等温水分活度及其对低水分食品中微生物抗热性的影响研究进展

水分活度（Water activity,a_w）是定义低水分食品（a_{w,25 ℃}<0.85）的关键指标,对低水分食品（LMFs）中微生物的抗热性起着决定性的作用。食品的水分活度受到食品组分、质构等的影响,并且与温度密切相关,在温度改变时呈现不同的变化趋势,是典型的温度依赖型指标。等温水分活度（a_w,T）反映了食品在高温灭菌过程中的实时水分活度,其准确测定或推算有助于学者量化低水分食品中微生物抗热性指标,进而设计、验证、完善相关热灭菌工艺。但商业化的水分活度仪只能测量低温区间（20~50 ℃）,人们对高温区间（>55 ℃）的水分活度还了解甚少。本文首先介绍了低水分食品微生物安全及其抗热性指标,然后对等温水分活度的定义、检测方法、模型预测、影响因素及其对微生物抗热性的影响研究进行综述。等温水分活度的认知与测定有利于食品企业降低低水分食品的微生物污染程度,保障消费者食品安全。     

Heating of milk powders at low water activity to 95°C for 15 minutes using hot air-assisted radio frequency processing achieved pasteurization

Salmonella persistence in milk powders has caused several multistate foodborne disease outbreaks. Therefore, ways to deliver effective thermal treatment need to be identified and validated to ensure the microbial safety of milk powders. In this study, a process of hot air-assisted radio frequency (HARF) followed by holding at high temperatures in a convective oven was developed for pasteurization of milk powders. Heating times were compared between HARF and a convection oven for heating milk powders to a pasteurization temperature, and HARF has been shown to considerably reduce the come-up time. Whole milk powder (WMP) and nonfat dry milk (NFDM) were inoculated with a 5-serotype Salmonella cocktail and equilibrated to a water activity of 0.10 to simulate the worst case for the microbial challenge study. After heating the sample to 95°C using HARF, followed by 10 and 15 min of holding in the oven, more than 5 log reduction of Salmonella was achieved in WMP and NFDM. This study validated a HARF-assisted thermal process for pasteurization of milk powder based on previously collected microbial inactivation kinetics data and provides valuable insights to process developers to ensure microbial safety of milk powder. This HARF process may be implemented in the dairy industry to enhance the microbial safety of milk powders.     

Air impingement technology for food processing: visualization studies

Food processing systems using air impingement consist of jets of high-velocity air (10-100 m/s) exiting from nozzles and impinging on a food product. The factors affecting efficiency of impingement systems include the nozzle exit velocity, nozzle design, boundary layer characteristics on the surface of the product and the design of the impingement equipment. In the present research, visualization studies were conducted to determine the importance and implication of these factors. Flow under the jets was visualized using planar flow visualization techniques for various nozzle diameters (D), lengths (L) and nozzle to plate spacings (H) for flow over flat surfaces and food products with single and double jets. Studies were conducted on the transition features, recirculation, confinement and boundary layer flow characteristics. Ideal range for the characteristic nondimensional ratio (H/D) was determined to be 6-8. The actual ratio will depend on the transition effect and the induction of turbulence in the jet wake, which depends on the Reynolds number (Re) based on nozzle exit conditions and the L/D ratio of the nozzle. Surface roughness affected the roughness Reynolds number (Re_p) which in turn influenced the boundary layer characteristics.     

室内空气的净化技术

本文介绍了净化室内空气的几种技术和措施,包括通风换气式、过滤式、 吸附式、催化式和室内绿化净化等,并对改善室内空气品质提出了建议。     

四氯乙烯商业干洗技术规范的标准化

研究了采用四氯乙烯作为干洗剂的商业干洗技术规范的标准化.通过分析国内外相关技术标准的现状,从干洗剂和干洗设备的选择、干洗时间和干洗程序的设定等方面探讨了影响商业干洗技术规范标准化的技术因素,并提出了四氯乙烯商业干洗技术规范的标准化方案.     

Antioxidant potential and quality characteristics of Mediterranean fruit‐based extruded snacks

‘Mediterranean snacks’ (dried fruits and nuts as principal ingredients), a little known food product with a high nutritional value, might be considered a good alternative for consumers looking for healthy snacks. The aim of this research was to determine the physicochemical properties and nutritional value of this type of food stuff (traditionally called ‘fruit cakes’ in Mediterranean countries) and to evaluate their phenolic content and antioxidant activity. All the fruit‐based extruded snacks studied are shelf‐stable at room temperature (because of their pH and water activity values). The final product has a low moisture (<32%) and high sugar content (>30%), the only sugars being those naturally present in the food. All the fruit‐based extruded snacks had a dietary fibre content higher than 10% (high‐fibre foods). Date extruded snack and apricot extruded snack showed the highest total phenolic and flavonoid content and also the highest antioxidant activity as determined by the DPPH and FRAP methods.     

