抹茶益生菌有机酸奶的研发及贮存期品质分析

以有机生牛乳和有机白砂糖为主要原料,添加抹茶粉和益生元等配料共同进行发酵,研发抹茶益生菌有机酸奶产品,并对其贮存期品质进行分析。通过单因素试验和正交试验分别考察抹茶粉添加量、菊粉添加量、发酵剂接种量和发酵时间对抹茶益生菌有机酸奶感官品质的影响。结果表明,抹茶益生菌有机酸奶的最优发酵工艺为白砂糖添加量8%、发酵温度42 ℃、发酵时间6 h、抹茶粉添加量0.09%、菊粉添加量1.5%、发酵剂接种量0.01%。在此优化条件下,抹茶益生菌有机酸奶感官评分为97分,酸度为78 °T,产品色泽明亮呈淡绿色、口感细滑、风味浓郁。     

Optimization of Corynebacterium glutamicum Glutamic Acid Production by Response Surface Methodology

Response surface methodology (RSM) was used to evaluate the effects of fermentation parameters for glutamic acid (GA) production by Corynebacterium glutamicum CECT690 in submerged fermentation using palm date waste as substrate. To attain this purpose at the first stage, inoculum size, substrate concentration, penicillin concentration, phosphate concentration, and inoculum age were optimized for GA production. The next stage, the level of air flow rate in a 5-l fermenter (batch mode) which was run in optimized conditions was determined. The first stage gave the following results for the fermentation conditions optimized using RSM in 500-ml shake flasks: inoculum size 2% (v/v), substrate concentration 25% (w/v), penicillin concentration 1 U/ml, phosphate concentration 4 g/l, and inoculum age 10 h. Moreover, the maximum GA amount predicted by the model was 39.32 mg/ml. This was in agreement with the actual experimental value (36.64 mg/ml). In the second stage of the study, the amounts of GA were 118.75, 142.25, and 95.83 mg/ml in optimized conditions with the three levels of air flow rate of 0.6, 1.2, and 1.6 vvm, respectively. The present results demonstrate the potential of date waste juice as a substrate for producing GA by cultivation of C. glutamicum.     

Thermal and rheological properties of the supersaturated sucrose solution in the presence of different molecular weight fractions and concentrations of dextran

In our current research work, we investigated the effects of molecular weight (M _w) and the concentration of dextran presence during cane sugar manufacturing on the rheological and glass transition properties of supersaturated sucrose solution. Three dextrans of various M _w, namely 100,000 g/mol (T ₁₀₀), 500,000 g/mol (T ₅₀₀) and 2,000,000 g/mol (T ₂₀₀₀), were admixed in concentrations between 1,000 and 10,000 ppm with 65 and 75% w/w sucrose solution. The results indicated that both the apparent viscosity and dynamic modulus increased with an increase in dextran concentrations and they demonstrated strong dependence on its M _w. Glass transition temperature (T _g) of the samples was measured by differential scanning calorimetry, and their dependence on dextran M _w and concentration was analyzed by the Fox and expanded Gordon–Taylor mathematical models. It was found that the higher the M _w and concentration of the dextran, the greater the increase in T _g. The expanded Gordon–Taylor equation has proved useful in predicting the T _g of the sucrose solution in the presence of polymer.     

响应面法优化菊糖酸奶的发酵工艺

将菊糖以不同的量添加到酸奶中,结果表明,菊糖能够刺激乳酸菌的增长,增加酸奶的持水力、黏度和甜度,降低酸奶的pH值,以及改变酸奶的组织状态。在接种量和发酵温度的单因素试验基础上,采用响应面分析方法,优化菊糖添加量、接种量、发酵温度的工艺参数。经Design-ExpertV8.0.6 软件对结果进行分析,确定菊糖酸奶生产的最优工艺参数为菊糖添加量47.85 g/L、接种量2.34%、发酵温度42 ℃。在此条件下,菊糖酸奶的感官得分92.12,理论值92.46与实验值的相对偏差是0.37%。     

