Medium Evaluation and Plastic Composite Support Ingredient Selection for Biofilm Formation and Succinic Acid Production by Actinobacillus succinogenes

Succinic acid production medium for Actinobacillus succinogenes was simplified. Vitamins and fatty acids were removed from the medium and industrial quality yeast extract was substituted to yield revised succinic acid medium. Customized plastic composite support (PCS) blends were screened for biofilm and succinic acid production. Twenty different PCS blends with and without mineral salt additions were evaluated in twenty simulated repeated-batch fermentations using MgCO₃ for pH control and CO₂ supply. Succinic acid concentrations, percentage yield succinic acid, and biofilm formation for each PCS blend were determined. No correlation was observed for biofilm formation and succinic acid production. The selected customized PCS blend for A. succinogenes succinic acid production consisted of 50% (wt/wt) polypropylene, 35% (wt/wt) dried ground soybean hulls, 5% (wt/wt) dried bovine albumin, 2.5% (wt/wt) soybean flour, 2.5% (wt/wt) yeast extract, 2.5% (wt/wt) dried red blood cells, and 2.5% (wt/wt) peptone, which demonstrated 70% yields for succinic acid compared to 64% yield for suspended cell fermentation.     

Medium Evaluation and Plastic Composite Support Ingredient Selection for Biofilm Formation and Succinic Acid Production by Actinobacillus succinogenes

Succinic acid production medium for Actinobacillus succinogenes was simplified. Vitamins and fatty acids were removed from the medium and industrial quality yeast extract was substituted to yield revised succinic acid medium. Customized plastic composite support (PCS) blends were screened for biofilm and succinic acid production. Twenty different PCS blends with and without mineral salt additions were evaluated in twenty simulated repeated-batch fermentations using MgCO₃ for pH control and CO₂ supply. Succinic acid concentrations, percentage yield succinic acid, and biofilm formation for each PCS blend were determined. No correlation was observed for biofilm formation and succinic acid production. The selected customized PCS blend for A. succinogenes succinic acid production consisted of 50% (wt/wt) polypropylene, 35% (wt/wt) dried ground soybean hulls, 5% (wt/wt) dried bovine albumin, 2.5% (wt/wt) soybean flour, 2.5% (wt/wt) yeast extract, 2.5% (wt/wt) dried red blood cells, and 2.5% (wt/wt) peptone, which demonstrated 70% yields for succinic acid compared to 64% yield for suspended cell fermentation.     

The effect of exogenous enzymes and mechanical treatment on mango purée: Microscopic,mesoscopic, and macroscopic evaluation

This paper addresses to what extent mango purée macroscopic properties (consistency) is related to its particle physical properties such as mesoscopic (particle size) and microscopic (morphology) properties. To manipulate mango purée particle sizes, high pressure homogenization (HPH) was used. Commercial fungal and bacterial (cell wall) polysaccharide degrading enzymes without/with HPH (different sequences) were used to understand the contribution of specific (cell wall) polysaccharides and the relevant parameters to consistency changes. The results reflect that, unlike endo-cellulase, pectin methylesterase (PME) together with endo-polygalacturonase (PG), and α-amylase significantly contributed to consistency decrease. HPH only, although largely changing the particle size, did not change the purée consistency, but the combination of HPH with an enzymatic treatment decreased it substantially. Enzymes, while having minimal effect on particle sizes, induced a type-dependent modification of particles’ morphology, showing the accessibility of particle polymers (in addition to the expected serum polymers) to enzymes.Industrial relevanceHigh consistency of mango purée that limits its processing is industrially decreased by dilution with water, requiring further flavor reconstitution and sugar addition. The consistency is believed to be related to pectin and starch. As physical and enzymatic pectin modifications are allowed by regulatory authorities, our study aimed at better understanding and controlling the flow properties of mango purée by both physical (high pressure homogenization) and enzymatic polysaccharides manipulations. Our findings highlight that in situ polysaccharide functionalization could be an industrially relevant alternative to commonly used additives in food systems for controlling the sensorial (i.e. taste and texture) properties.     

