Morphological, textural analysis and freeze-thaw stability of starches from legume grow in Cameroon / Análise morfológica, textural e de estabilidade de congelamento-descongelamento de amidos de leguminosas cultivadas em Camarões

Starches from some legume grown in Cameroon were evaluated for their granule structure and size, turbidity, firmness and gel strength, thermal and freeze-thaw properties. Amylose contents were in the range of 26.21%-44.85%. Morphological analysis of the starch granules showed bimodal distribution, multiple sizes and shapes from small spherical to the bigger kidney shape. Significant differences were observed among starch in light transmittance, firmness and gel strength. The thermal parameters of starches were evaluated using differential scanning calorimeter and significant differences were observed. The peak gelatinisation temperature was positively correlated to starch granule size but the amylose content showed no evidence of their impact on legume starch properties studied. The data reported can be useful to facilitate the selection of variety of legume and conditions closer to the desired application.

Neste trabalho, amidos de algumas leguminosas cultivadas em Camarões foram avaliados quanto à estrutura e tamanho dos grânulos, turbidez, firmeza e resistência do gel, propriedades térmicas e de congelamento e descongelamento. Os conteúdos de amilose estavam na faixa de 26,21% a 44,85%. A análise morfológica dos grânulos de amido mostrou distribuição bimodal, múltiplos tamanhos e formas desde o pequeno esférico até o maior formato de rim. Diferenças significativas foram observadas entre os amidos na transmissão de luz, firmeza e força do gel. Os parâmetros térmicos dos amidos foram avaliados usando calorímetro diferencial de varredura e diferenças significativas foram examinadas. A temperatura de pico de gelatinização foi positivamente correlacionada com o tamanho do grânulo de amido, no entanto, o teor de amilose não mostrou evidência de impacto nas propriedades do amido de leguminosas estudadas. Os dados informados podem ser úteis para facilitar a seleção de variedades de leguminosas e condições mais próximas da aplicação desejada.

Effect of antifreeze proteins on the freeze-thaw cycle of foods: fundamentals, mechanisms of action, current challenges and recommendations for future work.

Freezing is widely used in food preservation, but if not carried out properly, ice crystals can multiply (nucleation) or grow (recrystallization) rapidly. This also affects thawing, causing structural damage and affecting overall quality. The objective of this review is to comprehensively study the cryoprotective effect of antifreeze proteins (AFPs), highlighting their role in the freeze-thaw process of food. The properties of AFPs are based on their thermal hysteresis capacity (THC), on the modification of crystal morphology and on the inhibition of ice recrystallization. The mechanism of action of AFPs is based on the adsorption-inhibition theory, but the specific role of hydrogen and hydrophobic bonds/residues and structural characteristics is also detailed. Because of the properties of AFPs, they have been successfully used to preserve the quality of a wide variety of refrigerated and frozen foods. Among the limitations of the use of AFPs, the high cost of production stands out, but currently there are solutions such as the use the production of recombinant proteins, cloning and chemical synthesis. Although in vitro, in vivo and human studies have shown that AFPs are non-toxic, their safety remains a matter of debate. Further studies are recommended to expand knowledge about AFPs, to reduce costs in their large-scale production, to understand their interaction with other food compounds and their possible effects on the consumer.

Comparative Study of the Efficiency of Additives in the Extraction of Phycocyanin-C from Arthrospira maxima Using Ultrasonication

Several phycocyanin extraction methods have been proposed, however, most of them present economical or productive barriers. One of the most promising methods that has been suggested is ultrasonication. We have analyzed here the effect of operational conditions and additives on the extraction and purity of phycocyanin from Arthrospira maxima. We followed three experimental designs to determine the best combination of buffered pH solutions, additives, fresh and lyophilized biomass. We have found that additives such as citric acid and/or disaccharides could be beneficial to the extraction process. We concluded that the biomass-solvent ratio is a determining factor to obtain high extraction and purity ratios with short ultrasonication times.

Electrical Impedance to Easily Discover Undeclared Freeze-thaw Cycles in Slaughtered Bovine Meat.