Supplemental inulin does not enhance iron bioavailability to Caco-2 cells from milk- or soy-based,probiotic-containing,yogurts but incubation at 37 °C does

The in vitro effects of supplemental inulin (4%) on iron (Fe) availability in two different probiotic-containing yogurts were examined. Milk or soy-based yogurts, with and without inulin, were incubated (37 °C) for 48 h or without any incubation before comparison by an in vitro gastrointestinal digestion/Caco-2 cell culture model was used to assess iron bioavailability. The dialysable Fe fraction, cell ferritin formation, and cell associated Fe were monitored. Supplemental inulin decreased dialysable Fe only in non-incubated milk-based yogurt. In both yogurts incubation by itself increased dialysable Fe, and inulin increased the latter only in soy-based yogurt. Cellular ferritin concentration were higher after exposure to non-incubated milk-based than soy-based yogurt, although, after incubation the latter induced the highest ferritin formation. These data suggest that inulin does not have a direct effect on Fe bioavailability in the small intestine, and that probiotic bacteria play an enhancing role on Fe bioavailability.     

Microbiological and physicochemical properties of dry‐cured neck inoculated with probiotic of Bifidobacterium animalis ssp. lactis BB‐12

The effect of inoculum level of Bifidobacterium animalis ssp. lactis BB‐12 probiotic strain and ripening period on the quality of dry‐cured neck was studied. The microbiological parameters (Enterobacteriaceae, LAB and TVC) and physicochemical attributes (pH value, a_w, TBARS index, colour) were determined directly after fermentation at 15 °C for 3 weeks, after 6 and 12 months of ripening at 4 °C. The highest LAB count and a lower pH value were found in the meat inoculated with probiotic strain at 6.6 log cfu g^?1 (B2) followed by inoculation with probiotic strain at 6.3 log cfu g^?1 (B1). Level of inoculation had not had an influence on water activity, TBARS index and total colour parameters. Changes of fat oxidation during half‐year of ripening were limited in probiotic meat samples compared to naturally fermented control meat (C). Based on the results, it can be concluded that the most favourable physicochemical and microbiological parameters of the dry‐cured neck were obtained after 6 months of ripening. At that time, the Bifidobacterium BB‐12 at both levels is a good potential starter for meat fermentation.     

Milk Drink Using Whey Butter Cheese (queijo manteiga) and Acerola Juice as a Potential Source of Vitamin C

The production of a beverage from whey butter cheese (WBC) and acerola juice (AJ) presents good commercialization potential, uniting the benefits provided by the former with those of latter, including the ingestion of essential amino acids and increasing the vitamin C content, resulting in a product of differentiated nutritive value. Three beverage formulations were developed: B₁ (50% WBC–50% AJ v/v), B₂ (70% WBC–30% AJ, v/v), and B₃ (30% WBC–70% AJ, v/v). Lower protein and carbohydrate values were found for the formulations with less whey (p < 0.05). All the beverages presented an energy value below those declared for dairy beverages commercialized on the Brazilian market. The beverages B₁ and B₂ were considered food products that were sources of vitamin C. B₂ presented significant variations for all the sensory attributes evaluated (p < 0.05), although the results were similar to those obtained for B₁, suggesting the commercialization potential of these formulations.     

Hazelnut milk fermentation using probiotic Lactobacillus rhamnosus GG and inulin

Following the consumer demand of healthy vegetable products due to their interesting nutritional profiles and potential functionalities, the fermentation process of hazelnut milk with Lactobacillus rhamnosus GG and S. thermophilus was studied. The effect of different factors (glucose, inulin and inoculum contents) was analysed to ensure sufficient probiotic survivals in a minimum time. The shelf life of the optimised product was characterised in terms of its main physicochemical and quality parameters (probiotic survivals and sensory analysis). Results showed that the defined formulation allowed high probiotic survivals (≈10⁸ cfu mL^?1) throughout cold storage and >60% survived to the in vitro digestion process (≈10⁵ cfu mL^?1). Lactobacillus rhamnosus GG was no able to degrade inulin, which remained to exert health benefits in the host. The product was highly appreciated by the sensory panel during its shelf life despite the formation of a weak gel, which presented syneresis at the last storage time.     

