高压喷射灌浆技术在下石陂水库除险加固中的应用

通过介绍高压喷射灌溉技术在下石陂水库除险加固中的成功应用,研究了此类病险水库的高喷灌浆防渗结构形式与工程布置,探讨了施工工艺和质量控制问题,供类似工程参考.     

超声波对橙汁的杀菌特性研究

以鲜榨橙汁为原料,研究了超声波在不同橙汁特性以及仪器可变条件下,对菌落总数的影响,通过正交试验结果得出杀菌的较优条件是：杀菌时间：13min,振幅：70％,脉冲时间on：30s,脉冲时间off．25s、处理量：50ml;方差分析结果表明,杀菌时间、振幅、脉冲时间、处理量对杀菌率的影响差异极显著（p〈0．01）;相同杀菌条件．下超声波杀菌时间较传统的水浴热杀菌短,有利于保持食品品质。     

Use of mild-heat treatment following high-pressure processing to prevent recovery of pressure-injured Listeria monocytogenes in milk

This study examined the inactivation of Listeria monocytogenes in milk by high-pressure processing (HPP) and bacterial recovery during storage after HPP. We developed a technique to inhibit the bacterial recovery during storage after HPP (550 MPa for 5 min) using a mild-heat treatment (30-50 degrees C). Various mild-heat treatments were conducted following HPP to investigate the condition on which the bacterial recovery was prevented. Immediately after HPP of 550 MPa at 25 degrees C for 5 min, no L. monocytogenes cells were detected in milk regardless of the inoculum levels (3, 5, and 7 log(10)CFU/ml). However, the number of L. monocytogenes cells increased by >8 log(10)CFU/ml regardless of the inoculum levels after 28 days of storage at 4 degrees C. Significant recovery was observed during storage at 25 degrees C; the bacterial number increased by >8 log(10)CFU/ml after 3 days of storage in the case of an initial inoculum level of 7 and 5 log(10)CFU/ml. Even in the case of an initial inoculum level of 3 log(10)CFU/ml, the bacterial number reached the level of 8 log(10)CFU/ml after 7 days of storage. No bacterial recovery was observed with storage at 37 degrees C for 28 days. Milk samples were treated by various mild-heat treatments (30-50 degrees C for 5-240 min) following HPP of 550 MPa at 25 degrees C for 5 min, and then stored at 25 degrees C for 70 days. The mild-heat treatment (e.g., 37 degrees C for 240 min or 50 degrees C for 10 min) inhibited the recovery of L. monocytogenes in milk after HPP. No recovery of L. monocytogenes in milk was observed during 70-day storage at 25 degrees C in samples that received mild-heat treatments such as mentioned above following HPP (550 MPa for 5 min). Moreover, the mild-heat treatment conditions (temperature and holding time) required to inhibit the recovery of L. monocytogenes in milk was modelled using a logistic regression procedure. The predicted interface of recovery/no recovery can be used to calculate the mild-heat treatment condition to control bacterial recovery during storage at 25 degrees C after HPP (550 MPa for 5 min). The results in this study would contribute to enhance the safety of high-pressure-processed milk.     

High-pressure treatments induce folate polyglutamate profile changes in intact broccoli (Brassica oleraceae L. cv. Italica) tissue

In plant matrices, folates exist largely as folylpoly-γ-glutamates requiring deglutamylation to monoglutamates prior to absorption, which might impair dietary folate bioavailability. This study investigated folylpoly-γ-glutamate stability and conversions in broccoli tissue during thermal (25–90 °C, 30 min) and high-pressure treatments (0.1–600 MPa, 25–45 °C, 30 min) after vacuum packaging. Folates were analyzed based on poly-γ-glutamate side chain length by RP-HPLC. During thermal treatments, folates were stable up to 90 °C, whereas differences in folylpoly-γ-glutamate profiles towards higher conjugated folylpoly-γ-glutamates were observed at elevated temperatures (70–90 °C). High-pressure treatments resulted in significant folate losses (48–78%). Depending on the pressure–temperature combinations studied, folylpoly-γ-glutamates were converted to folylmono- and folyldi-γ-glutamates, which was shown to occur mainly during the initial stages of the high-pressure treatments, i.e. during pressure build-up and subsequent equilibration. Targeted application of high-pressure treatments can hence be applied to obtain broccoli with higher monoglutamate folate content. Implications towards folate bioavailability in relation to the observed folate degradation, however, requires further investigation.     

