食品工程类专业微生物学教学改革与实践

《微生物学》是食品科学类专业重要的专业基础课,课程组结合学校粮油食品学科传统特色专业,对食品微生物学教学内容、多媒体课件运用及实验教学等进行了改革。结果显示,改革后的课程教学组织方式有利于加强学生对理论知识的理解和应用,有利于提高学生的动手能力、创新能力和科学思维能力。     

A role for proline synthesis and transport in Listeria monocytogenes barotolerance

Aims: To assess the contribution of proline biosynthesis to listerial barotolerance. Methods and Results: Using a Listeria monocytogenes proBA deletion mutant, incapable of synthesizing proline, together with a proline‐overproducing strain, the contribution of proline synthesis to listerial barotolerance was determined. The ΔproBA strain does not survive as well as the wild type when subjected to treatment of 500 MPa in rich media and 400 MPa in minimal media (c. 1 log lower survival in both conditions). Betaine and carnitine decrease the ability of the wild type to survive at low pressures (300 MPa), but confer normal or slightly increased levels of protection at higher pressures (350 and 400 MPa). Conclusions: A functional proline synthesis system is required for optimal survival of Listeria following treatment at high‐pressure (HP) levels (500 MPa in brain heart infusion and 400 MPa in defined medium), particularly where other compatible solutes are absent or limiting. Significance and Impact of the Study: Given the potential of HP processing as an effective food processing/safety strategy, understanding how pathogens such as Listeria have evolved to cope with such stresses is an important food safety consideration. In this context, the work presented here may help to develop safer and more effective processing regimens.     

Recent developments in the use of viability dyes and quantitative PCR in the food microbiology field

The increase in foodborne outbreaks highlights the need for rapid, sensitive and specific methods for food safety monitoring, enabling specific detection and quantification of viable foodborne pathogens. Real‐time PCR (qPCR) combined with the use of viability dyes, recently introduced, fulfils all these requirements. The strategy relies on the use of DNA‐binding molecules such as propidium monoazide (PMA) or ethidium monoazide (EMA) as sample pretreatment previous to the qPCR. These molecules permeate only membrane‐compromised cells and have successfully been applied for different types of foodborne pathogens, including bacteria and viruses. Moreover, those dyes have been explored to monitor different food manufacturing processes as an alternative to classical cultural methods. In this review, state‐of‐the‐art information regarding viability PCR (v‐PCR) is compiled.     

生物钟信号调控的营养学

近日节律是生物界普遍存在的一种生理现象,而内源性生物钟是产生近日节律的物质基础,它能使生物体感知并适应环境中的光、温度和食物等周期信号,从而使生物体与外界环境保持周期同步。研究表明,葡萄糖、胆固醇、腺苷、咖啡因、维生素A和视黄酸等营养物质能通过各自不同的方式调控哺乳动物的生物钟,影响其近日节律的信号输出。本文概述了至今为止研究发现的各类与生物钟信号调控相关的营养物质及功能的相关研究进展。     

Effect of ante- and postmortem hide clipping on the microbiological quality and safety and ultimate pH value of beef carcasses in an EC-approved abattoir

Aims:  Effect of ante- and postmortem hide clipping on the microbiological quality of beef carcasses. Methods and Results:  Bovine carcasses (362) were tested for indicator micro-organisms and the presence of pathogens. Prior to slaughter, hide cleanliness of each animal was categorized on a scale of 1–5 (clean to dirty). Lowest mean aerobic colony counts (ACC) (log₁₀ 3·0 CFU cm⁻²) came from carcasses where clipping had been performed in lairage, antemortem. ACC from animals clipped online (log₁₀ 3·2 CFU cm⁻²) were significantly higher (P < 0·05) than those clipped in lairage, but comparable to those carcasses from Category 1 and 2 animals. There were no significant differences in the detection of pathogens from any of the carcass groups. Ultimate pH values for carcasses from Category 3 and 4 animals showed clipping animals in lairage, as opposed to online, resulted in a small, but significant increase (P < 0·05) in pH value (mean pH 5·66 and 5·59, respectively). Conclusions:  Hide clipping does not adversely affect microbiological quality of carcasses, although higher ultimate pH values indicate increases in antemortem stress. Significance and Impact of the Study:  Hide clipping carcasses both ante- and postmortem appears to be an effective intervention to minimize transfer of hide microflora to carcasses during slaughtering operations. Online clipping offers advantages for animal welfare and improves safety for operatives.     

