Fermented Dairy Ingredients for Bread: Effects on Dough Rheology and Bread Characteristics'

Cereal Chem. 72(2):151-154 Fermented dairy ingredients prepared with Lactobacillus casei subsp. differ from that of standard milk bread. When milk was the main comrhamnosus and containing variable proportions of milk, whey, and whole ponent of the fermented dairy ingredient (no whey or flour), the quality wheat flour were incorporated in a pan bread formulation and tested of the bread was about equivalent to that of standard milk bread (dough according to their effect on dough rheology and bread scoring. In general, water absorption, bread specific volume, firmness, scoring). As compared according to their pH, fermented dairy ingredients did not change dough to whole wheat flour, the addition of buckwheat, oats, or wheat flour water absorption but did reduce peak time, dough mixing stability, and to the dairy medium before fermentation had the most positive effect bread specific volume and increased bread firmness after one or seven on bread volume and flavor among the 11 tested flours. days. Dough proof time, bread scoring, and mold-free shelf life did not Variety breads have become very popular in recent years. They are very attractive to consumers looking for products with different appearance and flavor (van Osnabrugge 1988). Sourdough is a good example of high-flavored bread. However, it has a production process that is still quite empirical, long, and difficult to control: a starter is taken from a ripe dough, activated with water and flour, fermented to optimum, and baked. Overall, the fermentation process usually lasts several hours (Stear 1990). Short-time procedures for sourdough have been proposed (Lorenz 1983). For example, Kline (1983) used a freeze-dried culture of Lactobacillus sanfrancisco to better control sourdough production. Commercial dry bases are also available to shorten fermentation times, but they sometimes lead to off-flavors (Oura et al 1982). Shenkenberg et al (1972) also described a sourdough process where cottage cheese, whey, and vinegar are added. Another way to improve the sourdough process is to use a high-flavored dairy ingredient, derived from sweet whey or milk (Gelinas et al 1992). With careful selection of lactic cultures, bread flavor may be enhanced (Gelinas and Lachance 1995); such bread would also benefit from milk nutritional properties and its technological improvements in bread production such as better fermentation tolerance of the dough (Pyler 1988, Doerry 1989). The use of low concentrations of this type of fermented dairy ingredient in the no-time dough process would partly compensate for lack of flavor, a characteristic of bread made from this most accelerated breadmaking process. However fermented dairy ingredients have a negative effect on bread specific volume (Shenkenberg et al 1972, Gelinas and Lachance 1995). Previously, we focused on the use of selected bacteria and growth media to optimize the flavor of fermented dairy ingredients and bread prepared from it (Gelinas and Lachance 1995). Here, we report on the effect of some ingredients on dough rheology; we searched for optimized ingredients that did not impair bread quality (proof time, loaf volume, scoring, mold-free shelf-life, and firmness). MATERIALS AND METHODS Dairy Ingredient Preparation A volume of 1 L of preferment was prepared with equal mixtures (20% dairy solids) of reconstituted high-heat skimmed milk and 'Contribution 335 from the Food Research and Development Centre, 3600 Casavant Blvd. West, St. Hyacinthe, Quebec, Canada J2S 8E3. Part of these results were presented at the AACC 74th Annual Meeting, Washington, DC, October 1989. 2 Campus Haute-Technologie Agro-Alimentaire de Saint-Hyacinthe. © 1995 Department of Agriculture and Agri-Food, Government of Canada. sweet whey. The medium was supplemented with 1% (w/ v) sodium citrate and inoculated with 2.5% (-4 X 108 cells g-1 of dairy preparation) of a freeze-dried lactic starter, Lactobacillus casei subsp. rhamnosus (Institut Rosell, Inc., Montreal, Canada). Variable proportions of whole wheat flour were then added to the dairy preparation (0, 10, or 30 g/ 100 ml of reconstituted dairy product). Besides whole wheat, other flour types were also evaluated at a concentration of 30% (w/v) in the dairy preparation: arrowroot, barley, buckwheat, corn, millet, oats, rice, rye, soy, and wheat (second patent flour). Fermentation was performed at 38C for 24 hr and 140 rpm in 500-ml Erlenmeyer flasks containing about 350 ml of dairy preparation. Fermented dairy ingredients were then cooled at 40C. For the dough rheology tests, ingredients were freeze-dried, then stored in bags at 40 C. Breadmaking Process Except where indicated, white pan bread was produced by the no-time dough procedure using: 100% flour (14% moisture), 4% sugar, 3% yeast (30% solids), 