Structural Relaxation of Salmon Gelatin Films in the Glassy State

Mechanical relaxation of glassy carbohydrates has been reported extensively in the literature; however, little work is available on protein-based systems. This study deals with the structural relaxation of salmon (Salmo salar) gelatin in the glassy state. Skin gelatin was obtained by an acid–alkaline extraction method. Molecular weight (M _w) was determined by capillary viscometry. Films prepared by casting (7% w/v) were equilibrated to a moisture content of ~18.4% (db). The glass transition temperature (T _g) and enthalpic relaxation were determined by differential scanning calorimetry (DSC). Mechanical properties were assessed using a texture analyzer at constant temperature and moisture content. DSC showed a T _g ~34°C, and the selected storage temperature (T _a ) was 29°C (T _g − T _a = 5°C). The films were aged for 0, 4, 8, 16, and 40 h. Viscometry produced values of M _w ~90.2 kDa. The stress relaxation was modeled by the Kohlrausch–Wlliams–Watts (KWW) equation, reporting an increase in relaxation time (τ ₀) as the ageing time increased (τ ₀ ~6.41E + 03 s for 0 h; τ ₀ ~9.01E + 05 s for 40 h). β parameter was smaller for the aged films, indicating a spread of relaxation times. The derivative of KWW equation (dφ/dt) indicated a more rapid relaxation in a fresh sample compared with aged films. DSC showed an excess in enthalpy (ΔH) on the aged samples due to the non-equilibrium state of the matrix. ΔH increased with ageing time with values of ΔH ~2.42 J/g for the films aged for 40 h. This work demonstrated molecular relaxation process of gelatin in the glassy state, which must be taken into account if this material is used as a structure forming matrix.     

Steady and dynamic shear rheological properties of sweet potato flour dispersions

Korean sweet potato flour dispersions at different concentrations (6, 7, 8, 9, and 10%) were evaluated for their steady and dynamic shear rheological properties. The steady shear rheological properties showed that sweet potato flour dispersions at 25 °C showed a shear-thinning fluid (n=0.31–0.41) exhibiting a yield stress. The magnitudes of Casson yield stress (σ_oc), consistency index (K) and apparent viscosity (η_a,100) increased with an increase in concentration. Within the temperature range of 25–70 °C, the apparent viscosity obeyed the Arrhenius temperature relationship with high determination coefficient (R ²=0.97–0.99) with activation energies (Ea) ranging 0.015–0.024 KJ/mol. Both power law and exponential type models were used to establish the relationship between concentration and apparent viscosity (η_a). Magnitudes of G′ and G″ increased with an increase in concentration. G′ values were higher than G″ over the most of the frequency range (0.63–63 rad/s), being frequency dependent. The sweet potato flour dispersions did not closely follow the Cox–Merz rule at concentrations lower than 10%.     

EFFECT OF COLD STORAGE ON CULTURE VIABILITY AND SOME RHEOLOGICAL PROPERTIES OF FERMENTED MILK PREPARED WITH YOGURT AND PROBIOTIC BACTERIA

ABSTRACT

We examined the effect of storage time on culture viability and some rheological properties (yield stress, storage modulus, loss modulus, linear viscoelastic region, structural recuperation and firmness) of fermented milk made with Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus acidophilus (LA) and Bifidobacterium animalis ssp. lactis in coculture with Streptococcus thermophilus (ST). Acidification profiles and factors that affect viability (postfermentation acidification, acidity and dissolved oxygen) were also studied during 35 days at 4C. Fermented milk prepared with a coculture of ST and Bifidobacterium lactis gave the most constant rheological behavior and the best cell viability during cold storage; it was superior to ST plus LA for probiotic fermented milk production.

