Changes in colour and antioxidant activities of Hizikia fusiformis cooking drips by gamma irradiation

To utilize the cooking drips produced during the seaweed drying process, the effect of gamma irradiation on microbial contamination, colour, and antioxidant activities of Hizikia fusiformis cooking drips (HCD) was investigated. A two log cycles reduction of total aerobic bacteria and yeast and moulds counts was obtained irradiating HCD at 1 kGy. The Hunter L^∗ value of the HCD ethanol extract was increased by the gamma irradiation treatment, but the a^∗ and b^∗ values decreased upon irradiation depending on the absorbed dose. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging and β-carotene bleaching activities of the HCD extracts increased as a result of gamma irradiation, which was rationalized by the observed increase in polyphenolic compounds content. These results suggest that wasted cooking drips can be used as a functional component by the food and cosmetic industries if the irradiation technology were applied.     

Changes in membrane fatty acids and murein composition of Bacillus cereus and Salmonella Typhi induced by gamma irradiation treatment

This present study was carried out to evaluate the effects of gamma irradiation on the fatty acids (FA) and mureins composition of two different radiotolerant bacteria. Bacillus cereus LSPQ 2872 and Salmonella Typhi ATCC 19430 were used for this study. The bacterial strains were treated with a sublethal radiation dose of 1 kGy to cause a cellular damage. Gas chromatography (GC) and high performance liquid chromatography (HPLC) analysis were performed to demonstrate respectively the modification of the FA composition and the changes in muropeptide profile. Results obtained show, for both bacteria, that this treatment had a significant effect (P ≤ 0.05) on the FA content with an increase of unsaturated FA percentage. Substantial changes were also noticed for the relative percentage and the number of the muropeptides. This study represents one of the few to demonstrate the modifications on bacterial membrane as a cellular response to survive the ionising radiation stress.     

Steady and dynamic shear rheology of starches from different oat cultivars in relation to their physicochemical and structural properties

Starches isolated from eight oat cultivars were tested for their physicochemical, structural, and rheological properties. The isolated starches had low levels of ash and nitrogen contents with amylose ranging from 21.8 to 32.3 g/100 g. The amount of water released from starch gels decreased significantly (p < 0.05) with increase in freeze thaw cycle. The scanning electron micrographs revealed the presence of polygonal to irregularly shaped starch granules. All the starches exhibited A-type X-Ray diffraction pattern typically characteristic of cereal starches. The rheological properties of pastes were well described by the Herschel-Bulkley model at a shear rate of 0–100 s^?1 (R² > 0.99). The starch pastes behaved like a pseudoplastic fluid and exhibited shear thinning fluid characteristics with values of flow behaviour index considerably less than 1. Both the storage and loss moduli of the pastes increased sharply initially and then dropped after reaching the gelatinization peak. The magnitude of the dynamic rheological parameters varied significantly (p < 0.05) between the cultivars. All the starch pastes were highly elastic than viscous as evidenced by the lower tan δ values. Structure property relationships were established between starches using principal component analysis.     

Effects of gamma irradiation on the development and reproduction of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

The inhibitory effects of gamma irradiation were demonstrated on the development and reproduction including egg hatch, pupation, adult eclosion and oviposition of Plodia interpunctella. Failure of all these events increased with increasing doses from 0.1 to 1.0 kGy. However, the rates of developmental inhibition were different among three behavioral events. Egg hatch was almost completely inhibited by 0.5 kGy and higher doses. Pupation was completely inhibited by 0.25 kGy, but adult eclosion was not completely inhibited even by 1.0 kGy. In addition, different age groups within the egg and final larval stages differed in their susceptibility to 0.1 and 0.25 kGy doses; the rates of both hatching and pupation were lower when young individuals were irradiated. Fecundity and hatchability of eggs were greatly reduced when pupae were irradiated at 0.1 kGy and completely inhibited at 0.25 kGy and higher doses. This suggests that although some adults eclosed from pupae irradiated at 0.25 kGy and higher doses, they were not able to lay eggs. Our results suggest that irradiation at 0.5 kGy is appropriate for the inhibition of development and reproduction of P. interpunctella.     

