淡腌黄鱼微生物生长动力学参数的初步研究

对淡腌黄鱼产品在不同温度条件下进行贮藏性实验,研究贮藏期间产品的微生物生长情况及产品的品质变化,根据实验数据用运Gompertz动力学方程,得出产品中微生物生长动力学参数。从产品感官、TVBN评价和微生物生长动态分析中,得出产品在不同贮藏条件下的货架期。通过温度对微生物生长速率的影响,分析栅栏效应。食品在联合栅栏作用下,存在着微生物生长／非生长界面,探讨通过从微生物生长动力学模型的参数来限定微生物生长/非生长界面的可能性,即量化栅栏技术。为开发一种最低限度影响产品质量和保障产品安全的新一代食品保藏技术提供一些有用的实验参数。     

软烤贻贝中蜡样芽孢杆菌生长/非生长界面模型建立与评价

建立软烤贻贝中蜡样芽孢杆菌标准菌株(ATCC49064与DSMZ 4312)在不同贮藏温度(T)、pH、水分活度(Aw)下生长/非生长界面模型,对其拟合情况和来自软烤贻贝蜡样芽孢杆菌(YB001)的验证情况进行分析和评价,并与已建立的脑心浸出液肉汤(BHI)中蜡样芽孢杆菌生长/非生长界面模型进行比较。所建模型总方程为Lopit(P)=-208.457-2.167·T+35.304·pH+705.573·Bw+1.117·T·pH-7.072·T·Bw-174.946·pH·Bw,其中R2-Nagelkerke=0.979和χ~2=0.019(df=8,P=1)显示拟合度较高,而且其预测一致率明显高于BHI培养基中建立的模型,表明该模型在预测软烤贻贝中蜡样芽孢杆菌的生长/非生长情况有很高的精确度和很好的适用性。此外,贮藏温度、水分活度、pH及其交互作用显著影响蜡样芽孢杆菌的生长/非生长(P0.05)。因此可以通过所建生长/非生长界面模型量化温度、水分活度、pH值等栅栏因子并结合其交互效应来确保软烤贻贝的高品质与安全性。     

蜡样芽胞杆菌生长/非生长界面模型的建立和评价

蜡样芽胞杆菌是软烤虾仁产品的主要变质菌,它是一种条件致病菌,通过产生腹泻毒素和呕吐毒素导致食物中毒。该研究旨在建立一种概率模型来预测出蜡样芽胞杆菌的生长/非生长情况或者生长概率。用lo-gistic回归模型建立不同温度、水分活度和pH环境因子作用下蜡样芽胞杆菌的生长/非生长界面模型。实验结果表明蜡样芽胞杆菌在脑心浸液肉汤培养基中生长的最低温度为9.99℃,最低水分活度为0.931,最小pH值为4.5。在此基础上建立的蜡样芽胞杆菌生长/非生长界面模型的χ2=49.73,P<0.000 1。用logistic回归模型建立的生长/非生长模型拟合效果达到极显著水平。模型的预测值同时很好地量化了环境因子对蜡样芽胞杆菌的协同作用,为软烤虾仁产品中蜡样芽胞杆菌的生长/非生长界面模型的建立提供了参考。     

软烤贻贝中蜡样芽孢杆菌生长/非生长界面模型的构建

基于不同贮藏温度、pH值和水分活度,使用R软件建立软烤贻贝中蜡样芽孢杆菌的生长/非生长界面logistic回归模型。分析结果得到,R2-Nagelkerke=0.979,Hosmer-Lemeshow检验中χ~2=0.0189,P=1,表明logistic回归模型拟合度高。此外,贮藏温度、水分活度、pH值及其交互作用对蜡样芽孢杆菌的生长/非生长情况影响显著(P0.05),并且贮藏温度、水分活度或pH值越低,蜡样芽孢杆菌受到的抑制越强。随着温度、水分活度或pH值的升高,它们对蜡样芽孢杆菌生长概率的主要影响因素地位被其余两个因素的交互作用所取代,而且交互作用中两因素的影响中一个增强,另一个减弱。建立的生长/非生长界面模型对实际生产有重要的指导意义,可以量化栅栏因子,并结合其交互效应,保证微生物的安全,及产品本身的营养和感官品质。     

