Viability of microencapsulated Bifidobacterium animalis ssp. lactis BB12 in kefir during refrigerated storage

The viability of free and immobilized cells of Bifidobacterium animalis ssp. lactis BB12 incorporated into kefir was studied for 28 days during refrigerated storage. The immobilized bifidobacteria were added directly to previously prepared kefir. Titratable acidity, pH, ethanol, fat, protein and lactose were evaluated in the kefir with bifidobacteria after the storage. The survival of the free and microencapsulated bifidobacteria was evaluated during the storage period and in simulated gastric juice. The pH of kefirs ranged from 4.3 to 4.6. Encapsulation improved significantly the survival of bifidobacteria during exposure to nisin, during the storage period and in simulated gastric juice.     

超高压杨梅复合果蔬汁的研制及贮藏品质

本文以杨梅、西瓜和茭白为混合原材料,研究了不同比例的杨梅汁、西瓜汁及茭白汁对复合果蔬汁感官指标的影响,同时以菌落总数、糖、酸和V_C含量为指标,研究4 ℃环境下超高压复合果蔬汁的贮藏品质变化。在单因素实验基础上,应用Box-Behnken响应面优化配方参数。结果表明,复合果蔬汁最优配方为杨梅汁为52.1%、西瓜汁为29.4%、茭白汁为18.5%。优化条件下模型预测感官得分为92.28分,验证试验结果(91.42±0.50,n=7)与模型预测结果接近。超高压处理能有效杀灭微生物,对糖、酸、V_C含量无显著影响。在4 ℃下贮藏12 d,超高压复合果蔬汁菌落总数上升了0.43 lg CFU/mL,V_C含量下降了2.09%,糖酸度均无显著性变化,很好地保持了复合果蔬汁的贮藏品质。     

酶技术在果菜汁饮料生产中的应用

讨论了果胶酶、纤维素酶、溶菌酶等十几种酶在水果汁、蔬菜汁饮料加工和储藏中的应用；讨论了酶技术对果菜汁饮料稳定性、营养成分、色泽和风味的影响。     

Complex Coacervation as a Novel Microencapsulation Technique to Improve Viability of Probiotics Under Different Stresses

A physicochemical approach has been undertaken to develop polymeric microcapsules for delivering probiotic bacteria with improved viability in functional food products. Two probiotic strains of Lactobacillus paracasei subsp. paracasei (E6) and Lactobacillus paraplantarum (B1), isolated from traditional Greek dairy products, were microencapsulated by complex coacervation using whey protein isolate (WPI, 3 %?w/v) and gum arabic (GA, 3 %?w/v) solutions mixed at 2:1 weight ratio. The viability of the bacterial cells during processing (heat treatment and high salt concentrations), under simulated gut conditions (low pH and high bile concentrations) and upon storage, was evaluated. Entrapment of lactobacilli in the complex coacervate structure enhanced the viability of the microorganisms when exposed to a low pH environment (pH 2.0). Both encapsulated strains retained high viability in simulated gastric juice (>73 %; log scale), especially in comparison with non-encapsulated (free) cells (<19 %). Moreover, after 60 days of refrigerated storage at pH 4.0, the viability of microencapsulated cells was more than 86 %, implying improved protection in comparison with the free cells (<59 %). Complex coacervation with WPI/GA has the potential to deliver live probiotics in low pH foods or fermented products; it is also important to note that the complexes can dissolve at pH 7.0 (gut environment) releasing the microbial cells (desired feature of target delivery systems).     

Haze Development in Aerobically or Anaerobically Produced Clarified Apple Juices

Haze production in aerobically or anaerobically produced Red Delicious apple juice was assessed following heating, aeration, and protein addition. Stored aerobic juice produced haze in 6 wk, but anaerobic juice was haze-free unless oxygen was introduced. Phenolic material was incorporated into haze in both systems. HPLC (detection at 420 nm) of concentrated juice and addition of 100 mg/L BSA suggested the presence in both juices of ‘reactive’ material which could complex and precipitate during storage. Phenolic compounds, heating, and especially oxidation during processing (and storage) appear to be major determinants of ‘haze potential’ in clarified apple juice.     

