Effect of cross-linking on the physicochemical and physiological properties of corn starch

Corn starch was chemically modified by cross-linking with STMP/STPP (99:1. w/w) and the physicochemical and physiological properties (in vitro and in vivo) of the cross-linked corn starch were investigated as a function of the degree of cross-linking. Cross-linking decreased the solubility, swelling factor, and paste clarity of corn starch. While the swelling factor was highly correlated with the degree of cross-linking (R² = 0.878), the X-ray diffraction patterns did not show any significant alteration in the crystallinity of corn starch. It was shown by SEM measurement that a black zone was observed on the surface of crossed-linked starch granules, which did not occur with native starch. When mice were fed the diets containing the corn starch with low (CLCS-5) and high (CLCS-12) degree of cross-linking (51.3 and 99.1%, respectively), significant effects on the final body weight, weight gain as well as perirenal weight of the mice (p < 0.05) were observed. Also, significant decreases in total lipid, triglyceride, and total cholesterol concentrations in serum were detected in CLCS-5 and CLCS-12 groups (p < 0.05). While total lipid level in the liver decreased with increasing degree of cross-linking, the triglyceride level was not affected by the supplementation with both of CLCS-5 and CLCS-12 corn starch samples.     

Elucidation of structural difference in theaflavins for modulation of starch digestion

The relationship between structure and activity of theaflavins against human pancreatic α-Amylase was investigated by in vitro and in silico methods. The IC₅₀ and total energy value showed that inhibitory effects followed the order: theaflavin-3, 3’-di-O-gallate > theaflavin-3’-O-gallate > theaflavin-3-O-gallate > theaflavin. Inhibitory activity was depended on hydroxyl groups and galloyl moieties of theaflavins to interact with the catalytic residues of the active site of α-Amylase by hydrogen bonds and π–π (aromatic–aromatic) interactions. The galloylated theaflavin has higher binding affinity with α-Amylase than non-galloylated theaflavin. The study showed that theaflavins might act as natural enzyme inhibitors with potential health benefits, which provide a foundation for designing novel functional food for effective controlling of starch digestion and postprandial glucose levels.     

In vitro digestibility,structural and functional properties of starch from pigeon pea (Cajanus cajan) cultivars grown in India

Starches isolated from two pigeon pea cultivars (AL-15 and AL-201) were evaluated for their in vitro digestibility, structural and functional properties. Both the cultivars exhibited a characteristic C-type diffraction pattern with relative crystallinity values of 31.9% and 34.2%, for AL-15 and AL-201, respectively. The structural characterization obtained using high performance size exclusion column chromatography revealed that molecular weight of amylopectin and amylose was higher for AL-201 (396 and 3.92 × 10⁶ g/mol, respectively) in comparison to AL-15 starch (354 and 3.31 × 10⁶ g/mol, respectively). AL-201 exhibited higher values for transition temperatures, enthalpy of gelatinization, pasting temperature and percentage retrogradation in comparison to AL-15 starch. Slowly digestible starch, readily digestible starch and resistant starch contents of AL-15 and AL-201 cultivars were observed to be 31.0, 8.1 and 60.9% and 29.6, 5.2 and 65.2%, respectively. The hydrolysis index and RS values indicated that pigeon pea starches were highly resistant to digestion.     

Wettability of starch gel films

Contact angles for water, glycerol, formamide, ethylene glycol and diiodomethane on polymethyl methacrylate (PMMA) covered by gelatinized corn and potato starch films were measured and statistically no significant differences between them were found. The contact angles were correlated with starch content in a gel and a straight linear relationship was confirmed by making use of Student t-test. Using this correlation the Lifshitz–van der Waals component and electron-acceptor and -donor parameters of the acid–base components of the film surface free energy were calculated. The obtained relationship between the Lifshitz–van der Waals component and starch content in a gel was also linear. Linear relationships were also obtained for the electron-acceptor and -donor parameter as a function of starch content in a gel film. For the Lifshitz–van der Waals component and electron-acceptor parameter a very small decrease was observed. This component decreased from 33.7 to 31.4 mJ/m² for corn gel and from 32.7 to 31.0 mJ/m² for potato gel, and the electron-acceptor parameter decreased from 1.4 to 0.6 mJ/m² for corn gel and from 1.3 to 0.8 mJ/m² for potato gel. However, the electron-donor parameter increased substantially from 31.2 to 70.6 mJ/m² for corn gel and from 32.2 to 63.3 mJ/m² for potato gel. It was suggested that starch gel surface attempted to maintain maximal hydrophobic character with polar domains formed by functional groups of d-glucose units.     