A comparative study of heat and high pressure induced gels of whey and egg albumen proteins and their binary mixtures

Large deformation rheological studies of either egg albumen or whey protein isolate (15% protein w/w) gels induced by heating at 90 °C for 30 min were compared to those induced by a range high pressures (400–800 MPa for 20 min). Gels made by heating indicated higher gel strength and Young's modulus values for whey protein from pressures of 400–600 MPa for 20 min but similar values at 650–800 MPa. In contrast, egg albumen showed no gelation below 500 MPa for 20 min, but there was an increase in both gel strength and Young's modulus with increasing pressure, although values remained lower than those of the heat-induced gels. A mixture of 10:5 whey/egg albumen showed the highest gel strength and Young's modulus for both heated and high pressure-treated (400–600 MPa) gels, although, the heated mixture had the highest values. Electron micrographs indicated that high pressure-treated gels had a porous aggregated network for egg albumen while whey proteins showed a continuous fine stranded network. The heated mixtures of whey:egg albumen (7.5:7.5) showed large dense aggregates whereas high pressure-treated mixtures produced smaller aggregates. Raman spectroscopy of both heated and high pressure-treated whey and egg albumen (15% w/w in D₂O pD7) and their binary mixtures (7.5:7.5, protein w/w) indicated changes in β-sheet structures in the Amide 111′ region (980–990 cm⁻¹); however, peak intensity was reduced for high pressure-treated samples. β-Sheet structure (1238–1240 cm⁻¹) present in heated whey was absent in high pressure-treated whey and in egg albumen. Involvement of hydrophobic regions was reflected by changes in the CH (1350 cm⁻¹) and CH₂ (1450 cm⁻¹) bending vibrations. In addition to the Trp residues at 760 cm⁻¹, there were broad peaks at 874–880 cm⁻¹ and tyrosine 1207 cm⁻¹ in the high pressure-treated samples. Disulphide bands (500–540 cm⁻¹) in heated whey and egg albumen proteins showed higher peak intensities compared to high pressure-treated samples. Differences in the experimental and theoretical spectra indicated changes in the hydrophobic regions, tyrosine (1207 cm⁻¹) and tryptophan (880 cm⁻¹) and CH₂ bending in high pressure-treated samples, whereas heated samples indicated marked changes in β-sheet structures (987 and 1238 cm⁻¹) as well as hydrophobic regions CH (1350 cm⁻¹) and CH₂ (1450 cm⁻¹) bending vibrations.     

Changes in characteristics of sweet potato flour prepared by different drying techniques

The changes occurring in the characteristics of sweet potato flour as a result of processing were investigated. Pasting behaviour of drum dried and hot air-dried sweet potato flour was determined using Rapid Visco-Analyser. The pasting characteristics decreased due to gelatinization of starch during processing. The degradation of starch by amylases during hot air drying further lowered the water binding capacity/viscosity and total amylose and increased the digestibility compared to those of drum dried and native flour. Swelling power and solubility of the flours increased as a result of processing which subsequently increased with increase in temperature. Scanning electron micrographs of starch granules showed tendency of clustering, especially in drum dried samples. X-ray diffraction patterns showed alteration from Ca-type to V-type with a marked reduction in crystallinity index as a result of processing. The ¹³C NMR spectra of processed starches showed reduced peak intensities and line widths due to depolymerizing effects, and also pointing to their change in crystallinity.     

NaCl-induced changes in structure and water mobility in potato tissue as determined by CLSM and LF-NMR

This study for the first time reports the combined use of low-field nuclear magnetic resonance (LF-NMR) and confocal laser scanning microscopy (CLSM) in the study of the effects of salting on low and high dry matter (DM) potato tissue. The simultaneous use of CLSM and NMR resulted in important information in relation to the interpretation of the origin of the NMR water populations. Salting caused the raw potato cells to loose weight, which in the microscopic images was observed as loss of turgor pressure still further away from the edges of the samples with increased salting time. The total water loss after salting was lowest for high DM potatoes. The LF-NMR analyses revealed that this could be ascribed to a faster T₂ relaxation time of the cytoplasmatic and extracellular water and thus to water being more restricted in high DM potatoes. In addition, a tendency to a faster T₂ relaxation time was observed for both low and high DM potatoes with increasing salting time, which reveals a salt-induced restriction of the cytoplasmatic and extracellular water population. The paper illustrates the aptitude of NMR and CLSM to determine and elucidate structural changes and associated changes in water mobility in potato tissue.     

Water content of natural cyclodextrins and their essential oil complexes: A comparative study between Karl Fischer titration and thermal methods

The paper presents a comparative study regarding the water determination in natural cyclodextrins and in their essential oil complexes (Apiaceae, Liliaceae, and Cupressaceae families) by using Karl Fischer titration (KFT) and thermal methods. For the natural cyclodextrins, the influence of the solvent hydrophobicity and the preheating temperature on the water extraction process were evaluated. The water contents, estimated by KFT in both methanol and methanol–octanol solvent systems, were 10.6% and 14.4% for α- and β-cyclodextrin, respectively; the water content, estimated by KFT in a more hydrophilic solvent system, methanol–formamide, was 0.4–0.6% higher. Thermogravimetric evaluation of water conducts to lower values. For the essential oil/cyclodextrin complexes, the KFT water content were in the range of 6.4–8.1%, higher values being obtained in the case of Juniperus essential oil/β-cyclodextrin complexes (7.5–8.1%). With some exceptions, thermal analyses of complexes are in good agreement with the KFT results.     