Tribo-rheological properties of acid milk gels with different types of gelatin: Effect of concentration

We investigated the effect of low concentrations (0.1 to 1%, wt/wt) of gelatin (types A and B) on the properties of acid milk gels in terms of rheology, tribology, texture, and water-holding capacity to better understand the role of gelatin in yogurt. The 2 types of gelatin showed similar effects on the properties of milk gels, with some minor differences, such as lubrication behavior at low concentrations. During acidification, gelatin at ≤0.4% caused an increase in the gel strength, and at higher concentrations it showed a negative effect. However, during cooling and annealing, we observed a positive effect on gel strength with 0.8 and 1% gelatin. Gelling and melting occurred at 0.8 and 1% concentrations of both types of gelatin. The addition of gelatin tended to decrease the storage modulus of milk gels and increase the apparent viscosity, pseudoplasticity, consistency, and yield stress. The firmness of the gels was decreased by gelatin at medium concentrations, but increased at high concentrations. Gelatin significantly enhanced the water-holding capacity of the gels; we observed no serum at concentrations ≥0.4%. With the addition of gelatin at concentrations ≥0.4%, the particle size of gels was greatly reduced, and their lubrication properties were significantly improved. This study showed that 0.4% was an effective concentration in acid milk gel; above this concentration, the properties of the milk gels were greatly changed. Tribology provided important information for understanding the role of gelatin in milk gels.     

Addition of sodium caseinate to skim milk increases nonsedimentable casein and causes significant changes in rennet-induced gelation,heat stability,and ethanol stability

The protein content of skim milk was increased from 3.3 to 4.1% (wt/wt) by the addition of a blend of skim milk powder and sodium caseinate (NaCas), in which the weight ratio of skim milk powder to NaCas was varied from 0.8:0.0 to 0.0:0.8. Addition of NaCas increased the levels of nonsedimentable casein (from ～6 to 18% of total casein) and calcium (from ～36 to 43% of total calcium) and reduced the turbidity of the fortified milk, to a degree depending on level of NaCas added. Rennet gelation was adversely affected by the addition of NaCas at 0.2% (wt/wt) and completely inhibited at NaCas ≥0.4% (wt/wt). Rennet-induced hydrolysis was not affected by added NaCas. The proportion of total casein that was nonsedimentable on centrifugation (3,000 × g, 1 h, 25°C) of the rennet-treated milk after incubation for 1 h at 31°C increased significantly on addition of NaCas at ≥0.4% (wt/wt). Heat stability in the pH range 6.7 to 7.2 and ethanol stability at pH 6.4 were enhanced by the addition of NaCas. It is suggested that the negative effect of NaCas on rennet gelation is due to the increase in nonsedimentable casein, which upon hydrolysis by chymosin forms into small nonsedimentable particles that physically come between, and impede the aggregation of, rennet-altered para-casein micelles, and thereby inhibit the development of a gel network.     

Physicochemical Properties of Starch of Intermediate-Amylose and Waxy Rices Differing in Grain Quality

Starches from two crops of 7 intermediate-amylose and 7 waxy milled rices differing in eating qualities were characterized. Among the nonwaxy rice starches, those of softer cooked rice had gelatinization temperature of ≥ 70°C, medium to soft gel (110 mg/2 ml) consistency, low alkali viscograph peak viscosity, and greater Amylograph breakdown and lower Amylograph setback and consistency than low gelatinization temperature starches. Among waxy starches, gels of low gelatinization temperature samples had greater freeze-thaw stability than gels of high gelatinization temperature samples. A 12% paste gave better differentiation in Amylograph viscosity than 10% paste of intermediate-amylose milled rice. Water-extractable substances that suppressed the Amylograph viscosity of milled waxy rices were lipids and polysaccharides.     

