乳酸菌代谢低聚果糖/菊粉途径及机理的研究进展

合生元又称合生素,指益生元与益生菌结合使用的生物制剂（微生态制剂）,近年来,越来越多研究表明合生元具有多种益处,益生元和益生菌的选择对其最终效果起着至关重要的作用。低聚果糖和菊粉是合生元中常见的益生元,可被肠道内的乳酸菌选择性吸收,通过促进益生菌增殖的方式来改善机体健康。本文综述了乳酸菌对低聚果糖和菊粉的代谢差异及代谢途径,并从分子水平阐述水解酶、转运系统、调控蛋白的作用机制,以期为探明乳酸菌调控低聚果糖和菊粉的代谢网络提供依据;同时总结了近年来低聚果糖/菊粉合生元的应用,为益生元与益生菌的进一步联用提供参考。     

添加益生元对酸乳凝胶过程及微观结构的影响

为研究菊粉、低聚果糖和低聚半乳糖3 种益生元对酸乳凝胶过程及微观结构的影响,以未添加益生元的酸乳为对照,利用光学微流变仪、Turbiscan稳定分析仪和扫描电子显微镜分别检测添加益生元酸乳在发酵期间及后熟贮藏期间流变学参数、稳定性和微观结构,并进行对比研究。结果表明：添加菊粉更有助于酸乳形成较为均匀、疏松的微观结构;含低聚果糖的酸乳固液平衡值低于0.5,更有利于增强酸乳的固体性质;添加低聚半乳糖的酸乳微观稳定性较好。因此,3 种益生元对酸乳的凝胶过程及微观结构的影响各不相同,未来还可对3 种益生元进行复配处理,添加到酸乳中进一步探究对其综合品质的影响。     

添加益生元对复合益生菌枸杞酸奶发酵的影响

研究了木糖醇、菊粉、低聚果糖、低聚异麦芽糖和蔗糖的混合对复合益生菌枸杞酸奶发酵的影响,实验测试了复合益生菌枸杞酸奶的产酸速率、质构、感官、p H值、益生菌菌落数等指标。结果表明:4种益生元成分均对复合益生菌枸杞酸奶的发酵有促进作用,其中6%低聚果糖添加后对益生菌增殖效果最佳,产酸速率最快,发酵出的酸奶口感、质地也较为理想。     

天然菊粉对鸡肉肌原纤维蛋白凝胶特性的影响

为改善鸡肉肌原纤维蛋白凝胶性能,研究了不同添加量天然菊粉对蛋白凝胶色度、质构、保水性、蒸煮得率、流变特性及微观结构的影响。结果表明,随菊粉添加量的增加,蛋白凝胶L~*值下降,a~*值、b~*值上升。菊粉添加量为2.5%时,蒸煮得率与保水性均达到最大值,分别为81.84%与87.98%;此时质构特性最好,硬度为453 g、弹性为0.956、恢复性为0.450。流变测定结果表明,菊粉能够提高凝胶的形成能力,G′的初始值和终值都随菊粉添加量的增加而升高。添加2.5%菊粉的蛋白凝胶具有紧密有序的微观结构。添加适量的天然菊粉,可明显改善鸡肉肌原纤维蛋白凝胶品质。     

魔芋甘露寡糖对酸奶免疫调节活性的影响

益生元用于发酵乳制品可改善其质构特性和感官品质,同时强化其健康功效。本研究采用环磷酰胺（cyclophosphomide,CTX）诱导BALB/C小鼠建立免疫抑制模型,评价功能性低聚糖类益生元——魔芋甘露寡糖（konjac mannanoligosaccharides,KMOS）的添加对于酸奶免疫调节活性的影响。结果表明,KMOS可强化酸奶对于CTX诱导小鼠免疫抑制的改善作用。KMOS添加量为0.5%（以鲜牛乳质量计）时酸奶对免疫抑制小鼠基本生理状态、腹腔巨噬细胞吞噬活性、脾淋巴细胞增殖率、血清中免疫球蛋白质量浓度以及腹腔巨噬细胞炎症因子的释放等均有显著改善作用,且添加KMOS的酸奶可提高免疫抑制小鼠肠道中非优势菌群的相对丰度,抑制梭菌属的增殖并增加有益菌数量,从而调节免疫抑制小鼠肠道菌群结构及组成。本研究可为基于功能性低聚糖的新型发酵乳制品开发提供借鉴。     