A portable electrical impedance spectroscopy device was developed to monitor the bioimpedance resistive component of bovine meat by injecting a sinusoidal current of 1 mA at 65 kHz. Both right and left longissimus dorsi muscles were trimmed from 4 slaughtered cows. The left muscle portions were frozen to -18 °C for 7 days while the right ones were meantime maintained at 5 °C. Mean value of impedance per length (Ω/cm) of frozen and thawed left samples was 31% lower than that of right non-frozen one (P = 0.0001). It was concluded that the device is reliable for monitoring the maturation of beef meat in situ with the possibility of revealing undeclared freeze-thaw cycles.

Microbial Succession under Freeze-Thaw Events and Its Potential for Hydrocarbon Degradation in Nutrient-Amended Antarctic Soil.

The polar regions have relatively low richness and diversity of plants and animals, and the basis of the entire ecological chain is supported by microbial diversity. In these regions, understanding the microbial response against environmental factors and anthropogenic disturbances is essential to understand patterns better, prevent isolated events, and apply biotechnology strategies. The Antarctic continent has been increasingly affected by anthropogenic contamination, and its constant temperature fluctuations limit the application of clean recovery strategies, such as bioremediation. We evaluated the bacterial response in oil-contaminated soil through a nutrient-amended microcosm experiment using two temperature regimes: (i) 4 °C and (ii) a freeze-thaw cycle (FTC) alternating between -20 and 4 °C. Bacterial taxa, such as Myxococcales, Chitinophagaceae, and Acidimicrobiales, were strongly related to the FTC. Rhodococcus was positively related to contaminated soils and further stimulated under FTC conditions. Additionally, the nutrient-amended treatment under the FTC regime enhanced bacterial groups with known biodegradation potential and was efficient in removing hydrocarbons of diesel oil. The experimental design, rates of bacterial succession, and level of hydrocarbon transformation can be considered as a baseline for further studies aimed at improving bioremediation strategies in environments affected by FTC regimes.

Adaptive evolution and selection of stress-resistant Saccharomyces cerevisiae for very high-gravity bioethanol fermentation

Background: In industrial yeasts, selection and breeding for resistance to multiple stresses is a focus of current research. The objective of this study was to investigate the tolerance to multiple stresses of Saccharomyces cerevisiae obtained through an adaptive laboratory evolution strategy involving a repeated liquid nitrogen freeze­thaw process coupled with multi-stress shock selection. We also assessed the related resistance mechanisms and very high-gravity (VHG) bioethanol production of this strain. Results: Elite S. cerevisiae strain YF10-5, exhibiting improved VHG fermentation capacity and stress resistance to osmotic pressure and ethanol, was isolated following ten consecutive rounds of liquid nitrogen freeze­thaw treatment followed by plate screening under osmotic and ethanol stress. The ethanol yield of YF10-5 was 16% higher than that of the parent strain during 35% (w/v) glucose fermentation. Furthermore, there was upregulation of three genes (HSP26, HSP30, and HSP104) encoding heat-shock proteins involved in the stress response, one gene (TPS1) involved in the synthesis of trehalose, and three genes (ADH1, HXK1, and PFK1) involved in ethanol metabolism and intracellular trehalose accumulation in YF10-5 yeast cells, indicating increased stress tolerance and fermentative capacity. YF10-5 also showed excellent fermentation performance during the simultaneous saccharification and fermentation of VHG sweet potato mash, producing 13.40% (w/ v) ethanol, which corresponded to 93.95% of the theoretical ethanol yield. Conclusions: A multiple-stress-tolerant yeast clone was obtained using adaptive evolution by a freeze­thaw method coupled with stress shock selection. The selected robust yeast strain exhibits potential for bioethanol production through VHG fermentation.

Antarctic yeasts: analysis of their freeze-thaw tolerance and production of antifreeze proteins, fatty acids and ergosterol.

BACKGROUND: Microorganisms have evolved a number of mechanisms to thrive in cold environments, including the production of antifreeze proteins, high levels of polyunsaturated fatty acids, and ergosterol. In this work, several yeast species isolated from Antarctica were analyzed with respect to their freeze-thaw tolerance and production of the three abovementioned compounds, which may also have economic importance. RESULTS: The freeze-thaw tolerance of yeasts was widely variable among species, and a clear correlation with the production of any of the abovementioned compounds was not observed. Antifreeze proteins that were partially purified from Goffeauzyma gastrica maintained their antifreeze activities after several freeze-thaw cycles. A relatively high volumetric production of ergosterol was observed in the yeasts Vishniacozyma victoriae, G. gastrica and Leucosporidium creatinivorum, i.e., 19, 19 and 16 mg l- 1, respectively. In addition, a high percentage of linoleic acid with respect to total fatty acids was observed in V. victoriae (10%), Wickerhamomyces anomalus (12%) and G. gastrica (13%), and a high percentage of alpha linoleic acid was observed in L. creatinivorum (3.3%). CONCLUSIONS: Given these results, the abovementioned yeasts are good candidates to be evaluated for use in the production of antifreeze proteins, fatty acids, and ergosterol at the industrial scale.

