Application of high‐pressure treatment in the mashing of white malt in the elaboration process of beer

In this study, high‐pressure treatment (HPT) was applied to the mashing stage of beer production, which involves drying and milling of white malt and subsequent mixing with water. The following parameters were evaluated after pressurisation: β‐glucanase activity, starch gelatinisation and sugar extraction. Evaluation of starch hydrolysis from the malted barley endosperm after HPT was performed by measuring β‐glucanase activity after pressurisation; this enzyme breaks down gums and β‐glucans in wort and is desirable to obtain a good‐quality beer. Soaked malt samples pressurised at 200–600 MPa showed no increase in this activity compared with controls. Conversion of milled malt was evaluated indirectly by measuring the gelatinisation of starch, which began at 400 MPa. Soluble sugars were also measured in pressurised samples from the mashed liquid to investigate saccharification during the mashing stage. After 400 or 600 MPa treatment for 20 min, both the sucrose (g per 100 ml) and extract (l ° kg^?1) values were the same as those found in mashed samples following the standard procedure used in the brewing industry (65 °C,90 min). Starch gelatinisation was analysed at different high pressures (200–600 MPa) and it was shown that gelatinisation began at 400 MPa. The HPT time would have to be shorter to make the process commercially attractive. © 2002 Society of Chemical Industry     

Alkali Gelatinisation of Wheat Starch

Alkali gelatinisation of wheat starch was found to depend on starch and alkali concentration and was faster at higher temperatures and higher alkali/starch ratios. Viscosity of an alkaline starch slurry continued to increase after both in vitro digestibility and soluble amylose reached maximum values. Despite extensive granule swelling, deformation and bursting, birefringence was retained to some degree indicating differences in mechanism between alkali and heat gelatinisation.     

Determination of starch in plant material

Starch has been determined in the pasture legume Stylosanthes humilis (Stylo) by hydrolysis with amylo-glucosidase and subsequent analysis for glucose with glucose oxidase. Prior gelatinisation of starch granules within the plant sample by water at 130°c gave low values and it was concluded that the complete solubilisation of starch by alkali was necessary, with subsequent neutralisation of the extract with acetic acid. It was shown that the alkali also extracted material which inhibited one or more of the enzymes involved in the subsequent glucose analysis, but this inhibition was removed by treatment of the extract with charcoal. Under the above conditions the high acetate concentration decreased the efficiency of the final glucose analysis, but this effect was readily corrected by use of appropriate blank solutions. The proposed method of starch analysis is relatively economical in time compared with previous methods and is believed to give more meaningful values for plants with low starch content.     

Impact of Guar and Wheat Bran on the Physical and Nutritional Quality of Extruded Breakfast Cereals

Two non‐starch polysaccharides, guar gum and wheat bran, were used at 15% replacement level in a cereal base to produce an extruded breakfast cereal product from both wholemeal and high‐ratio wheat flour mixes. The inclusion of the non‐starch polysaccharides into the flour bases had no significant effect on the expansion ratio of the products. However, the product density and bulk density of the extruded products increased with guar gum and wheat bran addition. The pasting properties of the raw flour and polysaccharide base as well as the extruded products were altered with the incorporation of polysaccharides, with guar gum‐enriched products showing elevated peak and final viscosity readings. This appeared to be related to moisture manipulation and hence the regulation of gelatinisation. In vitro starch hydrolysis of the raw bases and the extruded samples illustrated that the extrusion process significantly increased the availability of carbohydrates for digestion. Additionally, the inclusion of non‐starch polysaccharides in the raw bases significantly reduced the rate and extent of carbohydrate hydrolysis. This potentially glycaemic reducing action was also evident in the extruded products where the incorporation of guar gum at 15% yielded a reduction of starch hydrolysis of 36% in the wholemeal base and 32% in the high‐ratio white wheat flour base.     