The impacts of Japanese food losses and food waste on global natural resources and greenhouse gas emissions

Japan depends heavily on imports for its food supply. Since 2000, the food self‐sufficiency ratio has remained approximately 40% on a caloric basis. Japanese food wastage (i.e., food losses and food waste) is estimated to have been 6.42 million tonnes (50 kg per capita of wastage) in 2012. These values indicate that food wastage leads to wasted natural resources and excessive greenhouse gas (GHG) emissions both in Japan and in countries that export to Japan. This study estimates Japanese food wastage by food item to evaluate impacts on land and water resources and global GHG emissions during the processing, distribution, and consumption phases of the food supply chain while also considering the feed crops needed for livestock production. Despite uncertainties due to data limitations, in 2012, 1.23 million hectares of harvested land were used to produce food that was eventually wasted, and 413 million m³ of water resources were wasted due to Japanese food wastage in agricultural production. Furthermore, unnecessary GHG emissions were 3.51 million tonnes of CO₂ eq. in agricultural production and 0.49 million tonnes of CO₂ eq. in international transportation. The outcomes of the present study can be used to develop countermeasures to food wastage in industrializing Asian countries where food imports are projected to increase and food wastage issues in the consumption stage are expected to become as serious as they currently are in Japan.     

Campylobacter bacteriophages and bacteriophage therapy

Members of the genus Campylobacter are frequently responsible for human enteric disease with occasionally very serious outcomes. Much of this disease burden is thought to arise from consumption of contaminated poultry products. More than 80% of poultry in the UK harbour Campylobacter as a part of their intestinal flora. To address this unacceptably high prevalence, various interventions have been suggested and evaluated. Among these is the novel approach of using Campylobacter-specific bacteriophages, which are natural predators of the pathogen. To optimize their use as therapeutic agents, it is important to have a comprehensive understanding of the bacteriophages that infect Campylobacter, and how they can affect their host bacteria. This review will focus on many aspects of Campylobacter-specific bacteriophages including: their first isolation in the 1960s, their use in bacteriophage typing schemes, their isolation from the different biological sources and genomic characterization. As well as their use as therapeutic agents to reduce Campylobacter in poultry their future potential, including their use in bio-sanitization of food, will be explored. The evolutionary consequences of naturally occurring bacteriophage infection that have come to light through investigations of bacteriophages in the poultry ecosystem will also be discussed.     

微流控芯片技术在食品领域中的应用

微流控芯片技术是一种全新的微量分析技术。介绍了微流控芯片技术的基本原理、特点及分类,并深入讨论了该技术在食品安全、营养、加工和风味等食品领域中的应用,包括有害化学物质、食品添加剂、转基因食品和食源性致病微生物等的检测,营养物质和功能成分的分析鉴定,食品工艺参数的调控以及食品风味成分的检测,展望了微流控芯片技术在食品领域的广阔应用前景。     

Effects of scarcity and excess of larval food on life history traits of Aedes aegypti (Diptera: Culicidae)

Few studies have assessed the effects of food scarcity or excess on the life history traits of Aedes aegypti (L.) (Diptera: Culicidae) independently from larval density. We assessed immature survival, development time, and adult size in relation to food availability. We reared cohorts of 30 Ae. aegypti larvae from newly hatched to adult emergence with different food availability. Food conditions were kept constant by transferring larvae each day to a new food solution. Immature development was completed by some individuals in all treatments. The shortest development time, the largest adults, and the highest survival were observed at intermediate food levels. The most important effects of food scarcity were an extension in development time, a decrease in the size of adults, and a slight decrease in survival, while the most important effects of food excess were an important decrease in survival and a slight decrease in the size of adults. The variability in development time and adult size within sex and treatment increased at decreasing food availability. The results suggest that although the studied population has adapted to a wide range of food availabilities, both scarcity and excess of food have important negative impacts on fitness.     