Leptin Improves Sperm Cryopreservation via Antioxidant Defense.

BACKGROUND: Leptin and its receptor are present in spermatozoa; however, the role of leptin in sperm function is still controversial. Our present study aimed at demonstrating the effect of cryopreservation on sperm DNA fragmentation (DNAf) and investigating the possible effects of sperm capacitation techniques and leptin in vitro incubation on frozen-thawed sperm DNAf and oxidative stress. METHODS: Samples of 45 normospermic men attending for infertility investigation at Vida Centro de Fertilidade, Rio de Janeiro, Brazil, were frozen and thawed with or without capacitation and leptin incubation prior to freezing. Sperm DNA fragmentation was evaluated by Sperm Chromatin Dispersion Assay before and after cryopreservation and oxidative stress parameters were measured by spectrophotometry with and without leptin incubation. Statistical analysis was performed using paired t test to compare DNAf between groups before and after freeze-thaw cycle, to compare groups before and after capacitation and leptin incubation and oxidative measurements before and after leptin incubation. Statistical significance was considered when p≤0.05. RESULTS: Our results revealed a significant post-thaw rise in sperm DNAf compared with fresh samples (p=0.0003). Sperm DNAf was significantly reduced when sperm capacitation was performed before freezing, when compared to those frozen with no previous capacitation (p=0.01). The addition of leptin to capacitated sperm before freezing reduced DNAf (p<0.0001) and enhanced superoxide dismutase (p=0.001) and glutathione peroxidase (p=0.02) antioxidant enzymes activity. CONCLUSION: The addition of leptin to capacitated sperm can improve sperm DNA quality following cryopreservation, possibly by inducing the activity of certain antioxidant enzymes.

Effec t of Freeze-Thaw Cycles on Lipid Oxidation and Myowater in Broiler Chickens

The present study was carried out to investigate the influence of freezing-thawing cycles (0, 2, 4 and 6) on lipid oxidation and myowater contents and distribution. Nine replicates of chicken breast meat samples were used for each cycle. Lipid oxidation was determined by measuring peroxide value, and malondialdehyde (MDA) concentrations, which reflect thiobarbituric acid reactive substance (TBARS). Color was determined with a digital colorimeter. Muscle moisture contents were determined by drip loss and thawing loss, water holding capacity, and nuclear magnetic resonance (NMR). The results showed that, as the number of freeze-thaw cycles increased, meat redness decreased and MDA and peroxide values increased. Drip loss and thawing loss tended to decreasing as the number of freeze-thaw cycles increased. Water holding capacity also decreased as a function of increasing freeze-thaw cycles. NMR relaxometry profile showed freeze-thaw cycles change the water distribution of meat subjected to multiple freeze-thaw cycles. In conclusion, multiple freezing and thawing rate (6 cycles) increased lipid oxidation, decreased myowater, and impaired the color of chicken meat.(AU)

Effec t of Freeze-Thaw Cycles on Lipid Oxidation and Myowater in Broiler Chickens

The present study was carried out to investigate the influence of freezing-thawing cycles (0, 2, 4 and 6) on lipid oxidation and myowater contents and distribution. Nine replicates of chicken breast meat samples were used for each cycle. Lipid oxidation was determined by measuring peroxide value, and malondialdehyde (MDA) concentrations, which reflect thiobarbituric acid reactive substance (TBARS). Color was determined with a digital colorimeter. Muscle moisture contents were determined by drip loss and thawing loss, water holding capacity, and nuclear magnetic resonance (NMR). The results showed that, as the number of freeze-thaw cycles increased, meat redness decreased and MDA and peroxide values increased. Drip loss and thawing loss tended to decreasing as the number of freeze-thaw cycles increased. Water holding capacity also decreased as a function of increasing freeze-thaw cycles. NMR relaxometry profile showed freeze-thaw cycles change the water distribution of meat subjected to multiple freeze-thaw cycles. In conclusion, multiple freezing and thawing rate (6 cycles) increased lipid oxidation, decreased myowater, and impaired the color of chicken meat.