抗应激功能食品研究概况

应激是机体受到外来刺激产生的非特异性反应，应激反应是当今社会普遍关注的问题。本文概述了应激的有关概念，对抗应激功能食品作了详尽介绍。     

气体射流冲击干燥花生实验工艺的优化研究

目的 探究气体射流冲击干燥装置对花生干燥特性和营养品质的影响及优化干燥工艺。方法 利用气体射流冲击干燥装置研究不同因素(干燥温度、风速、喷射间距)对花生的干燥特性、发芽率、营养品质的影响。以上述三因素进行单因素实验,分析实验结果确定待优化区间,并运用Box-Behnken响应面实验设计和隶属度综合评分法,对干燥工艺进行综合优化。通过数据分析与比较,得出最优干燥工艺。结果 温度45℃、风速5 m/s、喷射间距15 cm为最优干燥工艺。此时花生干燥速率为0.09 (g?g-1?min-1)、发芽率为95%、亚油酸含量为34%。结论 该工艺相比其他工艺,既能保证花生营养品质、发芽率,又可实现快速干燥,为气体射流冲击干燥技术应用于花生干燥中提供了一定的理论依据。     

特殊医学用途配方食品干法混合工艺研究及其与湿法工艺的对比

针对特殊医学用途配方食品(foods for special medical purposes,FSMP)干法混合工艺关键步骤,同时将其与湿法和干-湿法工艺进行对比分析,旨在为相关进行干法混合工艺的生产企业提供理论和实践依据。通过分析干法混合工艺的关键控制点,确定从物料添加顺序、混合时间和混合转速及工艺稳定性对其混合工艺均匀性进行分析。最终确定生产工艺条件:混合工艺1的流程添加物料,总混时间为20 min,总混频率为20 Hz(约14 r/min);在该工艺条件下,不同位置的维生素A和维生素B1相对标准偏差分别为4.37%和2.52%,与验证工艺的检测结果接近,说明产品混合均匀且工艺稳定,且各检测值符合法规和设计要求;最后,同湿法工艺和干湿法工艺对比后,干法混合工艺也表现出一定的优势。因此,该工艺可以满足特医食品全营养配方食品的干法生产。     

一种新型酚化木质素胺乳化剂的合成及其性能

以苯酚改性硫酸盐木质素得到了酚化木质素,再将其与脱氢枞酸单乙二酰胺、甲醛进行Mannich反应以引入脱氢枞酸单乙二酰胺甲基亲油基团,然后将反应产物进一步与二乙烯三胺、甲醛反应引入了二乙烯三胺甲基亲水基团,合成了一种新型酚化木质素阳离子乳a化剂。实验表明,在碱性条件下,当 n(苯酚)∶n(木质素)=1∶1、反应温度100℃、反应时间1.5 h时,所得产物酚化木质素的酚羟基含量较木质素增加了30.3%,相当于每个C9单元接枝了0~30个苯酚分子,质均分子质量增大7%,多分散性由1.49降至1.29;与木质素相比,酚化木质素中引入的脱氢枞酸单乙二酰胺甲基数量增加了1.1倍,引入的二乙烯三胺甲基数量增加了0.42倍;在pH值为2的稀盐酸溶液中,所合成的脱氢枞酸单乙二酰胺/二乙烯三胺/甲醛改性酚化木质素阳离子乳化剂的最大Zeta电位为38.0 mV,质量浓度为10 g/L时,表面张力为35.0 mN/m,甲苯乳液油水分层时间为70 min,均优于用未经酚化改性的木质素合成的产物。     

大豆蛋白肽对高蛋白焙烤食品质构的影响

焙烤食品添加高含量的大豆蛋白配料会导致产品质构硬化,口感变差。本文首先研究了大豆蛋白添加量对焙烤食品质构的影响,并系统研究了添加高水分活度的大豆肽及乳清浓缩蛋白(WPC)对高蛋白焙烤食品质构特性的影响。研究表明,高水分活度大豆肽可明显改善高蛋白焙烤食品的质构,弱化硬度,增加了产品的回复性,从而改善了产品的口感。