导　　师： 张宝善

学科专业： H3201

授予学位： 硕士

作　　者： ;

机构地区： 陕西师范大学

摘　　要： 果汁中的新型污染菌——酸土环脂芽孢杆菌(alicyclobacillusacidoterrestris)，即嗜酸耐热菌(tab)。它在国外屡见报道，该菌污染苹果汁，橙汁、葡萄汁等浓缩果汁及果汁饮料。tab的耐热性强，能够经受酸性果汁加工中的巴氏杀菌而存活，即使在极低的浓度下，也可导致果汁感官品质的劣变。但是，对果汁中tab的控制，目前尚无成熟可靠的技术。因此，研究有效控制果汁中tab的方法是亟待解决的问题。 乳酸链球菌素(nisin)作为一种天然生物防腐剂，有安全、高效、天然等独特性能。nisin能抑制大部分革兰氏阳性菌的生长，尤其对耐热芽孢杆菌，如肉毒杆菌的发芽，这些特性为其应用于果汁的防腐杀菌奠定了理论基础。有关nisin的研究和应用主要集中于近几年。komitopoulou、yamazaki等人研究了对苹果汁、桔子汁和葡萄柚汁中tab孢子的抑制作用，取得了可喜的结果。我国对tab的研究起步较晚，主要是对苹果浓缩汁中tab的研究。有关橙汁中tab的分离、nisin对果汁中tab抑制作用及其应用研究，在国内外极少报道。本文在对橙汁中tab进行分离培养的基础上，对分离菌的生理生长特性进行了全面、系统的研究，并研究了天然防腐剂nisin对橙汁中tab的抑制作用，获得了防止橙汁酸败的有效途径和方法，为果汁的生物杀菌、防腐提供了理论基础和工艺参数。本论文的研究主要获得了如下结论： 1橙汁中tab生长特性的研究 1.1从已败坏的橙汁中分离出了一株与标准tab菌特征相似的菌株。 1.2分离的tab菌株最佳生长条件为：402培养基，生长ph3.7，培养温度45℃。 1.3通过对菌落特征、菌体显微特征、生化特性的鉴定，得出分离菌株就是目标tab菌株。 1.4橙汁中tab菌株在45±1℃下生长快于常温下生长。低温存放的橙汁其tab菌株生长缓慢。 1.580±1℃下，ph3.8的橙汁中tab芽孢的d值为38.31min；95±1℃下d值为4.25min，温度对橙汁中tab的芽孢抗热性影响较大，随着温度的升高，tab芽孢的耐热性显著下降。因此，tab菌株芽孢在不同温度下均具有较强的抗热性，能够经受高温瞬时灭菌而存活下来。 1.6ph值也影响橙汁中tab芽孢抗热性。80±1℃下，ph4.3的橙汁中tab的d值为42.37min；ph3.0的橙汁中tab的d值为35.84min。得出ph4.3时，tab芽孢抗热性较ph3.0时的强。因此，橙汁酸性越高，橙汁灭菌温度越高，均显著影响tab芽孢抗热性。 2nisin对橙汁中tab生长的抑制研究 2.1在酸性条件下，nisin溶液随着温度的升高，抑菌效果逐渐降低。而nisin经115℃和121℃高温处理后仍具有活性；在酸性条件下，随着ph值的降低，nisin抑菌效果增强，当ph＞4时，随ph值的升高，抑菌效果下降；ph及温度联合作用对nisin的抑菌效果影响增强；nisin浓度越大，抑菌效果越好。500mg/kgnisin溶液能够完全抑制6.1×104cfu/mltab菌株。 2.2nisin对tab菌株抗热性的影响为在橙汁中添加nisin后，其中的tab菌株抗热性降低，随着温度的升高，nisin处理的tab菌株芽孢对热越敏感，抑菌效果越好，橙汁中加入nisin可降低杀菌温度和缩短热处理时间。 2.3温度影响nisin对橙汁中tab最低抑制浓度。在常温下nisin对ph3.8的橙汁中tab最低抑制浓度为25mg/kg，在45℃下nisin对橙汁中tab最低抑制浓度为80mg/kg。tab的芽孢对nisin的敏感性要比营养体的敏感性强。 Alicyclobacillus acidoterrestris,also named TAB, is one kind of New polluted bacteria in syrup.It was reported repeatedly on foreign journal. Many kind of syrup such as cider, orange juice, grape juice and ade can be polluted by TAB.TAB has strong heat-resistant characteristic. It can survive in acid syrup used pasteurisation treatment.It can also lead the good sense quality of syrup to badness even its concentration bally low. But at present there is no mature and reliable technology to control TAB in syrup. Therefore it is urgent to solve the problem that how to effectively control TAB in syrup.Nisin is a kind of savageness biology antiseptic and has the special characteristic of safe, high effect and savageness. A majority of bacteria of gram-positive,especially thermotolerant bacillus coagulans such as burgeoning Clostridium botulinum can be inhibited by Nisin .It establish theory foundation by there characters for applying nisin to antisepsis and sterilization of syrup. The study and application of nisin focus on recently a few years. Komitopoulou and Yamazaki et al study the inhibition of nisin on TAB spore in cider, orange juice and grape juice and get delightful result. The study of TAB in our country was relatively late and mainly focused on concentrated apple juice. It is very few reports about the separateness of TAB from orange juice, the inhibition of nisin to TAB and applications of nisin in syrup. In the article, based on separateness of TAB from orange juice, the study is entire and systemic on the physiological and growing character of separated bacteria, the inhibition of nisin on TAB in orange juice. Some effective measures and approaches were obtained from the study and offer theory foundation and technology parameter, the study result are as following:1 Study on the growth character of TAB in orange juice1.1 It was successful to separated one bacteria strain similar with standard TAB bacteria from reechy orange juice. 