Inactivation of Saccharomyces cerevisiae and Lactobacillus plantarum in orange juice using ultra high-pressure homogenisation

Yeasts and lactic acid bacteria are the usual contaminants in orange juice and responsible for decreasing the shelf life of the product. Ultra high-pressure homogenisation has been shown to be an alternative to the traditional thermal pasteurisation of pumpable foods. The product was pumped through a homogeniser valve at 100 MPa, 150 MPa, 200 MPa, 250 MPa and 300 MPa using two synchronized overlapped intensifiers at a flow rate of approximately 270 mL/min. The inlet temperature was kept at 10 °C, pH at 4.1 and soluble solids at 10.0 °Bx. After processing, the product was immediately cooled to 4 °C and the microbiological count was determined. The study showed that Lactobacillus plantarum and Saccharomyces cerevisiae are sensible to ultra high-pressure homogenisation treatment. The results indicated that pressures higher than 250 MPa were able to completely destroy initial loads of 1.2 × 107 UFC/mL of L. plantarum and 2.9 × 105 UFC/mL of S. cerevisiae in orange juice, making this technology a promising way to nonthermally process orange juices.Industrial relevanceThis paper deals with inactivation of microorganism contaminants of orange juice using dynamic ultra high process technology. It is of industrial interest and relevance to evaluate the use of this non-thermal emerging technology to process fluid foods that may result into better taste, optimum product functionality, safety and quality characteristics.     

植物乳杆菌和酿酒酵母发酵菠萝汁的性能比较及产物分析

采用植物乳杆菌（Lactobacillus plantarum）和酿酒酵母（Saccharomyces cerevisiae）分别进行单菌与混菌发酵菠萝汁,并比较分析不同接菌方式下菠萝汁的发酵性能及发酵体系中的产物。结果表明,相同接种量发酵72 h后,植物乳杆菌单独发酵活菌数可达108 CFU/mL,分别约为酿酒酵母单独发酵和二者混合发酵活菌数的3倍和10倍;植物乳杆菌的接入使发酵液pH降至3.21,而酿酒酵母的接入使菠萝汁中氨基酸态氮降至3.15×10-4 mg/L,糖类物质几乎被消耗殆尽。发酵产物分析结果发现,植物乳杆菌单独发酵产生大量乳酸（每升增加12.02 g/L）和少量乙酸（每升增加0.40 g/L）,影响了口感,而酿酒酵母单独发酵则使菠萝汁中原有的香气物质损失较多（4种）。综合分析,采用二者混合发酵,既可保有菠萝本身的营养物质和特有香气,又可赋予其一定的发酵风味,获得口感良好的菠萝发酵饮品。     

气调储藏对接种酵母菌鲜榨桔汁变质过程的影响

采用不同比例的CO₂（20%、40%、60%、80%）对接种一定量的酵母菌的鲜榨桔汁进行储藏,检测果汁中主要成分糖、酸、醛、醇及环境气体的变化量,研究气调储藏对接种酵母菌的鲜榨桔汁变质过程的影响。研究结果显示,20%CO₂初始浓度对果汁酵母菌的影响效果微弱,果汁酵母菌的数量始终最多,导致相对于其它组,20%组果汁糖消耗最大,醇和酸的产率较大。在果汁糖代谢一定的情况下,60%组酵母菌受环境影响,主要代谢产物为醇。而CO₂初始浓度为40%时,酵母菌发酵主要产酸,并且此气调比例能够抑制果汁酵母菌的繁殖,降低果汁酵母菌的数量和果汁糖消耗,同时能使环境气体CO₂在储藏前期保持稳定,适于鲜榨桔汁的保藏。      

酿酒酵母菌含量对控制橙汁腐败的影响

以酿酒酵母为模式微生物,研究了GB 19297-2003中规定的酵母菌含量对橙汁中酿酒酵母生长延滞期的影响,以及在5、8、25、35℃下,低菌含量酿酒酵母在橙汁中的生长规律.研究表明,产品酵母数量≤20cfu/mL的橙汁,虽然符合GB 19297-2003要求,但是在25℃下仍能发生腐败,导致胀袋;允许酵母残留的橙汁产品,其温度必须控制在5℃以下.     

