Effect of sucrose concentration on the composition of enzymatically synthesized short-chain fructo-oligosaccharides as determined by FTIR and multivariate analysis

Gelation behavior and mechanism of low methoxyl pectin in the presence of erythritol and sucrose: The role of co-solutes

Co-solutes such as sucrose and sugar alcohol play a significant part in low methoxyl pectin (LMP) gelation. To explore their gelation mechanism, we investigated the gelation behavior of LMP in the presence of erythritol and sucrose with Ca2+. Results revealed that the introduction of erythritol and sucrose improved the hardness of the gels, fixed more free water, accelerated the rate of gel structuring, and enhanced the gel strength. FT-IR confirmed the reinforced hydrogen bonding and hydrophobic forces between the pectin chains after introducing co-solutes. And it could be observed clearly by SEM that the cross-linking density of gel network enhanced with co-solutes. Furthermore, gel disruption experiments suggested the presence of ionic interaction, hydrogen bonding, and hydrophobic forces in LMP gels. Finally, we concluded that the egg-box regions cross-linked only by LMP and Ca2+ were too weak to form a stable gel network structure. Adding co-solutes could increase the amount of cross-linking between pectin chains and enlarge the cross-linking zones, which favored the formation of a dense gel network by more hydrogen bonding and hydrophobic forces. Sucrose gels had superior physicochemical properties and microstructure than erythritol gels due to sucrose's excellent hydration capacity and chemical structure characteristics.

Simultaneous Content Determination of Mono-, Di-, and Fructo-oligosaccharides in Citrus Fruit Juices Using an FTIR-PLS Method Based on Selected Absorption Bands

A quantification method was developed to determine the sugar components, either following addition or enzymatic treatment, in citrus fruit juices containing additional fructo-oligosaccharides using midinfrared spectroscopy. For the quantification, we compared the results obtained by applying the simultaneous equation method, which uses very little wavenumber information, and the partial least squares (PLS) regression method, which requires a lot of wavenumber information. In order to prevent overfitting in the PLS method, we concentrated on reducing the amount of spectral data used in the analysis. The corresponding FTIR-PLS method led to an accurate quantification of the sugar contents, even in enzymatically treated orange juices with complicated compositions. The spectral data used for model calibration were significantly reduced by focusing on the absorption and assignment information of the sugar components. The RMSEs of Glc, Fru, Suc, GF2, and GF3 in enzyme-treated orange juice before and after spectral data reduction were 0.50, 0.46, 0.61, 0.74, and 0.61 g/L and 0.51, 0.49, 0.73, 0.86, and 0.61 g/L, respectively. The developed method could be easily implemented for practical applications, using a simple measuring instrument since only absorption information at the limited absorption bands is required.

Inulin-whey protein as efficient vehicle carrier system for chlorophyll: Optimization, characterization, and functional food application

Natural chlorophylls mostly found in vegetables such as spinach (Spinacia oleracea) could be employed as a possible substitute for synthetic colorants because of their intense green properties. However, the stability of natural chlorophyll is a major challenge to its utilization in the food industry. In this study, spray drying as an encapsulation technique was used to improve the stability of natural chlorophyll. Box-Behnken design was utilized to optimize the spray drying conditions for chlorophyll. Optimum conditions were given as inlet temperature, 132°C; inulin-to-whey protein isolate ratio, 61%:39%; pump rate, 25%, resulting in 92.3% encapsulation efficiency, 69.4% solubility, and -13.5 mV zeta potential at a desirability level of 0.901. The particle size, Carr index, bulk and tapped density, polydispersity index, and color showed satisfactory results. Crystallinity, endothermic peak melting temperature, and the enthalpy of chlorophyll-loaded microcapsules increased when compared to the blank microcapsules suggesting decreased hygroscopicity and enhanced thermal stability. In addition, the suitability of fabricated microcapsules using yogurt as a food model was assessed. Yogurt incorporated with chlorophyll-loaded microcapsules showed no significant pH modification with better apparent viscosity than control and sodium copper chlorophyllin (SCC) yogurt after 9 days of refrigerated storage. Based on the studied responses, the spray drying process could be optimized to achieve optimal output and product quality. PRACTICAL APPLICATION: Spray drying is a cheap and convenient approach for microencapsulating bioactive compounds such as chlorophyll. However, the physico-chemical and functional properties of the spray-dried microcapsules are influenced by operating conditions, such as inlet temperature, type and concentration of wall materials, and feed flow rate. Therefore, to maximize and obtain a superior quality of the final product, there is a need to optimize the spray drying process. The Box-Behnken design employed in this study could be utilized as an appropriate technique to design, enhance, and develop process parameters for the fabrication and better retention of the physico-chemical properties of spray-dried chlorophyll microcapsules.