Characterization of Propylene Glycol-Mitigated Freeze/Thaw Agglomeration of a Frozen Liquid nOMV Vaccine Formulation by Static Light Scattering and Micro-Flow Imaging.

UNLABELLED: The purpose of this work was to investigate the susceptibility of an aluminum adjuvant and an aluminum-adjuvanted native outer membrane vesicle (nOMV) vaccine formulation to freeze/thaw-induced agglomeration using static light scattering and micro-flow Imaging analysis; and to evaluate the use of propylene glycol as a vaccine formulation excipient by which freeze/thaw-induced agglomeration of a nOMV vaccine formulation could be mitigated. Our results indicate that including 7% v/v propylene glycol in an nOMV containing aluminum adjuvanted vaccine formulation, mitigates freeze/thaw-induced agglomeration. LAY ABSTRACT: We evaluated the effect of freeze-thawing on an aluminum adjuvant and an aluminum adjuvanted native outer membrane vesicle (nOMV) vaccine formulation. Specifically, we characterized the freeze/thaw-induced agglomeration through the use of static light scattering, micro-flow imaging, and cryo-electron microscopy analysis. Further, we evaluated the use of 0-9% v/v propylene glycol as an excipient which could be included in the formulation for the purpose of mitigating the agglomeration induced by freeze/thaw. The results indicate that using 7% v/v propylene glycol as a formulation excipient is effective at mitigating agglomeration of the nOMV vaccine formulation, otherwise induced by freeze-thawing.

Freezing regime and trade-offs with water transport efficiency generate variation in xylem structure across diploid populations of Larrea sp. (Zygophyllaceae).

PREMISE OF THE STUDY: The impact of changing temperature regime on plant distributions may depend on the nature of physiological variation among populations. The arid-land genus Larrea spans habitats with a range of freezing frequency in North and South America. We hypothesized that variation in xylem anatomy among populations and species within this genus is driven by plasticity and trade-offs between safety from freeze-thaw embolism and water transport efficiency. METHODS: We measured vessel density and diameter distributions to predict freeze-thaw embolism and water transport capacity for high and low latitude populations of three Larrea species grown in the field and a greenhouse common garden. KEY RESULTS: Among field-grown L. divaricata, low latitude plants had larger mean vessel diameter and greater predicted freeze-thaw embolism, but higher water transport capacity compared with high latitude plants. Though high latitude L. tridentata and L. nitida had abundant smaller vessels, these plants also produced very large vessels and had semi ring-porous wood structure. Thus, their predicted embolism and water transport capacity were comparable to those of low latitude plants. Differences among field-grown and common-garden-grown plants demonstrate that plasticity contributes to population differentiation in xylem characters, though high latitude L. divaricata exhibited relatively lower plasticity. CONCLUSIONS: Our results indicate that a trade-off between transport safety and efficiency contributes substantially to variation in xylem structure within the genus Larrea. In addition, we suggest that xylem plasticity may play a role in negotiating these trade-offs, with implications for responses to future climate change.

Effect of several extenders in frozen-thawed buffalo semen submitted to thermo-resistence test / Efeito de diferentes diluidores na congelação e pós-descongelação de sêmen bubalino, submetido ao teste de termo-resistência

Samples of frozen semen (N = 139) from four water buffaloes (Jafarabadi and Murrah crossbred), with three years of age, were collected from January to November of 1990, were used. Semen was collected weekly and evaluated by microscope for physical characteristics of turbulence; concentration; motility and vigor. Fresh semen was diluted in solution prepared with seven extenders: yolk-lactose; TRIS-I; TRIS-II; TRIS-III; yolk-cytrate; TES-TRIS and MEN-Eagle medium. Concentrations of glycerol (7%); egg-yolk (20%) and distilled water to complete 100ml were constant for all extenders. The Thermo-Resistance Test (TRT) was used to achieve motility and vigor in frozen-thawed semen at zero and five hours of incubation. There was no difference among extenders (P>0.01) for motility and vigor at zero hour of incubation; but at five hours there were differences (P 0.01) among semen frozen with yolk-lactose; TRIS-I and TES-TRIS. TES-TRIS showed higher motility and vigor than the TRIS-I. Based on these results it is possible to freeze-thaw buffalo semen with these extenders. An appropriate concentration of sugar in the solution could improve motility of thawed buffalo semen.

