Effect of maltodextrin weight fraction on the amorphous state and critical storage conditions of freeze-dried juices

Diagrams relating to water activity (a_w), equilibrium moisture content (X_w) and glass transition temperature (Tg) are valuable tools for predicting amorphous fruit powders' storage procedure and stability. Thus, T_g–a_w–X_w diagrams were constructed to characterise the amorphous state and define the critical values of water content (X_wc) and water activity (a_wc) of freeze-dried juices of strawberry, pineapple, kiwi and prickly pear prepared with maltodextrin at the dry mass fraction (W_MD) of 0, 0.4 and 0.8. The T_g and sorption data were fitted with a polynomial equation and the Guggenheim–Anderson–de Boer (GAB) model respectively. A Tukey test was performed to evaluate the difference between critical values of the powders (P < 0.05). The a_wc and X_wc increase with W_MD and depend on the chemical composition of the powders. The highest critical values were found in pineapple powders, ranging from 0.174 to 0.632 and 0.029 to 0.142 dry basis (d.b.), and the lowest ones in kiwi juice powders ranging from 0.029 to 0.550 and 0.013 to 0.129 (d.b.). For W_MD of 0.8, however, regardless of juice composition, stable powders in an amorphous state were obtained up to an a_w of 0.52 at 25°C.     

Radical scavenging and anti‐proliferative capacity of three freeze‐dried tropical fruits

Tropical fruits are rich in antioxidant and anticancer phytochemicals, but their nutraceutical potential could be enhanced by drying technologies. Mango cv. Ataulfo, papaya cv. Maradol and pineapple cv. Esmeralda ripe pulps were freeze‐dried (?42 °C, 0.12 torr, 48 h) and their physicochemical and phytochemical profile, radical scavenging and antiproliferative capacity evaluated. The content of soluble solids, phenolic compounds and ascorbic acid was higher in mango (16.1^oBrix, 9.9 mg GAE per g and 9.6 mg g^?1) than in papaya/pineapple, but the later had more flavonoids (0.45 ± 0.05 mg QE per g). A fruit‐specific phenolic profile was detected by HPLC‐ESI‐QTOF‐MS, being shikimic (mango), chlorogenic (papaya), and protocatechuic (pineapple) acids the most abundant. Mango was the strongest radical scavenger and showed antiproliferative capacity (IC₅₀, μg mL^?1) in RAW 264.7 (100.7), HeLa (193.1) and L929 (138.5) cell lines. Papaya and pineapple extracts showed no antiproliferative activity. Freeze‐dried mango is a ready‐to‐eat functional food with better cancer preventing properties than papaya or pineapple.     

A novel approach for the liquefaction of wood powder: usage of pyrolytic bio‐oil as a reaction medium

In this study, Scots pine wood (Pinus sylvestris L.) powder was liquefied in the presence of pyrolytic bio‐oil as a reaction medium/reagent. Firstly, the bio‐oil was produced via pyrolysis of the same wood species at three different temperatures by using an extruder type pyrolyzer. Then, the wood powders were liquefied at different ratios of the wood to pyrolytic bio‐oil in a sealed pressure‐proof tube. The liquefaction reactions were carried out under pressure ranging between atmospheric and 8.5‐MPa pressures according to the experimental conditions. The effects of the reactant ratios and the process parameters such as reaction time and temperature on the wood conversion percentage were studied. The chemical composition of the pyrolytic bio‐oil and liquefied wood oil were analyzed by means of GC‐MS technique. The higher heating value (HHV) and UV–Vis spectrophotometric analysis of the pyrolytic bio‐oil and liquefied wood oil were also performed. The results showed that the wood powder could easily be liquefied in the pyrolytic bio‐oil at different temperatures under pressure. The highest wood conversion (97.40%) was obtained at 250 °C for 150 min at a wood to bio‐oil ratio of 1:7 with the heavy fraction of the pyrolytic bio‐oil. The amount of wood residue diminished dramatically when the reaction temperature rose at the same wood to bio‐oil ratio. The HHV of the liquefied wood oil was almost similar to that of the pyrolytic bio‐oil. As a result, it could be inferred that the usage of pyrolytic bio‐oil instead of the phenol and acid catalyst was quite efficient in the wood liquefaction process. Copyright © 2016 John Wiley & Sons, Ltd.     

Catalytic Hydration of Benzonitrile and Acetonitrile using Nickel(0)

The homogeneous catalytic hydration of benzo‐ and acetonitrile under thermal conditions was achieved using nickel(0) compounds of the type [(dippe)Ni(η²‐NCR)] with R=phenyl or methyl (compounds 1 and 2 , respectively), as the specific starting intermediates. Alternatively, the complexes may be prepared in situ by direct reaction of the precursor [(dippe)NiH]₂ ( 3 ) with the respective nitrile. Hydration appears to occur homogeneously, as tested by mercury drop experiments, producing benzamide and acetamide, respectively. Addition of Bu₄NI did not lead to catalysis inhibition, suggesting the prevalence of Ni(0) intermediates during catalysis. Hydration using analogous complexes of 3 , such as [(dtbpe)NiH]₂ ( 4 ) and [(dcype)NiH]₂ ( 5 ) was also addressed.     