Chickpeas' and Lentils' Soaking and Cooking Wastewaters Repurposed for Growing Lactic Acid Bacteria

Legumes processing involves large amounts of water to remove anti-nutrients, reduce uncomfortable effects, and improve organoleptic characteristics. This procedure generates waste and high levels of environmental pollution. This work aims to evaluate the galacto-oligosaccharide (GOS) and general carbohydrate composition of legume wastewaters and assess their potential for growing lactic acid bacteria. Legume wastewater extracts were produced by soaking and/or cooking the dry seeds of chickpeas and lentils in distilled water and analysed using high-performance liquid chromatography with refractive index detection. GOS were present in all extracts, which was also confirmed by Fourier transform infrared spectroscopy (FTIR). C-BW extract, produced by cooking chickpeas without soaking, provided the highest extraction yield of 3% (g/100 g dry seeds). Lentil extracts were the richest source of GOS with degree of polymerization ≥ 5 (0.4%). Lactiplantibacillus plantarum CIDCA 83114 was able to grow in de Man, Rogosa, and Sharpe (MRS) broth prepared by replacing the glucose naturally present in the medium with chickpeas' and lentils' extracts. Bacteria were able to consume the mono and disaccharides present in the media with extracts, as demonstrated by HPLC and FTIR. These results provide support for the revalorisation of chickpeas' and lentils' wastewater, being also a sustainable way to purify GOS by removing mono and disaccharides from the mixtures.

Formulation and Characterization of Emulgel-Based Jelly Candy: A Preliminary Study on Nutraceutical Delivery

The development of consumer-friendly nutraceutical dosage forms is highly important for greater acceptance. In this work, such dosage forms were prepared based on structured emulsions (emulgels), where the olive oil phase was filled within the pectin-based jelly candy. The emulgel-based candies were designed as bi-modal carriers, where oil-soluble curcumin and water-soluble riboflavin were incorporated as the model nutraceuticals. Initially, emulsions were prepared by homogenizing varied concentrations (10% to 30% (w/w)) of olive oil in a 5% (w/w) pectin solution that contained sucrose and citric acid. Herein, pectin acted as a structuring agent-cum-stabilizer. Physico-chemical properties of the developed formulations were thoroughly analyzed. These studies revealed that olive oil interferes with the formation of polymer networks of pectin and the crystallization properties of sugar in candies. This was confirmed by performing FTIR spectroscopy and DSC studies. In vitro disintegration studies showed an insignificant difference in the disintegration behavior of candies, although olive oil concentration was varied. Riboflavin and curcumin were then incorporated into the jelly candy formulations to analyze whether the developed formulations could deliver both hydrophilic and hydrophobic nutraceutical agents. We found that the developed jelly candy formulations were capable of delivering both types of nutraceutical agents. The outcome of the present study may open new directions for designing and developing oral nutraceutical dosage forms.

Dataset on the Life Cycle Assessment of fructo- and galacto-oligosaccharides (FOS and GOS) produced by synthesis or hydrolysis

