Industrial Fermentation nondairy products

Pickles are fermentation products of fresh cucumbers, and as is the case for sauerkraut production, the starter culture generally consists of the normal mixed biota of cucumbers. In the natural production of pickles, the following lactic acid bacteria are involved in the process in order of increasing prevalence: L. mesenteroides, E. faecalis, P. cerevisiae, L. brevis, and L. plantarum. Of these, the pediococci and L. plantarum are the most involved, with L. brevis being undesirable because of its capacity to produce gas. L. plantarum is the most essential species in pickle production, as it is for sauerkraut.

In the production of pickles, selected cucumbers are placed in wooden brine tanks with initial brine strengths as low as 5%NaCl (20◦ salinometer). Brine strength is increased gradually during the course of the 6- to 9-week fermentation, until it reaches around 60◦ salinometer (15.9% NaCl). In addition to exerting an inhibitory effect on the undesirable Gram-negative bacteria, the salt extracts water and water-soluble constituents from the cucumbers, such as sugars, which are converted by the lactic acid bacteria to lactic acid. The product that results is a salt-stock pickle from which pickles such as sour, mixed sour, chowchow, and so forth may be made.

The general technique of producing brine-cured pickles has been in use for many years, but it often  leads to serious economic loss because of pickle spoilage from such conditions as bloaters, softness,  off-colors, and so on. The controlled fermentation of cucumbers brined in bulk has been achieved, and this process not only reduces economic losses of the type noted, but leads to a more uniform product over a shorter period of time. The controlled fermentation method employs a chlorinated brine of 25◦ salinometer, acidification with acetic acid, the addition of sodium acetate, and inoculation with P. cerevisiae and L. plantarum, or the latter alone. The course of the 10- to 14-day fermentation is represented in Figure 8–2.

With a final pH of 4.0, pickles undergo spoilage by bacteria and molds. Pickle blackening may be caused by Bacillus nigrificans, which produces a dark water-soluble pigment. Enterobacter spp., lactobacilli, and pediococci have been implicated as causes of a condition known as “bloaters,” produced by gas formation within the individual pickles. Pickle softening is caused by pectolytic

Figure 8–2 Controlled fermentation of cucumbers brined in bulk. Equilibrated brine strength during fermentation, .4%NaCl; incubation temperature = 27◦C.

organisms of the genera Bacillus, Fusarium, Penicillium, Phoma, Cladosporium, Alternaria, Mucor, Aspergillus, and others. The actual softening of pickles may be caused by any one or several of these or related organisms. Pickle softening results from the production of pectinases, which break down the cementlike substance in the wall of the product.

List of literature

1.      James M. Jay, Modern Food Microbiology - Sixth Edition / Aspen Publishers, Inc. Gaithersburg, Maryland 2000.

2.      Martin R. Adams and Maurice O. Moss,  Food Microbiology - Third Edition / RSC Publishing, University of Surrey, Guildford, UK 2008.

3.      Bibek Ray, Arun Bhunia, Fundamental Food Microbiology – Fourth Edition/ CRC Press, 2008. 

4.      P. G. Smith, Introduction to Food Microbiology – Seventh Edition / Springer Press, University of Nevada Las Vegas, 2003.

2