Continuous Flow Microwave‐Assisted Processing and Aseptic Packaging of Purple‐Fleshed Sweetpotato Purees

ABSTRACT: Pumpable purees from purple‐flesh sweetpotatoes (PFSP) were subjected to microwave heating using a 60 kW, 915 MHz continuous flow system, followed by aseptic packaging in flexible containers to obtain a shelf‐stable product. Initial test runs were conducted using a 5 kW 915 MHz microwave system to measure dielectric in‐line properties and examine the puree temperature profiles. The results demonstrated uniformity in heating of the puree at sterilization temperatures (>121 °C), and the dielectric constants and loss factors were within the range of published values for orange‐fleshed sweetpotato purees. The pilot‐scale test runs in a 60 kW microwave unit produced shelf‐stable puree packages stable at room temperature. Polyphenolic content of the PFSP purees were evaluated and the results showed that while total phenolics increased (5.9%) and total monomeric anthocyanins slightly decreased (14.5%) with microwave application, antioxidant activity determined by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC) assays did not significantly change as a result of microwave processing. Color values showed that microwave‐processed samples differed from fresh puree in saturation and hue angle, but not in overall color change. PFSP purees increased in gel strength when microwave processed, packaged, and stored, but the gel could be easily disrupted into flowable purees. Overall, high‐quality retention can be obtained by microwave processing and aseptic packaging of PFSP purees so that they can be used as functional food ingredients.     

软包装榨菜的超高压杀菌工艺研究

采用正交试验设计研究了超高压处理对榨菜杀菌效果以及理化指标的影响。结果表明,超高压工艺对榨菜的脆度影响很小,杀菌的优化工艺条件为:压力300 MPa,保压时间为20 min,中盐(8.5%)可以有效杀灭微生物,防止胖袋并且大肠菌群小于30个。     

五香兔肉软包装技术的研究

本文以獭兔肉为原料,通过腌制、卤煮后制得的五香兔肉,在不添加任何防腐剂的前提下,通过对包装材料和不同杀菌方式的选择,对软包装后五香兔肉的保存效果进行比较,从而得出一种比较理想的五香兔肉产品软包装方法。     

酸性电解水对鸡白痢沙门氏菌杀灭效果的研究

家禽和禽产品中的沙门氏菌是引起人类沙门氏菌感染和食物中毒的主要潜在来源,沙门氏菌通常被认为是生产者和消费者所面临的最严重的致病菌之一.研究不同电解质种类和电解时间等参数条件下制得的酸性电解水对鸡白痢沙门氏菌的杀灭效果,确定了酸性电解水 pH 值和有效氯浓度对杀菌效果的影响.结果表明,酸性电解水对鸡白痢沙门氏菌具有较强的杀灭效果,当酸性电解水pH值小于3或有效氯浓度超过1 mg/kg 时可以100%杀灭鸡白痢沙门氏菌,且 NaCl、KCl 溶液制得的酸性电解水的杀菌效果优于 CaCl2、MgCl2溶液制得的酸性电解水.     

鲜乳超声波除菌技术研究

研究了不同功率、时间的超声波处理鲜乳后的杀菌效果。结果表明,经600W,3min超声波处理的原料乳,杀菌率达93%。并研究了超声波结合巴氏杀菌技术对鲜乳处理后,4℃贮藏条件下牛乳品质变化情况。结果表明,经600W,3min超声波处理的原料乳结合63℃,30min的热处理后,乳品质保持最好,4℃贮藏条件下贮藏期达16d左右。     

高压CO_2处理对西瓜汁的影响

以海南麒麟西瓜为原料,榨汁后进行HPCD(高压CO2)杀菌处理,处理温度为25℃,压力为20 MPa和30 MPa,处理时间分别为10、30和60 min,测定HPCD处理后西瓜汁的主要理化指标、细菌总数和PME酶(果胶甲基酯酶)活性变化。结果表明:HPCD处理后西瓜汁pH值降低0.3～0.7、可溶性固形物无明显变化、颜色更红、浊度增加,细菌总数降低可达到2个对数,果胶甲基酯酶活性可降低50%。