Use of continuous bubble separation process for separating and recovering starch and mucilage from yam (Dioscorea pseudojaponica yamamoto)

The yam (Dioscorea pseudojaponica Yamamoto) tuber is abundant in both starch and mucilage. It is difficult to separate yam starch from its tuber because of the presence of viscous polysaccharide polymers (glycoprotein). The surface-active polysaccharide-containing complexes are capable of forming foams. The goal of this study was to develop a continuous bubble separation process for separating and recovering starch and mucilage from yam tubers in the absence of undesirable chemical additives or treatments. The results showed that the highest concentration (13.2 g/100 g) of yam slurry mucilage was obtained with a reasonably high yield of recovered starch (91.2 g/100 g) by treating the starch paste with 1 g/100 g Viscozyme^® L and Pectinex^® Ultra SP-L. In comparison with the total amount of yam fed into the system, the yield of soluble carbohydrates and protein in separated mucilage were 98.8 g/100 g and 74.1 g/100 g, respectively. The chemical composition of the separated freeze-dried mucilage was shown to be high in soluble carbohydrates (52.5 g/100 g, dry basis) and protein (40.3 g/100 g, dry basis). A very low amount of starch (0.8 g/100 g) remained in the mucilage. This method is simple, low in operational and capital costs, and especially suitable for polysaccharide–protein-containing complexes recovering from a starch-containing system.     

Fat contributes to the buffering capacity of chicken skin and meat but enhances the vulnerability of attached Salmonella cells to acetic acid treatment

Chicken skin and chicken meat display different buffering effects which may impact the survival of Salmonella attached to them when treated with acids. This study investigated the role that differences in fat composition of chicken skin and meat play in their buffering capacity. The survival of Salmonella attached to chicken skin and meat in the presence of fat, and treated with acetic acid was also investigated. Fat was extracted from chicken skin and meat and the buffering capacities of chicken skin, meat, extracted fat and their respective remnants were determined. Two strains of Salmonella Typhimurium and two strains of S. Enteritidis were attached independently to each of the chicken component listed above and enumerated before and after treatment with 0.3 M acetic acid. Chicken skin has a higher fat content as compared to chicken meat. Skin (13 mmol H⁺/(pH1 kg)) had a stronger buffering capacity (p < 0.05) than the extracted fat alone and skin remnants alone (7.0 mmol H⁺/(pH 1 kg) and 6.9 mmol H⁺/(pH 1 kg) respectively). From an initial inoculum (~ 9 log CFU/g), Salmonella cells attached better (p < 0.05) to chicken meat (~ 8 log CFU/g) and chicken skin (~ 7 log CFU/g) than extracted fat (~ 1.5 log CFU/g). Skin remnants without fat were better (p < 0.05) at protecting attached Salmonella than other chicken components. For example S. Typhimurium ATCC 33062 decreased ~ 1 log CFU/g (p < 0.05) on skin remnants after acetic acid treatment while its viable counts on other components decreased from ~ 1.5 to 7 log CFU/g (p < 0.05). We suggest that the fat content present in the skin may enhance the vulnerability of attached cells to acetic acid.     

Structural and physicochemical properties and in vitro digestibility of recrystallized linear α-d-(1 → 4) glucans derived from mild-acid-modified cassava starch

Molecular structure and recrystallization method influence the techno-functional behaviour of recrystallized starch as a functional ingredient in foods. The physicochemical properties of debranched and recrystallized mild-acid-modified cassava starch were studied. Cassava starch was treated with 0.14 mol/L hydrochloric acid for 24, 96 and 216 h at 40 °C prior to debranching with pullulanase. The debranched starches (DS) were recrystallized by annealing (ANN-DS), temperature-cycling (TC-DS) or heat-moisture treatment (HMT-DS) and the particle distribution, crystallinity, thermal properties, solubility, water binding and in vitro digestibility were analyzed. Acid treatment increased the fraction of linear α-d-(1 → 4) glucans comprising 13–30 monomers. Particles comprised loosely to firmly coalesced primary elements forming aggregates of mono- or bi-modal size distribution at ?5 μm and ?20 μm. The relative crystallinities ranged between 31.1–56.1%. Water binding decreased significantly with acid treatment whereas both solubility and water binding were influenced by the recrystallization method and decreased in the order: DS > ANN-DS > TC-DS > HMT-DS. Major thermal transitions occurred at 80–130 °C and 130–160 °C, and the in vitro digestibility rates of 6.8–62.8% correlated significantly (p < 0.001) with relative crystallinity and melting enthalpy.     