菊粉对绿豆蛋白低脂植物酸奶品质的影响

本研究考察菊粉作为脂肪替代物对绿豆蛋白低脂植物酸奶品质的影响。以添加3%葵花籽油的绿豆蛋白酸奶作为高脂酸奶对照,通过分析不同浓度的菊粉（2%、4%、6%）对绿豆蛋白低脂酸奶（1%葵花籽油）的粘弹性、质构、持水力、微观结构及感官品质的影响,评价菊粉的代脂效果。结果表明,与对照绿豆蛋白高脂酸奶相比,添加2%菊粉的绿豆蛋白低脂植物酸奶的粘弹性、硬度、咀嚼性、持水力和感官品质与绿豆蛋白高脂酸奶相当（P>0.05）,表现出均匀致密的蛋白质网络结构。添加4%菊粉的绿豆蛋白低脂酸奶的硬度和咀嚼性分别显著提高了21.56%和32.34%（P<0.05）,持水能力达到88.55%。此时,绿豆蛋白低脂酸奶也表现出致密的网络结构,整体的感官品质最佳。添加6%菊粉的绿豆蛋白低脂酸奶的粘弹性、硬度、咀嚼性和持水力显著高于绿豆蛋白高脂酸奶（P<0.05）,但是其微观结构表现出多孔以及不均匀的蛋白质网络结构,质地和口感变差,总体感官品质最差。因此,添加2%~4%的菊粉能够显著提升绿豆蛋白低脂酸奶的品质,具有较好的脂肪替代效果。本研究结果为研发高品质的绿豆蛋白低脂酸奶提供理论依据。     

菊粉对低糖低脂酸奶品质的影响

菊粉是一类天然果聚糖的混合物,具有膳食纤维和益生元的双重功效。实验以脱脂奶粉为原料,以木糖醇为甜味剂,通过添加不同量的菊粉加工凝固型酸奶,研究菊粉的添加量对酸奶发酵的速度、产酸量及产品的持水性、质构和感官品质的影响。结果表明,随着菊粉添加量的增加,各项指标都有明显改善,添加的质量分数为2%~4%时,产品的品质最好。因此最终确定低糖低脂酸奶加工的工艺参数为:木糖醇7%、发酵剂菌粉1g/L、发酵时间4~4.5h、菊粉添加的质量分数为2%~4%。     

干酪乳杆菌纯种发酵水苏糖合生元酸奶的菌种筛选与工艺

针对目前我国合生元功能性乳制品研发水平低,大多采用益生菌与传统酸奶菌混种发酵的现状,以分离自天然发酵食品、保健品和微生物制剂等的18株新型益生菌和3种商品化发酵剂中所含益生菌为试验菌株,以传统酸奶发酵菌株保加利亚乳杆菌和嗜热链球菌为对照菌株,研究菌株发酵牛乳的凝乳时间、产酸能力、感官品质,分析菌株利用水苏糖的增殖效果,筛选能利用水苏糖作为益生元生产合生元酸奶的益生菌菌株;测定了菌株在纯牛乳基础培养基中的生长曲线;研究了益生元增殖培养基中水苏糖的最适添加量;优化了水苏糖合生元酸奶产品的发酵工艺条件;检测了0 d和贮藏21 d合生元酸奶产品的质量。结果表明：新型益生菌干酪乳杆菌07-211具有发酵牛乳的能力,可利用水苏糖进行显著增殖,活菌数由3.19×108 CFU/mL增至2.05×109 CFU/mL;益生元增殖培养基中水苏糖的最适添加量为0.8%;干酪乳杆菌07-211纯种发酵水苏糖合生元酸奶的最佳工艺条件是：接种量3%,蔗糖添加量4%,发酵温度42 ℃,合生元酸奶凝乳时间4.15 h,pH 4.65,滴定酸度64.27 °T,活菌数3.96×109 CFU/mL,感官品评得分8.78分（10分制）。其中,0 d和贮藏21 d的合生元酸奶的质量均优于国标。本研究结果为工业化生产干酪乳杆菌纯种发酵水苏糖合生元酸奶产品提供理论依据,也为其它功能性合生元乳制品的研发提供借鉴。     

菊粉对切达干酪品质的影响

菊粉是一种天然的脂肪替代物,且具有一定的益生作用。通过向标准化后的原料乳中添加不同质量比(w/w)的菊粉,研究菊粉对切达干酪理化特性、活菌数量、质构和感官评定的影响。结果表明,9%菊粉能够显著地提高切达干酪的水分含量(p0.05),并能够改善切达干酪的质构特性,从而得到低脂肪含量的软质切达干酪。研究结果为新型切达干酪的开发提供了新思路。     

