Gluten-free breads are usually characterized by deficient quality characteristics as compared to wheat breads. Problems related to volume and crumb texture are associated with gluten-free breads even when rice flour is used, which seems to be the best raw material for this type of bread. The potential use of cyclodextrin glycosyl transferase (CGTase) as a rice bread improver is presented. The effect of CGTase addition to rice flour on dough rheology and bread quality was investigated. In addition, an experimental design was developed to optimize the levels of CGTase, hydroxypropylmethylcellulose (HPMC), and oil. The addition of CGTase produced a reduction in the dough consistency and also in the elastic modulus. With regard to the rice bread quality, better specific volume, shape index, and crumb texture were obtained. The amount of cyclodextrins in the bread crumb was quantified to explain the action of this enzyme. The data indicate that the improving effect of the CGTase results from a combination of its hydrolyzing and cyclizing activities, the latter being responsible for the release of cyclodextrins, which have the ability to form complexes with lipids and proteins.

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The title enzyme was incorrectly named throughout and should be as it appears above.

Juices from oranges, mandarins and hybrids were thermally treated in a plate exchanger at different conditions to evaluate the effects of treatment on fresh taste and on residual pectinmethylesterase (PME) activity. Freshness was significantly higher in fresh juices than in samples treated at 70°C or higher temperatures for 10 seconds of retention time, whereas no differences were found among samples heated at temperatures from 70 to 90°C for the same time, however at 95°C fresh taste decreased again. Residual PME activity was about 20% in samples treated at 70°C for 5, 10 and 20 seconds and in those heated at 80°C for 5 and 10 seconds, decreasing to 15%, also at 80°C, when retention time increased to 20 seconds. A drastic reduction to about 3% of residual activity was observed at 85°C for 10 seconds. Minimum activities of 0-1% corresponded to samples treated at 95°C. Considering the results of sensory and residual enzyme analyses, the treatment at 85°C for 10 seconds can be considered suitable. In these conditions fresh taste did not differ from that of juices treated at lower temperatures but residual enzyme activity was clearly smaller and acceptable for chilled juices, products of high quality but short shelf life. On the other hand, a deeper reduction of PME activity increasing the temperature to 95°C does not seem advisable since fresh taste decreases. Mandarin juices pasteurised at 85°C for 10 seconds and pasteurised again at the same conditions did not show a further decrease of fresh taste. Two heat treatments were usually applied when packing plants receive the juice from other factories.

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