环境因子及接种量对单增李斯特菌生长/非生长界面的影响

单增李斯特菌在实验设定的环境条件下,通过10倍梯度稀释将菌悬液分别稀释到101、103、105、107CFU/m L四个接种水平,然后接种到TSB-YE肉汤中,培养基置于恒温培养箱中进行培养,然后通过肉眼观察培养基浊度并结合涂布TSA-YE平板对其生长/非生长情况进行判定,通过Logistics多项式回归模型对处理的数据建立了单增李斯特菌生长/非生长的界面模型。实验结果表明不同生长温度,p H和盐度的交互作用对单增李斯特菌的生长/非生长界面的影响较大,接种量的大小也会影响单增李斯特菌生长/非生长过渡区域的具体位置,但具体原因和作用机制还有待进一步研究。该研究为抑制单增李斯特菌生长的环境因子条件范围和实际产品中的污染严重程度提供一定的参考依据,对于有潜在单增李斯特菌污染的产品来说,这为加强产品的栅栏因子,优化工艺条件以提高其安全度也提供了重要的参考。     

接种量对单增李斯特菌生长/非生长界面的影响

在4个水平(10~1,10~3,10~5,10~7 CFU/m L)接种浓度下,通过肉眼观察培养基浊度结合涂布TSA-YE平板,对TSB-YE肉汤中培养的单增李斯特菌在温度(0~30℃)、盐度(0.5%~8.5%)、pH(4.0~7.5)条件下的生长/非生长响应进行测定,结果表明:接种量影响单增李斯特菌生长/非生长界面的位置。通过对各种生长条件下单增李斯特菌生长/非生长数据的分析,用多项式逻辑回归模型,建立单增李斯特菌生长/非生长的界面模型,模型拟合的一致性为83.8%到89.6%,拟合结果较好。接种量对微生物生长的起点有重要影响,为微生物生长受初菌数的影响提供定量分析数据,也为建立实际产品中微生物的生长/非生长界面模型提供参考依据。     

接种量对单增李斯特菌生长期及生长界面的影响

为了初步了解接种量对单增李斯特菌生长状况及生长/非生长界面的影响,本实验对单增李斯特菌在0、4、10、25℃下通过培养菌液在600nm下的吸光光度值对其生长周期曲线分别进行了测定,并分析了不同接种量的单增李斯特菌菌液在25℃下的生长周期状况,探讨了纯培养条件下不同盐度和pH下,接种量对单增李斯特菌生长/非生长状况的影响。结果表明:不同的温度下,单增李斯特菌的生长周期有很大的差别;而在相同温度下,接种量对单增李斯特菌的生长周期有较大的影响,随着接种水平的降低,菌种生长所需的延滞时间越长,接种量为107CFU/mL时,其生长延滞期为0~4h,而当接种量减少为10CFU/mL时,其生长延滞期为0~16h;而对于单增李斯特菌的生长/非生长界面而言,接种量对其也有一定的影响,但其作用机制还有待进一步深入的研究。     

淡水鱼防腐保鲜栅栏因子的研究进展

淡水鱼是一种含有丰富蛋白质和脂肪的食品原料,因此,微生物的控制是其捕获后防腐保鲜的关键环节。栅栏技术是通过将多种抑菌、杀菌因子科学地组合,从而抑制保鲜期间淡水鱼中微生物的生长和繁殖,保证其安全和品质的一种保鲜技术。本文概述了栅栏效应与微生物的关系,以及淡水鱼保鲜中常用栅栏因子的研究现状与组合方式,以期为淡水鱼栅栏保鲜技术的研究和应用提高参考。     

鲜切哈密瓜贮藏期间微生物生长模型的研究

研究不同贮藏温度下鲜切哈密瓜中微生物的生长趋势及其与感官质量的关系。测定在4、10、25℃下鲜切哈密瓜中的微生物总数,利用修正的Gompertz模型研究微生物生长规律,并通过微生物数目和感官得分探讨鲜切哈密瓜的货架期。结果表明,试验中所建立的修正Gompertz模型能有效地拟合在不同贮藏温度下鲜切哈密瓜中微生物总数的动态变化,鲜切哈密瓜的最佳贮藏温度为4℃。当微生物总数≤104cfu/g,鲜切哈密瓜保持新鲜状态,无明显的褐变和腐败发生。     

多靶栅栏因子技术在肉类制品中的应用

德国人Leistner和Roble于1976年首先提出微生物的栅栏技术,其机理是利用多种内外因素或保藏技术来控制肉类食品中微生物的生长,将能够抑制腐败菌生长、控制食物腐败变质的因素确定为栅栏因子。因此,为了保障食品的安全卫生,必须阻止微生物生长繁殖的栅栏因子。     