不同益生元对酸奶游离氨基酸及风味的影响

为研究添加不同益生元发酵对酸奶游离氨基酸及风味的影响,以用低聚木糖、低聚异麦芽糖、低聚半乳糖、蔗糖发酵的酸奶为研究对象,在利用乳品综合成分指标分析仪检测蛋白质含量、脂肪含量、非脂乳固体含量等基本营养成分的基础上,利用电子舌技术、高效液相色谱-质谱联用技术对游离氨基酸进行检测,并结合味道强度值、主成分分析法、相关性分析、氨基酸评分进行综合评价。结果表明,添加不同益生元酸奶的蛋白质、脂肪、总固形物、非脂乳固体含量均符合国家标准;各组分间除酸味外,其他风味差异较小,酸味大小依次为:低聚木糖低聚半乳糖低聚异麦芽糖对照组;添加益生元发酵酸奶中共检测出17种游离氨基酸,添加低聚木糖酸奶中总游离氨基酸含量为119.31 mg/g,显著高于其他益生元添加组及对照组,且对照组中总游离氨基酸含量为112.49 mg/g,显著高于低聚半乳糖中的79.48 mg/g,但与低聚异麦芽糖中的108.93 mg/g差异不大;低聚木糖组甜味、鲜味、苦味氨基酸含量显著高于对照组及其他实验组,对照组甜味与苦味氨基酸含量高于低聚异麦芽糖及低聚半乳糖组,低聚半乳糖组各呈味氨基酸含量均最低;各组分氨基酸模式评分值大多数高于氨基酸模式标准值。综合来看,并非全部益生元均会对酸奶发酵产生正向影响,添加低聚木糖酸奶中游离氨基酸含量最高且风味较好。这为益生元酸奶的工业生产过程中基本营养成分及风味调控提供参考。     

Effects of the addition of microencapsulated Bifidobacterium BB-12 on the properties of frozen yogurt

Samples of frozen yogurt were added with microcapsules containing Bifidobacterium BB-12 produced with different contents of carrier agents (reconstituted skim milk and inulin). The viability of this probiotic culture was evaluated, as well as the effect of addition of microcapsules on the chemical and rheological properties of frozen yogurt during 90 days of storage. The counts of bifidobacteria maintained practically constant in the samples added with the microcapsules, while the frozen yogurt added with free bacteria showed a decrease of about 34% after 90 days. The addition of the microcapsules increased the total solids content and the overrun values. The highest pH values were noted in the samples containing microcapsules produced with reconstituted skim milk. All the melted frozen yogurts showed non-Newtonian behavior with shear thinning characteristics. The samples added with microcapsules had greater apparent viscosity and those added with microcapsules produced with inulin showed a larger hysteresis area at the end of storage period.     

Application of Response Surface Methodology to Improve Fermentation Time and Rheological Properties of Probiotic Yogurt Containing Lactobacillus reuteri

Response surface methodology was employed to investigate the combined effects of inulin addition (0–4% w/w), probiotic inoculum level (1–3% v/v), and fermentation temperature (37–45 °C) on fermentation time and rheological properties of nonfat-set yogurt. The rheological characteristics were measured by dynamic oscillatory rheometery. The second-order polynomial model was fitted to the fermentation time (T _f), structure strength (A value), resistance to mechanical force or yield stress (τ _y), and complex viscosity (ŋ*) of runs as the responses. Analysis of variance revealed that the quadratic models are well adjusted to predict the experimental data. Lack-of-fit tests were not significant and determination coefficients (R ²) were higher than 88.6%. The results showed that fermentation time decreased with increasing inulin content, incubation temperature, and probiotic inoculum level. Rheological properties significantly influenced by independent variables. Inulin addition had a softening effect on yogurt. However, the effect of incubation temperature on structure strength was positive. Medium levels of probiotic inoculum resulted in stronger gels.     