PRACTICAL APPLICATIONS

Probiotic cultures should grow quickly in milk, provide adequate sensory and rheological properties to the product, and remain viable during storage. Commercially, it is very common to use yogurt starter culture (i.e. Streptococcus thermophilus[ST] and Lactobacillus delbrueckii ssp. bulgaricus) in combination with the probiotic bacteria in order to reduce fermentation time. However, LB tends to post acidify fermented milk, which reduces the viability of the probiotic bacteria; thus, it is recommended to use starter cultures devoid of this species. We found that the technological properties and the viability of the probiotic bacterium Bifidobacterium animalis ssp. lactis BL O4 in coculture with ST make it suitable for probiotic fermented milk production; it produces rheological characteristics similar to those of yogurt.     

Modelling of rheological,microbiological and acidification properties of a fermented milk product containing a probiotic strain of Lactobacillus paracasei

The simultaneous effect of fermentation temperature (FT, 36.7–43.4°C), milk total solid level (TS, 11.3–14.7%, w/v) and total inoculum concentration (TI, 2.16–3.84 v/v) on the acidification process and the rheological properties of fermented milk products with Lactobacillus paracasei ssp paracasei B117, Lactobacillus delbrueckii ssp bulgaricus Y 6.15 and Streptococcus thermophilus Y 4.10 was explored by means of response surface methodology. Maximum storage modulus (G′_max), minimum loss tangent (tan δ_min), rate of gelation (I_E) and onset of gelation were the rheological parameters studied. Maximum acidification rate (V_m), time at which maximum acidification rate was observed (T_m), and time to reach the end of fermentation (T_e) characterized the kinetics of acidification, whereas the increase in the number of the three bacteria at the end of fermentation was chosen as the microbiological parameter of the system. The growth/survival of microorganisms and the organic acid profile during cold storage as well as the overall product acceptability by a consumer panel were also assessed. TS strongly affected G′_max and tan δ_min; high TS resulted in large increase in G′_max and decrease in tan δ_min. Increasing fermentation temperature gave a decrease in the onset of gelation, V_m, T_m and T_e, and an increase in the gelation rate (I_E). Under conditions of relatively low FT (37–40°C), high TS (about 14%) and high TI (3–4%), relatively high gelation and low acidification rates were observed, fermentation took a longer time to finish, but the formed gels were firmer, showing higher G′_max and lower tan δ_min values. Low FT (36–38°C) enabled higher increase in the number of L. paracasei B 117. The probiotic strain showed good compatibility with the S. thermophilus Y 4.10 and L. bulgaricus Y 6.15, and satisfactory levels of all bacteria were found during fermentation and storage at 4°C for 21 days. No major differences in lactic and uric acid contents were seen between the control (probiotic strain-free product) and the probiotic fermented milk, whereas the latter contained slightly higher amounts of citric, pyruvic and orotic acids. Moreover, the probiotic fermented milk was graded by the consumer panel with a similar acceptability score as the control product.     

Mechanical Properties of Ovalbumin Gels Formed at Different Conditions of Concentration,Ionic Strength,pH, and Aging Time

Ovalbumin gels were prepared by heat treatment at constant pH and ionic forces. Ovalbumins are widely utilized as emulsifying or binding agents. However, due to their protein origin, mechanical properties of ovalbumins are enclosed in a wide range of rheological responses depending on concentration, ionic strength, pH, and aging time. The objective of this work was to study the effect of processing conditions (pH, ionic strength, and protein content) on the textural attributes of an ovalbumin protein system by means of uniaxial compression. Gels were prepared by dispersing proteins (purity 98%) (8.3–12.5% w/w) until complete dissolution in deionized water at 90°C by 45 min, pH (6.3–9.1) was adjusted using citric acid, and the ionic strength (0–100 mM of NaCl) was adjusted using NaCl. The storage of gels was done at 63°C (24–168 h). The rheological tests of gels were done by uniaxial compression. A rupture force peak was observed at high protein content together with an increase in the Young’s modulus. At fixed conditions of ion content (NaCl 50 mM) and pH of 7, the gels presented a maximum in fracture force and Young's modulus after 7 days of storage. The addition of minimum amount of citric acid increases the stability of ovalbumin gels. This information is useful to ensure that the final product will remain stable during storage time at longer shelf lives.     