Influence of assay conditions on the in vitro hindgut digestibility of dry matter

In vitro assays have been developed to predict dry matter digestibility (DMD) in the human colon, but there is little information on the effect of assay variables. The effect of altering pH, duration of incubation, presence of shaking during incubation and the concentration of faecal inoculum or digestive enzymes on DMD was investigated for three in vitro hindgut digestibility assays. Three mixed human diets varying in the type and ratio of soluble and insoluble dietary fibre were used as substrates. The pH, duration of incubation and the concentration of inoculum relative to substrate significantly (P > 0.05) affected predicted DMD for the two in vitro methods employing faecal inocula. The method using synthetic enzymes showed little sensitivity to alteration of assay variables and gave highly variable results and for this reason was not pursued further. Shaking did not affect (P > 0.05) digestibility for any method or diet. The different methods led to large differences in predicted hindgut DMD within each of the three diets. In vitro hindgut digestibility assay variables need to be optimised and the predicted DMD data validated against in vivo data.     

Effect of the addition of fatty acids on rice starch properties

The effect of the addition of the two fatty acids (stearic and linoleic acid) on starch pasting, thermal properties and the leaching of amylose during the gelatinization process are presented. The addition of stearic acid (C18:0) at 1.0% level (w/w, on the basis of starch) significantly changed starch pasting characteristics in peak viscosity (P < 0.05), breakdown (P < 0.001) and time to peak viscosity (P < 0.001) as measured by RVA. In contrast, the addition of linoleic acid (C18:2) showed less impact on the three RVA parameters. Thermal studies with DSC suggested that the addition of both fatty acids did not significantly influence the starch gelatinization behaviour as reflected in peak width and enthalpy but there was a decrease in peak temperature. However, the addition of the saturated fatty acid produced a significant decrease in the retrogradation endotherm (P < 0.01) compared to that of native starch. It is suggested that the saturated fatty acid complexes with amylose and is preferentially introduced into the starch granule. The double bond in the linoleic acid apparently hinders complexation. After complexation, hydrophobicity was further enhanced with the content of amylose in the hot-water soluble fraction being significantly reduced (P < 0.01) as determined by HPLC.     

Studies on the granular structure of resistant starches (type 4) from normal,high amylose and waxy corn starch citrates

Granular and crystalline structure of starch citrates from normal, high amylose and waxy corn starch were characterized using scanning electron microscopy (SEM), optical microscopy, X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) in this study. SEM showed that citric acid treatment induced changes in the morphology of starch granules. The granule structure of starch citrates was not collapsed or destroyed even after heating. Normal and high amylose corn starch citrates maintained birefringence but lost it upon heating at 100 °C for 30 min. However, waxy corn starch citrate showed no birefringence, even before heating. Starch citrates showed different X-ray diffraction patterns before and after heating. A new peak at 1724 cm⁻¹ (ester bond) was observed in FT-IR for all starch citrates before and after heating, indicating starch citrates were heat-stable. After the deconvolution of spectra, the intensity ratio of 1016 cm⁻¹/1045 cm⁻¹ was used to calculate the ratio of amorphous to crystalline phase in the starch citrates. The ratio of 1016 cm⁻¹/1045 cm⁻¹ increased with an increase in the degree of substitution.     