The prebiotics like FOS and GOS are receiving special attention in the food industry due to their potential health benefits. They can be produced by enzymatic synthesis by using disaccharides or other substrates as raw materials or by extraction and hydrolysis from different natural sources (roots, legumes). However the environmental footprints of these different production schemes are lacking. This dataset presents Life Cycle Assessment (LCA) of the production of FOS and GOS by enzymatic synthesis from glucose (to get FOS) or lactose (to get GOS) and hydrolytic production from extraction of yacon potato (to get FOS) or chickpea (to get GOS). A cradle-to-gate approach was considered in the two scenarios under assessment (the phases of use and/or final disposal of FOS/GOS were not considered). The functional unit was defined as 100 g of FOS/GOS produced. LCAs were performed using data collected at the laboratory scale during experiments, supplemented with data from technical and scientific literature. Ecoinvent database provided background data. SimaPro was used for the LCA modeling with the midpoint impact EF2.0 characterization method to calculate environmental impacts. For each scenario (FOS produced by synthesis, FOS produced by hydrolysis, GOS produced by synthesis, GOS produced by hydrolysis), the Life Cycle Inventory (LCI) and the Life Cycle Impact Assessment (LCIA) are provided. These data can be used (i) to identify the main environmental hotspots of the production process, (ii) to compare the different process alternatives between them and (ii) to suggest eco-design options to upscale these processes. They could also be re-used in other LCA studies which would include FOS and/or GOS in the production system.

Enzymatically synthesised fructooligosaccharides from sugarcane syrup modulate the composition and short-chain fatty acid production of the human intestinal microbiota

Fructooligosaccharides can be produced by direct enzymatic conversion from sucrose-rich sugarcane syrup (SS) consisting of 58.93% sucrose yielding 21.28 g FOS/100 g sucrose. This study evaluated the prebiotic effect of unpurified/purified SS containing FOS for the modulation of the human intestinal microbial composition and short-chain fatty acid production. The unpurified and purified FOS substrates, which were a mixture of 1-kestose, nystose and 1^F-fructosylnystose, were supplemented into human faecal culture using a pH-controlled batch fermentation system and significantly increased the Bifidobacterium counts after 5 h fermentation, while Bacteroides/Prevotella counts were highest throughout 24 h fermentation. Meanwhile, Lactobacillus/Enterococcus exhibited a slight increase after 5 h fermentation before reaching a plateau afterwards. The steady Bacteroides/Prevotella growth and increased Bifidobacterium population promoted an increase in the production of short-chain fatty acids acetate (58 ± 2.70 mM), propionate (9.19 ± 5.94 mM) and butyrate (7.15 ± 2.28 mM). These results provide evidence that representative gut microbiota could utilise the enzymatically synthesised FOS to generate short-chain fatty acids as metabolites in pH-controlled conditions, thus FOS from SS are a potential prebiotic ingredient for foods and health drinks.

Application of ATR-FTIR spectroscopy for profiling of non-structural carbohydrates in onion (Allium cepa L.) bulbs

Qualitative and quantitative composition of non-structural carbohydrates comprising glucose, fructose, sucrose and fructooligosaccharides (FOS) is one of the key determinants of market suitability, storability and technological processability of onions. To develop a cost-effective and rapid tool for carbohydrate profiling, applicability of attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy of onion juice was investigated with special regard to FOS patterns. As reference, detailed carbohydrate profiles of onion juices were generated by high-performance liquid chromatography coupled with evaporative light scattering detection (HPLC-ELSD). Hierarchical cluster analysis (HCA) of ATR-FTIR spectra was successfully applied for classifying onions into fresh market, storage and dehydrator type according to HPLC-ELSD profiles. A bootstrapping method for automatized test-set validation by projection to latent structures (PLS) algorithms using HPLC and ATR-FTIR spectroscopy data was developed. Model statistics showed promising perspectives for reliable quantification of individual saccharides and sum parameters. The presented methodology allows estimating the nutritional and pre-biotic value directly during cultivation and processing.

Fructose derived oligosaccharides prevent lipid membrane destabilization and DNA conformational alterations during vacuum-drying of Lactobacillus delbrueckii subsp. bulgaricus