Analysis of Flavonoids in <Emphasis Type="Italic">Portulaca oleracea</Emphasis> L. by UV–Vis Spectrophotometry with Comparative Study on Different Extraction Technologies

Portulaca oleracea L. is a traditional edible and medicinal plant in China. Flavonoids are one of the main active ingredients of this plant. Five extraction technologies of flavonoids from P. oleracea L. were investigated and compared, including microwave-assisted extraction, ultrasonic extraction, reflux extraction, Soxhlet extraction, and marinated extraction. The results showed that microwave-assisted extraction was most suitable for the extraction of flavonoids from P. oleracea L. because of its high effect and short extraction time. The found optimum extraction conditions were that the ethanol concentration was 70% (v/v), solid–liquid ratio was 1:50, extracting temperature was 50 °C and irradiation time was 9 min. Quantification was performed by means of UV–Vis spectrophotometry with chromogenic system of NaNO₂–Al (NO₃)₃–NaOH. Under the optimum conditions, the calibration curve for the analyte was linear with the correlation coefficients greater than 0.9999. The average recovery was 102.6%, and its RSD was 1.13%(n = 5). Eight types of P. oleracea L. according to different habits were investigated. The total content of flavonoids was 7.16, 7.10, 9.38, 6.82, 6.78, 11.36, 5.12, and 1.76 mg g⁻¹, respectively.     

Evaluation and Improvement of Extraction Methods for the Analysis of Aflatoxins B1, B2, G1 and G2 from Naturally Contaminated Maize

The extraction procedure for aflatoxin determination in maize is based on a methanol–water (8 + 2 v/v) or an acetone–water (85 + 15 v/v) mixture. Initially, the extraction efficiency of two solvents was evaluated for each aflatoxin. Different results were obtained for highly contaminated maize: significantly higher levels of aflatoxin B₁ were obtained by acetone–water, on the contrary higher levels of aflatoxin G₂ were achieved by methanol–water. Then, acetone–water mixtures in different proportions (7 + 3, 6 + 4 and 5 + 5 v/v) were tested to improve the extraction of aflatoxin G₂. Applying these extraction mixtures, the values both of aflatoxin B₁ and of other aflatoxins were generally higher compared to those obtained by acetone–water 85 + 15; moreover, acetone–water (6 + 4) and (7 + 3) showed the best extraction efficiency for all aflatoxins.     

响应面法优化菊粉山药酸奶发酵工艺研究

以菊粉、山药粉和脱脂牛乳为原料,研究了菊粉山药酸奶的发酵工艺。以感官评分为评价指标,在单因素试验的基础上,采用响应面法进行分析,优化了菊粉、山药粉、木糖醇和发酵剂接种量,最终得出菊粉山药酸奶最佳生产工艺参数为：菊粉添加量0.8%、山药粉添加量0.5%、木糖醇添加量10%、发酵剂接种量0.5 U/L,以此条件发酵出的菊粉山药酸奶感官评分为92.66分,与预测值93.19分较一致。     

Development and application of predictive models for fungal growth as tools to improve quality control in yogurt production

The effect of storage temperature (0–40 °C) and inoculum size (10¹–10⁵ spores) on the mycelium growth kinetics of 12 fungal species on yogurt were monitored. A cardinal model with inflection (CMI) was used to describe the effect of temperature on the growth rate (μ) and the lag time (λ) of each isolate. Significant differences on the temperature dependence of the mycelium growth between the tested species were observed. Depending on the strain, the estimated minimum, optimum and maximum temperature parameters for μ (T_min, T_opt, T_max) ranged from −7.6 to 9.6, 19.5 to 37.8 and 29.8 to 46.9 °C, respectively. Only λ was found to be affected by the inoculum size and a linear relation between Ln (λ) and Log (inoculum size) was revealed. The inoculum level did not influence the values of T_min, T_opt and T_max for λ. Based on the above observations, the combined effect of inoculum size and temperature on λ was modeled using a modified CMI. The parameter λ_opt (λ at optimum conditions) was expressed as a function of the inoculum size. Validation studies showed a good performance of the developed models. The application scheme of the models for improving fungi control in yogurt productions is discussed.     