Proso millet (Panicum miliaceum L.): An Evaluation of the Microstructural Changes in the Endosperm during the Malting Process by Using Scanning‐Electron and Confocal Laser Microscopy

Scanning electron microscopy (SEM) and confocal scanning laser microscopy (CLSM) were used to investigate the micro‐structural changes in the endosperm during the malting process. SEM was a suitable tool to characterise the microstructural constitution of starch granules in proso millet and the changes occurring during malting. An early visible degradation (after 24 h) of starch granules located in the floury endosperm, which is close to the embryo, could be observed. Due to this degradation, using confocal scanning laser microscopy, a less dense packaging of this part of the endosperm was observed. Degradation of starch granules in the vitreous endosperm was obvious at a distinct later stage of malting (78 h) and a preferred attack of small granules (>2.5 μm) was detected. Changes in protein structure could not be detected by either SEM or CLSM.     

A comparative study on the effectiveness of chlorine dioxide gas, ozone gas and e-beam irradiation treatments for inactivation of pathogens inoculated onto tomato, cantaloupe and lettuce seeds

The increase in reported food-borne outbreaks linked with consumption of raw fruits and vegetables has motivated new research focusing on prevention of pre-harvest produce contamination. This study evaluates and compares the effectiveness of three non-thermal technologies, chlorine dioxide gas, ozone gas and e-beam irradiation, for inactivation of Salmonella enterica and Escherichia coli O157:H7 on pre-inoculated tomato, lettuce and cantaloupe seeds, and also their corresponding effect on seeds germination percentage after treatments. Samples were treated with 10 mg/l ClO₂ gas for 3 min at 75% relative humidity, with 4.3 mg/l ozone gas for 5 min and with a dose of 7 kGy electron beam for 1 min. Initial load of pathogenic bacteria on seeds was ~ 6 log CFU/g. Results demonstrate that all treatments significantly reduce the initial load of pathogenic bacteria on seeds (p < 0.05). In particular, after ozone gas treatments 4 log CFU/g reduction was always observed, despite the seeds and/or microorganisms treated. ClO₂ and e-beam treatments were noticeably more effective against Salmonella on contaminated tomato seeds, where 5.3 and 4.4 log CFU/g reduction were respectively observed. Germination percentage was not affected, except for cantaloupe seeds, where the ratio was significantly lowered after ClO₂ treatments. Overall, the results obtained show the great applicability of these non-thermal inactivation techniques to control and reduce pathogenic bacteria contamination of seeds.     

欧姆加热对豆浆风味物质的影响

为研究蛋白酶影响豆浆风味的作用机理,在豆浆机制备豆浆中分别添加不同浓度的木瓜蛋白酶（15000、30000、45000、60000、75000 U/L）、氨基肽酶（500、1000、1500、2000、2500 U/L）、风味蛋白酶（100、150、200、250、300 U/L）和碱性蛋白酶（500、1500、2500、3500、4500 U/L）进行酶解,以不加酶的豆浆机制备豆浆为空白对照组、传统方法制备的豆浆为生豆对照组,对热生香后的豆浆进行感官评价,测定酶解、热生香后豆浆中的多肽和氨基酸态氮含量及变化量,并分析其与感官风味指标的相关性。采用顶空固相微萃取结合气相色谱-质谱联用技术,分析了豆浆中的挥发性风味物质。结果表明,空白对照组热生香后豆浆的豆腥味、豆香味比生豆对照组更淡,而多肽和氨基酸含量分别比生豆对照组降低了37.98%和25.78%。实验组添加250 U/L风味蛋白酶的豆浆感官评分最高,与空白对照组相比提高了118.41%。除添加4500 U/L碱性蛋白酶处理组外,添加蛋白酶后豆浆的感官评分均显著高于空白对照组（P<0.05）。加酶样品中与豆腥味相关的正己醛、2-戊基呋喃、正己醇、反,反-2,4-癸二烯醛等挥发性化合物含量均低于空白对照组和生豆对照组,与豆香气相关的挥发性化合物含量和种类均有不同程度提升。添加外源蛋白酶处理能明显提高豆浆中多肽和氨基酸含量,其中添加4500 U/L碱性蛋白酶时多肽含量最高（2.30±0.15 g/L）,添加2500 U/L氨基肽酶时氨基酸含量最高（0.087±0.0045 g/L）。风味蛋白酶处理组中酶解豆浆氨基酸态氮含量与豆香味得分呈显著正相关（P<0.05）,其他三种酶的多肽增加量均与豆腥味得分呈显著或极显著正相关（P<0.05,P<0.01）,氨基肽酶处理组中,氨基酸态氮增加量与豆腥味、豆香味和总分呈显著负相关（P<0.05）。以上结果表明,添加外源蛋白酶可以增加豆浆中多肽和氨基酸等风味前体物质的含量,制成豆腥味更淡、豆香味更丰富的豆浆。本研究为豆浆制备工艺的优化提供了理论指导。     