Inactivation of Saccharomyces cerevisiae suspended in orange juice using high-intensity pulsed electric fields

Saccharomyces cerevisiae is often associated with the spoilage of fruit juices. The purpose of this study was to evaluate the effect of high-intensity pulsed electric field (HIPEF) treatment on the survival of S. cerevisiae suspended in orange juice. Commercial heat-sterilized orange juice was inoculated with S. cerevisiae (CECT 1319) (10(8) CFU/ml) and then treated by HIPEFs. The effects of HIPEF parameters (electric field strength, treatment time, pulse polarity, frequency, and pulse width) were evaluated and compared to those of heat pasteurization (90 degrees C/min). In all of the HIPEF experiments, the temperature was kept below 39 degrees C. S. cerevisiae cell damage induced by HIPEF treatment was observed by electron microscopy. HIPEF treatment was effective for the inactivation of S. cerevisiae in orange juice at pasteurization levels. A maximum inactivation of a 5.1-log (CFU per milliliter) reduction was achieved after exposure of S. cerevisiae to HIPEFs for 1,000 micros (4-micros pulse width) at 35 kV/cm and 200 Hz in bipolar mode. Inactivation increased as both the field strength and treatment time increased. For the same electric field strength and treatment time, inactivation decreased when the frequency and pulse width were increased. Electric pulses applied in the bipolar mode were more effective than those in the monopolar mode for destroying S. cerevisiae. HIPEF processing inactivated S. cerevisiae in orange juice, and the extent of inactivation was similar to that obtained during thermal pasteurization. HIPEF treatments caused membrane damage and had a profound effect on the intracellular organization of S. cerevisiae.     

酿酒酵母与植物乳杆菌复合发酵对面条储藏特性的影响

为探究酿酒酵母与植物乳杆菌复合发酵对面条储藏特性的影响.采用质构仪(TA)、低场脉冲核磁共振仪(LF-NMR)、X-射线衍射仪(XRD)对面条在4℃储藏期间的品质变化进行分析.结果表明,与空白组相比,发酵面条的断条率低,吸水率无显著性差异(P>0.0.5),pH下降,可滴定酸(TTA)值上升;在相同储藏时间内发酵面条的...     

Shelf-life prediction of fresh blood orange juice

Fresh blood orange juice is successful on the market because of its taste and nutritional value. Yet, it requires accurate control of the cold chain during storage and distribution. A kinetic study was carried out both on growth of spoilage microorganisms (i.e. yeasts) and on decrease of nutritional value (i.e. ascorbic acid and anthocyanin contents) of pasteurised fresh blood orange juice. Kinetic equations were used to set up mathematical models to predict shelf-life of pasteurised fresh blood orange juice under isothermal and non-isothermal conditions. The mathematical model was also able to predict yeast growth in unpasteurised fresh blood orange juice during shelf-life.     

Arginine dihydrolase pathway in Lactobacillus plantarum from orange.

Lactobacillus plantarum N8 and N4 strains isolated from orange degraded L-arginine to citrulline, ornithine and ammonia. Citrulline and ornithine were consumed. Lactobacillus plantarum N4 utilized arginine and ornithine to a higher extent than Lactobacillus plantarum N8. Urea was not detected during arginine degradation, indicating that the amino acid degradation was carried out only by the arginine dihydrolase pathway. Citrulline increased the growth of the two strains, arginine only increased the growth of Lactobacillus plantarum N4. Ornithine did not modify the growth of the strains studied. With different behavior, Lactobacillus plantarum N8 and N4 strains were able to derive energy and ammonia from arginine or citrulline catabolism. This is interesting for microorganisms developing in a stressful environment.     