Effect of whey protein concentrate addition on the physical properties of homogenized sweetened dairy creams

The influence on their whipping properties of homogenization at first and second stage pressures of 3.5/1.5 MPa and addition of whey protein concentrate (WPC) powder at three different (0.7, 1.4, and 2.1 wt percentage) concentrations to sweetened and homogenized creams was studied. Homogenization of cream significantly decreased maximum overrun and made the foam microstructure less open, while increasing whipping time, cream and foam lightness (Hunter L -value) and apparent viscosity. It also resulted in a less elastic foam structure with an increased drainage. Addition of WPC decreased the amount of maximum overrun, foam drainage and its lightness in parallel with developing a more compact microstructure. It increased the whipping time, apparent viscosity of unwhipped creams and foams, and resulted in a less elastic foam structure. The apparent viscosity of whipped cream with 2.1 wt percentage WPC, however, was lower than that of whipped cream with 1.4 wt percentage WPC, due most probably to the start up of gel formation at 2.1% WPC concentration in sweetened cream when it was sheared. Fresh foam whipped from sweetened cream with 2.1 wt percentage WPC also tended to have a slightly but not statistically significant lower elastic modulus (G') than fresh foam whipped from sweetened cream with 1.4 wt percentage WPC. This concentration can be considered as the critical value for gel formation in sweetened creams enriched by whey proteins when sheared. This study indicated the potential of WPC powder for reducing foam drainage from whipped homogenized sweetened cream.     

Competitive Adsorption Between Sodium Caseinate and Oil-Soluble and Water-Soluble Surfactants in Oil-in-Water Emulsions

Competitive adsorption between sodium caseinate and either a water-soluble surfactant, Tween 60 (polyoxyethylene sorbitan monostearate—PSM) or an oil-soluble surfactant, Span 60 (sorbitan monostearate—SM) was studied in oil-in-water emulsions. Surfactants were present during homogenization. Surface concentration of protein in freshly prepared emulsions decreased as concentration of PSM or SM increased. However, only partial displacement of protein was observed with either surfactant. The reduction in protein surface concentration was greater in the presence of PSM. Interfacial protein composition was independent of surfactant type. In the absence of surfactant, preferential adsorption of β-casein occured in emulsions containing ≤1.0 wt % protein. On addition of surfactant preference for β-casein at the interface was reduced.     

Comparison of polysaccharide degradations by dynamic high-pressure homogenization

The mechanical degradation of polysaccharides was investigated using dynamic high and ultra-high-pressure homogenization (HPH). The objectives were to reduce the molar mass of polymer chains, and simultaneously, the apparent and intrinsic viscosity of polysaccharides in solution. The influence of homogenization pressure (up to 200 MPa) and cycles was compared on polysaccharides with different physical and structure properties: namely, guar gum, hydroxyethylcellulose (HEC), sodium carboxymethylcellulose (Na-CMC), sodium alginate (Na-alginate) and gum arabic. HPH was applied on semi-dilute solutions. The apparent changes in molar mass, gyration radius and intrinsic viscosity were deduced from size exclusion chromatography coupled on-line with multi-angle laser light scattering, differential viscometer detector and differential refractive index detector (SEC/MALS/DV/DRI), while the evolution of the critical overlap concentration (C^∗) was obtained by viscosimetry. A method based on a succession of homogenization cycles and polymer pre-concentration steps was developed to determine the minimum molar mass achieved at constant pressure. Molar mass, and intrinsic viscosity were shown to fall simultaneously while logically C^∗ increased during HPH for all polysaccharides, except gum arabic, probably because of its globular and branched structure. This highlights that the differences of polysaccharide structures and conformation (linear, branched…) exhibit a stronger impact on HPH treatments than polymer charge or molar mass. Finally, via an empirical approach linking the decrease of both molar masses and viscosities, we have evidenced a specific scaling exponent that should characterize the flexibility of the treated polymer (i.e. its ability to be degraded by HPH).     