Absorption of whey protein isolated (WPI)-stabilized β-Carotene emulsions by oppositely charged oxidized starch microgels

β-Carotene is a natural antioxidant that is beneficial for human health. β-Carotene is well known for its aqueous insolubility and its sensitivity to environmental stimuli. To achieve the targeted delivery of β-Carotene to human intestine, a microgel system was developed. The microgel is made of oxidized potato starch polymers, which are obtained by chemical cross-link process by sodium trimetaphosphate (STMP). At pH < pI (WPI: pH 5), as in the acidic condition in stomach, the positively charged WPI emulsified β-Carotene nanoemulsion droplets were absorbed by the negatively charged starch microgel particles, which prevented the early release of β-Carotene in stomach. At pH > pI, as in the intestinal condition, WPI–β-Carotene nanoemulsion droplets and microgel particles both carry negative charges. Under this condition, β-Carotene will be released from microgel. In this study, we investigated the absorption capacity of β-Carotene nanoemulsion droplets by oxidized starch microgel particles of various degrees of oxidation (DO) and the cross-link density (R_{cross-linker/polymer(w/w)}) is investigated as a function of pH and salt concentrations. We found that DO30% with R_{cross-linker/polymer(w/w)} = 0.1 was the optimal gel type for nanoemulsion droplets absorption, and pH 3 and ionic strength of 0.06 M were the optimal conditions for nanoemulsion droplets absorption. The swelling capacity of the microgel particles rather than its ζ-potential was dominant in governing the absorption capacity. The in vitro release experiment under stimulated gastrointestinal fluids suggested that β-Carotene emulsions droplets remained stable at the gastric condition and were majorly released under the intestinal condition. The results suggested that the oxidized starch microgel could be used to prevent the early release of β-Carotene in the stomach and target delivery of them to the intestine.     

Effect of native crystalline structure of isolated potato starch on gelatinization behavior and consequently on glycemic response

Effect of crystalline structure of two isolated potato starches on gelatinization and glycemic response was studied. Both starches showed to possess different fine structures. Starch 1 exhibited a typical B-type X-ray diffraction pattern, while Starch 2 exhibited an X-ray diffraction pattern suggesting the presence of imperfections of the general B-type crystalline structure (peak at 5.5° 2θ was absent), hence disarraying the structure order. This difference was reflected in the gelatinization behavior and consequently in the glycemic response. Starch 2 started to melt at lower temperature than Starch 1 (e.g. T_o was 60.9 and 61.84 °C, respectively, to native starches), and residual gelatinization enthalpy (ΔH) of Starch 2 was always smaller than that of Starch 1 when heated at 54–65 °C for 10 min. Glycemic response was increased as gelatinization degree (DG) increased in starches independent from the native crystalline structure (area under curve = 2.59 × DG-75.83, R² = 0.986; maximum concentration of postprandial blood glucose = 0.042 × DG-0.23, R² = 0.935). Results suggested that native crystalline structure of isolated potato starch affects the glycemic response of heated starches by affecting the gelatinization behavior.     

Brining of cod fillets: effects of phosphate,salt, glucose,ascorbate and starch on yield,sensory quality and consumers liking

In order to study how triphosphate, salt, glucose, ascorbate and starch, both separately and in mixture, could affect the quality and the yield of brined cod fillets, an experimental design was applied. Salt was the variable with highest pronounced effect on yield and appearance, followed by triphosphate, glucose, starch and sodium ascorbate. By treating skinless frozen/thawed cod fillets with brine consisting of 25 g salt/l, 10 g triphosphate/l, 5 g glucose/l, 5 g sodium ascorbate/l and 5 g starch/l in a vacuum tumbler for 15 min, a 35% weight increase was obtained. The products retained a natural appearance with a homogenous surface. Next, an experiment was carried out to assess the effect of this brining mixture on sensory properties and consumers liking of both fresh and frozen/thawed cod fillets. Sensory analyses showed that the intensity of the sensory attributes cod taste, cod smell, juiciness, whiteness and glossiness could be heightened by brining, while the intensities of old/stale taste and smell could be lowered. The effects were prominent for products subjected to freezing before and/or after processing, while the characteristics of the fresh products were little influenced by brining. Using an in-house consumer panel, it was shown that the frozen/thawed products were the less preferred products. However, brining considerably enhanced the preferences for frozen and thawed cod fillets, obtaining preferences similar to the fresh, nonbrined product (F).     

