All-purpose wheat flour is a useful long-term storage commodity, but is subject to off-odor formation. Although flour stored in a low oxygen atmosphere should inhibit rancid odor formation, it elicits consumer complaints about odor. The purpose of this study was to examine off-odor development in all-purpose wheat flour during ambient and elevated storage by determining the effect of low oxygen atmosphere and enrichment-bleaching on quality as measured by, free fatty acids (FFA), flour descriptive sensory analysis, conjugated dienes, headspace volatiles, bread consumer sensory analysis, color, loaf volume, and vitamin analysis. Enriched, bleached (EB) and unenriched, unbleached (UU) flour was stored in a low and normal oxygen atmosphere in no. 10 cans at 22, 30, and 40°C for 24 weeks. Moisture remained constant throughout the study. Headspace oxygen was < 0.1% in flour stored in a low oxygen atmosphere and decreased in flour stored in a normal oxygen atmosphere. FFA increased with storage time and temperature. The "fresh flour" descriptive aroma of flour decreased during storage and decreased more rapidly in a low oxygen atmosphere. The "cardboard/stale" aroma increased in flour stored in a normal oxygen atmosphere. The "acid-metallic" aroma increased in flour stored in a low oxygen atmosphere and was determined to be the off-odor from consumer complaints. Conjugated dienes and volatiles generally increased more rapidly in flour stored in a normal oxygen atmosphere and in EB flour, suggesting that the acid-metallic odor did not result from lipid oxidation. Bread consumer sensory analysis identified EB flour stored in a normal oxygen atmosphere to have the lowest acceptance scores for aroma, overall acceptability, and flavor. The acid-metallic odor dissipated within 24 hours when the container was opened and was not detrimental to consumer acceptance of bread made from the flour. Oxygen absorbers prevented the darkening of flour but not the reddening or yellowing. A low oxygen atmosphere resulted in higher bread loaf volumes. Vitamin degradation is not a concern under normal storage conditions. Bleaching appears to increase flour oxidative rancidity more than enrichment. Although storage at a low oxygen atmosphere results in an off-odor present in newly opened cans, it gave higher quality flour and bread. A low oxygen atmosphere should continue to be used in flour stored long-term, and consumers should be made aware that the off-odor present in cans of flour dissipates after opening.

Made available in DSpace on 2015-03-26T13:36:41Z (GMT). No. of bitstreams: 1 texto completo.pdf: 807848 bytes, checksum: a4aec48375faa02fed8c2ce2de053e55 (MD5) Previous issue date: 2011-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present work aimed to study the influence of the PVC (polyvinyl chloride) film of different concentrations of KMnO4 (ethylene absorbent) and the oxygen absorber sachet (O-Buster) on the quality and postharvest conservation of 'Oso Grande strawberries. In order to achieve this physical-chemical, enzymatic and visual analyses were performed every 2 days on fruits stored for 14 days at 4 °C. The presence of PVC was essential to maintain the visual characteristics and reduction of weight loss of the fruits during the storage period. The fruits treated with different doses of KMnO4 (1, 2, 3 and 4 g) generally showed similar behavior to the fruits of the control treatment with PVC film, which kept the values of titratable total acidity (TTA), increased the total soluble sugars (TSS) and decreased the reducing sugars (RS) at 14 days of storage. The activity of the polyphenol oxidase (PPO), peroxidase (POD) and alcohol dehydrogenase (ADH) enzymes decreased in fruits stored with KMnO4 sachets, however, regarding to ADH and the fruits treated with KMnO4 differed from the fruits of the control treatment with PVC. There was accumulation of ethanol in the fruits of the treatments used at the end of storage. The dosage of 1 g of KMnO4 (T3) was effective in delaying the visible growth of fungi in fruits stored for 14 days, contaminated fruits could only be seen in the last day of storage. The treatments with sachets of oxygen and ethylene had synergistic effect on the fruits that were stored for 14 days. The combination of the two absorbers kept the values of ATT, the PPO and ADH enzyme activity, and increased the AST in the fruits. In the remaining variables, the treatments with oxygen and ethylene absorbers and the combination of both in the same package of PVC did not differ among themselves and have retained the values of AR and the POD activity, and accumulated a small quantity of ethanol in the fruits at the end of storage. The combination of oxygen and ethylene absorbing sachets was effective in delaying the visible growth of fungi within 12 days of storage. The best way preserve strawberries, according to the results, was the storage in packages containing oxygen and ethylene absorbing sachets, sealed with PVC film and stored at 4 °C for 12 days. / Com o presente trabalho objetivou-se estudar a influência do filme de PVC (cloreto de polivinila), de diferentes dosagens de KMnO4 (absorvedor de etileno) e do sachê absorvedor de oxigênio (O-Buster) sobre a qualidade e conservação pós-colheita de morangos Oso Grande . Para isto foram feitas análises físico-químicas, enzimáticas e visual de 2 em 2 dias nos frutos armazenados por 14 dias, aos 4 °C. A presença do PVC foi indispensável para manter as características visuais e a redução da perda de massa fresca dos frutos ao longo do período de armazenamento. Os frutos tratados com diferentes dosagens de KMnO4 (1, 2, 3 e 4 g), de modo geral, tiveram comportamento semelhante aos frutos do tratamento controle com filme de PVC, que mantiveram os valores de acidez total titulável (ATT), aumentaram os açúcares solúveis totais (AST) e diminuíram os açúcares redutores (AR) aos 14 dias de armazenamento. A atividade das enzimas polifenoloxidase (PPO), peroxidase (POD) e álcool desidrogenase (ADH) diminuiu nos frutos armazenados com sachê de KMnO4; entretanto, quanto a ADH os frutos tratados com KMnO4 diferiram dos frutos do controle com PVC. Houve acúmulo de etanol nos frutos dos tratamentos utilizados ao final do armazenamento. A dosagem de 1 g de KMnO4 (T3), foi eficaz em retardar o crescimento visível de fungos nos frutos armazenados por 14 dias, sendo visualizados frutos contaminados apenas no último dia de armazenamento. Os tratamentos com sachês absorvedores de oxigênio e de etileno tiveram efeito sinérgico sobre os frutos armazenados durante 14 dias. A combinação dos dois absorvedores manteve os valores de ATT, a atividade das enzimas PPO e ADH, e aumentou os AST nos frutos. Nas demais variáveis analisadas, os tratamentos com absorvedores de oxigênio e etileno e a combinação dos dois na mesma embalagem de PVC não diferiram entre si e mantiveram os valores de AR e a atividade da POD, e acumulou pouco etanol nos frutos ao final do armazenamento. A combinação dos sachês absorvedores de oxigênio e de etileno foi eficaz em retardar o crescimento visível de fungos em até 12 dias de armazenamento. A melhor forma de conservação dos morangos, de acordo com os resultados, foi armazenamento em embalagens contendo sachês absorvedores de oxigênio e de etileno, fechadas com filme de PVC e armazenadas aos 4 °C, durante 12 dias.