Fibres as carriers for Lactobacillus rhamnosus during freeze-drying and storage in apple juice and chocolate-coated breakfast cereals

The capability of different fibre preparations to protect the viability and stability of Lactobacillus rhamnosus during freeze-drying, storage in freeze-dried form and after formulation into apple juice and chocolate-coated breakfast cereals was studied. In freeze-drying trials wheat dextrin and polydextrose proved to be promising carriers for the L. rhamnosus strains: both freeze-drying survival and storage stability at 37 degrees C were comparable to the control carrier (sucrose). Using apple fibre and inulin carriers resulted in powders with fairly good initial freeze-drying survival but with poor storage stability at 37 degrees C. When fresh L. rhamnosus cells were added into apple juice (pH 3.5) together with oat flour with 20% beta-glucan the survival of the cells was much better at 4 degrees C and at 20 degrees C than with sucrose, wheat dextrin and polydextrose, whereas with freeze-dried cells no protective effect of oat flour could be seen. The stability of freeze-dried L. rhamnosus cells at 20 degrees C was higher in chocolate-coated breakfast cereals compared to low pH apple juice. Similar to freeze-drying stability, wheat dextrin and polydextrose proved to be better carriers than oat flour in chocolate-coated breakfast cereals. Regardless of their differing capability to adhere to fibre preparations the two L. rhamnosus strains studied gave parallel results in the stability studies with different carriers.     

The potential of immobilized cell technology to produce freeze-dried, phage-protected cultures of Lactococcus lactis

Lactococcus lactis cells were immobilized in calcium alginate beads and added to growth media to enable biomass production in the gel. The immobilized population was then freeze-dried. Survival during freeze-drying (FD), stability upon high-temperature storage and residual humidity were evaluated. This culture was compared to a classical liquid starter and fresh beads of immobilized L. lactis in simulated quarg manufacture. Acidifying characteristics, proteolytic activity, sensitivity to bacteriophage and sensory properties of quarg products were evaluated.

The population in the beads prior to FD was 7 × 10¹⁰ CFU/g. The best survival rate to FD (62–79%) was obtained when the beads were mixed with a milk-based protective solution. In the absence of protective ingredients (milk solids, sucrose and vitamin C) the alginate beads had high water content following FD. Survival of the immobilized cells during FD was as high for immobilized cells as that of free cells. Stability of the immobilized cells at high-temperature storage (45–55°C) was higher than for the free cells. Quarg cheese was succesfully produced in 5 h with the immobilized freeze-dried (IFD) culture, but sensory evaluation confirmed a significant texture difference between cheeses made with free or IFD cultures. Higher inoculation rates were required with the IFD culture to obtain the same acidifying activity as classical fresh liquid starters. The IFD culture performed well under phage contamination; following a 6-h fermentation, 30% of the cells remained viable and active in the phage-contaminated sample. Increase in non-protein amino compounds (0·2 g/100 g cheese) over a 30-day storage period at 4°C was similar in quarg cheeses made with fresh or IFD starters, despite the higher inoculation rate used with the IFD culture.     

制汁工艺对芦荟凝胶原汁贮藏稳定性的影响

以中华芦荟为试材 ,比较研究了热榨和酶解制汁工艺获得的凝胶原汁经高温杀菌处理后 ,在室温下避光贮藏过程中的粘度、色泽等感官质量和主要营养物质、功能成分变化。结果表明 ,在 3 0d的贮藏期内 ,热榨原汁比酶解原汁的营养成分损失少、多糖保存率高 ,粘度下降慢 ,色泽和体态较稳定。选用热榨处理 ,90℃、60s杀菌工艺生产的芦荟凝胶原汁在室温下可保藏 2 0d ,品质基本不变     

浑浊型光皮木瓜果汁的稳定性研究

浑浊型光皮木瓜果汁中由于不溶性固形物含量较高,对产品的稳定性提出了更高要求。以新鲜光皮木瓜为原料,研究了取汁方式、不同稳定剂和杀菌方式对果汁稳定性的影响。结果表明,打浆取汁的不溶性固形物含量为（36.56 ± 1.27）%,显著高于压榨法,更有利于产品香气、营养成分等的保留;黄原胶、瓜尔豆胶、结冷胶最适复配添加量分别为0.02%、0.02%、0.10%时,果汁的加权稳定性最高,其中黏度值为（23.55 ± 0.78）mPa·s,悬浮稳定性为（94.19 ± 0.91）%;果汁经高温短时杀菌（121 ℃/0.1 MPa/30 s）,贮藏期40 d以内果汁菌落总数均低于限值（2 lg CFU/mL）,悬浮稳定性保持至（65.17 ± 0.83）%,显著高于巴氏杀菌,感官品质处于较好的水平（感官评分>8）。该研究为提高果汁在加工与贮藏中的稳定性提供理论依据。     