Dehydration of lactic acid bacteria for technological purposes conducts to multilevel damage of bacterial cells. The goal of this work was to determine at which molecular level fructose-oligosaccharides (FOS) and sucrose protect Lactobacillus delbrueckii subsp. bulgaricus CIDCA 333 during the vacuum-drying process. To achieve this aim, the cultivability and metabolic activity of vacuum-dried bacteria were firstly determined (plate counting and absorbance kinetics). Then, the membrane integrity and fluidity were assessed using propidium iodide and Laurdan probes (general polarization -GP-), respectively. Finally, bacterial structural alterations were determined using high throughput methods (fluorescence confocal microscopy and Raman spectroscopy coupled to Multivariate Curve Resolution analysis -MCR-). The vacuum-drying process directly affected the microorganism's cultivability and membrane integrity. Non-dehydrated cells and sugar protected bacteria (both with FOS or sucrose) presented high GP values typical from the gel state, as well as phospholipids microdomains laterally organized along the cytoplasmic membrane. On the contrary, bacteria dehydrated without protectants presented low GP values and greater water penetration, associated with membrane destabilization. Raman spectroscopy of vacuum-dried cells revealed DNA conformational changes, B-DNA conformations being associated to non-dehydrated or sugar protected bacteria, and A-DNA conformations being higher in bacteria vacuum-dried without protectants. These results support the role of FOS and sucrose as protective compounds, not only acting at the membrane organizational level but also preventing conformational alterations of intracellular structures, like DNA.

Investigation on thermokinetic suppression of ammonium polyphosphate on sucrose dust deflagration: Based on flame propagation, thermal decomposition and residue analysis

In this investigation, ammonium polyphosphate (APP) is applied to suppress the deflagration of sucrose dust. Through the systematic research on flame propagation images and temperature, decomposition behavior of powder samples and the compositions of deflagration residue, the suppression performance and mechanism of APP on sucrose deflagration are profoundly summarized. Timing diagrams show that APP contributes to reduce deflagration flame brightness, increases ignition delay time and flame fault area. The minimum inerting concentration of APP for sucrose deflagration is determined to be 8 %. From the collected deflagration flame temperature curves, it is confirmed that APP can delay peak temperature arrival time, weaken temperature fluctuation, and decrease peak values of flame temperature and temperature rising rate. Through the analysis on thermal decomposition of samples and deflagration residue, it is reflected that APP has superior composite suppression effect. It can not only absorb reaction heat, but also decrease deflagration exotherm to improve thermal stability of sucrose particles. Thus, the easily oxidized components in sucrose are protected, and deflagration intensity is effectively weakened. This work provides a new solution for prevention and suppression deflagration of dust waste in sugar industry.

Enzymatic synthesis of fructo-oligosaccharides using Pectinex® Ultra SP-L: A study of experimental conditions

The obvious benefits of employing prebiotics as functional components in many foods and feed products have resulted in higher demand for their industrial production, necessitating the development of more efficient and cost-effective manufacturing procedures. As a result, the goal of this study was to synthesize confirmed prebiotics, namely fructo-oligosaccharides (FOS), using sucrose as a substrate, since it allows the synthesis of oligosaccharides with lower polymerization degree, and consequently, a more pronounced prebiotic effect. Due to its availability, low market price, and high stability under industrial conditions, a commercial enzymatic mixture, Pectinex® Ultra SP-L, is used as a source of enzyme - fructosyltransferase (FTase). By varying key experimental conditions such as pH, temperature, enzyme and substrate concentrations, as well as the duration of the process, the composition of the FOS mixture can be adjusted to fit the potential applications. It was found that by performing the reaction in an aqueous medium (pH 7), at a temperature of 50 °C using an enzyme concentration of 1% (v/v) and any sucrose concentration in the range of 200-700 g/L, it was possible to achieve maximum FOS yield of 60% of total carbohydrates within a 24 h. The produced syrup with a high content of FOS can be further used as an adequate food additive, or else, developed processes should be used for the transformation of various food products (such as juices, jams, fillings, candies, cakes, etc.) in which sucrose dominates, creating products with lower caloric and higher functional value.

Recent advances in the knowledge of wine oligosaccharides

Oligosaccharides are carbohydrates with a low polymerization degree containing between three and fifteen monosaccharide residues covalently linked through glycosidic bonds. Oligosaccharides are related to plant defense responses and possess beneficial attributes for human health. Research has focused in wine oligosaccharides only in the last decade. In this paper, a summary of these works is provided. They include: (i) wine oligosaccharides origins, (ii) techniques for isolating oligosaccharide fraction and determining their content, composition and structure, (iii) their dependence on the grape origin and cultivar and winemaking process, and (iv) the connection between oligosaccharides and wine sensorial attributes. Further research is required regarding the impact of agricultural aspects and winemaking techniques on wine oligosaccharides. The knowledge concerning their influence on sensorial and physicochemical properties of wines and on human health should also be improved. The implementation of laboratory methods will provide better understanding of these compounds and their performance within wine's matrix.