In vitro evaluation of the fermentation of added‐value agroindustrial by‐products: cactus pear (Opuntia ficus‐indica L.) peel and pineapple (Ananas comosus) peel as functional ingredients

Agroindustrial by‐products derived from fruit processing are an important source of biocompounds that can be used as functional food ingredients. The objective of this work was to evaluate cactus pear and pineapple peel flours as an alternative carbon source during fermentation using bacteria with probiotic potential. The total fibre content of both flours was over 60%, with total soluble carbohydrate content around 20%, indicating a good carbon source for lactic acid bacteria. Kinetic parameters indicate that peel flours are a suitable carbon source because the lactic acid bacteria grow (mean growth rate constant, k, values close to glucose, 1.52 h) and acidify the culture media (maximum acidification rate, V_max, approximately 1.60 pH × 10^?3 min^?1). There was no difference in prebiotic potential or prebiotic activity score for both the peel flours. Pediococcus pentosaceus performs better during fermentation. In this respect, cactus pear and pineapple peel flours can be used as functional ingredients due to their fermentable properties.     

Ethanol yield and volatile compound content in fermentation of agave must by Kluyveromyces marxianus UMPe-1 comparing with Saccharomyces cerevisiae baker's yeast used in tequila production

In tequila production, fermentation is an important step. Fermentation determines the ethanol productivity and organoleptic properties of the beverage. In this study, a yeast isolated from native residual agave must was identified as Kluyveromyces marxianus UMPe-1 by 26S rRNA sequencing. This yeast was compared with the baker's yeast Saccharomyces cerevisiae Pan1. Our findings demonstrate that the UMPe-1 yeast was able to support the sugar content of agave must and glucose up to 22% (w/v) and tolerated 10% (v/v) ethanol concentration in the medium with 50% cells survival. Pilot and industrial fermentation of agave must tests showed that the K. marxianus UMPe-1 yeast produced ethanol with yields of 94% and 96% with respect to fermentable sugar content (glucose and fructose, constituting 98%). The S. cerevisiae Pan1 baker's yeast, however, which is commonly used in some tequila factories, showed 76% and 70% yield. At the industrial level, UMPe-1 yeast shows a maximum velocity of fermentable sugar consumption of 2.27g·L(-1)·h(-1) and ethanol production of 1.38g·L(-1)·h(-1), providing 58.78g ethanol·L(-1) at 72h fermentation, which corresponds to 96% yield. In addition, the major and minor volatile compounds in the tequila beverage obtained from UMPe-1 yeast were increased. Importantly, 29 volatile compounds were identified, while the beverage obtained from Pan1-yeast contained fewer compounds and in lower concentrations. The results suggest that the K. marxianus UMPe-1 is a suitable yeast for agave must fermentation, showing high ethanol productivity and increased volatile compound content comparing with a S. cerevisiae baker's yeast used in tequila production.     

Molecular rearrangements in extrusion processes for the production of amaranth-enriched,gluten-free rice pasta

Gluten-free pasta represents a challenge for food technologists and nutritionists since gluten-free materials used in conventional formulations have poor functional and nutritional properties. A novel extrusion-cooking process was set up to improve the textural characteristics of rice-based pasta, and to enrich it with amaranth. Mineral and fiber content, and protein digestibility were improved by amaranth enrichment. Extrusion-cooking of a 75/25 mixture of rice flour and amaranth prior to pasta-making gave the best results as for the textural characteristics of the final product. The firmness of cooked pasta increased due to the extrusion-cooking process, that also decreased protein solubility in the amaranth-enriched pasta. The content in accessible thiols also decreased in amaranth-enriched pastas, indicating that amaranth proteins may be involved in forming disulphide bonds during the pasta-making process. Our results suggest that starch in rice flour interacts best with amaranth proteins when starch gelatinization occurs simultaneously to protein denaturation in the extrusion-cooking process.     

Characterization of Extruded Blends of Corn and Beans (Phaseolus Vulgaris) Cultivars: Peruano and Black-Querétaro under Different Extrusion Conditions

The effect of extrusion conditions in blends of corn and beans (Phaseolus vulgaris) of cultivars Peruano and black-Querétaro were investigated in this study, as an alternative to obtain snack foods. The type of cultivar and beans percentage, and also the extrusion conditions (moisture and temperature) influenced the physicochemical (color and breaking strength) and the functional (water absorption index, water solubility index, and oil absorption capacity) properties of the extrudates. The microstructures showed the presence of cavities and starch granules gelatinized (melted) and plasticized; while, the x-ray powder diffraction patterns revealed the presence of monohydrate glucose due to starch dextrinization. The results demonstrate that extrudates with good properties can be obtained from blends of corn and beans, under selected extrusion conditions, depending on the bean cultivar.     

Effect of reagent type on the acetylation of barley and maize starches

The objective of this work was to study the effect of reagent type on properties of acetylated barley starch (BS) and maize starch (MS) after modification with acetic anhydride (AA) and vinyl acetate (VA) at similar molar concentration for mole of glucose of both reagents. Degree of substitution (DS), morphological characteristics and granule size distribution, gelatinization and retrogradation, pasting properties, and X‐ray diffraction pattern were evaluated. Acetylation disturbs the short and long range order, and the effect was higher with AA than VA, and for BS than MS. This is due to the higher DS determined in AA–BS. In the pasting profile, acetylated starch showed the maximum peak viscosity at lower temperature, this effect was strongest for BS and anhydride acetic‐acetylation. Differential scanning calorimetry showed decrease in gelatinization parameters in acetylated starches (temperatures and enthalpy), and retrogradation was suppressed by acetylation. This effect was stronger in starches acetylated with AA despite their higher DS. This pattern can be explained from the occurrence of surface effects in acetylation with AA.