Characterization of functional, biochemical and textural properties of synbiotic low-fat yogurts during refrigerated storage

This study examined the influence of exopolysaccharides (EPS) produced in situ on the viability of Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus and probiotics, the proteolytic and ACE-inhibitory activities, and textural and rheological properties of inulin-containing probiotic yogurt during refrigerated storage. Two types of yogurt were prepared using strains of S. thermophilus not producing EPS (NEPY) and producing EPS (EPY). The yield of crude EPS increased (by 2.4 times) until day 21 of storage. Presence of EPS showed a protective effect on the survival of L. delbrueckii ssp. bulgaricus and Lactobacillus acidophilus but not on S. thermophilus, Lactobacillus casei and Bifidobacterium longum. No changes in post-acidification, lactic acid content or the ACE-inhibition activity of the two types of yogurt were observed. Overall, EPS containing yogurts exhibited higher proteolysis in the presence of inulin and probiotics (0.698 units) than the corresponding control (0.563 units). The storage and loss moduli (Pa), yield stress (Pa), consistency index (Pa s) and thixotrophic behaviour (Pa s⁻¹) of both samples were similar at day 1 and the influence of EPS was observable only after day 7. Such a variation of the effect of EPS on the textural and rheological properties of low-fat yogurt appears to be partially due to the presence of probiotics.     

脱脂乳的不同热处理工艺对酸奶质构和微观结构的影响

为研究双孢蘑菇粉对酸奶理化性质的影响,以酸奶为原料,探究将不同质量分数（0.0%、1.5%、3.0%、4.5%、6.0%和7.5%）的双孢蘑菇粉（Agaricus bisporus powder,ABP）添加到酸奶中,并对在不同ABP添加量下的酸奶流变学和质构特性进行研究。结果表明：当ABP添加量为1.5%时,酸奶的动态黏弹性、表观黏度、稠度、硬度和内聚性对比对照组均有所降低;而当ABP添加量高于1.5%时,酸奶的动态黏弹性、表观黏度、稠度、硬度和内聚性会随ABP添加量的增加而增大;扫描电镜结果表明,ABP添加量为0.0%和1.5%的酸奶表现为具有较多空隙的酪蛋白纤维状网络结构,并且随着ABP添加量的增加,纤维网络中的空隙逐渐被ABP颗粒所填充,形成致密连续的空间结构,使酸奶的硬度、粘稠度和稳定性得到增强。综合分析可知,当ABP的添加量为1.5%~3.0%时,可使酸奶具有较好的流变性和质构特性。本研究结果为双孢蘑菇风味乳制品的研究和开发提供了理论和数据支持。

     

Production of functional probiotic, prebiotic, and synbiotic ice creams

In this work, 3 types of ice cream were produced: a probiotic ice cream produced by adding potentially probiotic microorganisms such as Lactobacillus casei and Lactobacillus rhamnosus; a prebiotic ice cream produced by adding inulin, a prebiotic substrate; and a synbiotic ice cream produced by adding probiotic microorganisms and inulin in combination. In addition to microbial counts, pH, acidity, and physical and functional properties of the ice creams were evaluated. The experimental ice creams preserved the probiotic bacteria and had counts of viable lactic acid bacteria after frozen storage that met the minimum required to achieve probiotic effects. Moreover, most of the ice creams showed good nutritional and sensory properties, with the best results obtained with Lb. casei and 2.5% inulin.     

酸浆果保健酸乳的质地及理化性质研究

以蛋白质含量、脂肪含量、pH值、持水力、流变学特性和质构特性为主要测定指标,通过单因素试验,研究了酸浆果浆添加量 对酸乳理化及感官性质的影响。结果表明,酸浆果浆添加量的变化对酸乳的理化及感官性质有明显影响;酸浆果浆添加量为10%的 酸乳样品在5组样品中感官评分最高（94.7分）,各项理化指标均符合发酵乳国家标准;酸乳样品的黏聚性和胶着性分别与硬度具有 显著相关性（P＜0.05）;所酿造的酸浆果保健酸奶呈现均匀的橙黄色,组织细腻,具有酸浆果特有的香味,酸甜爽口。     

菊糖酸奶对小鼠免疫器官指数和血清免疫球蛋白的影响

以脾脏指数、胸腺指数、体质量及免疫球蛋白（immunoglobulin,Ig）IgG、IgA、IgM含量为评价指标,研究菊糖酸奶对小鼠免疫器官指数和血清免疫球蛋白的影响。结果表明：菊糖能够刺激酸奶中乳酸菌的增加。与普通酸奶相比,菊糖酸奶能够更好地提高小鼠免疫功能,经相关性分析发现IgG、IgA与酸奶中乳酸菌的含量显著相关。由此可见,菊糖刺激了酸奶中乳酸菌的增加,从而增强了酸奶对机体免疫功能的影响。在菊糖添加量为50 g/L时,菊糖酸奶对小鼠的免疫增强效果最好。