 ).
Shelf Life of Quark
The shelf life of quark under pilot plant
studies is limited to less than 14 days due to
the growth of contaminating microorganisms
(Ailsa et al. 1969 ); therefore quark should be
kept at refrigerated temperatures and con-
sumed within few days. Contamination by
yeasts and moulds may reduce the shelf life
of quark. At higher storage temperatures,
fl avor deterioration and syneresis occurs,
hence affecting the quality (Walstra et al.
2006 ).