Spectroscopic FTIR and NMR study of the interactions of sugars with proteins

FTIR and NMR spectra were measured in parallel for specific two-components mixtures of various proteins with different sugar molecules, such as arabinose, glucose, and sucrose. In the FTIR spectra of arabinose with some of these proteins, the bands assigned to the vibrational modes of the CH and COH groups disappeared, and new ones, related to an arabinose-protein CN mode, appeared. Similar changes were observed in the FTIR spectra of lyophilized mixtures of arabinose with different amino acids. In additional FTIR spectra, measured for other protein-sugar mixtures, the bands correlated to the ring modes of arabinose, in the range 1150-1000 cm^-1, disappeared, and two new very strong narrow bands became dominant, indicating ring opening or some kind of arabinose decomposition. Contrary to the prevailing opinion that complexes between sugars and proteins are formed mainly by hydrogen bonds, the IR and NMR spectra of the sugar-protein mixtures studied here suggest that significant chemical reactions also take place between the interacting sugar and the protein. Two types of sugar-protein chemical reactions can be distinguished on the basis of these IR spectra, leading to the formation of a new CN bond and to the decomposition of sugar skeletal bonds. The new IR bands suggest that the latter reaction results in the formation of new bonds, which are related to new polyether moieties. These results highlight the often ignored non-specific chemical reactions that take place between sugars and proteins, and demonstrate that the simultaneous application of FTIR and NMR spectroscopic analyses can detect and further characterize these types of sugar-protein interactions.

On the characteristic and stability of iron diet supplements

The iron diet supplements: AproFER 1000 and AproTHEM were subjected to various chemical, microbial and magnetic analysis. The microbial analysis revealed no presence of pathogenic bacteria in the studied products. No significant changes in iron content or forms (bivalent/trivalent) were observed in EPR analysis of supplements stored at different conditions for a long period of time. The chemical and magnetic analysis showed that both AproFER 1000 and AproTHEM contain a high concentration of bivalent iron so they can be used as an iron diet supplements.

Synthesis of fructo-oligosaccharides using grape must and sucrose as raw materials

Grape must market has been rising and there is an increasing interest to use it as a "natural" replacement for traditional sugars. Food or beverages with prebiotic compounds, including fructo-oligosaccharides (FOS), emerge as an alternative for the new health style trend. The aim of this work was to investigate whether the combination of grape must with sucrose was a suitable raw material for the synthesis of FOS. This way, a prebiotic syrup containing fructose and FOS, potentially useful for the formulation of foods and beverages, could be obtained. The main process consisted of three stages, namely conditioning of grape must (oxidation of the initial glucose concentration, stage 1), synthesis of FOS [incorporation of 20, 30 and 55% (w/w) sucrose, and 3.5% v/v Viscozyme L - 4.2 U/mg-, stage 2], and conditioning of the final product (oxidation of the glucose generated during the synthesis, stage 3). At stage 1, glucose concentration decreased from 222.8 mg/mL to 47.2 mg/mL, representing a decay of about 80% regarding the initial concentration of glucose. At stage 2, incorporating 20% (w/w) sucrose was not enough to impulse FOS synthesis. In turn, although 30 and 55% (w/w) sucrose produced very similar concentrations of total FOS (DP3 + DP4), 55% (w/w) sucrose led to higher glucose generation and less DP4 formation. Hence, 30% (w/w) sucrose was the condition selected for the synthesis and further conditioning of the obtained product (stage 3). In these conditions, the final product consisted of more than 30% of short chain FOS (19% and 13% of DP3 and DP4, respectively), 55% fructose and less than 11% of glucose and sucrose. Considering that fructose has approximately double sweetening power than glucose, the obtained syrup has a bigger sweetening power in comparison with the original grape must, also providing the prebiotic benefits of FOS.

