Bio-mediated generation of food flavors – Towards sustainable flavor production inspired by nature

BackgroundThe consumers’ trend toward naturalness and “clean-label” products advocates the development of “bio-mediated” tools including new processes for the generation of flavors. Today, many fundamental studies demonstrate the feasibility of producing individual flavor compounds or more complex flavoring preparations by fermentation or by enzymatic reactions. However, to turn research into industrial applications, the processes have to be simplified and optimized by combining chemistry, biology and process engineering know-how.Scope and approachThis review summarises recent basic research and development on cell and enzyme based formation of volatile flavors with focus on smart combinations of biocatalytic and thermal steps to enrich the natural flavor profile of foods. Ideally, targeted bioconversion of specific raw materials and ingredients will release flavor precursors required to generate the desired flavor profile by appropriate thermal processing.Key findings and conclusionsThe combination of fermentation or enzymatic treatment of raw materials with heat-induced food processes (e.g. drying, extrusion, roasting) represent an elegant approach in industrial food processing to generate flavors under mild conditions. This requires a good control of fermentation or enzymatic reaction steps to produce suitable substrates at the optimal concentrations adapted to the thermal processes. Using traditional cooking and minimal processing conditions (nature-inspired strategies) has become an attractive approach to generate authentic flavor profiles resonating with consumers’ demand for more naturalness.     

Biodegradation of Ammonia Nitrogen Using a Novel Candida sp. Strain N6 Immobilization

固定化假丝酵母菌株N6降解氨氮的研究

王 凯^1,2，孙亚文¹，李斯琪¹，张瑛洁¹，程喜全¹，马 军²

（1. 哈尔滨工业大学(威海)， 海洋科学与技术学院，山东 威海 264209；

2. 哈尔滨工业大学 市政与环境工程学院，哈尔滨 150090）

创新点说明：

发现一株假丝酵母菌株，具有较高的氨氮降解能力，采用固定化技术，将其固定化后用于模拟生活污水的处理效果仍然显著，表明将该菌固定化后具有较高的应用价值。

研究目的：

将高氨氮处理效率的菌株N6固定化，以期通过固定化的形式将其应用于废水处理中。

研究方法：

从山东威海金海湾排污口分离出一株假丝酵母菌，该菌株具有较高的氨氮处理效率。采用包埋固定化技术将N6固定，考察了固定化N6的氨氮降解能力以及稳定性，通过单因素以及正交试验确定了固定化材料以及最佳固定化条件。利用SBR反应器探究固定化N6的应用情况。

研究结果：

1）当固定化材料PVA, SA, CaCl2的浓度分别为9%, 1.5%, 2%时最适合N6固定化，在此条件下，固定化N6的氨氮去除率达到了97.97%。

2）稳定性测试表明固定化N6具有很强的稳定性，固定化小球在测试条件下未出现破碎现象。

3）固定化N6的最佳固定化条件为：固定化24h，N6接种量3%，pH 8。

4） 固定化N6在SBR反应器中表现出非常好的氨氮降解能力，去除率稳定在95%-99%。

5）在固定化N6的应用过程中，最适添加量为15%。

结论：

固定化高效菌株用于废水处理具有广阔的前景。高氨氮处理效率的假丝酵母N6固定化后氨氮降解能力仍然较强。固定化N6具有潜在的应用价值，将固定化N6应用到SBR中，具有较高且稳定的氨氮去除率。

关键词：氨氮废水；固定化；假丝酵母菌属；脱氮效率

     

Preparation and optimisation of liposome‐in‐alginate beads containing oyster hydrolysate for sustained release

Oyster (Crassostrea gigas) hydrolysate shows antihypertensive effect in our previous study. Oral administration of oyster hydrolysate can loss bioactive peptides due to enzymatic degradation in vivo. To maximise its bioavailability, liposome‐in‐alginate (LA) beads were used to encapsulate the oyster hydrolysates to protect from degradation and obtain sustained release. The preparation conditions of the LA beads were optimised by response surface method using a model peptide of tyrosylalanine (YA). Their characterisation, swelling and release properties were investigated. The optimised conditions for the concentration of calcium chloride, sodium alginate and the amount of ethanol‐dissolved lecithin (EDL) were 0.5 m , 3% and 95.4 mg, respectively. The encapsulation efficiencies of YA and the oyster hydrolysate in the optimised condition were 74.9% and 84.3%, respectively. The release time of the oyster hydrolysate in the simulated gastrointestinal fluid was up to 16 h. The LA beads can be recommended to encapsulate oyster hydrolysate for bioavailability improvement.     

Validation of a Method for Quantitation of Soybean Lectin in Commercial Varieties

Soybean agglutinin (SBA) protein, also known as soybean lectin, is regarded as an anti‐nutrient due to its negative effect on the ability of monogastric animals to gain weight following consumption of raw soybean seed. Historically, SBA has been measured using a time‐consuming and cumbersome hemagglutination procedure. The objective of our research was to obtain a validated methodology that is precise and accurate in the measurement of SBA while allowing minimally equipped laboratories to effectively conduct the analysis, thus our focus was on evaluating an existing commercially available ELISA, an enzyme‐linked‐lectin‐assay (ELLA), and a hybrid ELISA/ELLA. A new ELLA technique that can detect and quantify lectins was chosen and modified specifically for the quantitation of SBA in soybean seed. The proposed ELLA methodology is similar to a standard sandwich ELISA, and uses polyacrylamide‐linked N‐acetylgalactosamine (Gal–NAc–PAA) for a capture phase and the biotinylated version (Gal–NAc–PAA–Biotin) for detection. Based upon the validation data, the ELLA method can precisely and accurately determine soybean lectin levels in soybean seed. The validated ELLA method was used to quantify SBA in nine commercial soybean varieties introduced between 1972 and 2008 and demonstrated that the natural variability of SBA is subject to the effects of genotype and environment.     

One‐Pot Lipase Entrapment Within Silica Particles to Prepare a Stable and Reusable Biocatalyst for Transesterification

In order to enhance the reusability, Rhizomucor miehei lipase was entrapped in a single step within silica particles having an oleic acid core (RML@SiO₂). Characterization of RML@SiO₂ by scanning and transmission electron microscopy and Fourier transform infrared studies supported the lipase immobilization within silica particles. The immobilized enzyme was employed for transesterification of cottonseed oil with methanol and ethanol. Under the optimum reaction conditions of a methanol‐to‐oil molar ratio of 12:1 or ethanol‐to‐oil molar ratio of 15:1, stirring speed of 250 revolutions/min (flask radius = 3 cm), reaction temperature of 40 °C, and biocatalyst concentration of 5 wt% (with respect to oil), more than 98 % alkyl ester yield was achieved in 16 and 24 h of reaction duration in case of methanolysis and ethanolysis, respectively. The immobilized enzyme did not require any buffer solution or organic solvent for optimum activity; hence, the produced biodiesel and glycerol were free from metal ion or organic molecule contamination. The activation energies for the immobilized enzyme‐catalyzed ethanolysis and methanolysis were found to be 34.9 ± 1.6 and 19.7 ± 1.8 kJ mol^?1, respectively. The immobilized enzyme was recovered from the reaction mixture and reused in 12 successive runs without significant loss of activity. Additionally, RML@SiO₂ demonstrated better reusability as well as stability in comparison to the native enzyme as the former did not lose the activity even upon storage at room temperature (25–30 °C) over an 8‐month period.