Impact of Processing and Physicochemical Parameter on Hibiscus sabdariffa Calyxes Biomolecules and Antioxidant Activity: From Powder Production to Reconstitution.

Hibiscus sabdariffa is a tropical plant with red calyxes whose anthocyanins, phenols, and antioxidant activity make it attractive to consumers both from a nutritional and medicinal standpoint. Its seasonality, perishability, and anthocyanin instability, led to the setup of stabilization methods comprising drying and powdering. However, its properties can often be altered during these stabilization processes. Treatments such as dehumidified-air-drying, infrared drying, and oven-drying, and their combination showed better quality preservation. Moreover, powder production enables superior biomolecule extractability which can be linked to a higher bioaccessibility. However, the required temperatures for powder production increase the bioactive molecules degradation leading to their antioxidant activity loss. To overcome this issue, ambient or cryogenic grinding could be an excellent method to improve the biomolecule bioavailability and accessibility if the processing steps are well mastered. To be sure to benefit from the final nutritional quality of the powder, such as the antioxidant activity of biomolecules, powders have to offer excellent reconstitutability which is linked to powder physicochemical properties and the reconstitution media. Typically, the finest powder granulometry and using an agitated low-temperature reconstitution media allow for improving anthocyanin extractability and stability. In this review, the relevant physicochemical and processing parameters influencing plant powder features from processing transformation to reconstitution will be presented with a focus on bioactive molecules and antioxidant activity preservation.

Impact of Lacticaseibacillus rhamnosus GG on the Emulsion Stability of Raw Milk.

Lactic acid bacteria (LAB) have been studied for several decades to understand and determine their mechanism and interaction within the matrix into which they are introduced. This study aimed to determine the spatial distribution of Lacticaseibacillus rhamnosus GG (LGG) in a dairy matrix and to decipher its behaviour towards milk components, especially fat globules. Two strains of this widely studied bacterium with expected probiotic effects were used: LGG WT with pili on the cell surface and its pili-depleted mutant-LGG ΔspaCBA-in order to determine the involvement of these filamentous proteins. In this work, it was shown that LGG ΔspaCBA was able to limit creaming with a greater impact than the wild-type counterpart. Moreover, confocal imaging evidenced a preferential microbial distribution as aggregates for LGG WT, while the pili-depleted strain tended to be homogenously distributed and found as individual chains. The observed differences in creaming are attributed to the indirect implication of SpaCBA pili. Indeed, the bacteria-to-bacteria interaction surpassed the bacteria-to-matrix interaction, reducing the bacterial surface exposed to raw milk. Conversely, LGG ΔspaCBA may form a physical barrier responsible for preventing milk fat globules from rising to the surface.

Effect of controlled differential sieving processing on micronutrient contents and in vivo antioxidant activities of Hibiscus sabdariffa L. calyxes powder.

Sun-dried calyxes of Hibiscus sabdariffa were finely grinded and fractionated by controlled differential sieving processing (CDSp) into four granulometric classes. The obtained powder fractions were examined for their micronutrient contents and in vivo antioxidant properties in high-fat diet induced oxidation model rats. Unsieved powder and lyophilized ethanolic extract were used for comparison. Micronutrient contents and antioxidant properties were significantly influenced (p < 0.05) by particle sizes. The mineral, vitamin, carotenoid and anthocyanin contents were shown to be higher in smaller powder particles. Comparatively, the ethanolic extract powder had the higher carotenoid, vitamin and anthocyanin contents while the superfine powders < 180 µm and 180-212 µm had the higher mineral contents and antioxidant properties which was characterized by high superoxide dismutase, catalase activities and low malondialdehyde production. Plant grinding followed by CDSp may be an option to improve micronutrient content and antioxidant activity of plant powders.

Micronutrients and in vivo antioxidant properties of powder fractions and ethanolic extract of Dichrostachys glomerata Forssk. fruits.

Dichrostachys glomerata powders were processed by sieve fractionation and ethanolic extraction followed by freeze-drying. The micronutrient contents and the in vivo antioxidant properties of powder fractions in rats' high-fat diet-induced oxidation model were determined. Sieved fractionation was achieved by finely grinding the Dichrostachys fruits and fractionating on a sieve column to retain particle of sizes <180, 180-212, 212-315, and ≥315 µm. Unsieved powder and lyophilized ethanolic extract were used as control. All the powders were examined for the minerals, total carotenoids, and vitamins contents. For in vivo antioxidant properties assessment, the individual powder was dissolved in water and administered to rats at the dose of 250 mg/kg body weight. Oxidation was induced by treating the rat with high-fat diet, and the measured parameters were malondialdehyde, superoxide dismutase, and catalase activities. The results showed a significant influence (p < .05) of particle size on the micronutrient contents and in vivo antioxidant properties. The smaller the particle size of the powder fractions, the higher the minerals, vitamins, total carotenoids contents, and antioxidant properties. Comparatively, the ethanolic powder had the highest carotenoids content, while the powders of particle size <180 µm and 180-212 µm had the highest minerals and vitamin contents. The highest antioxidant properties were characterized by high superoxide dismutase, catalase activities, and low malondialdehyde production. The grinding of Dichrostachys fruit followed by controlled differential sieving process may compete with ethanol extraction for an efficient concentration of bioactive compounds and micronutrients except carotenoids.

