Modelling the survival of starter lactic acid bacteria and Bifidobacterium bifidum in single and simultaneous cultures

The inactivation kinetics at 4 degrees C of Bifidobacterium bifidum, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, cultured alone or consociated in a laboratory medium (modified MRS broth), were modelled through the Weibull model and a second-order polynomial equation. The initial cell number of S. thermophilus and L. delbrueckii subsp. bulgaricus was approximately 6-7log (CFU/ml); the viability loss after 30 days of storage was 2.87 and 1.99log (CFU/l) for L. delbruckii subsp. bulgaricus and S. thermophilus, cultured alone, respectively; whereas the consociation of lactobacilli and streptococci with bifidobacteria reduced viability loss during storage (0.28 and 0.54log CFU/l for lactobacilli and streptococci, respectively). Finally, the consociation of lactobacilli and streptococci with B. bifidum improved their oxygen uptake.     

Purification and characterisation of antioxidative peptides from unfractionated rice bran protein hydrolysates

Crude rice bran protein (CRBP) was prepared by alkaline extraction and then treated with 0.6 m HCl to remove phytic acid. The phytate‐free rice bran protein (PFRBP) was hydrolysed with proteases M, N, S, P and pepsin under optimal conditions. Hydrolysates obtained from various hydrolysis periods were subjected to analysis for their degree of hydrolysis (DH) and functional properties. The hydrolysates were fractionated by reversed‐phase column chromatography on Kaseigel ODS resin (120–140 μm) using a stepwise gradient of aqueous ethanol, and their activities were measured. The 40% ethanol fraction of protease P 4 h‐hydrolysate was separated by successive reversed‐phase high‐performance liquid chromatography and the amino acid sequences of isolated antioxidative peptides were determined by a protein sequencer and matrix‐assisted laser desorption ionisation‐time of flight mass spectrometry. Crude rice bran protein had higher antioxidative activity than PFRBP, due to the presence of phytic acid. Phytate contents of rice bran, CRBP and PFRBP were 2.5%, 1.42% and 0%, respectively. The activity of PFRBP increased upon protease digestion. Protease M hydrolysates showed the highest DH, but the lowest antioxidative activity. Hydrolysates with DH below 10% had higher antioxidative activity than those above 20%. This result indicates that the antioxidative activity of the hydrolysates is inherent to their characteristics amino acid sequences of peptides depending on the protease specificities.     

Protective effect of fresh and processed Jalapeño and Serrano peppers against food lipid and human LDL cholesterol oxidation

The potential of fresh and processed Jalapeño and Serrano pepper extracts for the control of lipid oxidation in several systems was investigated. The assays used included β-carotene/linoleate model system, striped corn oil, ground pork meat and Cu(II)-induced oxidation of human low-density lipoprotein (LDL). The results showed that all extracts were effective in at least one system, although their potency varied. Extracts of smoked Jalapeño were particularly effective. The lipid-protective effect of the extracts was mainly due to the presence of phenolic compounds, but other phytochemicals, such as chlorophylls were also involved.     

Analysis of oligosaccharides in beer using MALDI-TOF-MS

Oligosaccharides in four different brands of beer (Cass, Hite, Budweiser, Miller) were systematically analysed with three different dihydroxybenzoic acid (DHB) isomer matrices (2,4-DHB, 2,5-DHB, and 2,6-DHB) using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS). Different experimental conditions, such as dilution (up to 1000-fold) and cationisation agents (sodium chloride or sodium trifluoroacetate) were analysed. No ionised peaks of oligosaccharides were observed with 2,4-DHB matrix. 2,6-DHB was more effective than 2,5-DHB in most of the investigated concentration ranges. 2,6-DHB with 4-fold dilution was the most effective. In certain cases, a cationisation agent was necessary to detect the signals of the oligosaccharides, and sodium chloride provided greater ionisation than sodium trifluoroacetate.     

Bioactivity evaluations of ingredients extracted from the flowers of Citrus aurantium L. var. amara Engl

Citrus aurantium L. var. amara Engl, a member of genus Citrus (Rutaceae), widespread in China, is used as folk medicine for the treatment of helping digest, phlegm, enteritidis, stomachic and other deceases. In the present research, silica gel column, Sephadex LH-20, mass spectrometer (MS) and nuclear magnetic resonance (NMR) were used to separate and identify the chemical compounds from the flowers of C. aurantium var. amara, and several bioactivity assays were used to evaluate their antioxidant, anti-inflammatory, anti-virus and antitumour activities. Two major compounds, 5-hydroxy-6,7,3′,4′-tetramethoxyflavone (HTF) and limonexic acid (LA), were isolated and identified from C. aurantium var. amara for the first time. The results of the bioactivity assays showed that HTF and LA displayed significant antioxidant activities and showed significant inhibition effects on the B16 cell lines at a concentration range from 6.25 to 50 μg/ml, and on the SMCC-7721 cell lines from 12.5 to 200 μg/ml. The antitumour effect, anti-inflammatory activity and the inhibiting expression of HBsAg and HBeAg of 2.2.15 cells displayed the tendency in a concentration-dependent manner. These two compounds from C. aurantium var. amara could potentially be used as a promising natural agent in the pharmaceutical industries.     

