Exudate gums: chemistry,properties and food applications – a review

Gums are complex carbohydrate molecules which have the ability to bind water and form gels at low concentration. These carbohydrates are often associated with proteins and minerals in their structure. Gums are of various types such as seed gums, exudate gums, microbial gums, mucilage gums, seaweeds gums, etc. Exudate gums are plant gums which ooze out from bark as a result of a protection mechanism upon injury. Exudate gums have been used by humans since ancient times for various applications due to their easy availability. The main characteristics which make them fit for use in various applications are viscosity, adhesive property, stabilization effect, emulsification action and surface-active property. Major applications of these gums are in food products, the paper, textile, cosmetics and pharmaceutical industries, oil-well drilling, etc. In the present paper, the chemistry, properties, processing and applications of commercially available exudate gums such as acacia gum or gum arabic, karaya gum, ghatti gum and tragacanth gum are discussed. Recent literature reveals that apart from the above mentioned applications, these gums also have nutritional properties which are being explored. Other gums cannot replace them because of their certain unique characteristics. © 2020 Society of Chemical Industry     

Effect of the homogenization process on the sensory and rheological properties in model system

High pressure homogenization has been used for preparation and stabilization of emulsions and suspensions, promoting physical changes in products, such as viscosity change. However, its use in model systems for fruit nectar is innovative. This study aimed to evaluate the effect of the processing in high pressure homogenizer on the rheological behavior and the sensory attributes in model system of gellan gum. Gellan gum (0.05%), organic acids (0.3%), and sucrose (10%) were used to prepare the solutions, which were subsequently homogenized (0—control, 25 and 50 MPa) at 25°C. Rheological and sensory analyses were performed. The samples presented pseudoplastic behavior without residual stress and were characterized by the Ostwald-de-Waele model. The homogenization pressure (P_H) altered the viscosity of the model systems, reduced the consistency index and apparent viscosity, and increased the flow behavior index. The stimuli sour taste and viscosity differed among the parameters evaluated in the time-intensity analysis. No differences were observed for the maximum intensity of viscosity between the treated samples (25 and 50 MPa), which exhibited a similar temporal profile. Therefore, studies on the rheological and sensory behavior are fundamental to product development and process optimization. The present study shows new trends on the use of the high pressure homogenizer and the sensory profile in model systems that can be used for fruit nectar. This study evaluated the sensory attributes through the time-intensity analysis. The sensory data indicate that the homogenization pressure altered the viscosity perception, but did not alter the perception of the acid taste for the same organic acid used. Sensory as well as rheological data present new alternatives for product development. These findings are interesting for future research, equipment design, and process optimization.     

Pyropia columbina phycocolloids as microencapsulating material improve bioaccessibility of brewers’ spent grain peptides with ACE-I inhibitory activity

The effects of wall hydrocolloids on delivery and bioaccessibility of encapsulated brewers’ spent grain ACE-I inhibitory peptides after simulated gastrointestinal digestion were assessed. Microencapsulation of peptides was carried out by spray drying using locust bean gum, P. columbina phycocolloids, or its mixtures as wall materials. Microcapsules presented round external surfaces with some concavities, negative surface charge and encapsulation efficiencies higher than 90%. The incorporation of phycocolloids to formulations increased the encapsulation efficiency, negative surface charge and resistance against digestive enzymes of microcapsules. Encapsulated peptides with P. columbina phycocolloids showed lower IC₅₀ value of ACE-I inhibition than un-encapsulated peptides (2.4 ± 0.2 vs. 7.2 ± 0.3 mg mL⁻¹ protein), but higher than that obtained for hydrolysate (1.5 ± 0.2 mg mL⁻¹ protein), indicating a 75% protection of bioactivity. Electrostatic and hydrophobic interactions between P. columbina phycocolloids and brewers’ spent grain peptides could be implicated in the protection of peptides during gastrointestinal digestion.     

