Original article: Incorporations of blueberry extracts into soybean‐protein‐isolate film preserve qualities of packaged lard

The effect of blueberry‐extract incorporation into soybean‐protein‐isolate edible film on the quality of packaged lard was compared with vitamin E or butylated hydroxyl anisole (BHA) incorporations individually during the storage at 36 °C and relative humidity of 40% for 5 weeks. Blueberry‐extract incorporations into soybean‐protein‐isolate film showed a greater tensile strength, lower water vapour permeability and lower oxygen permeability than vitamin E or BHA incorporations individually. On the other hand, the antioxidant capacity of soybean‐protein‐isolate film incorporated with the blueberry extract was greater than that incorporated with vitamin E and similar to that incorporated with BHA. Moreover, soybean‐protein‐isolate film incorporated with the blueberry extract showed a greater capacity to delay the lard hydrolysis than that incorporated with BHA, and a similar capacity to that incorporated with vitamin E. Consequently, blueberry‐extract incorporations into soybean‐protein‐isolate film not only improved mechanical and barrier properties, but also delayed the oxidation and hydrolysis of packaged lard. Therefore, blueberry‐extract incorporations into soybean‐protein‐isolate films have potential as a packaging material which will preserve the qualities of stored lard.     

Evaluation of Lepidium sativum seed and guar gum to improve dough rheology and quality parameters in composite rice–wheat bread

The effects of hydrocolloids in rice–wheat flour were studied. Hydrocolloids at 0%, 0.3%, 0.6% and 1% w/w (flour basis) and guar (G), Lepidium sativum seed (L) and guar-L. sativum seed (GL) gum were tested as additives to the rice/flour in various combinations. The quality parameters for the experiment were assessed with farinography, extensography, amylography and texture profile analysis. The evaluation of dough rheology showed that water absorption, dough development time, dough stability and viscosity all increased with the addition of hydrocolloids alone or in a combination. It was demonstrated that G₁L₁ promoted the highest effect. The mixing tolerance index and gelatinization temperature decreased with an increased hydrocolloid concentration. Extensibility value for the dough that incorporated guar and L. sativum seed gum increased with increasing hydrocolloid concentration from 0.3% to 0.6% and then decreased at 1%. The water activity of all bread didn't have significant differences with increasing hydrocolloids concentration but this parameter 24 decreased during storage. Firmness decreased with increasing hydrocolloid concentration and increased with increasing storage time. The sensory evaluation by a consumer panel gave the higher score for overall acceptability to G_0.3L_0.3 and G_0.3L_0.6 samples. The results also showed that G₁L₁, G₁L_0.6 and G_0.6L₁ samples had high specific volume and porosity.     

Partitioning of α-lactalbumin and β-lactoglobulin from cheese whey in aqueous two-phase systems containing poly (ethylene glycol) and sodium polyacrylate

Partitioning behavior of the whey proteins α-lactalbumin (α-la) and β-lactoglobulin (β-lg) in aqueous two-phase systems prepared with poly ethylene glycol (PEG) and sodium polyacrilate (NaPA) was investigated as a function of pH and polymer concentrations. It was observed that α-la concentrated in the PEG phase while β-lg concentrated in the NaPA phase. Response surface methodology was applied to optimize protein partitioning and to achieve the best conditions for their fractionation. Thermodynamic analysis based on isothermal titration microcalorimetry indicated that the partitioning of α-la was accompanied by endothermic heat and was entropically driven, while β-lg partitioning was accompanied by exothermic heat and was enthalpically driven at low polymer concentrations and entropically driven at high polymer concentrations. Purification and yield parameters were determined using fresh whey and the results allowed for conclusion of the great applicability of this new system for α-la and β-lg fractionation.     

Plasmid stability in a recombinant S cerevisiae strain secreting a bifunctional fusion protein

The recombinant Saccharomyces cerevisiae strain, YPB‐G, producing and secreting Bacillus subtilis α‐amylase and Aspergillus awamori glucoamylase as a fusion protein yielded efficient utilisation of starch. A segregated population balance model has been used to determine the probability of plasmid loss and plasmid copy number. The kinetics of cell growth and product (fusion protein) formation were based on a genetically structured model. The predictions were compared with the experimental observations obtained for the unstable recombinant S cerevisiae cells in a 1.5 dm^?3 batch bioreactor with 30 g dm³ initial starch under non‐aerated conditions. The main advantage of the present model is that three different genetic classes were defined on the basis of the existence of plasmid and of the expression of the enzymes, ie cells containing plasmids and expressing the gene product, x₁; cells containing plasmids and but not expressing the gene product, x₂; and cells without plasmids, x₃. It is confirmed by this model that the cells without plasmids outgrow and dominate in the fermentation medium (2.27 g dm^?3 vs 0.51 g dm^?3) as more and more glucose becomes available by the degradation of starch. © 2001 Society of Chemical Industry     

