Influence of amylases and xylanase on chemical, sensory, amylograph properties and microstructure of chapati

Effect of enzymes on the quality of chapati - the flat unleavened bread made from different wheat varieties was studied. Doughs treated with fungal α-amylase, bacterial α-amylase, xylanase and combination of bacterial α-amylase and xylanase were examined for chapati making quality. The shear force of chapatis treated with bacterial α-amylase, xylanase, fungal α-amylase and combination of bacterial α-amylase and xylanase were in the range of 2.5-2.8 N, 2.3-2.5 N, 3.5-3.7 N and 2.2-2.5 N, respectively, and they were found to be lower and significantly different than that of their corresponding controls (4.7-6.5 N). Soluble starch and soluble amylose content of the chapatis prepared from dough treated with amylases were significantly different than that of control. Chapatis prepared from dough treated with bacterial α-amylase had shown higher amount of soluble amylose (around 0.5 g/100 g) compared to other treatments (0.2-0.25 g/100 g). In chapatis prepared from dough treated with bacterial α-amylase, and combination of bacterial α-amylase and xylanase, the amylograph paste viscosities were 38-66 BU, and were very much lower and significantly different from that of control (232-390 BU) may be due to the residual enzyme activities. The microstructures of chapatis prepared from dough treated with enzymes were uniform with distorted starch granules surrounded with protein matrix, while in control, the starch granules were spherical with protein matrix overlapping on one another to form aggregation. Chapatis prepared from dough treated with enzymes had softer texture, better pliability and higher overall quality scores compared to control.     

Mango peel powder: A potential source of antioxidant and dietary fiber in macaroni preparations

Antioxidants like phenolics and carotenoids both as additives in foods or pharmaceutical supplements can scavenge reactive oxygen species and protect against degenerative diseases like cancer, cardiovascular diseases. Mango peel, which is a by-product obtained during processing of mango products such as mango pulp and amchur, is currently discarded and thus, causing environmental pollution. In the present study, mango peel was incorporated into macaroni at three different levels (2.5, 5.0, 7.5%) and studied its effect on the cooking properties, firmness, nutraceutical and sensory characteristics of macaroni. The total dietary fiber content in macaroni increased from 8.6 to 17.8%. The content of polyphenols increased from 0.46 to 1.80 mg/g and carotenoid content increased from 5 to 84 μg/g of macaroni with 7.5% incorporation of mango peel powder. The macaroni products incorporated with mango peel exhibited improved antioxidant properties. The cooking loss of macaroni increased from 5.84 to 8.71%, and the firmness increased from 44 to 73.45 gf upon incorporation of mango peel powder. Incorporation of 5% mango peel powder into semolina yielded macaroni with acceptable quality. Thus, the results suggest that by incorporating mango peel powder, it is possible to enhance the nutritional quality of macaroni without affecting its cooking, textural and sensory properties.Industrial relevanceMango is one of the important tropical fruits. As mango is a seasonal fruit, it is processed into various products and during its processing, huge amount of peel is generated as a by-product and its disposal is a major problem. The peel constitutes about 15–20% of the fresh fruit. The peel contains various bioactive compounds and the peel extract exhibited potential antioxidant properties. In the present study, mango peel was incorporated into macaroni at three different levels and found that incorporation up to a 5% level into the formulation of macaroni yielded an acceptable product with improved nutraceutical properties. Thus, mango peel, a waste from mango industry can be utilized for the preparation of macaroni with improved nutritional properties.     

Influence of fibre from different cereals on the rheological characteristics of wheat flour dough and on biscuit quality

Demand for health oriented products such as sugar-free, low calorie and high fibre products is increasing. One such recent trend is to increase the fibre content in food products to overcome health problems such as hypertension, diabetes, and colon cancer, among others. Consumption of high fibre products consisting of indigestible cellulose, hemicellulose, lignin and gums have several health benefits. Apart from these benefits, β-glucan-rich fibres have the benefit of reducing the absorption of glucose. Fibre sources from wheat, rice, oat and barley were used to study their influence on rheological characteristics of wheat flour dough and biscuit making quality. Ash, total protein and dietary fibre content of bran samples ranged between 4% and 10%, 12% and 14% and 20.4% and 49.5%, respectively. Farinograph characteristics of the wheat flour-bran blends showed increase in water absorption from 60.3% to 76.3% with increase in the level of bran from 0% to 40%. The resistance to extension values as well as extensibility of the dough decreased with increase in the bran level. The spread ratio of the biscuits prepared from wheat, rice and oat bran blends decreased from 8.38 to 7.52, whereas the same increased to 9.3 for biscuits prepared from barley bran blends. The breaking strength values of biscuits ranged between 1.34 and 3.83 kg. Highly acceptable biscuits could be obtained by incorporating 30% of oat bran or 20% of barley bran in the formulation.     