Evaluation of tilapia skin gelatin as a mammalian gelatin replacer in acid milk gels and low-fat stirred yogurt

Tilapia skin gelatin (TSG) was studied in a 3-stage process (cooling, annealing, and heating) for pure gelatin gels and in a 4-stage process (acidification, cooling, annealing, and heating) for acid milk gels and cultured yogurt. The aim was to evaluate the use of TSG as a replacement for mammalian gelatin in yogurt. In pure TSG gels, stronger gels with higher melting temperatures were formed with increasing TSG concentrations. Compared with bovine gelatin (BG), which gelled at a concentration of 2.5%, TSG gels had lower gelling (14.1°C) and melting (24°C) temperatures but comparable storage moduli during annealing. In acid milk gels, addition of TSG increased the firmness of the gels with increasing concentration. Gelling and melting points of TSG in milk gels were observed at sufficient concentrations during cooling and heating. Strands and sheets were observed in the electron micrographs of milk gels with 1% TSG and a very dense structure was observed with 2.5% TSG. Yogurt with 0.4% TSG had similar viscosity, consistency, pseudoplasticity, and thixotropy as yogurt containing 0.4% BG; no difference was perceived by sensory panelists according to a triangle test. Addition of 0.4% TSG completely prevented whey separation from the acid milk gel and yogurt. The results suggest that TSG could be a suitable replacement for mammalian gelatin in low-fat stirred yogurt.     

虫草花多糖提取工艺优化及其抗氧化特性

采用超声辅助法提取虫草花多糖,在单因素试验的基础上,通过L9（34）正交试验优化了虫草花多糖提取工艺;并就虫草花多糖对羟基自由基（·OH）、1,1-苯基-2-苦肼基（DPPH）自由基的清除作用和还原能力进行研究。结果表明：虫草花多糖最佳提取工艺条件为超声功率300 W,液料比30∶1（mL∶g）,超声时间30 min,超声温度45 ℃。在此优化条件下,多糖的平均提取率为3.88%。抗氧化活性试验结果表明,虫草花多糖质量浓度在2.9～14.7 mg/L范围内,随着虫草花多糖质量浓度的增加,其OH、DPPH自由基清除能力及还原能力均逐渐增强,虫草花多糖质量浓度为14.7 mg/L时,对·OH和DPPH·清除率分别达到44.39%和56.34%,说明虫草花多糖具有较强的抗氧化活性。     

Inulin-enriched dairy desserts: Physicochemical and sensory aspects

The aim of this work was to study how adding inulin of different average chain lengths (long-chain, native, and short-chain inulin) at a concentration of 7.5% (wt/wt) would affect the physicochemical and sensory characteristics of starch-based dairy desserts formulated with either skim or whole milk. The results have shown that the effect of adding 7.5% inulin of different average chain length can give rise to products with different rheological behavior and different sensory characteristics. The skim milk sample with long-chain inulin and the whole milk sample without inulin showed similar flow behavior. Both samples were perceived to have the same creaminess and consistency intensity, but addition of long-chain inulin increased roughness intensity and, consequently, the sensory quality could be negatively affected. The information obtained may be of great interest in designing new products with nutritional and sensory characteristics that meet consumer demands.     

一步法制备羧甲基灵芝多糖

通过半合成羧甲基灵芝多糖,以达到充分利用灵芝和提高灵芝多糖得率的目的.利用贝利微粉机获得灵芝超微粉;在乙醇-水溶液中一步法半合成羧甲基灵芝多糖,采用铜盐沉淀法测定其取代度.通过FTIR鉴定了羧甲基灵芝多糖的结构;筛选出制备羧甲基灵芝多糖的最佳条件:乙醇浓度80 %,NaOH浓度2.5 mol/L,氯乙酸浓度1.55 m...     

Microstructure and textural and viscoelastic properties of model processed cheese with different dry matter and fat in dry matter content

The aim of this work was to examine the effect of a different dry matter (DM) contents (35 and 45% wt/wt) and fat in DM contents (40 and 50% wt/wt) on the textural and viscoelastic properties and microstructure of model processed cheeses made from real ingredients regularly used in the dairy industry. A constant DM content and constant fat in DM content were kept throughout the whole study. Apart from the basic chemical parameters, textural and viscoelastic properties of the model samples were measured and scanning electron microscopy was carried out. With increasing DM content, the rigidity of the products increased and the size of the fat globules in the model samples of the processed cheeses decreased. With increasing fat in DM content, the rigidity of the processed cheeses decreased and the size of the fat globules increased.     