Antimicrobial activity of nisin-adsorbed silica and corn starch powders

The antimicrobial peptide nisin is an effective bacterial inhibitor and has been adsorbed onto various surfaces and added to packaging films. In the present study, nisin was adsorbed onto food-grade powders then evaluated for nisin activity in a series of three experiments. Adsorbent powders used were calcined diatomaceous earth, synthetic calcium silicate, hydrate, two diatomaceous earth, and corn starch powders. Adsorption was conducted by placing the powders in agitated nisin solutions, followed by dehydration of the powder pellet after centrifugation. The dehydrated powders were then tested for inhibitory activity against either Lactobacillus plantarum or Listeria monocytogenes. Activity was measured by placing the nisin-adsorbed powders in solutions of 0.1% peptone water inoculated with one of the test bacterial strains. Cel-pure 65 adsorbed then released from 74.7% to 94.7% of the nisin activity contained in the original solution (500–800 IU/ml) in which the powders were agitated. Corn starch adsorbed then released from 45.4% to 60.5% of nisin activity when from 300 to 700 IU/ml nisin activity adsorbing solutions were utilized. One percent of nisin-absorbed Celpure 100 and Celpure 65 powders in 30 ml of log 4.5 cfu/ml L. monocytogenes inoculum reduced populations to below detection levels (<10¹ cfu/ml) within 24 and 6 h, respectively. Thus, nisin-adsorbed powders were highly efficient at both adsorption and release of antimicrobial activity.     

Steady and oscillatory shear behaviour of semi-concentrated starch suspensions

The viscoelastic moduli G’ and G” of aqueous suspensions with 40% (w/v) normal corn starch (NCS) and waxy corn starch (WCS) were determined by oscillation rheometry. The oscillatory shear flow experiments at heating from 30° to 75 °C and maintaining at this temperature showed changes from a behaviour predominant viscous (G”>>G’) to predominant elastic (G’>G”) for both starches at 60.5 °C for WCS, respectively 70,85 °C for NCS, WCS having higher values of G’ and G” as NCS. After the gelatinisation temperature was attired, NCS showed no significant changes, both moduli remaining relatively constant. Peaks of both moduli G’ and G” were obtained for WCS at its maintaining at 75^oC, these changes being attributed to the changes in the amylopectin structure in the absence of amylose for this starch type. The frequency influenced the results; analysis at constant low frequency (10 s^-1) gave big oscillations during the measurements and made the analysis impossible, whereas frequencies as 50 s^-1 or 100 s^-1 gaves reproducible and similar results. The shear flow measurements realised at angular frequencies ω from10^-1 to 10³s^-1 at 25^oC showed that changes from a behaviour predominant elastic (G’>G”) to predominant viscous (G”>>G’) occurred when ω attired the values 10 s^-1 for WCS and 3 s^-1 for NCS. The calculation of the ‘Power-Law’ parameter B showed that NCS forms a physical gel structure, whereas WCS behaves as a covalent gel in the frequency domain 10^-1 to 10 s^-1 and as physical gel in the frequency domain 10 to 10² s^-1.     

Probiotic properties of folate producing Streptococcus thermophilus strains

This study aimed at assessing the probiotic potential of two high folate producing Streptococcus thermophilus strains (RD102 and RD104) isolated from Indian fermented milk products by both in vitro and in vivo tests. These strains were able to survive at pH 2.5 and 2% bile with a good bile salt hydrolase activity, cell surface hydrophobicity and sensitivity to most of the clinically important antibiotics. On evaluation for gastrointestinal transit tolerance these showed a viable count of 5 log cfu mL^?1 and 7 log cfu mL^?1, respectively in simulated gastrointestinal juice of pH 2.0 and 2% bile. During the in vivo feeding trial in mice the strains showed a viable count of about 7 log cfu g^?1 faeces and 6 log cfu g^?1 of large intestine, respectively. These strains were hence observed to possess favorable strain specific probiotic properties and have the potential to be a source of novel probiotics.     