Evaluation of Kluyveromyces marxianus endo-polygalacturonase activity through ATR-FTIR

The endo-polygalacturonase enzyme (endoPG: EC 3.2.1.15) plays an important role in the fruit juice and wine industries, so the development of new tools for the quantitative and qualitative analysis of its enzymatic action is necessary. In this work, we report the development of a simple, fast and practical method that did not use any chemical reagent to identify and evaluate the action of the endoPG enzyme, produced by the yeast Kluyveromyces marxianus CCT3172, using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy combined with principal component analysis-linear discriminant analysis (PCA-LDA). This method evaluated the action of the endoPG enzyme on the polygalacturonic acid (PGA) substrate at 5 different times (0, 10, 15, 20 and 30 minutes), and at each time interval the samples were analyzed by ATR-FTIR. It was demonstrated that there was clear segregation between the samples that were and that were not subjected to the action of the endoPG enzyme, and it was also possible to distinguish the samples that were subjected to different incubation times with the enzyme. Through PCA-LDA it was possible to obtain wavelengths that are biomarkers for this enzymatic reaction and the observed changes as a function of hydrolysis duration were found to be in agreement with the breakdown of the glycosidic chain (1011 cm^-1-CH-O- CH stretching) of PGA and release of oligosaccharides (1078 cm^-1 C-OH elongation). The activity of the endoPG enzyme and the release of galacturonic acid were verified by the dinitrosalicylic acid (DNS) method in all samples. The efficacy of an automatic classifier using a principal component analysis-linear discriminant classifier (PCA-LDC) was evaluated to diagnose the action of the endoPG enzyme. The results showed an accuracy of 100% for the identification of the endoPG enzyme action and from 91.67% to 100% for classification according to the hydrolysis duration in which PGA was exposed to endoPG. The present study indicates that this methodology may be a new approach for the qualitative evaluation of the endoPG enzyme with the potential to be used in laboratories and industries.

Technological Aspects of the Production of Fructo and Galacto-Oligosaccharides. Enzymatic Synthesis and Hydrolysis

Fructo- and galacto-oligosaccharides (FOS and GOS) are non-digestible oligosaccharides with prebiotic properties that can be incorporated into a wide number of products. This review details the general outlines for the production of FOS and GOS, both by enzymatic synthesis using disaccharides or other substrates, and by hydrolysis of polysaccharides. Special emphasis is laid on technological aspects, raw materials, properties, and applications.

Dehydration of fructose over thiol- and sulfonic- modified alumina in a continuous reactor for 5-HMF production: Study of catalyst stability by NMR

In the present study, the synthesis of an organic group-modified alumina by the sol-gel method is proposed. This material has shown to have an enhanced catalytic performance with grafted organic groups and showed an improved stability. The prepared material has shown to have several O - H groups and an enhanced surface acidity. The alumina acidity was improved by incorporating thiol groups by grafting method, which promotes the tautomerization of fructose to its furanose form. Furthermore, the grafting of sulfonic groups catalyzes its dehydration. The modified alumina was thermally treated up to 200 °C to improve the functional groups stability. After, this modified material was packed into a continuous reactor system, designed and built by this group, to obtain 5-hydroxymethylfurfural (5-HMF) from fructose dissolved in a single-phase solution of tetrahydrofuran (THF) and H2O (4:1 w/w). The catalytic activity of this material was evaluated by the reaction of fructose dehydration at different reaction temperatures (60, 70, 80 and 90 °C). Fructose conversion and selectivity toward 5-HMF were determined by high performance liquid chromatography (HPLC), obtaining 95% and 73% respectively for the highest temperature. The catalyst showed an efficient stability after 24 hours in continuous flow at 70 °C. The loss of sulfur content was 15%, but the fructose conversion yield and the selectivity to 5-HMF after 24 hours of continuous reaction did not undergo significant changes (less than 5%). The nuclear magnetic resonance (NMR) tests confirmed the presence of the thiol and sulfonic groups before and after 24 hours of reaction, as well as the conservation of the same structure, demonstrating the efficient catalytic performance of the material. The catalysts were characterized by nitrogen adsorption/desorption, X-ray diffraction and infrared (IR) spectroscopy. Also, before and after use by utilizing elemental analysis and  1 H - 13 C cross-polarization magic-angle spinning (CPMAS) and dynamic-nuclear polarization (DNP)-enhanced  1 H - 13 C and  1 H - 29 Si CPMAS as well as directly excited  29 Si magic-angle spinning (MAS) NMR methods in solid-state.

