<i>In-Vitro</i>Fermentation by Human Fecal Bacteria and Bile Salts Binding Capacity of Physical Modified Defatted Rice Bran Dietary Fiber

Defatted rice bran dietary fiber (DRBDF) was modified by micronization, ultrasound, microwave and extrusion cooking. We investigated the impacts of these physical treatments on the fermentation ability and bile salts binding capacity of DRBDF. In-vitro fermentation by human fecal bacteria of modified fibers showed that the major fermentation products were propionic, acetate and butyrate acid. Fermentation of extruded fiber gave the highest amounts of propionic and acetic acid 135.76 and 25.45 mmol/L respectively, while, the fermented product with microwaved fiber had the highest butyric acid content (10.75 mmol/L). The amount of short-chain fatty acid increased from 12 h to 24 h and propionic acid was the predominant. On the other hand,in-vitrobile salts binding showed that extruded fiber had higher affinity with sodium deoxycholate and sodium chenodeoxycholate (66.14% and 30.25% respectively) while microwaved fiber exhibited the highest affinity with sodium taurocholate (14.38%). In the light of obtained results we can affirmed that these physical treatments significantly improved the fermentation products and bile salts binding capacity of DRBDF. Extrusion compared to the other physical treatment methods used in this study has greatly and positively influenced the fermentation and bile binding capacity of DRBDF.

Effect of Combining Ultrasound and Mild Heat Treatment on Physicochemical, Nutritional Quality and Microbiological Properties of Pineapple Juice

Increasing consumer awareness regarding the health benefits of different nutrients in food has led to the requirement of assessing the effect of food processing approaches on the quality attributes. The present work focuses on understanding the effects of ultrasound (US) processing, mild heat pasteurization (65°C for 15 min), thermal pasteurization (80°C for 15 min) and their combination on physicochemical, microbiological properties and nutritional quality of pineapple juice through 60 days of storage at room temperature. Ultrasound treatment showed significantly lower browning degree. Ultrasound followed by ultrasound combined with mild heat pasteurization (UMP) treatments was effective in retaining the total phenolic content of pineapple juice as compared to the thermal treatment or the untreated juice sample at room temperature during 60 days of storage. Thermal pasteurization (TP) followed by ultrasound combined with mild heat pasteurization (UMP) and ultrasound (US) treatment, in increasing order, was found to be effective in delaying microbial growth in pineapple juice. This study demonstrates that ultrasound combined with mild heat pasteurization treatments could be able to effectively inactivate the microorganisms and pectin methylesterase in pineapple juice whilst preserving relatively high amount of phenols.

Effects of Pressurized Argon and Krypton Treatments on the Quality of Fresh White Mushroom (<i>Agaricus bisporus</i>)

Effects of argon, krypton and their mixed pressure treatments on the quality of white mushrooms were studied during 9 days of storage at 4℃. Among all treatments in this study, the minimum respiration rate, polyphenoloxidase activity, retained color change, antioxidants and delayed pseudomonas growth were observed with pressure argon (5 MPa) followed by mixing argon and krypton (2.5 MPa each) treatments. Respiration rates after 9 days of storage were 5.35%, 6.20%, 7.50%, 7.60%, 7.91% and 8.95% for HA5, HAK, HA2, HK5, HK2 and control, respectively. DPPH inhibition percentages of free radical for HA5, HAK, HK5, HA2, HK2 and control mushrooms were 28.03%, 25.24%, 24.96%, 21.87%, 20.56% and 19.06%, respectively, after 9 days of storage. The pressurized argon treatment was the most effective compared to pressurized krypton. Thus, application of pressurized argon and krypton treatments could extend the storage life of white mushrooms to 9 days at 4℃.

Dielectric properties of edible fungi powder related to radio-frequency and microwave drying

Edible fungi are rich in nutrition,but they are susceptible to spoilage,and often prolonged by drying.RF and microwave energy drying have the advantages of short drying time,high energy efficiency and good process control.However,to develop an effective dielectric drying method,it is important to understand dielectric properties,the major factor characterizing the interaction between the electromagnetic energy and the food.At present,there is a lack of research on dielectric properties of edible fungi.In this study,a vector network analyzer and an open-ended coaxial-line probe were employed to measure the dielectric parameters.The dielectric parameters were observed at different temperatures(25–85°C)for edible fungi powder with moisture content ranging from 5 to 30%wet basis over a frequency range of 1–3000 MHz.The relationship between the dielectric properties and frequency,temperature,and moisture content were obtained via regression analysis.Further,the dielectric penetration depth was calculated,and the effects of frequency,moisture content,and temperature on the penetration depth were also analyzed.The results showed that the dielectric properties of edible fungi powder increased with an increase in moisture content and temperature,while they decreased with increasing frequency.At high moisture content and temperature,the increase in dielectric properties was slightly larger than that at low moisture content and temperature.The dielectric properties changed more evidently at lower radio frequencies than at higher radio frequencies.The penetration depth decreased with an increase in temperature,moisture content,and frequency.It can be concluded that a large penetration depth at radio frequencies below 100 MHz could be used to dry edible fungi on a large scale,whereas microwave energy could be employed for drying edible fungi on a small scale.