Effect of sieved fractionation on the physical, flow and hydration properties of Boscia senegalensis Lam., Dichostachys glomerata Forssk. and Hibiscus sabdariffa L. powders.

This study aimed at evaluating the effect of successive grinding and sieving processes on the physicochemical properties of powders obtained from Boscia senegalensis seeds, Dichostachys glomerata fruits and Hibiscus sabdariffa calyxes. Plant powders were fractionated into four granulometric classes and their properties were compared to those of unsieved powders. Mean particle size exerted a significant influence (p < 0.05) on the plant powders properties. The smaller the particle size of the powder fraction, the higher the protein, lipid and ash contents and the lower the carbohydrate and fiber contents. The decrease in particle size increased particle sphericity and elongation and enhanced flowability of B. senegalensis and D. glomerata powders, whereas an inverse tendency seemed to be observed for H. sabdariffa powders. Water absorption capacity, water solubility index and dispersibility were improved for finer particles for all plants. Sieve fractionation is a novel approach for improving physicochemical properties of plant powders.

Successive grinding and sieving as a new tool to fractionate polyphenols and antioxidants of plants powders: Application to Boscia senegalensis seeds, Dichrostachys glomerata fruits, and Hibiscus sabdariffa calyx powders.

The present investigation aimed at evaluating the effect of powder fractionation based on particle size on the chemical composition in macronutrients, polyphenol contents, and antioxidant properties of powders of Boscia senegalensis seeds, Dichrostachys glomerata fruits, and Hibiscus sabdariffa calyces. Significant differences (p < 0.05) among granulometric classes of each plant were observed for the chemical composition in macronutrients. A decrease in particle size of plant powders was associated with an increase in ash, protein, and fat contents, while carbohydrate content was lowered. The following Granulometric classes, [0-180 µm] for Boscia senegalensis, [180-212 µm] for Dichrostachys glomerata, and [212-315 µm] for Hibiscus sabdariffa, respectively, were found to maximize total phenolic content and antioxidant activity. These results confirm that the grinding and controlled differential screening technology is an approach may serve as a useful guide to obtain optimum polyphenol extraction and enhance antioxidant activity of plant products.

Milk fat globule membrane glycoproteins: Valuable ingredients for lactic acid bacteria encapsulation?

The membrane (Milk Fat Globule Membrane - MFGM) surrounding the milk fat globule is becoming increasingly studied for its use in food applications due to proven nutritional and technological properties. This review focuses first on current researches which have been led on the MFGM structure and composition and also on laboratory and industrial purification and isolation methods developed in the last few years. The nutritional, health benefits and techno-functional properties of the MFGM are then discussed. Finally, new techno-functional opportunities of MFGM glycoproteins as a possible ingredient for Lactic Acid Bacteria (LAB) encapsulation are detailed. The ability of MFGM to form liposomes entrapping bioactive compounds has been already demonstrated. One drawback is that liposomes are too small to be used for bacteria encapsulation. For the first time, this review points out the numerous advantages to use MFGM glycoproteins as a protecting, encapsulating matrix for bacteria and especially for LAB.

Adhesive interactions between milk fat globule membrane and Lactobacillus rhamnosus GG inhibit bacterial attachment to Caco-2 TC7 intestinal cell.

Milk is the most popular matrix for the delivery of lactic acid bacteria, but little is known about how milk impacts bacterial functionality. Here, the adhesion mechanisms of Lactobacillus rhamnosus GG (LGG) surface mutants to a milk component, the milk fat globule membrane (MFGM), were compared using atomic force microscopy (AFM). AFM results revealed the key adhesive role of the LGG SpaCBA pilus in relation to MFGM. A LGG mutant without exopolysaccharides but with highly exposed pili improved the number of adhesive events between LGG and MFGM compared to LGG wild type (WT). In contrast, the number of adhesive events decreased significantly for a LGG mutant without SpaCBA pili. Moreover, the presence of MFGM in the dairy matrix was found to decrease significantly the bacterial attachment ability to Caco-2 TC7 cells. This work thus demonstrated a possible competition between LGG adhesion to MFGM and to epithelial intestinal cells. This competition could negatively impact the adhesion capacity of LGG to intestinal cells in vivo, but requires further substantiation.