杨梅果汁花色苷及其色泽稳定性的研究

本文就氧、维生素C(Vc)、包装材料、贮藏温度以及光等因素对杨梅汁花色苷及其色泽稳定性的影响作了探讨。结果表明:杨梅汁花色苷的降解遵循一级反应动力学规律(r<0.98)。氧及Vc均不利于花色苷及色泽保存。复合铝箔袋装杨梅汁其花色苷和色泽稳定性很高,涂料罐则又不宜装杨梅汁。低温(4℃)贮藏八个月的杨梅汁花色苷及其色泽变化甚微,高温(37℃)贮藏对花色苷和色泽破坏严重,一个月内杨梅汁即失去原有紫红色而呈褐色,且瓶底有大量褐色降解物。曝光贮藏会促进杨梅汁花色苷降解和色泽的变化。     

Yield and quality effects of electroplasmolysis and microwave applications on carrot juice production and storage

Electroplasmolysis as a pretreatment and microwave heating as an alternative to traditional heating were used in carrot juice production and the effects of these electrical methods on juice quality were investigated. Electroplasmolysis and microwave applications were optimized by response surface methodology. Optimum conditions were these: voltage gradient of 22.2 V/cm and treatment time of 60 s for electroplasmolysis, and flow rate of 90 mL/min with power of 900 W for microwave heating. Production of carrot juice was carried out by using these optimum conditions. After production, carrot juice samples were stored for 4 mo at +4 °C and analyses were performed at monthly intervals. As a result of electroplasmolysis, a 9.7% increase in juice yield was obtained. In addition, 100% pectin methylesterase inactivation was found with the microwave heating application. The results showed that the highest values for quality characteristics, such as antioxidant capacity and total pectin, total phenolic, and total carotenoid contents, were obtained with the combined applications of the electrical methods. In addition, these quality characteristics were protected better in the group of combined applications of the electrical methods (electroplasmolysis + microwave) during storage.     

Antioxidant and antiradical properties of cranberry juice and extracts

The antioxidant capacities of cranberry juice and three extracts isolated from frozen cranberries containing anthocyanins, water-soluble and apolar phenolic compounds, were evaluated at pH 2.5 and 7, respectively. The free radical-scavenging (FRS) and the lipid peroxidation inhibition (LPI) activities of each samples, and extracts, were studied using the N,N-diethyl-p-phenylenediamine (DPD) decoloration test and the thiobarbituric acid reactive substances (TBARS) assay, respectively. The cranberry phenols displayed good free radical-scavenging properties, but were less efficient at inhibiting the peroxidation of lipids. Of all the samples tested, the water-soluble phenolic compounds showed the greatest free radical-scavenging (68.2 mmol TE/mg phenol) and antioxidant (13.4 mmol TE phenol) activities. The polarity of the phenols, the pH of the medium and the juice process had a great influence on the antioxidant activities. The phenols isolated from cranberries with an aqueous solvent have greater antioxidant properties than those extracted with an organic solvent mixture. The antioxidant activity of the cranberry samples adjusted at pH 2.5 was greater than those adjusted at pH 7. Compared to the cranberry extracts, the juice exhibited a much lower antioxidant activity, especially when compared with the extract containing water-soluble compounds which the extraction conditions were similar to those used to obtain the juice.     

Effect of chlorine, blanching, freezing, and microwave heating on Cryptosporidium parvum viability inoculated on green peppers

Cryptosporidium parvum oocysts have been found on the surface of vegetables in both developed and developing countries. C. parvum can contaminate vegetables via various routes, including irrigation water. This study investigated the effect of individual treatments of chlorine, blanching, blast freezing, and microwave heating, as well as combined treatments of chlorine and freezing, and chlorine and microwave heating on the viability of C. parvum oocysts inoculated on green peppers. The viability of the oocysts after the treatments was assessed using propidium iodide and a flow cytometer. Based on the propidium iodide staining, the chlorine treatments did not affect the viability of the oocysts. Blast freezing significantly inactivated 20% of the oocysts. Microwave heating and blanching significantly inactivated 93% of oocysts. Treatment with chlorine followed by blast freezing did not affect the viability of the oocysts significantly. Treatment with chlorine and microwave heating was significantly more effective than microwave heating alone and inactivated 98% of the oocysts. The study indicates that C. parvum oocysts are sensitive to heat and, to some extent, to blast freezing, but are resistant to chlorine. Therefore, the use of chlorine during vegetable processing is not a critical control point for C. parvum oocysts, and the consumption of raw or minimally processed vegetables may constitute a health risk as C. parvum oocysts can still be found viable on ready-to-eat, minimally processed vegetables.     