Stability of lactobacilli encapsulated in various microbial polymers

Various microbial polymers, namely xanthan gum, gellan gum, pullulan gum and jamilan, were tested as a suitable encapsulating material for Lactobacillus plantarum CRL 1815 and Lactobacillus rhamnosus ATCC 53103. Resulting capsules were also studied for their pH and simulated gastrointestinal conditions tolerance. The morphology of the microcapsules was studied using scanning electron microscopy. pH tolerance was tested at pH 2.0, 3.5, 5.0 and 6.5 over a 6h incubation period. Simulated gastrointestinal conditions were assayed with simulated gastric and pancreatic juices and simulated bile over a 24h incubation period. Suspensions of probiotic organisms were used as a control. The results from encapsulation with microbial polymers indicate that mixtures of 1% xanthan gum with 0.75% gellan gum and 1% jamilan with 1% gellan gum were the most suitable for microencapsulation. Results for the pH tolerance tests showed no improvement in the viability of cells in relation to the control, except for pH 2.0 where lactobacilli encapsulated in xanthan:gellan gum (1%:0.75%) prolonged their viability by 6h exposure. Xanthan:gellan gum (1%:0.75%) was the most effective of the encapsulating materials tested in protecting L. plantarum and L. rhamnosus against simulated bile, improving its viability in 1-2 logCFU when compared with control. The results of this study suggest that microbial polymers are an interesting source of encapsulating material that should be taken into account for prospective studies of probiotic encapsulation for oral delivery applications.     

Water properties and salt uptake in Atlantic salmon fillets as affected by ante-mortem stress,rigor mortis,and brine salting: A low-field H NMR and H/Na MRI study

A low-field (LF) ¹H NMR T₂ relaxation and ²³Na/¹H MRI study was performed on Atlantic salmon to study the effect of ante-mortem handling stress and rigor mortis on muscle water properties and subsequent post-rigor salting. Compared to rested fish, exhausted fish exhibited a more rapid and stronger development of rigor mortis. This resulted in significant differences in post-rigor water-holding capacity and salt uptake. By LF NMR T₂ relaxation analysis significant differences in water distribution according to (1) ante-mortem handling, (2) fillet location, and (3) brine salting were detected. Furthermore, ²³Na MRI revealed differences between the two treatments in fillet salt distribution, where the salt penetration in exhausted fillets was more pronounced. By combining ¹H and ²³Na MR images, the salt diffusion and distribution seemed to be highly affected by the distribution of fat.     

Physical and chemical methods used to enhance the structure and mechanical properties of protein films: A review

Efforts for developing protein films as biodegradable packaging materials have increased in recent years. One of the drawbacks of such films is that their functional properties are generally inferior to those of synthetic films. Although protein films typically have excellent gas barrier properties, they tend to have higher water vapor permeability, are mechanically weaker, and have lower elongation as compared to most synthetic polymers. This paper will review the various methods that have been reported to enhance the physical and barrier properties of protein films. The effects of film formulation and preparation conditions, including plasticization, pH alteration, and lipid addition, on the functional properties of protein films are discussed. The paper also offers a comprehensive review of the various methods used to modify protein film functional properties, including cross-linking techniques induced by heat, chemical, enzymes, and irradiation, and use of nanocomposites to enhance their barrier properties. A critical comparison of the different technical solutions is offered, and the challenges and potential applications of these films are discussed.     

Physical, chemical and technological characteristics of Solanum lycocarpum A. St. - HILL (Solanaceae) fruit flour and starch

Fruit of wolf (Solanum lycocarpum A. St. - HILL), found in Brazilian cerrado, has been used in the initial ripening stage as flour and/or starch in popular medicine due to its hypoglycemiant action. The aim of this work was to study the occurrence of phytochemical compounds, physical, chemical and technological characteristics of fruit of wolf flour and starch in the initial ripening stage. Flour and starch were extracted using known popularly and experimental methods (with sodium bisulfite) and chemical composition and technological characteristics were analyzed. The results were comparatively assessed by Tukey's test (p < 0.05). The recommendation for use was the extraction of flour and starch products by previously removing peels and seeds of fruit of wolf. The most relevant finding in this study is the high content of fibers in flour (23 g/100 g) and high content of resistant starch (32 g/100 g) in the fraction of starch extracted from fruit of wolf, which can explain their use as hypoglycemic agent.