Use of imaging techniques to identify efficient controlled release systems of Lactobacillus rhamnosus GG during in vitro digestion.

Matrix composition plays a crucial role in the controlled release of viable and functional bacteria in the intestine. Imaging tools such as electronic and confocal microscopies were used in this work to investigate the influence of matrix composition on matrix integrity and porosity, bacterial spatial distribution and viability during simulated in vitro digestion. L. rhamnosus GG was encapsulated in matrices having different casein/whey protein ratios. The formulation with a casein/whey ratio of 60/40 presented a porous weak gel structure that resulted in its fast disintegration in gastric media showing the presence of dead bacteria in the intestine. For the formulation with a casein/whey ratio of 100/0, the matrix was dense with a strong gel structure. At the end of the intestine, total disintegration of microparticles was not achieved and bacteria were still embedded in the matrix instead of being liberated. Only the intermediate formulation (casein/whey-80/20) permitted a good bacterial protection in the stomach and release of viable bacteria during intestinal digestion.

Dehulling reduces toxicity and improves in vivo biological value of proteins in vegetal milk derived from two mucuna (Mucuna pruriens L.) seeds varieties.

The present work was carried out to evaluate the nutritive quality (proximate and antinutrients composition) of vegetable milks prepared from whole and dehulled mucuna bean flours. Casein and mucuna milk diets were fed to rats (four weeks old; n = 8 per group) for 28 days to determine protein efficiency ratio (PER), net protein efficiency ratio (NPER), true and apparent digestibility (TD and AD, respectively), organ-to-body weight ratios and hematological parameters. The experimental design was a factorial design with two variety of mucuna (cochinchinensis and veracruz) and two treatments (whole and dehulled beans). Protein, total sugar, dry matter and ash-content of mucuna milks ranged from 6.40 to 12.13 g/100 mL, 10.52 to 13.08 g/100 mL, 8.59 to 12.88 g/100 g and 0.31 to 0.92 g/100 g, respectively. Milks from dehulled flours had lower contents of tannins (80-87.08 %), phytates (76.67-78.16 %) and L-Dopamine (44.45-66.66 %) than that from whole flours. The PER of dehulled mucuna diets were 22.76-21.74 %, but negative PER and low NPER was observed for whole mucuna milk diets. TD for dehulled mucuna milk (85.15-85.96 %) were higher and similar to casein when compared to that of whole mucuna milk (47.87-51.17 %). Rats fed with diets containing whole mucuna milk lost weight and had higher kidney weight. In addition, the rats fed with milk from whole mucuna flours showed significantly lower levels of lymphocytes, granulocytes, red blood cells, hemoglobin and hematocrit than that fed with dehulled mucuna milk.

Physicochemical and micro-structural properties of flours, starch and proteins from two varieties of legumes: bambara groundnut (Vigna subterranea).

This work is part of a large study aimed to evaluate the potential of bambara groundnut (Vigna subterranea) flour as starting raw material for the preparation of a widely cherished legume-based food product known as koki. Towards this objective, the flours from two varieties of bambara groundnut along with their respective starch and protein isolates were analyzed for some physicochemical and microstructural properties. It was observed that bambara flour contained appreciable amount of proteins (24.0-25.5 g/100 g), carbohydrates (57.9-61.7 g/100 g), fiber (3.45-3.68 g/100 g) and ash (3.65-3.85 g/100 g) with marginal differences between both varieties. The properties of starch and proteins isolated from the flours were different from one variety to another. In particular the starch granules of the white variety were larger (size range 10-35 µm) and polygonal while those from the black variety were smaller (size range 6-15 µm) and spherical in shape. In addition, the peak of gelatinization temperature was higher for white variety (81.7 °C) than for black variety (77.5 °C). The gelatinization temperature and the enthalpy of gelatinization of starch in the flours were systematically lower than for the starch isolates, suggesting an interaction of starch with other components on the gelatinization process.

Impacts of pH-mediated EPS structure on probiotic bacterial pili-whey proteins interactions.