Biohydrogen production from autoclaved fruit and vegetable wastes by dry fermentation under thermophilic condition

Dark fermentative hydrogen production from organic waste is an attractive technique that simultaneously treats waste along with generation of renewable fuel. In this study, a relative new technology named dark dry fermentation was tested in a 55-L reactor to treat fruit and vegetable waste (FVW) along with simultaneous generation of biohydrogen. To understand the effect of autoclaving as a pretreatment method on FVW for subsequent biohydrogen production, two independent experiments were performed; one with autoclaved waste (experiment I) and another by using non autoclaved waste (experiment II). From the analyses, it was found that maximum hydrogen % obtained for experiment I was 41% (v/v%) whereas, for experiment II was 21%. In terms of total hydrogen produced, around 30% higher production was observed with experiment I compared to experiment II. The hydrogen yields for experiment I and experiment II were respectively, 27.19 and 20.81 NmL H₂/gVS (VS = volatile solid added), and the metabolites (VFAs) preferentially produced were acetic acid and iso-butyric acid.     

Molecular characterization of edible vegetable oils via free fatty acid and triacylglycerol fingerprints by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Free fatty acids (FFAs) and triacylglycerols (TAGs) are the main components of edible vegetable oils. In this work, electrospray ionisation (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was employed to characterise the molecular composition of FFAs and TAGs in various vegetable oils, including soybean, rapeseed, corn, sunflower, peanut, linseed and olive oils. Semiquantitative analysis of FFAs and structural analysis of TAGs by MS/MS were further conducted to reveal the differences in the molecular compositions of the various vegetable oils. It was found that each vegetable oil has characteristic fingerprints of FFAs and TAGs. MS/MS measurements showed that the high-abundance TAGs in each vegetable oil were mainly composed of their abundant FFAs and glycerol. FFA and TAG fingerprints of genetically modified (GM) and nongenetically modified (non-GM) vegetable oils were similar, exhibiting only subtle differences, as confirmed by principal component analysis (PCA).     

Amounts of malondialdehyde do not accurately represent the real oxidative level of all vegetable oils: a kinetic study of malondialdehyde formation

Malondialdehyde (MDA), a widely used oxidation indicator for both lipid and edible oil, has been suggested to be genotoxic and cytotoxic, thus attracting increasing attentions about its formation and exposure assessment. In this study, kinetics of MDA formation in vegetable oils and model oils were investigated by high-performance liquid chromatography. Results showed MDA contents firstly increased rapidly then kept to a plateau over time in both reaction systems at 100, 140 and 180 °C, significant temperature-dependent of MDA formation was observed. The rate constant and activation energy (E_a) were calculated from the fitted pseudo-first-order model and Arrhenius equation. E_a of MDA-formation was much lower in linseed oil, corn oil and rapeseed oil, indicating the higher degree of unsaturation resulted in the greater susceptibility to MDA formation. Besides, MDA content was inappropriate to assess the oxidation of palm oil and camellia oil possessing high level of saturated and/or monounsaturated fatty acid.     

Influence of xanthan gum and gluten on in vitro digestibility and textural properties of rice bread

Starch digestibility of gluten-free bread has been expected to be suppressed for the purpose of decreasing glycemic response. The objective of this study was to investigate the effects of adding xanthan gum and gluten on starch and protein digestibility of rice bread prepared using the developed recipe involving pickering stabilization of foams and emulsions. The extent of starch digestion of gluten-free bread was suppressed by adding 2% xanthan gum from 79.8% to 57.3%. This suppressive effect was diminished by using gluten and that of rice bread containing 2% xanthan gum and 20% gluten was 75.5%. The extent of starch digestion of gluten-free bread was similar or less than that of bread containing gluten. The gluten-free bread with 2% xanthan gum had significantly lower loaf volume, porosity, and sticker structure of breadcrumb than the control. The suppressive effects of xanthan gum on starch and protein digestion were mainly dependent on reducing accessibility of the enzyme into the inner structure.     

钢带式果蔬干燥设备温度控制系统设计及优化

本设计研发了一种用于钢带式果蔬干燥设备的温度控制系统,该系统采用PID温度调节器为核心控制器件,辅以温度调节阀,可使干燥仓内温度偏差控制在±3℃以内,并给出了控制原理及实验数据。该系统控制温度可靠,使生产过程实际干燥曲线自动拟合该物料的理论干燥特性曲线。