MICROBIOLOGY Study Guide - 2012

CHAPTER 15. FOOD MICROBIOLOGY

15.6. MICROBIOLOGY OF BAKERY PRODUCTS

15.6.3. Starters for Rye Dough

In terms of its baking properties, rye flour differs significantly from wheat flour. It contains active α-amylase, an enzyme that catalyzes The breakdown of starch into dextrins. Dextrins give the crumb a sticky, underbaked texture. To suppress α-amylase activity, the acidity of the dough is increased to 10–12 deg. To achieve this high acidity, rye dough is prepared using starters made from pure cultures of Yeasts and lactic acid Bacteria, with the latter playing the primary role in dough maturation.

Rye bread dough can be prepared using a firm starter, a liquid starter without scald, a liquid starter with scald, or a concentrated Yeast-free lactic acid starter (CFS).

Firm starter is used for making dough from whole-grain and sifted rye flour, as well as from various blends of rye and wheat flours. A firm starter should have a moisture content of 48–50%, an acidity of 13–16 deg, and a leavening capacity (determined by the ball method) of up to 25 min.

To propagate a firm starter, a combination of Lactobacillus strains L. plantarum 63, L. brevis 5, L. brevis 78 and a pure yeast culture of S. minor strain "Chernorechensky" grown on malt wort is used. If pure yeast culture is unavailable, compressed yeast may be used.

Liquid starter without scald. This starter has a moisture content of 70–75%, an acidity of 9–13 deg, and a leavening capacity (by the ball method) of up to 35 min. The preparation technology consists of two cycles: a multi-stage propagation cycle and a production cycle. In the propagation cycle, the liquid starter is obtained using a mixture of pure yeast cultures S. cerevisiae L-1 and S. minor strain "Chernorechensky" combined with a mixture of liquid lactic acid bacteria cultures: L. plantarum-30, L. rhamnosus-26, L. brevis-1, L. fermentum-34, or dry lactobacterin for liquid bread starters formulated from the same Lactobacillus strains. In the production cycle, half of the starter is used for dough preparation, while the remaining portion is used to inoculate a new batch of starter. The cycles of withdrawing and refreshing the starter are carried out every 3–4 hours once an acidity of 9–13 deg is reached.

Liquid starter with scald. The scalded starter should have a moisture content of 80–85%, an acidity of 9–12°, and a leavening capacity of up to 30 min. The starter is prepared using a pure yeast culture of S. cerevisiae L-1 combined with a mixture of lactic acid bacteria strains: L. plantarum-30, L. rhamnosus-26, L. brevis-1, L. fermentum-34.

Concentrated lactic acid starter (CFS) has a moisture content of 60–70%, a Temperature of 37–41 °C, and an acidity of 18–24 deg. The dough is prepared either in two stages (CFS → dough) or in three stages (CFS → sponge → dough). When kneading dough with CFS, compressed or liquid yeast is used as a biological leavening agent. In the propagation cycle, CFS is prepared using a mixture of liquid lactic acid bacteria cultures: L. plantarum-30, L. rhamnosus-26, L. brevis-1, L. fermenti-34, or dry lactobacterin for liquid bread starters.

Dry lactobacterin for bread starters. The technology for "Dry Lactobacterin for Bread Starters" was developed at the St. Petersburg branch of the State Research Institute of the Baking Industry (GosNIIP). This product is available in three types, the strain compositions of which are given in Table 15.

Class="center">Table 15. Species and strain composition of dry lactobacterin

Dry lactobacterin is a freeze-dried biomass of lactic acid bacteria supplied in Glass vials with a shelf life of up to 12 months when stored in a refrigerator at 4–8 °C. A single dose of lactobacterin (1 g) contains approximately 10⁹ viable lactic acid bacteria Cells.