果蔬汁常压低温浓缩新技术—界面渐进冷冻浓缩

冷冻浓缩是将天然果蔬汁中的部分水阈结成冰并将其分离去除,以得到高品质的浓缩汁或成品果蔬汁的收缩方法。界面渐进冷冻浓缩法与传统的悬浮结晶冷冻浓缩技术相比,是一种投资少,成本及能耗低的冷冻浓缩新技术,适合于果蔬汁浓缩工序采用。天然番茄汁通过界面渐进冻结可浓缩至40．8％。对浓缩汁稀释还原后的测试结果表明,除离子浓度外,酸度,维生系C及色度等与原汁相比几乎无可见差异。     

热协同超高压加工的鲜榨桃汁在贮藏过程中的稳定性变化

通过HPLC等方法分析用热协同超高压加工的鲜榨桃汁中酚类和Vc等物质在贮藏中的变化,发现果汁在贮藏中发生的非酶褐变主要是由酚类的氧化聚合而引起,可通过低温贮藏加以控制.聚原花色素、表儿茶素、绿原酸和Vc的损失以及果汁的褐变随贮藏时间的延长和温度的升高而加剧.果汁颜色变化先快后慢,L*值降低,a*值升高,b*值变化较小.氨基酸也参与了褐变反应,但Maillard反应不显著.缩合单宁的平均聚合度随贮藏时间的延长和温度的升高而变大.粒径分析表明贮藏过程中有新的颗粒产生.     

大蒜清汁加工中脱臭澄清净化技术研究

以大蒜为原料探究大蒜清汁的加工工艺,并对大蒜的脱臭温度、护色VC用量、果胶酶酶解条件及冷冻澄清进行研究,确定了合理的加工工艺和最佳参数.结果表明,大蒜清汁制取最佳工艺参数为：加热脱臭温度70℃,护色vC用量0.03％,酶解pH 4.62,酶解温度50℃,酶解时间45min.在此条件下得到的大蒜清汁澄清度最高.同时冷冻澄清（-18℃）的方法得到的大蒜出汁率最高,澄清稳定性最好.     

蔬菜汁生产中的质量问题及解决方法

综述了蔬菜汁在加工贮藏过程中容易发生的五大质量问题,即澄清菜汗的后混浊、带肉菜汗的分层及沉淀,颜色的变化、菜汁的败坏、营养成分及风味的改变等。分析了产生这些问题的原因,提出了相应的解决办法。     

Bioethanol production from sugar beet molasses and thick juice by free and immobilised Saccharomyces cerevisiae

The aim of this study was the investigation and comparison of the potential of sugar beet molasses and thick juice as raw materials for bioethanol production, as renewable and sustainable energy sources. Ethanol fermentation of a wide range of initial sugar concentrations (100–300 g/L) was performed using either free or immobilised Saccharomyces cerevisiae in calcium alginate beads in the absence of any added nutrients. In general, immobilised cells showed better fermentative performance, enhanced ethanol productivity, stability and cell viability compared with free cells, under the same fermentation conditions. The high concentration of non‐sugar components contained in molasses affected yeast fermentation performance and viability. Maximum ethanol concentration in fermented media of 84.6 and 109.5 g/L were obtained by immobilised cells for initial sugar concentrations of 200 and 250 g/L for molasses and thick juice, respectively. However, the highest ethanol yields of 31.7 L per 100 kg of molasses and 37.6 L per 100 kg of thick juice were obtained by immobilised cells at an initial sugar concentration of 175 g/L. In the high gravity fermentation process, thick juice resulted in a higher ethanol yield per mass of raw material compared with molasses. This study shows the advantage of immobilised yeast for the efficient production of high gravity bioethanol from thick juice, which was a more favourable raw material than molasses. © 2018 The Institute of Brewing & Distilling     

Survival of Brevibacterium linens (ATCC 9174) after Spray Drying, Freeze Drying, or Freezing

The objectives of this work were to: (1) contrast spray drying, freeze drying and freezing for large-scale preservation of B. linens, (2) determine the thermal resistance curves, and (3) measure the storage stability. When B. linens was freeze-dried and frozen in feed suspensions containing 3% (w/v) cell paste and 25% (w/w) total solids, survival was 100%. During spray drying, lethal thermal injury was the main cause of loss of viability. Accordingly, by extrapolation, 100% viability would be possible at an outlet-air temperature of 57°C. Spray-dried and freeze-dried cells were stable during storage at 4°C in the absence of oxygen and moisture.     

纳豆发酵及后处理生产工艺对纳豆激酶活性的影响

跟踪了纳豆发酵过程中纳豆激酶的变化.考察了纳豆冻干粉在模拟胃肠环境、冷冻干燥以及破碎过程中的酶活损失情况,为纳豆胶囊生产过程中工艺确立、剂型选择和食用方法提供了技术基础.