Foram analisadas 139 amostras de sêmen congelado, obtidas de quatro touros bubalinos mestiços Jafarabadi x Murrah, com três anos de idade, durante os meses de janeiro a novembro de 1990. O sêmen foi colhido semanalmente e avaliado microscopicamente, quanto às características físicas de turbilhonamento, concentração, motilidade e vigor. Os ejaculados foram diluídos a fresco em combinações preparadas com sete diluidores: Lactose-gema, TRIS-I, TRIS-II, TRIS-III, Citratogema, TES-TRIS e Meio de Mem-Eagle. As concentrações de glicerol (7%), gema de ovo (20%) e água destilada (veículo), foram constantes em todos os diluidores. O Teste de Termo-Resistência (TTR) foi utilizado para a avaliação pós-descongelação das características motilidade e vigor, às zero e 5 horas de incubação. Não houve diferença (P > 0,01) das características motilidade e vigor pós-descongelação entre os diluidores à zero hora, porém houve diferença (P 0,01) às 5 horas de incubação, entre os diluidores Lactose-gema, TRIS-I e TES-TRIS, sendo que o TES-TRIS superou o TRIS-I nas duas características avaliadas. Com base nos resultados do presente estudo, é possível a congelação de sêmen de búfalos com estes diluidores, sendo que concentrações adequadas de açúcares nas soluções tampões, podem melhorar a motilidade pós-descongelação.

Effect of several extenders in frozen-thawed buffalo semen submitted to thermo-resistence test / Efeito de diferentes diluidores na congelação e pós-descongelação de sêmen bubalino, submetido ao teste de termo-resistência

Samples of frozen semen (N = 139) from four water buffaloes (Jafarabadi and Murrah crossbred), with three years of age, were collected from January to November of 1990, were used. Semen was collected weekly and evaluated by microscope for physical characteristics of turbulence; concentration; motility and vigor. Fresh semen was diluted in solution prepared with seven extenders: yolk-lactose; TRIS-I; TRIS-II; TRIS-III; yolk-cytrate; TES-TRIS and MEN-Eagle medium. Concentrations of glycerol (7%); egg-yolk (20%) and distilled water to complete 100ml were constant for all extenders. The Thermo-Resistance Test (TRT) was used to achieve motility and vigor in frozen-thawed semen at zero and five hours of incubation. There was no difference among extenders (P>0.01) for motility and vigor at zero hour of incubation; but at five hours there were differences (P 0.01) among semen frozen with yolk-lactose; TRIS-I and TES-TRIS. TES-TRIS showed higher motility and vigor than the TRIS-I. Based on these results it is possible to freeze-thaw buffalo semen with these extenders. An appropriate concentration of sugar in the solution could improve motility of thawed buffalo semen.

Foram analisadas 139 amostras de sêmen congelado, obtidas de quatro touros bubalinos mestiços Jafarabadi x Murrah, com três anos de idade, durante os meses de janeiro a novembro de 1990. O sêmen foi colhido semanalmente e avaliado microscopicamente, quanto às características físicas de turbilhonamento, concentração, motilidade e vigor. Os ejaculados foram diluídos a fresco em combinações preparadas com sete diluidores: Lactose-gema, TRIS-I, TRIS-II, TRIS-III, Citratogema, TES-TRIS e Meio de Mem-Eagle. As concentrações de glicerol (7%), gema de ovo (20%) e água destilada (veículo), foram constantes em todos os diluidores. O Teste de Termo-Resistência (TTR) foi utilizado para a avaliação pós-descongelação das características motilidade e vigor, às zero e 5 horas de incubação. Não houve diferença (P > 0,01) das características motilidade e vigor pós-descongelação entre os diluidores à zero hora, porém houve diferença (P 0,01) às 5 horas de incubação, entre os diluidores Lactose-gema, TRIS-I e TES-TRIS, sendo que o TES-TRIS superou o TRIS-I nas duas características avaliadas. Com base nos resultados do presente estudo, é possível a congelação de sêmen de búfalos com estes diluidores, sendo que concentrações adequadas de açúcares nas soluções tampões, podem melhorar a motilidade pós-descongelação.