植物乳杆菌发酵盐渍辣椒汁培养基的优化

将盐渍辣椒汁作为植物乳杆菌发酵培养基主料,添加不同的碳源、氮源、磷源,通过单因素和正交试验确定碳源、氮源、磷源的最优添加量与配比,得出盐渍辣椒汁发酵培养基培养植物乳杆菌的最优条件。结果表明,接种1%的植物乳杆菌培养24h后,在葡萄糖添加量为2.5%,细菌学蛋白胨添加量为2.5%,磷酸氢二钠添加量为0.2%,培养温度为37℃,初始pH值为自然条件的培养基中植物乳杆菌生长最好。     

植物乳杆菌对高产酯酿酒酵母酒精发酵及酯醇代谢的影响

在高粱汁培养基内同时接种植物乳杆菌（Lactobacillus plantarum）和高产酯酿酒酵母（Saccharomyces cerevisiae）,探究植物乳杆菌及其代谢产物对高产酯酿酒酵母酒精发酵及酯醇代谢的影响。结果表明：植物乳杆菌对高产酯酿酒酵母生长及酒精发酵的影响不大,发酵结束后残糖量均＜5 g/L,乙醇含量为74～78 g/L;植物乳杆菌使高产酯酿酒酵母乙酸乙酯和高级醇产量下降,分别最多下降了15.31%、36.14%;培养基内不同乳酸质量浓度使酿酒酵母乙酸乙酯产量提高,乳酸质量浓度为7.1 g/L时,乙酸乙酯最多提高了39.84%;培养基内乳酸质量浓度在1.8～7.1 g/L时,高产酯酿酒酵母高级醇的产量明显降低,特别是苯乙醇的产量显著下降,下降了25.05%～75.64%。     

High pressure destruction kinetics of Leuconostoc mesenteroides and Saccharomyces cerevisiae in single strength and concentrated orange juice

High pressure (HP) destruction of Leucoonostoc mesenteroides and Saccharomyces cerevisiae in single strength and concentrated orange juice by high hydrostatic pressure treatment was evaluated at selected pressures (100–400 MPa) and holding times (0–120 min) at 20 °C. Kinetic analysis of the microbial survivor data was evaluated based on the biphasic destruction behavior consisting of: (i) an instantaneous pressure kill (IPK) effect due to pressurization–depressurization with no hold-time (pressure-pulse); and (ii) a subsequent semi-logarithmic (first order) destruction during the pressure hold-time. IPK values were enhanced at higher pressure levels and were more pronounced for S. cerevisiae than for L. mesenteroides. During the pressure-hold, as expected, the associated D values (decimal reduction time) decreased with an increase in pressure. However, S. cerevisiae had higher D values, especially in concentrated orange juice, suggesting a higher pressure resistance than L. mesenteroides. The pressure dependency of kinetic parameters was well described by the conventional death time model with associated z_p values (pressure range to result in a decimal change in D values) of 137 and 135 MPa in the single strength orange juice and 251 and 287 MPa in the concentrate, respectively, for L. mesenteroides and S. cerevisiae.     

植物乳杆菌与酿酒酵母共发酵对薏仁米发酵液品质及抗氧化活性的增效性

该文研究植物乳杆菌(Lactobacillus plantarum,LP)与酿酒酵母(Saccharomyces cerevisiae,SC)共发酵对薏仁米发酵液的品质和抗氧化活性的增效性。以基础理化特性(pH、总酸、还原糖和可溶性蛋白)、有机酸、多肽分子质量分布、游离氨基酸、总黄酮、总多酚、总三萜和可溶性膳食纤维等物质的含量及体外抗氧化活性为指标,比较分析LP、SC和LP与SC共发酵(LP+SC)薏仁米发酵液的差异。结果表明,与LP组和SC组相比,发酵结束后LP+SC组的pH分别降低了2.22%(P>0.05)和30.89%(P<0.05)、还原糖含量分别降低了23.79%(P>0.05)和49.87%(P<0.05)、可溶性蛋白含量分别降低了28.81%(P<0.05)和8.69%(P>0.05)、总酸含量分别提高了9.89%(P<0.05)和521.15%(P<0.05)、总黄酮含量分别提高了27.15%(P<0.05)和13.06%(P<0.05)、总多酚含量分别提高了6.35%(P>0.05)和13.59%(P...     