Characterization of a mycelial fructosyltransferase from Aspergillus tamarii NKRC 1229 for efficient synthesis of fructooligosaccharides

An efficient system for biotransformation of sucrose to fructooligosaccharides (FOS) was obtained using Aspergillus tamarii NKRC 1229 mycelial fructosyltransferase (m-FTase). Zymographic analysis confirmed mycelial localization of the FTase (36 U/g) and lyophilized fungal pellets were used for bioconversion. m-FTase had molecular weight ∼75 kDa with optimum activity at pH 7.0 and 20 °C. FOS production after parametric optimization (sucrose - 50% w/v, m-FTase dose - 4.5% w/v, inoculum age - 48 h and incubation time - 24 h) reached 325 g/L (55% yield) with 14% residual sucrose, 25% glucose and 6% fructose. FTase activity was enhanced after pre-treatment with organic solvents and SDS. FOS was purified in a single step using gel filtration matrix, Bio-Gel P2. FOS was characterized using Diffusion ordered spectroscopy-Nuclear Magnetic Resonance (¹H DOSY-NMR) and Fourier-transform infrared spectroscopy (FTIR). Continuous generation of FOS was achieved using recyclable mycelia upto 10 consecutive cycles.

Flour from mature Prosopis nigra pods as suitable substrate for the synthesis of prebiotic fructo-oligosaccharides and stabilization of dehydrated Lactobacillus delbrueckii subsp. bulgaricus

Prosopis nigra, a sucrose-rich crop, was used to enzymatically synthesize fructo-oligosaccharides (FOS). The obtained products were used as stabilizing matrices during freeze-drying and storage of Lactobacillus delbrueckii subsp. bulgaricus CIDCA 333. The centesimal composition of P. nigra flour was firstly determined. FOS were synthesized using Viscozyme L as biocatalyst. The progress of the enzymatic reaction was monitored by HPLC and compared with a reaction carried out using equivalent concentrations of pure sucrose as substrate (control). Then, P. nigra containing or not the obtained FOS (P. nigra + FOS or P. nigra) were used as matrices for freeze-drying and storage of L. delbrueckii subsp. bulgaricus CIDCA 333. P. nigra flour was rich in simple sugars (sucrose and fructose), total dietary fiber, and polyphenols. The main products of synthesis were FOS with degrees of polymerization (DP) within 3 and 5, and these results were comparable with those of the controls. DP3 was the first product obtained, attaining the maximal production after 1.29 hours of synthesis. The maximal production of total FOS (DP3 + DP4 + DP5) was achieved after 2.57 hours, indicating that larger FOS (DP4, DP5) were produced from DP3. Glucose was obtained as secondary product, but with significantly lower V_max and K_f (maximal velocity for the production and constant for the formation) than DP3. Both P. nigra + FOS or P. nigra matrices stabilized the highly sensitive L. delbrueckii subsp. bulgaricus CIDCA 333 strain during freeze-drying and storage for up to 140 days at 4 °C, and were significantly better protectants than the controls of sucrose (p <0.05). The concomitant presence of prebiotics (FOS), antioxidants (polypyhenols) and lactic acid bacteria in the matrices provides a smart strategy to increase the value of this underutilized regional crop, turning it in an interesting ingredient potentially useful in the food industry.

Quantification of free sugars, fructan, pungency and sweetness indices in onion populations by FT-MIR spectroscopy

BACKGROUND

To facilitate faster phenotyping of onions (Allium cepa L.), Fourier-transform mid infrared (FT-MIR) spectroscopy with partial least squares (PLS) regression modelling was evaluated for the determination of pungency (pyruvate), sweetness (free sugars) and fructan in juice samples (n = 605) expressed from bulbs from breeding populations.

RESULTS

Fourier-transform infrared (FTIR) spectra (range 1700-900 cm^-1 ) were obtained from droplets (30 μL) of unprocessed juice. Goodness-of-fit (r² ) and prediction errors (standard error of cross validation) for optimal PLS models were: soluble solids (0.997, 0.1 °Brix), pyruvate [0.825, 0.8 μmol g^-1 fresh weight (FW)], fructan (0.98, 1.9 mg g^-1 FW), glucose (0.941, 1.1 mg g^-1 FW), fructose (0.967, 1.0 mg g^-1 FW) and sucrose (0.919, 1.7 mg g^-1 FW). FTIR models for industry sweetness indices based on glucose or sucrose equivalents were also developed. Because of its very low concentration (0.8-12 μmol g^-1 FW) relative to other compounds, pyruvate was the weakest model developed. Fructan could be determined spectroscopically without the need for enzymatic digestion.