1.2 The best growth conditions for separated TAB strains is:402 culture medium, growth pH is 3.7,cultured temperature is 45 °C.1.3 It was proved by identifying the character of bacteria strains and thalli ,the biochemistry character of bacteria strains that the separated bacteria strains is TAB bacteria strains1.4 TAB bacteria strains on 45±1°C grow faster than normal temperature. TAB bacteria strains grow slow on low temperature in orange juice.1.5 On 80±l°C,the D value of TAB was 38.31 min when pH value of orange juice is 3.8 and the D value of TAB was 4.25min on 95±1'C. It had great effect on heat-resistant character of TAB spore by temperature, heat-resistant character of TAB spore was obviously drop with temperature increasing. TAB bacterial strains spore had strong heat-resistant character under different temperature and can survive after UHT.1.6 Heat-resistant character of TAB spore was effected by pH value, on 8O±l°C,the D value of TAB was 42.37 min when pH value of orange juice is 4.3 and the D value was 35.84 min upon pH value 3.0.Compared with pH 3.0, heat-resistant character of TAB spore was stronger upon pH 4.3.It was proved that the lower ph value and the higher temperature orange juice was, the better effect it was got on heat-resistant character of TAB spore.2 Study on inhibition of Nisin to growth of TAB in orange juice2.1 On acid condition, the antibacterial effect of Nisin liquor gradually worse, nisin still is active after treatment of 115*C and 121 °C. the antibacterial effect of Nisin strengthen with pH value decrease, when pH value was more than 4, the antibacterial effect of Nisin with pH value increasing, the combination of pH value and temperature strengthen the antibacterial effect of Nisin. the higher the concentration of nisin is, the better result it can get. 500mg//kg nisin liquor can completely control 6.1xl04cfu//ml TAB bacteria strains.2.2 When put nisin into orange juice, heat-resistant character of TAB bacteria strains obviously dropped. The higher the temperature was, the more sensitivity and antibacterial TAB bacteria strains were when they were appeared upon heat after be treated with nisin. It reduced sterilized temperature and cut the heat treatment time if nisin was put into orange juice. 2.3 There was great effect by temperature on minimum inhibiting concentration of nisin on TAB in orange juice, on 25 'C, minimum inhibiting concentration of nisin on TAB bacterial strains in orange juice was 25mg//kg. And it was 80mg//kg when on 45*C.Compared with nutritional body of TAB, TAB spore was more sensitivity when treated with nisin. 80mg//kg nisin liquor can completely control 2.4xl02cfu//ml TAB bacteria strains.

关 键 词： 橙汁 嗜酸耐热菌 分离培养 乳酸链球菌素 抑菌

分 类 号： [TS201.3 TS255.44]

领　　域： [轻工技术与工程] [轻工技术与工程] [轻工技术与工程] [轻工技术与工程]