Effect of cellulase/glucanase/xylanase (Roxazyme G2) enzymes combination on nutrients utilisation of vegetable meal (Amaranthus cruentus) fed as sole dietary protein source in rat assay

Amaranthus cruentus vegetable meal (ACVM) had 23% crude protein. Ca, Na, K, Mg and Fe were abundant at 2.0 g kg^?1, 7.1 g kg^?1, 4.8 g kg^?1, 2.5 g kg^?1, 1109 mg kg^?1, respectively. P‐phosporous, oxalates and tannins were noticeable. Lysine, methionine and cystine were limiting. Weight gain for rats on the reference (casein) diet 2 at 6.30 g ±2.87 was highest (P < 0.05) followed by diet 6 (12% ACVM with enzyme supplementation) at 5.01 g ±2.42. Feed intakes were similar (P > 0.05) for rats on the reference diet and for rats on 10% and 12% with/without enzyme supplementation ranging from 42.90 g ± 4.52 in reference diet to 45.12 g ± 3.64. Nitrogen retention was highest for rats on reference diet but similar (P > 0.05) to rats on 12% enzyme supplemented diet at 0.53 ± 1.12 and 0.53 ± 2.10, respectively. Other investigated protein evaluation parameters revealed similar results among rats kept on reference diet and the rats on ACVM based diets with enzyme supplementations. Enzyme supplementation had a complimentary role in ACVM nutrition in rat trial.     

Assessment of protein changes in farmed giant catfish (Pangasianodon gigas) muscles during refrigerated storage

Farmed giant catfish (Pangasianodon gigas) muscles (dorsal and ventral sites) were stored in a refrigerator (at 4 °C) for 14 days to determine the effect of refrigerated storage on biochemical and physical changes. The analyses were carried out at 0, 2, 4, 7, 10 and 14 days of storage. At day 14, Ca²⁺ ‐ATPase activity markedly decreased when compared to its value at day 1 (>90%), while a small decrease was observed for surface hydrophobicity and reactive sulfhydryls content. Total volatile basic nitrogen and trichloroacetic‐soluble peptide content gradually increased when the storage period was extended. The myosin heavy chain decreased slightly on SDS‐PAGE for both meat cuts with increased storage time. Expressible drip and cooking loss were highest during the first day of storage and slightly decreased with storage time. Instrumental hardness was significantly higher in the ventral compared to the dorsal muscle, while the toughness was the highest at the second day of storage. The muscle bundles with scanning electron microscopy were less attached, resulting in the observed big gaps over increasing storage time. Results indicated that changes of proteins have detrimental effects on the quality attributes of farmed giant catfish muscles during refrigerated storage, particularly physical and biochemical properties.     

The effect of limited proteolysis by different proteases on the formation of whey protein fibrils

Four proteases: trypsin, protease A, pepsin, and protease M were selected to modify whey protein concentrate (WPC) at a low degree of hydrolysis (0.1, 0.2, and 0.3%) before adjusting to pH 2.0 and heating at 90°C to gain insight into the influence of proteolysis on fibril formation. The kinetics of fibril formation were performed on native and modified WPC using the fluorescent dye thioflavin T in conjunction with transmission electron microscopy and far-UV circular dichroism spectroscopy for the morphological and secondary structural analyses. The change in surface hydrophobicity and content of free sulfhydryl groups were also observed during the formation of fibrils for the native and modified WPC. The content of aggregation and thioflavin T kinetic data indicated that the ability of fibril formation was apparently different for WPC modified by the 4 proteases. Whey protein concentrate modified by trypsin aggregated more during heating and the fibril formation rate was faster than that of the native WPC. Whey protein concentrate modified by the other proteases showed slower aggregation with worse amyloid fibril morphology. Compared with the native WPC, the structure of WPC changed differently after being modified by proteases. The state of α-helix structure for modified WPC played the most important role in the formation of fibrils. Under the mild conditions used in this work, the α-helix structure of WPC modified by trypsin caused little destruction and resulted in fibrils with good morphology; the content of α-helices for WPC modified by other proteases decreased to 36.19 to 50.94%; thus, fibril formation was inhibited. In addition, it was beneficial for the modified WPC to form fibrils such that the surface hydrophobicity increased and the content of free sulfhydryl groups slightly decreased during heating.