Quality degradation kinetics of pasteurised and high pressure processed fresh Navel orange juice: Nutritional parameters and shelf life

A kinetic study of post processing quality loss was conducted after high pressure processing (600 MPa, 40 °C, 4 min) or thermal pasteurisation (80 °C, 60 s) of fresh Navel orange juice. Selection of processing conditions was mainly based on pectin methylesterase inactivation. Ascorbic acid loss, colour, viscosity and sensory characteristics were measured during storage at different isothermal conditions (0–30 °C). Increased shelf life (based on ascorbic acid retention) was achieved for high pressurised compared to thermally pasteurised juice, ranging from 49% (storage at 15 °C) to 112% (storage at 0 °C). Activation energy values for ascorbic acid loss were 68.5 and 53.1 kJ/mol, respectively, for high pressurised and thermally treated juice. High pressure processing resulted in better retention of flavour of untreated juice and superior sensory characteristics compared to thermal pasteurisation. Colour change was linearly correlated to ascorbic acid loss for both types of processing. Slightly higher apparent viscosity values were determined for high pressurised juice.Industrial relevanceApplication of high hydrostatic pressure on orange juice industry. Fresh orange juice is a product of high commercial and nutritional value due to its rich vitamin C content and its desired sensory characteristics. High Hydrostatic Pressure (HHP) is an alternative non-thermal technology that has been proposed for application on orange juice. Such a treatment denaturates enzymes and eliminates microorganisms responsible for spoilage of orange juice without detrimental effects on the sensory and nutritional quality of juice. The effect of HHP on the stability of fresh orange juice has been studied by different research groups, while orange juices processed with the new technology have already been commercially available in Japan, U.S.A., Mexico and Europe. However, a systematic kinetic approach of the effect of HHP on different quality indexes (not only microbial spoilage) immediately after processing, as well as during a long term storage of the processed orange juice is needed, in order to achieve an optimal process design and a successful application of the new technology in orange juice industry. Such kinetic data for parameters related to the quality and nutritional value of fresh orange juice were gathered in the present work providing therefore industry with useful information for the HHP stabilization of orange juice and the production of a high quality product. Due to the great benefits of HHP compared to the conventional pasteurization that emerged from this work regarding the quality, shelf life and nutritional characteristics of fresh orange juice, HHP technology is an advantageous alternative process for high valued products like orange juice.     

一株具有益生特性的植物乳杆菌及其在发酵果蔬汁中的应用

为获得具有良好益生特性及发酵性能的乳酸菌菌株,从四川泡菜样品中筛选出1株植物乳杆菌581菌株。考察该菌株的胃肠道环境耐受能力、果蔬汁发酵能力,并采用小鼠便秘模型评价其通便功能。结果显示,植物乳杆菌581具有良好的胃肠道环境耐受能力,使其能到达肠道发挥生理功能。与模型组相比服用该菌株可有效缩短便秘小鼠的首次排便时间((201. 5±33. 8) min vs.(353. 8±59. 3) min),增加排便粒数(6. 9±3. 7 vs.2. 40±1. 35)、排便质量((0. 214 9±0. 204 3) g vs.(0. 071 7±0. 055 9) g),并提高小肠的墨汁推进速率((39. 88±9. 10)%vs.(29. 27±5. 11)%)。同时,植物乳杆菌581适于多种果蔬汁发酵,对胡萝卜汁的生冲气味有改善作用且发酵后活菌数可达1. 24×109CFU/m L。植物乳杆菌581同时具有润肠通便功能和良好的发酵特性,可用于具有益生功能的果蔬发酵饮料的开发。     

电子舌在鲜榨橙汁掺假识别中的应用研究

在鲜榨橙汁中分别添加不同比例的橙汁饮料,采用电子舌检测技术对其口味进行识别,对传感器所获得的响应信号进行主成分分析(PCA)、辨别因子分析(DFA)和偏最小二乘回归分析(PLS)。与PCA相比,DFA对样品的区分效果更好,随着掺假比例的增加,样品分布呈现一定的规律性;PLS分析法显示:橙汁饮料的不同掺入比例与电子舌响应信号有较好的相关性,相关系数为0.963 8;PLS模型预测误差值在1.85%~2.20%。证明电子舌技术能够有效的用于鲜榨橙汁掺假的鉴别。     

