gluten quality involves the addition of low levels of gluten, ied typically are compared to results obtained by some about 2%, to a standard test flour, which often is of a type of baking test. McDermott [85] compared baking "weak" type, and observing the effects on bread quality. (Chorleywood bake test) and other properties of 30 com-Water absorption is adjusted as appropriate for the gluten mercial glutens, mostly of European origin (Table 8), and levels added [23]. A stressed gluten-enriched baking test found that under his test conditions six samples were of was identified [31], which assumes that gluten is added to relatively poor quality; correlation between baking perfor-enable production of specialty breads using substantial mance and other measured properties was not high. levels of non-gluten-containing ingredients such as rye Weegels and Hamer [130] studied a group of 32 European flour, dietary fiber, bran and germ, or raisins [49]. Czucha-commercial glutens. These workers devised a test involv-j owska and Pomeranz [31] described a simple, repro-ing protein content, denaturation index (based on a series ducible method for baking undiluted gluten, highly corre-of sodium dodecyl sulfate sedimentation measurements), lated with the gluten-enrichment baking test. and extensigraph resistance; a model utilizing these tests A prime reason for performing end-use tests of func-was able to predict 59% of the baking quality variation of tionality, of course, is to monitor variations in the quality the glutens. Bushuk and Wadhawan [20] examined 27 of commercial wheat glutens that can occur. Differences commercial gluten samples, although only 8 were subject-among commercial gluten are usually attributable to varia-ed to extensive end-use testing; the highest correlation co-tions in the starting material, wheat or flour, and/or efficients were between loaf volume and acetic acid-solu-changes caused by production processing conditions. Dur-ble protein (r = 0.88) and between loaf volume and ing processing, the drying of gluten is critical, as noted fluorescence of acetic acid extract (r = 0.98). above, and investigators have shown that less than opti-mum heat treatment can lower the baking quality of gluten (b) Nonbaking Tests. Considerable efforts have been [14,49,98,111,130]. However, McDermott [85] reported expended in developing nonbaking tests to evaluate the no definite relationship between manufacturing variables quality or vitality of wheat gluten for baking purposes. The and gluten quality in a group of 30 commercial glutens. baking test is often cited as being labor intensive, relative-Dreese et al. [38] studied commercial and hand-washed ly expensive, requiring skilled workers, and not effectively lyophilized gluten and found that differences were more differentiating gluten quality [86]. The farinograph has attributable to washing procedures than to drying proce-been used to evaluate gluten for many years. The usual ap-dures. proach has been to test the gluten as a gluten-flour mixture Results obtained by other methods that have been stud-(e.g., Refs. 5, 18, 36, and 49), while an alternative method TABLE 8 Properties of 30 Commercial Glutens Baking performance Property Average Range Poor Average Good Increase in loaf volume, %a 10 7.7-12.2 8.3 10.2 11.8 Protein, %b 77.4 66.4-84.3 76.2 77.4 81.1 Moisture, % 7.55.3-10.2 8.877.7 Particle size, % <160 p.m 88.8 55.8-98 80.5 91 90.3 Color 68.3 56.5-75 65.2 68.9 69.5 Lipid, % 5.84.2-7.65.86.15.1 Ash, % 0.69 0.44-0.94 0.71 0.74 0.6 Chloride, %` 0.08 0.01-0.28 0.10.08 0.08 Water absorption, mug protein 2.37 1.84-2.93 2.26 2.45 2.29 SDS sedimentation volume, ml/g protein 99 55-159 70 107 127 Lactic acid sedimentation, % reduction in turbidity 18 2-68 49 11 7 Hydration time, min 0.90.2-10 2.72.40.6 Extensibility, units/min 3.80.7-9.33.23.93.9 Viscosity, cP 117 73-222 159 109 101 '2% gluten protein. Dry matter basis. `As NaCl. Source: Ref. 85.