CONCLUSIONS

All of the chemometric models developed are acceptable for screening purposes. Those for soluble solids, fructan and fructose are also suitable for routine analysis. FT-MIR can therefore be utilised for the simultaneous determination of pungency, sweetness and fructan in this crop. © 2018 Society of Chemical Industry.

Physico-chemical and structural properties of crystalline inulin explain the stability of Lactobacillus plantarum during spray-drying and storage

The stabilizing capacity of crystalline inulin during spray-drying and storage of Lactobacillus plantarum CIDCA 83114 was assessed. In a first step, the physical properties of the matrices were investigated, using amorphous inulin as control. Melting and glass transition temperatures, water sorption isotherms, water activity, and infrared spectra were determined. Microorganisms were spray-dried at a pilot scale in both amorphous and crystalline matrices. After that, scanning electronic and confocal microsopies provided a full landscape about the interactions between microorganisms and crystals, and also the bacterial location within the amorphous matrices. The technological properties of the dehydrated microorganisms (culturability and acidification capacity) during storage at different water activities were also evaluated. Both amorphous and crystalline inulins were adequate matrices to stabilize microorganisms. However, crystalline inulin was more stable than amorphous one, especially when the storage temperature was close to the glass transition temperature, resulting in a better matrix to protect microorganisms during pilot spray-drying and storage. Furthermore, no accumulation of insoluble inulin was observed after resuspending the dehydrated microorganisms in crystalline inulin matrices, which appears as a clear technological advantage with regard to the amorphous one. Considering the prebiotic character of inulin and the probiotic properties of L. plantarum CIDCA 83114, this work developed an integrated approach, both from a fundamental and from an applied viewpoint, supporting the incorporation of such ingredients in the formulation of food products.

A Combined Approach of Infrared Spectroscopy and Multivariate Analysis for the Simultaneous Determination of Sugars and Fructans in Strawberry Juices During Storage

In this work, a Fourier transform mid-infrared spectroscopy (FTIR)-based method was developed for simultaneously quantifying simple sugars and exogenously added fructooligosaccharides (FOS) in strawberry juices preserved for up to 14 d using nonthermal techniques (geraniol and vanillin+ultrasound). The main spectral differences were observed in the 1200 to 900 cm^-1 region. The presence of FOS was identified by the typical bands at 1134, 1034, and 935 cm^-1 . During storage, a significant decrease of sucrose was concomitant to an increase of glucose and fructose in juices stored without any previous preservation treatment, as determined by high-performance liquid chromatography (HPLC). A principal component analysis was performed on the FTIR spectra corresponding to the different treatments. The groups observed explained more than 94% of the variance and were related to changes in the carbohydrate composition during storage. Then, different partial least square models (PLS) were defined to determine the concentrations of glucose, sucrose, fructose, and those of exogenously added FOS with degrees of polymerization within 3 and 5. The carbohydrates' concentrations determined by HPLC were used as reference method. The models were validated with independent sets of data. The mean of predicted values fitted nicely those obtained by HPLC (correlation and R²  > 0.97), thus supporting the use of the PLS models to monitor the quality of strawberry juices in unknown samples. In conclusion, FTIR spectroscopy appears as an adequate analytical tool to quick assess whether juice formulations meet specifications in terms of authenticity, contamination and/or deterioration.

PRACTICAL APPLICATION

FTIR spectroscopy provided a method potentially transferable to the food industry when associated with the multivariate analysis. The robust 21 PLS models defined in this work provided reliable tools for the rapid monitoring of juices' authenticity and/or deterioration. In this regard, FTIR associated to multivariate analysis enabled the determination of different sugars in a single measurement without the need of pure sugars as standards. This experimental simplicity supports the use of FTIR at the production line, and also contributes to save time in determining carbohydrates' composition and stability, in an environmentally friendly way.