Simulated gastrointestinal fate of lipids encapsulated in starch hydrogels: Impact of normal and high amylose corn starch

The influence of starch type (resistant starch (RS) versus native (NS) starch) and concentration (10 and 35 wt.%) on the potential gastrointestinal fate of digestible lipid (corn oil) droplets encapsulated within starch hydrogels was studied using a simulated gastrointestinal tract (GIT). The NS used was a normal corn starch, whereas the RS used was a high amylose corn starch. Changes in morphology, organization, size, and charge of the particles in the delivery systems were measured as they passed through each stage of the GIT model: mouth, stomach, and small intestine. The GIT fates of three types of delivery system were compared: free lipid droplets; lipid droplets in RS-hydrogels; and, lipid droplets in NS-hydrogels. Encapsulation of the lipid droplets in the hydrogels had a pronounced influence on their GIT behavior, with the effect depending strongly on starch type. The starch granules in the RS-hydrogels remained intact throughout the simulated GIT because their compact structure makes them resistant to enzyme digestion. The initial rate of lipid digestion in the small intestine phase also depended on delivery system type: emulsion > RS-hydrogels > NS-hydrogels. However, the lipid phase appeared to be fully digested at the end of the digestion period for all samples. These results provide useful information for designing functional foods for improved health. For example, food matrices could be developed that slowdown the rate of lipid digestion, and therefore prevent a spike in serum triacylglycerols in the blood, which may be advantageous for developing functional foods to tackle diabetes.     

Enthalpy–entropy compensation in sorption phenomena of starch materials

The enthalpy–entropy compensation theory was applied to the experimental moisture adsorption and desorption isotherm data (water activity (a_w) range 0.006–0.982) of raw potato, potato starch gel, potato starch powder, highly amylopectin corn starch powder and highly amylose corn starch powder in the temperature range 30–60 °C. A linear relation existed between differential enthalpy (ΔH) and differential entropy (ΔS) for all the experimental data considered, thus satisfying the enthalpy–entropy compensation theory. Further analysis of the data indicated an enthalpy-controlled (isokinetic temperature (T_β) > harmonic mean temperature (T_hm)) and spontaneous (−ΔG) sorption process.     

Synthesis of dodecenyl succinic anhydride (DDSA) corn starch

Dodecenly succinic anhydride (DDSA) starches were prepared commercially by the base catalyzed reaction of DDSA in pre-emulsion with starch granular in aqueous slurry. The results indicated that the degree of substitution and reaction efficiency were 0.0256% and 42.7%, respectively, at the parameters for the preparation of DDSA starches in starch slurry 30%, DDSA/starch radio 10% (wt/wt), pH 8.5–9.0, reaction temperature 313 K. After modification, product surface chemical composite had been changed which was prone to migrate into less polar solution. The chemical structural characteristics were investigated by methods of FTIR and ¹H NMR. The results of X-ray diffraction showed the native A-type crystalline pattern, indicating that reaction of corn starch with DDSA caused no change in the crystalline structure. Compared to native starch, the hydrophobic performance of esters was greatly increased. With the DS increasing, contact angles were gradually increased, however, the adhesion works were decreased. The maximum contact angle of DDSA starch could attend to 123°, and the corresponding adhesion work was 33.2 mJ m⁻².     

Aerosol-assisted low pressure plasma deposition of antimicrobial hybrid organic-inorganic Cu-composite thin films for food packaging applications

An innovative low pressure plasma process for deposition of copper-containing hybrid organic-inorganic thin films was developed. The discharge was fed with an aerosol of an aqueous solution of a copper complex, i.e. bis(ethylenediamine)copper(II) hydroxide and argon. Polymeric films, incorporating inorganic Cu(I) and Cu(II) compounds, were obtained. Morphological and chemical characterizations of the coatings were carried out.Antimicrobial properties were assessed on two species of Pseudomonas spp. In vitro tests were carried out by contact of the optimized films, deposited on square polycarbonate samples (~ 4 cm²), with cell suspensions of 1 × 10⁴ CFU/mL for 18 h at 25 °C. It was demonstrated that, the hybrid organic-inorganic thin coatings have potential utilization as active packaging material, showing an antimicrobial effect of up to three orders of magnitude (final microbial concentration 10⁵ CFU/mL), compared to control polycarbonate (final microbial concentration 10⁸ CFU/mL).Industrial relevanceAn innovative low pressure plasma process for deposition of copper-based, hybrid organic-inorganic thin films was developed. The optimized thin coatings have potential industrial utilization as active packaging material, being very effective against pseudomonads. Viability of Pseudomonas was reduced by three orders of magnitude (from 10⁸ CFU/mL to 10⁵ CFU/mL) in the presence of developed films, thus suggesting further investigation of the technique under food packaging conditions.