The effect of individual and food characteristics on food retrieval and food sharing in captive Guinea baboons (Papio papio)

Access to food is of major importance to the fitness and survival of every individual, particularly in group-living animals, in which individual characteristics and food distribution can affect food intake. Additionally, several species of primates are known to share food under certain conditions. Such unresisted transfer of food from one individual to another appears to be adaptive, for instance as a tool to maintain and reinforce social bonds. In this study, we aimed to test how food retrieval and food sharing varies depending on the social relationship between individuals, and on the characteristics of the food. In six different test conditions, we provided a captive group of Guinea baboons (Papio papio, N = 23) with multiple food items, differing in quality, quantity, density, monopolizability, and effort required to obtain it. We further used behavioral observations to assess individual relationships and possible variations in grooming exchanges linked to food sharing events. Out of 424 events in which food items were retrieved by the subjects, we detected no instances of active food sharing and only 17 of passive food sharing. The way food was retrieved was affected by individual and food characteristics (i.e., quantity, quality, and monopolizability of food): Males and central individuals (i.e., those connected to many partners, and/or having partners with many connections in the social network) were more likely to retrieve food during test conditions. In particular, events of passive food sharing mostly happened when the quality of food was low, and between individuals belonging to the same community (i.e., having close relationships). No other food characteristics affected the probability to share food, and the occurrence of food sharing had no immediate effect on grooming exchanges. Overall, our findings suggest that food sharing is relatively rare in Guinea baboons unless the food has a low quality and individuals form close social bonds.     

Nutritive Egg Formation in the Marine Snails Crepidula dilatata and Nucella crassilabrum

Summary

Both frequency and morphology of the nutritive eggs in the snails Crepidula dilatata and Nucella crassilabrum were analyzed. In both species, nutritive eggs constitute over 90% of the eggs deposited in each capsule. Marked differences in nutritive eggs exist between these species with respect to morphological and cytological characteristics.

Nutritive eggs of C. dilatata remain uncleaved and in their cytological characteristics resemble oocytes whose development becomes arrested at the stage of germinal vesicle. Although the eggs of this snail are dimorphic in size, such dimorphism is not correlated with the fate of these cells. Nutritive eggs of N. crassilabrum typically abort their development at the stage of zygote cleavage divisions and anarchic cleavage occurs only in a small fraction of them (X = 5–6%).

The nature of these food eggs is discussed. Our findings suggest that, at least in C. dilatata, the mechanisms of nutritive egg formation reside in properties of the oocyte.     

传统与未来的碰撞：食品发酵工程技术与应用进展

随着生物技术的飞速发展,作为食品生物工程的主要组成部分,食品发酵工程技术不断升级,在传统发酵食品的菌种、发酵过程、产品品质得到改善的同时,生物制造的功能食品组分、未来食品等新型产品也应运而生。首先概述了由生物技术和信息技术的进步带来的食品发酵研究手段与生产方式的多层面变革,并重点阐释了利用食品合成生物学设计构建细胞工厂的思路和方法,以及食品生物工程在微生物分析、过程工程和分离工程方面的智能化进程。其次,介绍了现代食品生物工程技术在改善传统发酵食品品质及安全性、生产功能食品组分、添加剂和酶制剂、创制未来食品和开发新型益生食品方面的应用进展。最后,对全球和我国食品发酵产业面临的挑战和未来发展趋势进行了总结和展望,以期为食品发酵的技术革新和工业化应用提供参考。     

中国石龙子个体发育过程中头部两性异型和食性的变化

许多动物呈现个体大小、局部形态特征 (头部大小 )和体色的两性异形[5,14 ,15,2 1,2 2 ] 。 Darwin[12 ] 认为两性谋求各自最大的繁殖利益导致了两性异形 ,因此两性异形是性选择压力作用的结果。自 Darwin以来 ,许多同行认为性选择压力和非性选择压力均能导致动物的两性异形 ,两种选择压力在不同的动物中所起的作用是不同的 [2～ 5,7,10 ,16,2 1～ 2 6] 。性选择压力导致的两性异形与繁殖成功率直接有关。非性选择压力导致的两性异形与繁殖成功率无关或无直接的关系 ,如两性寿命的差异 [13 ]、两性食性的分离 [6,2 1]和两性分配用于生长的…     

