Drying Temperature Affect the Quality of Dehydrated Mint
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The quality of the mint dried at 55, 65, 75, 85, and 95 oC were compared during the drying process. The moisture content and water activity of the mint decreased with the drying time and drying temperature during the drying process. The moisture content of 7.0 % guaranteed the safety of the dehydrated mints from the view of the water activity. The drying temperature of 55 and 65 oC preserved the chlorophyll of the dehydrated mint. Hence, the drying temperature of 55 and 65 oC was a better option to dry the mint.Keywords:
Water activity
実用価値の高い中間水分肉のモデルを作製する目的で,グリセロール添加量の異なる塩漬肉を調製し,さらに低温風乾によりaWを低下させた試料についてもその状態変化について検討した結果,次のことが明らかとなった.(1) グリセロール濃度の増加に伴って水分含量,aWはともに減少した.水溶性タンパク質の抽出性はグリセロール濃度に影響されなかったが,塩溶性の筋肉構造タンパク質はグリセロール濃度の増加に伴ってaWが減少するにもかかわらず増加する傾向が認められた.(2) SDS-PAGEによりタンパク質の分子種を検討すると,塩溶性タンパク質量の増加は筋肉構造タンパク質のミオシンに起因することが明らかとなった.塩漬時における食塩濃度を増加させるとミオシンに由来する筋肉構造タンパク質の抽出量は低下するが,10%グリセロール添加はそれを大きく改善する効果のあることが判明した.(3) 10%グリセロール存在下で塩漬後,風乾によりaWを0.90に低下させた筋肉から調製した筋原線維はMg2+-ATPの添加による収縮能を有していた.また同一試料からCAF活性も測定され,低温条件で1ヶ月以上保存した供試肉でも生物活性を有することが明らかとなった.(4) この供試肉を38℃で1ヶ月間保存しても,筋肉のpHは全保存期間を通じて低い値を維持した.
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Aspergillus oryzae
Matrix (chemical analysis)
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Kelulut honey was dehydrated at 40, 55, and 70°C up to 84 h in a dehydrator. The changes of its properties and qualities in terms of moisture content, water activity, hygroscopicity, moisture adsorption isotherm, colour intensity, total phenolic content (TPC), viscosity, glass transition temperature (Tg), surface stickiness, hydroxymethylfurfural (HMF) content, and diastase activity were evaluated. The dehydration process for 18 h between temperatures of 55 and 70°C can safely produce Kelulut honey product with less than 8% moisture content and water activity below 0.6. Similar quality of Kelulut honey dehydrated at lower temperature between 40 and 55°C requires up to 36 h of dehydration. These recommended dehydration conditions were able to increase TPC of honey from 7.86% from its original value for the shorter duration of 18 h and lower dehydration temperature of 40°C and up to 70.9% for the longer duration of 36 h and higher temperature of 70°C. Dehydrated honey was darker, more viscous, and stickier. The increase of HMF content in dehydrated honey at 40 and 55°C up to 36 h was not significant which are at 0 and 5.81 mg/kg honey, respectively, and at 70°C, it was about 80 mg/kg honey. The honey was found to have very low diastase activity ranging from 0 to 0.75 DN, thereby causing its changes to be insignificant during dehydration.
Diastase
Water activity
Hydroxymethylfurfural
Osmotic dehydration
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The adductors were collected from the living Fairer' scallop and three levels of water activities aw were designed. By testing the relationship between moisture and aw in the scallop adductors and bacteria test, the results are that: 1) for the scallop product of Low-aw(0.60 aw 0.70), the safe moisture is below 17.3% ; with sugar and salt added, the safe moisture reaches 20.3 % , and then by using the mould inhibitor potassium sorbate, it reaches 24.1% ; 2) for the scallop product of M-aw(0. 70 aw 0. 90) which is vacuumized, the safe moisture reaches 38% ;3)for the scallop product of H-aw(0.90 aw 0.95)by decreasing aw and pH, vacuum package and pasteurization, the safe moisture may reaches 50%. So it' s possible to increase the safe moisture of scallop product by some scientific ways.
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Pasteurization
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Investigation was carried out to evaluate thermophysical properties such as density, Newtonian viscosity, thermal conductivity, specific heat and thermal diffusivity of enzyme clarified sapota (Achras sapota L.) juice at different moisture contents ranging from 38.01% to 88.64% (wet basis) corresponding to a water activity in the range of 0.839 to 0.987. The investigation showed that density and Newtonian viscosity of enzyme clarified sapota juice decreased significantly (p < 0.05) with increase in moisture content as well as water activity, whereas thermal conductivity increased significantly (p < 0.05) with increase in moisture content and water activity. The specific heat and thermal diffusivity were markedly affected by moisture content as well as water activity. Empirical mathematical models were established relating to thermophysical properties of enzyme clarified sapota juice with moisture content/water activity. Results indicated that there was a high significant (p < 0.0001) correlation between thermophysical properties with moisture content/water activity of enzyme clarified sapota juice. A significant (p < 0.0001) positive correlation between thermal properties and moisture content/water activity, whereas significant (p < 0.00001) negative correlation between physical properties with moisture content/water activity was observed. In general, the thermophysical properties of enzyme clarified sapota juice were markedly affected by moisture content/water activity.
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ABSTRACT A mechanical drying method for processing an intermediate moisture mullet roe was developed to replace the traditional sun‐drying method. Using a central composite experimental design, 20 combinations of three independent variables (salting time, dehydration temperature, and dehydration time) with constant desalting time and relative humidity were performed and analyzed for salt content and water activity value. It was discovered that various processing combinations exist that might produce products with the same level of salt and water activity. Product color was used in the selection of processing combinations in addition to salt content and water activity.
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Mullet
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Abstract A number of recent outbreaks related to pathogens in low‐moisture foods have created urgency for studies to understand the possible causes and identify potential treatments to improve low‐moisture food safety. Thermal processing holds the potential to eliminate pathogens such as Salmonella in low‐moisture foods. Water activity ( a w ) has been recognized as one of the primary factors influencing the thermal resistance of pathogens in low‐moisture foods. But most of the reported studies relate thermal resistance of pathogens to a w of low‐moisture foods at room temperature. Water activity is a thermodynamic property that varies significantly with temperature and the direction of variation is dependent on the product component. Accurate methods to determine a w at elevated temperatures are needed in related research activities and industrial operations. Adequate design of commercial thermal treatments to control target pathogens in low‐moisture products requires knowledge on how a w values change in different foods at elevated temperatures. This paper presents an overview of the factors influencing the thermal resistance of pathogens in low‐moisture foods. This review focuses on understanding the influence of water activity and its variation at thermal processing temperature on thermal resistance of pathogens in different low‐moisture matrices. It also discusses the research needs to relate thermal resistance of foodborne pathogens to a w value in those foods at elevated temperatures.
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Selection of water activity lowering agents for dehydration Tsai-tai with high moisture content was studied.The solution of 8 g/dL glucose,4 g/dL lactose,2 g/dLsodium chloride and 8% maltodextrin was determined to reduce the water activity of dehydration Tsai tai with high moisture content.The result of preservation experiments showed vacuum package and light avoiding storage could reduce the loss of ascorbic acid and chlorophyll and delay the browning.The quality of dehydration Tsai tai with high moisture content stored at 4 ℃ was better than 20 ℃ and 37 ℃.The dehydration Tsai – tai with 0.69-0.70 Aw and 20%~25% moisture content exhibited good stability with microorganism test.
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Osmotic dehydration
Maltodextrin
Browning
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