Characterization and heterologous expression of a class IIa bacteriocin,plantaricin 423 from Lactobacillus plantarum 423, in Saccharomyces cerevisiae

Lactobacillus plantarum 423 produces a small heat-stable antimicrobial protein designated plantaricin 423. This protein is bactericidal for many Gram-positive foodborne pathogens and spoilage bacteria, including Listeria spp., Staphylococcus spp., Pediococcus spp., Lactobacillus spp., etc. The DNA sequence of the plantaricin 423-encoding region on plasmid pPLA4 revealed a four open reading frame (ORF) operon structure similar to pediocin PA-1/AcH from Pediococcus acidilactici and coagulin from Bacillus coagulans I(4). The first ORF, plaA, encodes a 56-amino acid prepeptide consisting of a 37-amino acid mature molecule, with a 19-amino acid N-terminal leader peptide. The second ORF, plaB, encodes a putative immunity protein with protein sequence similarities to several bacteriocin immunity proteins. The plaC and plaD genes are virtually identical to pedC and pedD of the pediocin PA-1 operon, as well as coaC and coaD of the coagulin operon. Plantaricin 423 was cloned on a shuttle vector under the control of a yeast promoter and heterologously produced in Saccharomyces cerevisiae.     

Ascorbic acid degradation kinetics of sonicated orange juice during storage and comparison with thermally pasteurised juice

Ascorbic acid degradation kinetics of sonicated orange juice during storage were determined and compared to thermally pasteurised samples. Acoustic energy densities (AED) ranging from 0.30 to 0.81 W/mL and treatment times of 2-10 min were investigated. The degradation kinetics of sonicated samples followed first-order kinetics (R² ≥ 0.91) during processing. During storage ascorbic acid degradation of sonicated samples followed the Weibull model (R² ≥ 0.97) with β values ranging from 0.662 to 0.697. Comparatively, first-order degradation kinetics were observed during storage for thermally pasteurised (R² = 0.98) and control samples (R² = 0.96). Increased shelf life based on ascorbic acid retention was found for sonicated samples compared to thermally pasteurised samples. Predicted shelf life for sonicated orange juice ranged from 27 to 33 days compared to 19 days for thermally pasteurised juice during storage at 10 °C. These results indicate that sonication results in enhanced retention of ascorbic acid in orange juice during storage compared to thermal processing.     

新疆药桑果乳杆菌发酵饮料研制

以新疆药桑果为原料,利用植物乳杆菌发酵,研制具有药桑果特殊风味和营养价值的药桑果乳酸发酵饮料。采用响应面法优化药桑果饮料发酵工艺条件,在单因素实验基础上,选取菌种接种量、发酵时间、发酵温度、药桑果果汁料水比为影响因子,以发酵饮料感官评分为响应值,应用Box-behnken中心组合实验设计建立数学模型,进行响应面分析,并测定成品中乳酸菌总数、总黄酮含量、总酸、可溶性固形物。结果表明,药桑果发酵饮料最佳发酵条件为:植物乳杆菌接种量2%、发酵时间20h、发酵温度35℃、药桑果果汁料水比1∶21。在此条件下,发酵饮料的乳酸菌活菌数量为4.3×1010CFU/m L、感官评分为84.5。      

超高压处理对鲜榨橙汁品质的影响

研究比较超高压处理和热处理对鲜榨橙汁品质的影响。研究结果表明:鲜榨橙汁经处理后,其主要成分都呈现不同程度的损失,但超高压处理鲜榨橙汁效果较热处理好,且对色泽影响较小;鲜榨橙汁经处理后,其香气成分发生了变化,酯类、醇类、酮类总含量变化相对较小,醛类经热处理及超高压处理后与鲜榨橙汁比较有所降低,降低比例都在4倍以上;烃类及其它类物质含量与鲜榨橙汁比较也有所下降。