Production of Cutinase by Fusarium oxysporum on Brazilian Agricultural By-products and its Enantioselective Properties

The production of cutinase by solid-state fermentation, using by-products such as wheat bran, rice bran, or soybean rind, was carried out using a Fusarium oxysporum strain. The fermentation process was optimized using a central composite design. The best conditions for cutinase production were achieved at 28–30 °C, with water added at 100–150% (w/w) after 72 h of incubation, in the range of 11.7–15.5 U/mL. In addition, the resolution of (R,S)-2-octanol and (R,S)-ibuprofen was performed to evaluate the enantioselectivity of the preparations of cutinase. The cutinase produced from the soybean rind attained higher yields and enantioselectivity in the resolution of (R,S)-2-octanol with octanoic acid in isooctane (E = 9.6). For the (R,S)-ibuprofen resolution, the cutinase produced from rice bran reached the best yields (E = 5.6). This work demonstrated that the enzymes can be produced from different media, such as from by-products or residues rich in carbon sources that do not necessarily present the same biochemical properties, which may be useful for industrial applications.     

Development and application of a predictive model of Aspergillus candidus growth as a tool to improve shelf life of bakery products

Molds are responsible for spoilage of bakery products during storage. A modeling approach to predict the effect of water activity (a_w) and temperature on the appearance time of Aspergillus candidus was developed and validated on cakes. The gamma concept of Zwietering was adapted to model fungal growth, taking into account the impact of temperature and a_w. We hypothesized that the same model could be used to calculate the time for mycelium to become visible (t_v), by substituting the matrix parameter by t_v. Cardinal values of A. candidus were determined on potato dextrose agar, and predicted t_v were further validated by challenge-tests run on 51 pastries. Taking into account the a_w dynamics recorded in pastries during reasonable conditions of storage, high correlation was shown between predicted and observed t_v when the a_w at equilibrium (after 14 days of storage) was used for modeling (A_f = 1.072, B_f = 0.979). Validation studies on industrial cakes confirmed the experimental results and demonstrated the suitability of the model to predict t_v in food as a function of a_w and temperature.     

Modelling the Dynamic Inactivation of the Probiotic Bacterium <Emphasis Type="Italic">L. Paracasei</Emphasis> ssp. <Emphasis Type="Italic">Paracasei</Emphasis> During a Low-Temperature Drying Process Based on Stationary Data in Concentrated Systems

In order to better understand inactivation of cells during a drying process, the inactivation kinetics of concentrated Lactobacillus paracasei ssp. paracasei (F19) was measured under stationary conditions for different combinations of water activities and temperatures in a water activity range of a _w = 0.23–a _w = 0.75 and temperatures between 4°C and 50°C. It was shown that the inactivation kinetics of the probiotic bacterium L. paracasei at moderate temperatures could, for all conditions, be formally described by a first-order reaction with activation energies that are much lower than for thermal inactivation (E _a = 61 kJ/mol). With regard to the water activity, the reaction rate constants exhibit a maximum inactivation rate at intermediate water activity a _w = 0.52. As this behavior has direct implications for the stability of cells in a drying process, the stationary data were used to model the inactivation during test vacuum drying processes, where both temperature and water activity dynamically change. It is shown that—depending on the drying rate—dynamic effects have to be taken into account when modeling the survival during drying. Nevertheless, the model based on stationary inactivation data is capable to predict the characteristics of inactivation during a drying process. Therefore, it can serve as basis to optimize the drying process with regard to maximum survival of cells. However, a further refinement of the model with regard to the drying rate is necessary.