Supported quantum clusters of silver as enhanced catalysts for reduction

Quantum clusters (QCs) of silver such as Ag₇(H₂MSA)₇, Ag₈(H₂MSA)₈ (H₂MSA, mercaptosuccinic acid) were synthesized by the interfacial etching of Ag nanoparticle precursors and were loaded on metal oxide supports to prepare active catalysts. The supported clusters were characterized using high resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and laser desorption ionization mass spectrometry. We used the conversion of nitro group to amino group as a model reaction to study the catalytic reduction activity of the QCs. Various aromatic nitro compounds, namely, 3-nitrophenol (3-np), 4-nitrophenol (4-np), 3-nitroaniline (3-na), and 4-nitroaniline (4-na) were used as substrates. Products were confirmed using UV-visible spectroscopy and electrospray ionization mass spectrometry. The supported QCs remained active and were reused several times after separation. The rate constant suggested that the reaction followed pseudo-first-order kinetics. The turn-over frequency was 1.87 s^-1 per cluster for the reduction of 4-np at 35°C. Among the substrates investigated, the kinetics followed the order, SiO₂ > TiO₂ > Fe₂O₃ > Al₂O₃.     

Studies on pasting and structural characteristics of thermally treated wheat germ

In order to utilize wheat germ, a nutrient-dense by-product of wheat milling industry, in various food products, different moist and dry heat treatments were used to stabilize and to investigate its influence on protein sub-unit composition, starch pasting characteristics and structural characteristics. The raw germ contained 11% moisture, 31.4% crude protein, 18.4% dietary fibre and 7% fat. Different heat treatments, except for fluidized bed drying, inactivated the lipase activity in germ completely. On the other hand, various heat treatments inactivated lipoxygenase activity to varying extents (78–92%). Extent of gelatinisation, as assessed in electron micrographs was least in steamed and fluidized bed dried samples, while steamed and oven-dried germ and drum dried germ samples exhibited greater extent of gelatinisation. The extent of gelatinisation seemed to be more in drum-dried sample as no intact starch granule was observed. Electrophoretic pattern and sub-unit composition of germ samples remained similar, irrespective of their nature of treatment. Raw germ showed a gelatinisation temperature of 67.9 °C as measured in visco-amylograph and increased to 80.3–88.3 °C for differently treated germ samples, except for drum-dried sample. Differently heated germ samples, depending on their extent of pre-gelatinisation, gave significantly lower peak viscosity (221–268 BU) and break down values (0–9 BU).     

Effect of maltodextrin and emulsifiers on the viscosity of cake batter and on the quality of cakes

The effect of fat replacement by maltodextrin on cake batter viscosity and the quality of the resultant cakes was studied. The viscosity of batter was reduced significantly when fat was replaced with equal quantities of maltodextrin. Cakes prepared from this batter had low volume and firmer texture. Relatively better cakes were obtained when lower quantities of maltodextrin were used in the formulation. Viscosity of the above cake batter was relatively higher. A relationship between batter viscosity and cake volume was observed. Further improvement in cake volume could be achieved using emulsifiers. In the presence of glycerol monostearate little improvement in cake batter was observed, but the resultant cake volume was improved. However, sodium steroyl lactylate, which improved the batter viscosity, did not improve the cake volume or texture. Copyright © 2005 Society of Chemical Industry     

Studies on heat stabilized wheat germ and its influence on rheological characteristics of dough

Wheat germ, a nutrient dense by-product has a very poor shelf life. In order to improve its keeping quality, so that it can be used into different products, various heat treatments were tried and studied to investigate their influence on proximate composition as well as on the rheological characteristics of wheat flour dough. Different heat treatments have shown insignificant effect on proximate composition of wheat germ. Retention of vitamin E was greater in steamed and dried germ. Except for fluidized bed dried germ, all the heat treatments employed completely inactivated the lipase enzyme, whereas the lipoxygenase enzyme was inactivated to an extent of 80–92%. Quality evaluation of germ samples during 60 days storage indicated that steamed and dried germ retained the sensory attributes to a greater extent. Rheological study of wheat flour blends with germ upto 20%, showed marginal increase in water absorption and over-pressure values. However incorporation of treated wheat germ caused dough weakening in terms of reduction in dough stability and rupture at abscissa values.     