三因子金黄色葡萄球菌生长/非生长模型构建

运用统计分析R软件,建立金黄色葡萄球菌在温度、pH、盐浓度3种环境因子影响下的生长/非生长模型,构建的回归模型参数值a_1、a_2、a_3、a_4、a_5、a_6值均低于0.01,具有高度显著的拟合效果。分析各因子不同取值得到的方程式曲线图得出:在温度为10~25℃,pH值为4.5~5.5,盐浓度为0.5%~14.5%时,单因子对金黄色葡萄球菌生长/非生长影响显著;其他选值范围,3种因子协同影响。     

Control of growth and differentiation of the mammary gland by growth factors

Mammary gland development is a complex process regulated by various steroid and polypeptide hormones. Although the systemic importance of hormones, such as estrogen, progesterone, prolactin, and growth hormone, in the growth of the mammary gland has been well documented, these hormones are virtually incapable of stimulating mammary cell growth in vitro. Thus, the growth stimuli for mammary cells requires clarification. In recent years, a number of growth factors have been discovered; this has prompted interest in examining possible involvement of these biologically active agents in the process of mammary gland development. Results presented herein indicate that several growth factors including epidermal growth factor, transforming growth factor alpha and beta, basic fibroblast growth factor, insulin-like growth factor-I, and mesenchyme-derived growth factor participate in the regulation of mammary cell growth and differentiation.     

Effects of l-arginine on growth hormone and insulin-like growth factor 1

Food Science and Biotechnology - l-Arginine has been reported to promote cellular and organismal growth. In this study, the effects of l-arginine on the expression of growth hormone (GH) and...     

The boundary for growth of Zygosaccharomyces bailii in acidified products described by models for time to growth and probability of growth

Models to predict days to growth and probability of growth of Zygosaccharomyces bailii in high-acid foods were developed, and the equations are presented here. The models were constructed from measurements of growth of Z. bailii using automated turbidimetry over a 29-day period at various pH, NaCl, fructose, and acetic acid levels. Statistical analyses were carried out using Statistical Analysis Systems LIFEREG procedures, and the data were fitted to log-logistic models. Model 1 predicts days to growth based on two factors, combined molar concentration of salt plus sugar and undissociated acetic acid. This model allows a growth/no-growth boundary to be visualized. The boundary is comparable with that established by G. Tuynenburg Muys (Process Biochem. 6:25-28, 1971), which still forms the basis of industry assumptions about the stability of acidic foods. Model 2 predicts days to growth based on the four independent factors of salt, sugar, acetic acid, and pH levels and is, therefore, much more useful for product development. Validation data derived from challenge studies in retail products from the U.S. market are presented for Model 2, showing that the model gives reliable, fail-safe predictions and is suitable for use in predicting growth responses of Z. bailii in high-acid foods. Model 3 predicts probability of growth of Z. bailii in 29 days. This model is most useful for spoilage risk assessment. All three models showed good agreement between predictions and observed values for the underlying data.     

Regulation of ovarian follicular growth by somatotropin and insulin-like growth factors in cattle

Somatotropin (ST), insulin-like growth factor (IGF)-I, and IGF-II affect animal growth and lactation as well as animal reproduction. Understanding the effects of ST and the IGF on reproduction is important because ST and IGF-I undergo dynamic changes prior to the postpartum breeding period. In addition, administration of recombinant bovine somatotropin (rbST) to lactating cows is a common practice that increases blood concentrations of ST and IGF-I during the breeding period. In vivo, administration of rbST caused greater ovarian follicular development. The effects of rbST may represent direct actions of ST because ST receptors are found within granulosa cells as well as oocytes. Alternatively, the actions of ST may be indirectly mediated by increased IGF-I and (or) nutrient partitioning that occurs after rbST. Both IGF-I and IGF-II are synthesized within the ovary. Ovarian IGF are, therefore, a composite of IGF from both endocrine (liver) and autocrine and paracrine (ovary) sources. The IGF stimulate ovarian function by acting synergistically with gonadotropins to promote growth and steroidogenesis of ovarian cells. Actions of IGF-I and -II are restrained by a series of IGF binding proteins (IGFBP) that either originate from the blood or are synthesized locally within the follicle. Degradation and differential synthesis of IGFBP are important mechanisms regulating IGFBP amounts. The relative amounts of IGFBP may ultimately determine ovarian IGF action. Future studies of ST and IGFs should focus on the hormones, receptors, and binding proteins as well as the metabolic requirements for normal ovarian function in dairy cattle.     