Effect of non-starch polysaccharides on the in vitro digestibility and rheological properties of rice starch gel

The starch digestibility and rheological properties of gels were evaluated in the presence of three non-starch polysaccharides (agar, xanthan gum and konjac glucomannan) with rice starch. Each polysaccharide was added to 30% (w/w) rice starch suspension at defined concentrations and starch gels were prepared. The extent of starch gel digestibility was determined by an in vitro method and rheological properties by a dynamic oscillatory test and a compression test. The added polysaccharides suppressed starch hydrolysis in the gels compared with the control, and a concentration dependency of this suppressive effect was observed. Adding agar and xanthan gum increased the storage shear modulus (G′) of starch gels, while adding konjac glucomannan decreased G′ values. The results indicate that the suppressive effect of non-starch polysaccharides on starch digestibility appears to be not only due to the rigidity of the gel, but also the interaction between starch and non-starch polysaccharides.     

Effect of feed restriction on reproductive and metabolic hormones in dairy cows

The objective of this trial was to evaluate the effects of feed restriction (FR) on serum glucose, nonesterified fatty acids, progesterone (P4), insulin, and milk production in dairy cows. Eight multiparous Holstein cows, 114 ± 14 d pregnant and 685 ± 39 kg of body weight, were randomly assigned to a replicated 4 × 4 Latin square design with 14-d periods. During the first 8 d of each period, cows in all treatments were fed for ad libitum feed intake. Beginning on d 9 of each period, cows received 1 of 4 treatments: ad libitum (AL), 25% feed restriction (25FR), 50% feed restriction (50FR), and 50% of TMR replaced with wheat straw (50ST). Daily feed allowance was divided into 3 equal portions allocated every 8 h with jugular blood samples collected immediately before each feeding through d 14. In addition, on d 12 of each period, blood samples were collected before and at 60, 120, 180, 240, 300, 360, 420, and 480 min after morning feeding. The conventional total mixed ration and total mixed ration with straw averaged 15.1 and 10.8%, 32.1 and 50.5%, and 26.8 and 17.0% for concentrations of crude protein, neutral detergent fiber, and starch, respectively. Cows that were feed and energy restricted had reduced dry matter intake, net energy for lactation intake, circulating glucose concentrations, and milk production, but greater body weight and body condition score losses than AL cows. Circulating concentrations of insulin were lower for cows fed 50FR (8.27 μIU/mL) and 50ST (6.24 μIU/mL) compared with cows fed AL (16.65 μIU/mL) and 25FR (11.16 μIU/mL). Furthermore, the greatest plasma nonesterified fatty acids concentration was observed for 50ST (647.7 μEq/L), followed by 50FR (357.5 μEq/L), 25FR (225.3 μEq/L), and AL (156.3 μEq/L). In addition, serum P4 concentration was lower for cows fed AL than cows fed 50ST and 25FR. Thus, FR reduced circulating glucose and insulin but increased P4 concentration, changes that may be positive in reproductive management programs.     

玉米淀粉-玉木耳多糖复配体系理化及结构性质

选用不同添加量的玉木耳多糖,制备玉米淀粉-玉木耳多糖复配体系,并对其理化及结构性质进行研究。结果表明：与玉米淀粉相比,复配体系的峰值黏度增大和峰值时间延长,崩解值及回生值降低;峰值温度TP显著增加,热焓值ΔH降低,表明添加玉木耳多糖使体系具有较好的稳定性和抗老化性,且随着多糖添加量增加,效果更加显著。添加玉木耳多糖后,体系稠度系数K增大,流体指数n降低,假塑性增强且更易剪切稀化,储能模量和损耗模量增加,其中添加0.5%玉木耳多糖时体系的储能模量最大。扫描电子显微镜观察表明,玉木耳多糖使体系内部孔隙变小,添加0.5%和1.0%玉木耳多糖的复配体系具有更加均匀、致密的凝胶结构。红外光谱分析可知,体系未形成新的基团,当添加0.5%玉木耳多糖时,淀粉结构的有序程度升高,添加1.0%、2.0%、5.0%和10.0%玉木耳多糖时,淀粉结构的有序程度下降。本研究可为玉木耳多糖在淀粉基食品中的应用提供一定参考。