Apple pomace as a source of dietary fiber and polyphenols and its effect on the rheological characteristics and cake making

Apple pomace, a by-product of apple juice industry, is a rich source of fibre and polyphenols. Also in view of the antioxidant property of pomace, it would play an important role in prevention of diseases. Apple pomace procured from fruit juice industry, contained 10.8% moisture, 0.5% ash and 51.1% of dietary fibre. Finely ground apple pomace was incorporated in wheat flour at 5%, 10% and 15% levels and studied for rheological characteristics. Water absorption increased significantly from 60.1% to 70.6% with increase in pomace from 0% to 15%. Dough stability decreased and mixing tolerance index increased, indicating weakening of the dough. Resistance to extension values significantly increased from 336 to 742 BU whereas extensibility values decreased from 127 to 51 mm. Amylograph studies showed decrease in peak viscosity and cold paste viscosity from 950 to 730 BU and 1760 to 970 BU respectively. Cakes were prepared from blends of wheat flour containing 0–30% apple pomace. The volume of cakes decreased from 850 to 620 cc with increase in pomace content from 0% to 30%. Cakes prepared from 25% of apple pomace had a dietary fibre content of 14.2% The total phenol content in wheat flour and apple pomace was 1.19 and 7.16 mg/g respectively where as cakes prepared from 0% and 25% apple pomace blends had 2.07 and 3.15 mg/g indicating that apple pomace can serve as a good source of both polyphenols and dietary fibre.     

Spaghetti making potential of Indian durum wheat varieties in relation to their protein,yellow pigment and enzyme contents

The research was carried out to evaluate spaghetti making potential of 12 Indian durum wheat varieties in relation to their protein and yellow pigment content and peroxidase, polyphenol oxidase, lipoxygenase, and protease activities. The protein content of the durum wheat varieties varied from 12.1% to 15.9% and their yellow pigments content ranged from 3.8 to 7.2 ppm. The peroxidase activity in these wheat varieties varied from 269 to 1010 U/g and polyphenol oxidase activity from 58.8 to 78.3 U/g. The lipoxygenase activity of durum wheats ranged between 1.44 and 6.88 U/g. Protease activity was in the range of 1.1–5.1 U/ g. The data for varieties MACS-1967, MACS-3125, MACS-2846, DWR-2006, HI-8498 and N-59 were indicative of their potential for the preparation of pasta products.     

Effect of microbial transglutaminase on spaghetti quality

ABSTRACT:  To examine the potential application of microbial transglutaminase (MTG) on semolina dough properties and quality of raw and cooked spaghetti, the effects of various MTG addition levels on the solubility of proteins, SDS-PAGE pattern of semolina dough proteins, and textural and structural properties of raw and cooked spaghetti were investigated using semolina from a high-protein good variety (MACS 1967) and a low-protein poor variety (PDW 274) durum wheat. To increase the concentration of lysyl residues and possibly enhance the extent of cross-linking of protein matrix by MTG, a commercial soy protein isolate (SPI) was added at a level of 3% (w/w) in combination with MTG, and its effect on semolina dough properties and spaghetti quality was investigated. The addition of MTG significantly decreased the solubility of semolina dough proteins. SDS-PAGE results showed that with increasing levels of MTG, a progressive decrease in the intensity of the bands corresponding to molecular weight of around 66 kDa was observed. Protein cross-linking reaction catalyzed by MTG resulted in changes in dough properties, dry spaghetti quality, cooking quality characteristics, and microstructure of cooked spaghetti. However, the quality improvements were more evident in spaghetti from the poor variety PDW 274 than from the good variety MACS 1967. The results also showed the ability of MTG in the formation of heterologous polymers between SPI and durum wheat proteins to improve the quality of spaghetti samples.