3% shortening, 2% salt, 100 ppm ascorbic acid, 60 ppm potassium bromate, 6% fermented dairy ingredient (dry weight), and water (variable). In triplicate, each batch was produced from 2 kg of flour with a Hobart mixer (A-200T), giving nine doughs scaled to 330 g. Doughs were rounded, bench-rested for 10 min, molded, and proofed to constant height (2.5 cm above rim) at 400C and 100% rh. Bread was baked at 213'C for 20 min; 1 hr after baking, loaf volume was measured by rapeseed displacement. On the following day, breads were scored by an expert in the field for internal and TABLE I Scoring Values Used to Evaluate Pan Bread Quality Maximum Score External (30 points) Specific volume 10 Crust color 8 Symmetry 3 Evenness of bake 3 Character of crust 3 Break and shred 3 Internal (70 points) Grain 15 Taste 15 Crumb color 10 Aroma 10 Keeping quality 10 Texture 10 Total 100 Vol. 72, No. 2,1995 151 external characteristics (Table I). Milk bread (6% milk solids, flour basis) was prepared as a reference. Dough Rheology, pH, and Total Titratable Acidity Dough water absorption, peak time, and mixing stability were evaluated in triplicate with the farinograph by AACC method 54-21 (AACC 1983). When dairy preferment contained flour, its quantity (50 g) was removed from the amount of flour necessary to perform the test. Table II presents the farinogram parameters according to the type of dairy ingredient. Conditions included: 1) flour only; 2-4) nonfermented dairy ingredients; 511) fermented dairy ingredients. All tests were performed at 6% (on a dairy solid/flour basis), except for condition 8 (5.45%, dairy solids) and condition 9 (4.62%, dairy solids) where whole wheat flour was incorporated in the dairy ingredient before fermentation, somewhat reducing the dairy solids proportion. In condition 10, the concentration of the fermented dairy ingredient containing 30% flour (w/v) was corrected to give 6% dairy solids (flour basis). Before performing the farinograms, the flour content of the dairy ingredients already containing flour was considered, except for condition 11. Dough pH was taken twice (3X repetitions) upon completion of the farinograph test by directly immersing the electrode in the doughs. Total titratable acidity (TTA) and pH of fermented dairy ingredients were determined in duplicate (3X repetitions) on 9 g of dairy ingredient supplemented with 18 g of water. TTA was measured in duplicate with NaOH N/9 to pH 8.6, using phenolphtalein (American Public Health Association 1985). For bread samples, a modified procedure was used: 15 g of bread crumb (from the center of the loaf) was shaken for 30 min in 100 ml of water and TTA was measured twice (3X repetitions) by titration to pH 6.6 with NaOH N/9 (Sutherland 1989). TTA was expressed as meq. mol lactic acid/g, calculated as: vol NaOH (ml) X Normality (meq. mol. ml-')/ weight of sample (g). Bread Mold-Free Shelf-Life and Firmness In triplicate, molding of bread was determined visually on two bread samples, each wrapped in two plastic bags and stored on racks at 211C until mold appeared. After one and seven days, TABLE II Dough pH and Farinogram Parameters According to Dairy Ingredient Compositiona Absorption Peak Time Stability Ingredient Dough pH (min) (min) (min) I. Reference (flour) 5.92 b 62.0 b 6.5 a 10.7 b 2. Milk 6.06 a 63.1 cd 9.5 e 14.7 d 3. Whey 5.94b 60.1 a 8.8 de 12.7 c 4. Milk-whey 6.00 a 62.1 b 9.5 e 15.5 d 5. Fermented milk 5.52 c 64.3 e 7.8 bc 10.7 b 6. Fermented whey 5.52 c 60.4 a 8.3 cd 11.0 bc 7. Fermented milk-whey (0% flour) 5.51 c 62.9 c 8.2 cd 10.0 b 8. Fermented milk-whey (10% flour; w/v) 5.15 d 62.9 c 8.0 b-d 10.7 b 9. Fermented milk-whey (30% flour; w/v) 4.78 e 63.3 cd 6.7 a 6.2 a 10. Fermented milk-wheyb (30% flour; w/v) 4.58 f 63.5 d 6.8 a 6.3 a 11. Fermented milk-wheyc (30% flour; w/v) 4.77 e 69.4 f 7.2 ab 7.0 a LSD 0.088 0.513 0.932 1.899 aAll data are means of triplicate measurements, except pH (6). Means in a column followed by the same letter are not different at the 5% significance level (Fisher Least Significant Difference test) (LSD). Except where indicated, all ingredients were tested at 6% (flour basis) and the amount of flour brought by each ingredient was considered before running the farinograph. Ingredient tested at 15% solids (flour basis). 'Ingredient tested at 15%o solids (flour basis), except that the amount of flour present in ingredient was not considered before running the farinograph. staling was evaluated on two bread samples with a universal testing machine (Instron model 4201) according to AACC method 74-09 (AACC 1983) with the following specifications: 30 mm sample height (two slices of bread, 15 mm each), 36 mm diameter plunger, 50 N full-scale load and 50 mm/min crosshead speed. Stress and load were reported at 25% of compression, and test ended when compression exceeded 40%. Bread was sliced just before measuring