and the remainder are preserved by refrigeration. Despite this recent
trend, fermentation does have a number of advantages over other
methods.
(1) Fermented cucumbers have flavour and texture characteristics
not possessed by the other products.
(2) Bulk fermentation techniques facilitate quick and easy processing
in busy harvest seasons.
(3) Under these conditions, products can be stored in bulk until they
are required for further processing, so that year-round working is
possible.
(4) Fermentation is more economical with energy than techniques
which require pasteurization or an efficient cold chain.Cucumber fermentations can be divided into essentially two different
types: high-salt, or salt stock, and low-salt fermentations. Salt stock
cucumbers are fermented in a brine containing 5–8% salt until they are
stabilized by conversion of all the fermentable sugars to organic acids
and other products. Lb. brevis,Lb. plantarumandPediococcus pent-
osaceusare most commonly isolated. At these levels of saltLeuconostoc
mesenteroidesdoes not play the same crucial role as in sauerkraut or
kimchi production and at 8% salt it is often not even detected. During
the first phase of the fermentation which lasts for 2–3 days the microflora
contains a large diversity of bacteria, yeasts and moulds. The environ-
ment is selective for LAB and yeasts which increase while other organ-
isms decrease. The fermentation process is not restricted to the
surrounding brine but also occurs within the cucumbers as a result of
organisms entering through stomata. Sometimes this can lead to defects
in the product known as ‘bloaters’. Carbon dioxide accumulates within
the fruit and is unable to diffuse out, some of this gas production arises
from endogenous respiration of the tissues but much is the result of
microbial action such as the malo-lactic fermentation and the heterofer-
mentation of sugars. In a controlled fermentation process which has been
developed, measures taken to control this problem include the use of
strongly homofermentative starter cultures containing Lactobacillus
plantarumorPediococcus pentosaceusand intermittent purging of CO 2
from the system by bubbling nitrogen through the fermentation.
Genuine dill pickles are fermented in a lower salt brine (3–5%) in the
presence of dill (an umbellifer, Anethum graveolens) and spices. The
fermentation resembles sauerkraut production in the sequence of lactic
acid bacteria that develops though it is usually conducted at a slightly
higher temperature, 20–26 1 C compared with 18 1 C for sauerkraut. The
full curing process can take up to 8 weeks although active fermentation
usually lasts for only 3–4 weeks. The product brine has a pH of 3.2–3.6
342 Fermented and Microbial Foods