Benard Muinde Kimatu

Development, physiochemical characterization and forming mechanism of Flammulina velutipes polysaccharide-based edible films

Edible films of Flammulina velutipes polysaccharide were prepared and characterized in terms of rheological, optical, morphologic, mechanical and barrier properties to evaluate their potential application in food packaging. Results suggested that FVP film prepared by the solution of 1:150 (w/v) had the optimal mechanical property, smooth and uniform surface, and good barrier property to water (37.92±2.00gmm/m(2)hkPa) and oxygen (37.92±2.01meq/kg). The capacity of film-formation might be related to inter-molecular and intra-molecular hydrogen bonds of FVP and formation of β-glycosidic bonds during the process of film-formation. These findings will contribute to a theoretical basis for the development of FVP film in food packaging.

Antioxidant potential of edible mushroom (Agaricus bisporus) protein hydrolysates and their ultrafiltration fractions

Mushroom protein isolate (MPI) from Agaricus bisporus was hydrolyzed using Alcalase, Pancreatin, Flavourzyme, Alcalase-Pancreatin and Alcalase-Flavourzyme. The obtained hydrolysates (MPHs) were ultrafiltered to generate peptide fractions (UFs) of molecular sizes (<1, 1-3, 3-5 and 5-10kDa). The electrophoretic profile results indicated that the enzymatic systems were efficient in hydrolyzing the MPI into low molecular weight peptides. Hydrolysate yields of >57% and protein recoveries of >43% were obtained. Effective concentration that scavenged 50% (EC50) of DPPH radicals was similar for the MPHs while inhibition against linoleic acid oxidation was strongest (66.49%) for Alcalase-Flavourzyme hydrolysate on day 5 of incubation. UFs exhibited a concentration-dependent FRAP, with the highest activity for fractions from Alcalase and Pancreatin recorded in 1-3kDa. The antioxidant activities of MPHs and their UFs suggested that they could be potential bioactive ingredients for use in the formulation of functional foods as well as natural antioxidants in lipid food systems.

Comparison of flavour qualities of mushrooms (Flammulina velutipes) packed with different packaging materials

To clarify the dynamic changes of flavour components in mushrooms packed with different packaging materials during storage, comprehensive flavour characterization, non-volatile and volatile compounds of Flammulina velutipes were evaluated using electronic nose (E-nose), electronic tongue (E-tongue) technology and headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS), respectively. Results showed that volatile compounds of fresh F. velutipes mainly consisted of ketones and alcohols, with 3-octanone being the predominant compound. After storage, volatile components significantly changed in mushrooms packed with normal packaging material (Normal-PM) according to the GC-MS analysis and radar fingerprint chart of electronic nose. The ethanol accumulation was inhibited by nanocomposite packaging materials (Nano-PM). Besides, both radar graph and PCA of E-tongue signals could differentiate the samples from different packaging and storage time. In general, these results may provide a profile of flavour substances and explain mechanism of flavour changes in F. velutipes over storage period.

Inside Front Cover: Impacts of Dietary Pleurotus eryngii Polysaccharide on Nutrient Digestion, Metabolism, and Immune Response of the Small Intestine and Colon-An iTRAQ-Based Proteomic Analysis

Pleurotus eryngii polysaccharides have been shown to exert significant biological activities to the host. However, few studies have been conducted on its effects on gastrointestinal tract (GIT) health alteration. In the present study, small intestinal and colonic proteome alterations generated by dietary supplementation with a novel homogeneous P. eryngii polysaccharide (PEP) in C57BL/6 mice, based on the isobaric tag for relative and absolute quantification (iTRAQ) proteomics, are investigated. Compared to the control group, PEP supplementation result in a total of 113 and 194 significant differential proteins (DPs) in the small intestine and colon, respectively. Interestingly, DPs in small intestine are mainly related to the transport and biosynthetic process, along with the digestion and absorption pathway of nutrients, whereas the colonic DPs are significantly found participating in numerous metabolic processes. Moreover, the alterations of some DPs in small intestine and colon are speculated to correlate with the colonic microbiota structure and are involved in the regulation of host immune response. Subsequently, some critical DPs of small intestine and colon are selected and validated by Western blotting. The current research facilitated the generation of potential insights into the health benefit activities and functional mechanisms of polysaccharides from P. eryngii.

Non-volatile flavour components in Lentinus edodes after hot water blanching and microwave blanching

ABSTRACT Microwave blanching (MB) and hot water blanching (HB) samples of L.edodes were first analysed by electronic tongue and then analysed by high performance liquid chromatography (HPLC) for the content of non-volatile flavour components (soluble sugars (mannitol), organic acids, 5ʹ-nucleotides, and free amino acids). The results showed that contents of bitterness and astringency changed markedly (p < 0.05) when the blanching conditions were 60 s (HB) and 300 w 90 s (MB), respectively. The contents of non-volatile flavour components in HB samples (60 s) were relatively low, whereas contents in MB samples (300w 90s) were significantly higher (p < 0.05) as compared to HB, especially the taste-active amino acids and 5ʹ-nucleotides, which were attributed to the equivalent umami concentration (EUC) values. In addition, the EUC values of MB samples did not differ significantly from the fresh ones, suggesting that MB could effectively preserve the MSG (monosodium glutamate)-like components of L.edodes compared to HB.