纳米技术与非织造布产业

最近在巴尔的摩召开的由非织造布工业协会与世界纸浆、造纸和印染加工工业技术协会(INDA—TAPPI)举办的国际非织造布技术会议上，人们发现用于非织造布制造的技术种类越来越多，也越来越复杂。随着非织造布工业的发展，围绕非织造布生产的主要工艺流程和原材料的学术     

1993 Industry growth

According to industry tracker Technomic Inc., 1993 food purchases in noncommercial foodservice will increase only slightly, moving up a little less than 1%. While this is greater than the 1992 growth rate of 0.3%, it's still less than half as strong as that of the commercial market.     

Analysis of a novel class of predictive microbial growth models and application to coculture growth

In this paper, a novel class of microbial growth models is analysed. In contrast with the currently used logistic type models (e.g., the model of Baranyi and Roberts [Baranyi, J., Roberts, T.A., 1994. A dynamic approach to predicting bacterial growth in food. International Journal of Food Microbiology 23, 277–294]), the novel model class, presented in Van Impe et al. (Van Impe, J.F., Poschet, F., Geeraerd, A.H., Vereecken, K.M., 2004. Towards a novel class of predictive microbial growth models. International Journal of Food Microbiology, this issue), explicitly incorporates nutrient exhaustion and/or metabolic waste product effects inducing stationary phase behaviour. As such, these novel model types can be extended in a natural way towards microbial interactions in cocultures and microbial growth in structured foods. Two illustrative case studies of the novel model types are thoroughly analysed and compared to the widely used model of Baranyi and Roberts. In a first case study, the stationary phase is assumed to be solely resulting from toxic product inhibition and is described as a function of the pH-evolution. In the second case study, substrate exhaustion is the sole cause of the stationary phase. Finally, a more complex case study of a so-called P-model is presented, dealing with a coculture inhibition of Listeria innocua mediated by lactic acid production of Lactococcus lactis.     

Interaction between lactose levels and antimicrobial growth promoters on growth performance of weanling pigs

In experiment 1, 224 pigs (initially 8.85 kg and 28 ± 2 days of age) were used in a 2 × 2 factorial arrangement of treatments to investigate the interaction between lactofeed (LF70) (860 g kg^?1 whey permeate, 140 g kg^?1 soya bean meal) level (175 g kg^?1 and 350 g kg^?1) and avilamycin (0 and 40 mg kg^?1) inclusion in piglet starter diets. Pigs were fed starter diets from day 0 to day 22 and a transition diet was fed from day 23 to day 39. The inclusion level of LF70 in the transition diet was 75 g kg^?1 and 150 g kg^?1. Pigs fed 350 g kg^?1 LF70 had a higher daily gain (ADG) (p < 0.01) and an improved feed conversion ratio (FCR) (p < 0.05) during the starter period than the pigs fed 175 g kg^?1 LF70. Pigs fed medicated diets had a higher ADG (p < 0.05) and an improved FCR (p < 0.05) than the non‐medicated fed pigs during the starter period. There was an increase in feed intake (AFI) (p < 0.05) during the transition period with increasing levels of LF70. There was an improvement in FCR during the transition period with the inclusion of avilamycin (p < 0.01). There was a significant interaction (p < 0.01) between LF70 and avilamycin for ADG during the transition period. The inclusion of avilamycin at 175 g kg^?1 LF70 inclusion had no effect (p > 0.05) on ADG. However at 350 g kg^?1 LF70 inclusion the pigs offered medicated diets had a higher ADG (p < 0.001) compared with non‐medicated diets. In experiment 2, 224 pigs (initially 8.85 kg and 28 ± 2 days of age) were used in a 2 × 2 factorial to investigate the interaction between LF70 level (175 g kg^?1 and 350 g kg^?1) and zinc oxide (ZnO) (0 and 3.1 g kg^?1) inclusion in piglet starter diets. The inclusion level of LF70 in the transition diet was 75 g kg^?1 and 150 g kg^?1 and of ZnO was 2 g kg^?1. There was a significant increase (p < 0.05) in ADG with increasing levels of LF70 during the starter period. The inclusion of ZnO during the starter period resulted in an increase in ADG (p < 0.001) and FCR (p < 0.05) compared with no ZnO inclusion. Neither the inclusion of zinc oxide not of LF70 had an effect (p > 0.05) on performance during the transition period. In conclusion the supplementation of starter diets with increasing levels of LF70, ZnO and avilamycin resulted in increased ADG and improved FCR. Copyright © 2004 Society of Chemical Industry