环境因子对干酪乳杆菌产酸的影响

研究了葡萄糖酸-δ-内酯(GDL)、葡萄糖(GLC)、接种量以及发酵温度等环境因子对干酪乳杆菌产酸的影响,结果表明:当葡萄糖酸-δ-内酯的添加量为0.848647%、葡萄糖的添加量为0.366162%、接种量为8.063693%和发酵温度31.595266℃时,干酪乳杆菌产酸量最大,pH值为4.232400.     

Influence of environmental factors,wet processing and their interactions on the biochemical composition of green Arabica coffee beans

Although cultivation of Arabica coffee trees at high elevation is known to favourably affect the final quality of the beverage, quantitative data describing the influence of climatic conditions on the chemical composition of the seed are still lacking. Similarly, post-harvest treatments of the beans are known to affect the generation of flavour, but the chemical transformations that occur during wet processing are poorly understood. To better characterise the effects of the environment, wet processing and their possible interactions, we quantified the changes in the main chemical components of the coffee seed (lipids, chlorogenic acids, sugars and caffeine) caused by wet processing, and analysed how these changes were affected by the variations induced by the environment before harvest. Using 16 experimental plots in Reunion Island displaying broad climatic variations, we showed that chlorogenic acids and fatty acids in the seed were controlled by the mean air temperature during seed development. By contrast, total lipid, total soluble sugar, total polysaccharide and total chlorogenic acid contents were not influenced by climate. Glucose content was positively affected by altitude, while sorbitol content after wet processing depended directly on the glucose content in fresh seeds.     

Acetic acid removal by Saccharomyces cerevisiae during fermentation in oenological conditions. Metabolic consequences

The commercial Saccharomyces cerevisiae strains used in champagne winemaking were tested for their ability to metabolise acetic acid during alcoholic fermentation. Fermentation tests were performed in conditions close to oenological ones using a Chardonnay grape juice supplemented with acetic acid. The amount of acetic acid metabolised by wine yeast increased with increasing initial acetic acid concentration and this elimination occurred during the second part of the exponential growth phase. When the initial acetic acid concentration exceeds 1 g/l, and whatever the yeast strain used, the concentration of acetic acid in the resulting wine cannot be reduced to an acceptable level according to the current legislation. Acetic acid removal modified yeast metabolism, since more acetaldehyde, less glycerol and less succinic acid were produced. Considering the reduction of the NADPH/NADP⁺ ratio following acetic acid consumption, we propose, as a new hypothesis, that acetic acid could modify yeast metabolism by reducing the activity of the NADP⁺ dependent aldehyde dehydrogenase Ald6p.     

Pressurised water extraction of polyphenols from pomegranate peels

Pomegranate peels are one of the most valuable by-products of the food industry in terms of polyphenols which are conventionally extracted from plant materials by organic solvents, especially with methanol. Pressurised water extraction was investigated for the extraction of polyphenols from pomegranate peels. The most important factors affecting the extraction results were found to be particle size, temperature, and static time. The results indicated that pressurised water extraction was as effective as conventional methanol extraction for the recovery of polyphenols from pomegranate peels. Total phenolic contents of pomegranate peels obtained by pressurised water extraction at optimised conditions and conventional solid–liquid methanol extraction were determined as 264.3 and 258.2 mg/g tannic acid equivalents, respectively. Hydrolyzable tannins were the predominant polyphenols of pomegranate peels corresponding to 262.7 mg/g tannic acid equivalents. Punicalagin content of pomegranate peels by pressurised water extraction was found to be 116.6 mg/g on dry matter basis.     

响应面法优化产酸丙酸杆菌丙酸发酵条件的研究

采用Box-Behnken设计和响应面分析法(Response surface methodology,RSM),以产酸丙酸杆菌发酵甘油产丙酸的3个关键因素(培养温度、pH和接种量)为自变量,以丙酸产量为响应值,对上述因素的最佳水平范围进行了探讨与优化。实验结果表明,培养温度和pH对丙酸产量有显著性影响,并据此建立了相关的数学模型。得到的工艺参数的优选结果是:培养温度为29.75℃、pH为6.61、接种量为6.15%(v/v),丙酸产量最大预测值为17.96g/L。经过优化,丙酸产量提高了27.9%,实验值与预测值基本相符。