Food and feeding preferences of Himalayan gray goral (Naemorhedus goral bedfordi) in Pakistan and Azad Jammu and Kashmir

Himalayan gray goral is endemic to Himalayas and Hindukush ranges. Analysis of 15 fecal samples and field observations from different areas of Pakistan and Azad Kashmir suggest that goral consumes foliage of a minimum of 28 plant species. Trees, shrubs and grasses appear in the ratio of 1:36:63 and hence the species is a grazer, though may opt for browsing when forced. The species mainly subsists on six species of grasses (Chrysopogon aucheri=17.97%, Themeda anathera=13.03%, Poa pratensis=11.23%, Digitaria decumbens=9.30%, Apluda mutica=7.51%, Aristida cyanatha=3.15%), though leaves of shrubs (Myrsine africana=11.38%, Daphne oleoides=8.87%, Carissa opaca=5.94%, Dodonaea viscose=4.79%, Rubus ellipticus=2.93%, Gymnosporia royleana=1.29%) are also consumed. Food preference indices (consumed/availability) suggest that grasses are highly preferred (16.86 times of availability), followed by shrubs (3.3 times of availability), whereas trees and herbs are not preferred. Food plants contain water (77.9±0.56%), ash (8.6±0.38%), sugars (6.8±0.16%), proteins (5.6%±0.28%) and fats (1.3±0.08%). Food provides 4,440 kcal of energy and 5.45 L of water/day/adult goral, which is sufficient to meet the requirements of the species. Grasses need to be ensured in the protected area separated for management of goral population. Zoo Biol 27:371–380, 2008. © 2008 Wiley‐Liss, Inc.     

The Immediate Influence of a Food Safety Incident on Japanese Consumers’ Food Choice Decisions and Willingness to Pay for Safer Food

In January 2008, 10 people from three families living in Chiba and Hyogo Prefectures in Japan were found to be poisoned after eating frozen dumplings that had been imported from Tianjin, China. This incident had a big influence in the short term on Japanese consumers’ consumption choice of imported food from China as well as the willingness to pay (WTP) for food with higher safety guarantees. Using data from a Web-survey of 1500 respondents covering the whole of Japan, two regression models show that firstly, after the incident, consumers intending to buy Chinese food products reduced from 92.5% to 27.6%, and the change of purchase decision is mostly affected by consumers’ prior risk perception and attitude about Chinese products and presents a regional difference. Secondly, Japanese consumers are willing to pay 64,300 yen per year for safer food on average after the incident, and those whose purchase decision is influenced by the incident have a higher WTP of 54,000 yen than those who are not influenced. The most significant factor to decide the WTP is the framing of questions in the survey. The influence of demographic factors is less important and inconsistent in the two models.     

Seasonal and Spatial Overlap between Cladocerans in Humic Lakes

Seasonal and vertical distribution, migratory patterns and reproductive effort in coexisting cladocerans were investigated in three humic lakes with different, but low phytoplankton abundances and varying fish predation pressure. Seasonal and vertical habitat or niche overlap varied, but were high within most pairs of species in all localities. Migration was conspicuous in presence of planktivorous fish, less so in the fish free lake. Despite algal densities below incipient limiting level (30–200 μg C I⁻¹) and a low ratio (3–10) of algal to cladoceran biomass, zooplankton distribution and reproductive parameters were not clearly related to algal biomass. Bacterial biomass equalled 10–50% of phytoplankton biomass, while detritus by far was the largest of the particulate compartements. It was concluded that with a possible exception of the early summer algal bloom, additional carbon sources (bacteria, detritus) are important to cladoceran nutrition in these humic lakes. A large share of N- and P-poor detritus in the diet would give zooplankton productivity limitation by food quality in terms of elemental composition rather than food quantity. This would permit coexistence even of species with rather high food overlap, but give low production rates for all species in agreement with the observations.