Probiotic bacteria are routinely incorporated into dairy foods because of the health benefits they can provide when consumed. In this work, the marked pH-dependence of the pili/EPS organization at the outer surface of Lactobacillus rhamnosus GG is characterized in detail by Single Cell Force Microscopy and cell electrophoretic mobility measurements analyzed according to formalisms for nanomechanical contact and soft particle electrokinetics, respectively. At pH 6.8, LGG pili are easily accessible by AFM tips functionalized with whey proteins for specific binding, while at pH 4.8 the collapsed EPS surface layer significantly immobilized the LGG pili. This resulted in their reduced accessibility to the specific whey-coated AFM tip, and to stronger whey protein-pili rupture forces. Thus, pili interactions with whey proteins are screened to an extent that depends on the pH-mediated embedment of the pili within the EPS layer.

Mucilage chemical profile and antioxidant properties of giant swamp taro tubers.

The yellow (YP) and white (WP) sections of giant swamp taro (GST) contain 40.0 g/kg and 51.5 g/kg (dry wt) respectively of pure mucilage made up of D-glucose (44.95-78.85 %), D-galactose (8.70-25.35 %), D-mannose (3.20-10.45 %), D-arabinose (2.45-5.20 %) and small amounts of glucuronic acid and rhamnose. Arabinogalactan-proteins (5.30-8.83 g/kg) contain mainly arabinose and galactose (in a 1:1 proportion) and also significant amounts of rhamnose, xylose, glucuronic acid and mannose. Antioxidant activity of YP was higher than those of WP while chelating ability and reducing power increased with mucilages content. Generally YP and WP showed better reducing power (1.06 ± 0.35 at 5 mg/mL) than ascorbic acid (0.89 ± 0.22). WP and YP chelated ferrous ions by 20.0-76.0 % and 16.4-71.0 % respectively. Effective concentrations (EC50) of mucilages (WP 1.28 ± 0.05 mg/mL; YP 1.42 ± 0.04 mg/mL) were lower than those of citric acid (1.58 ± 0.04 mg/mL). Generally mucilage from the WP and YP sections are excellent sources of chelating agents.

Chemical composition, functional and sensory characteristics of wheat-taro composite flours and biscuits.

The physicochemical, alveographic and sensory characteristics of precooked taro-wheat composite flours and their biscuits were investigated. A 2x7 factorial design consisting of two varieties of taro flour (Red Ibo Ngaoundere, RIN, and egg-like varieties) and 7 levels of wheat substitutions (0, 5, 10, 15, 20, 25 and 30 %) was used for this purpose. It was observed that water absorption capacity (range 95-152 g/100 g), water solubility index (range 18.8-29.5 g/100 g) and swelling capacity (range 125.4-204.6 mL/100 g) of composite flours significantly (p < 0.05) increased with increase in taro level. Conversely the dough elasticity index (range 59.8-0 %), extensibility (78-22 mm) and strength (range 281-139 × 10(-4) joules) significantly (p < 0.05) diminished with increase in wheat substitution. Up to 10 % substitution with RIN taro flour and 15 % with egg-like taro flour, the composite taro-wheat dough exhibited elasticity indices acceptable for the production of baking products, whereas at all levels of taro substitution, the composite biscuits samples were either acceptable as or better (5-10 % substitution with RIN flour) than 100 % wheat biscuit.

Laccase-catalysed functionalisation of chitosan by ferulic acid and ethyl ferulate: evaluation of physicochemical and biofunctional properties.

Chitosan and its derivatives functionalized by laccase-catalyzed oxidation of ferulic acid (FA) and ethyl ferulate (EF) were characterised for their physico-chemical, antioxidant and antibacterial properties. The enzymatic grafting of oxidised phenols led to FA-coloured and EF-colourless chitosan derivatives with good stability of colour and grafted phenols towards the chemical treatment by organic solvents. The efficiency of FA-products grafting onto chitosan was higher than that of EF-products. Moreover, the enzymatic grafting of phenols onto chitosan changed its morphological surface, increased its molecular weight and its viscosity. Furthermore, the chitosan derivatives presented improved antioxidant properties especially for FA-chitosan derivative when compared with chitosan with good antioxidant stability towards thermal treatment (100°C/1h). Chitosan and its derivatives showed also similar antibacterial activities and more precisely bactericidal activities. This enzymatic procedure provided chitosan derivatives with improved properties such as antioxidant activity, thermal antioxidant stability as well as the preservation of initial antibacterial activity of chitosan.

Compositional, spectroscopic and rheological analyses of mucilage isolated from taro (Colocasia esculenta L. Schott) corms.

Tropical roots and tubers generally contain mucilage. These mucilages exhibit unique rheological properties with considerable potential as a food thickener and stabilizer. A one-step extraction procedure was used to isolate starch free mucilage and associated proteins from a number of taro (Colocasia esculenta) varieties. The monosaccharide and amino acid composition, the structural and flow properties were investigated. The results showed that yield of mucilage fraction varied from 30 to 190 g.kg(-1). A negative correlation (r = -0.87; p < 0.05) was observed between the crude protein level and the yield. The monosaccharide profiles revealed that galactose, mannose and arabinose were the main monosaccharides in the hydrolysate of the mucilage. From the 17 amino acids analyzed, aspartic acid/asparagine (14.4-17.2%) and glutamic acid/glutamine (10.3-13.6%) were prominent in the mucilage as well as the flour. No significant differences were observed in the FT-IR spectra and in the viscosity behavior of the mucilage dispersions. The greatest difference in the mucilage is based on its monosaccharide profile while the protein composition, which reflects that of the flour, is relatively stable.

Laccase-catalysed oxidation of ferulic acid and ethyl ferulate in aqueous medium: a green procedure for the synthesis of new compounds.

The enzymatic oxidation of ferulic acid (FA) and ethyl ferulate (EF) with Myceliophthora thermophila laccase, as biocatalyst, was performed in aqueous medium using an eco-friendly procedure to synthesize new active molecules. First, the commercial laccase was ultrafiltrated allowing for the elimination of phenolic contaminants and increasing the specific activity by a factor of 2. Then, kinetic parameters of this laccase were determined for both substrates (FA, EF), indicating a higher substrate affinity for ethyl ferulate. Additionally, enzymatic oxidation led to the synthesis of a FA-major product, exhibiting a molecular mass of 386 g/mol and a EF-major product with a molecular mass of 442 g/mol. Structural analyses by mass spectrometry allowed the identification of dimeric derivatives. The optical properties of the oxidation products showed the increase of red and yellow colours, with FA-products compared to EF-products. Additionally, enzymatic oxidation led to a decrease of antioxidant and cytotoxic activities compared to initial substrates. Consequently, this enzymatic procedure in aqueous medium could provide new compounds presenting optical, antioxidant and cytotoxic interest.

Interactions among lactose, ß-lactoglobulin and starch in co-lyophilized mixtures as determined by Fourier Transform Infrared Spectroscopy.

Processing and storage change food powders containing a large quantity of lactose due to lactose crystallization and interactions among components. Model food systems were prepared by co-lyophilization of lactose, ß-lactoglobulin (BLG), and gelatinized starch. A mixture design was used to define the percentage of each mixture component to simulate a wide range of food powders. Interactions among lactose, BLG and starch were studied using Fourier Transform Infrared (FT-IR) at different relative humidities (RH), before and after 3 months storage. Results showed the presence of hydrogen bonds among these components. Moreover, interactions or formation of hydrogen bonds among lactose, starch and BLG preserved BLG against freezing and freeze-drying shocks. Lactose crystallization could be identified by comparing infrared spectra of amorphous and crystallized lactose at O - H and C - H stretching vibration bands.

Effect of dairy powders fortification on yogurt textural and sensorial properties: a review.

Yogurts are important dairy products that have known a rapid market growth over the past few decades. Industrial yogurt manufacture involves different processing steps. Among them, protein fortification of the milk base is elemental. It greatly enhances yogurt nutritional and functional properties and prevents syneresis, an undesirable yogurt textural defect. Protein enrichment can be achieved by either concentration process (evaporation under vacuum and membrane processing: reverse osmosis and/or ultrafiltration) or by addition of dairy ingredients. Traditionally, skim milk powder (SMP) is used to enrich the milk base before fermentation. However, increased quality and availability of other dairy ingredients such as milk protein isolates (MPI), milk protein concentrates (MPC) whey protein isolates (WPI) and concentrates (WPC), micellar casein (MC) and caseinates have promoted their use as alternatives to SMP. Substituting different dry ingredients for skim milk powder in yogurt making affects the yogurt mix protein composition and subsequent textural and sensorial properties. This review focuses on various type of milk protein used for fortification purposes and their influence on these properties.

Effect of dairy powder rehydration state on gel formation during yogurt process.

Protein fortification and solubilisation into the milk base are important parameters enhancing yogurt texture. In this study, the milk base prepared from reconstituted skim milk powder was fortified with 2% of 'aged' (1 year old) or 'fresh' micellar casein (MC) powder. Micellar casein powders were left to rehydrate at 20°C for different times (5 or 180, 300, 480, 900 or 1440 min) before acidification with glucono-delta-lactone. The rehydration of the MC powders into milk was monitored with a granulo-morphometer equipment, thus, for the first time, allowing the elucidation of MC rehydration process into an opaque environment such as milk. Whereas the gel point was delayed proportionally to the powder rehydration length, the storage modulus appears unaffected. Besides, the gelation onset was not altered by the powder age.