Investigation and modelling of natural convection and conduction heat exchange: study on food systems with modified starch by means of computational fluid dynamics

This study is focused on the effects of starch gelatinisation on heat exchange in food systems containing four modified starch concentrations (0, 2, 6 and 10%). Viscosity profiles of samples were experimentally measured: the effect of gelatinisation was evident, particularly at 6% and 10%, where the viscosity increased from 0.010 to 70 Pa s and to 1507 Pa s, respectively. The heat exchange rate showed a decrease with the increasing of starch concentration, and the effects were observed until 6%. Four Computational Fluid Dynamics (CFD) models were also developed, experimentally validated (RMSE < 1.5 °C) and used to study the heat exchange. Velocity profiles showed that the convective flows slowed down from 2.5 to 0 mms^?1 after the gelatinisation. Finally, the effects on the slowest heating/cooling zone (SHZ/SCZ) location in the CFD models were studied: at 0% and 2%, the SHZ settled 15 and 80 mm from the bottom of jars in heating and cooling phase, respectively. At 6% and 10%, before the starch gelatinisation phase, the SHZ was located in a similar position of the 0% and 2% while when the gelatinisation occurred the SHZ slightly moved towards the geometric centre (50 mm) as for an only‐conductive product.     

Methods for the preparation of cell walls from potatoes

A group of new methods is described for preparing cell walls from potatoes and processed potato products. Starting from raw domestic potatoes, starch is degraded enzymatically after a very brief 100 °C gelatinisation step conducted after homogenisation to minimise the time required for heat transfer. Protein is removed by detergent and phenol extraction. This procedure (method 1) gave cell wall preparations containing <5% starch, with minimal degradation of wall polysaccharides. It did not, however, remove starch efficiently from industrial potatoes in which the starch content is much higher. A different procedure, method 2, was used in this case. In method 2 a 20 min starch gelatinisation step was used but the temperature was restricted to 70 °C and the pH to 4.0, with the aim of protecting pectins from depolymerisation. Method 2 and method 1A, which is a hybrid procedure involving the starch gelatinisation step from method 2 and other steps from method 1, gave low‐starch cell walls from industrial as well as domestic potatoes. These methods are suitable for a range of potato types and potato products and are either more efficient or more convenient than previous procedures for cell wall isolation. © 2002 Society of Chemical Industry     

A Simplified Isolation of High‐Amylose Maize Starch Using Neutral Proteases

Breeding projects aimed at increasing starch amylose would benefit by having a rapid starch extraction method requiring only non‐hazardous reagents and leaving the native granule intact for functional analyses. A study was, therefore, designed to investigate the use of a neutral protease for the removal of protein during the starch extraction process from the grain of high‐amylose corn. Sets of F2 ears presumed to be homozygous for the recessive amylose‐extender (ae) allele and segregating high amylose modifier gene(s) were used in the study and ranged in amylose content from 55% to around 70%, although several non‐mutant genotypes (˜25%) occurred because of visual misclassification of the ae kernels. Starches from samples were all initially extracted by grinding and filtering, then further treated in three ways including either 1) no protein removal, 2) toluene and saline washes or 3) use of neutral proteases. In general, amylose values corresponded among samples extracted using the three methods. Samples purified using proteases had higher mean amylose values (62.5%) attributed to the lower presence of contaminating protein compared to samples prepared with toluene (61%) and grinding/filtration only (57.5%). Little change occurred among the starches as a result of the protease treatments according to thermal properties obtained using differential scanning calorimetry. In addition, gel permeation chromatography profiles (GPC) were unaffected by this treatment. A low level of amylase activity from the protease was found which degraded less than 1% of the starch sample. The results demonstrated that this protease method gave an increased yield of starch with a quality similar to that of starch prepared with toluene.     

Functional properties and retrogradation behaviour of native and chemically modified starch of mucuna bean (Mucuna pruriens)

Mucuna bean (Mucuna pruriens) starch was isolated and subjected to chemical modification by oxidation and acetylation. The proximate analysis of the non‐starch components of the native starch on a dry weight basis was 92 g kg^?1 moisture, 5 g kg^?1 ash, 2 g kg^?1 fat, 7 g kg^?1 crude fibre and 19 g kg^?1 protein. Chemical modification reduced the values for all the non‐starch components except the moisture level. For all the samples, swelling power and solubility increased as the temperature increased in the range 50–90 °C. The swelling power of mucuna native starch (MNS) and mucuna acetylated starch (MAS) increased with increasing acidity and alkalinity, while that of mucuna oxidised starch (MOS) only increased with increasing pH in the acidic range. The maximal solubility of all the starches was observed at pH 12. All the starch samples absorbed more oil than water. The lowest gelation concentration followed the trend MAS < MNS < MOS. Chemical modification reduced the gelatinisation temperature (Tp), while peak viscosity (Pv), hot paste viscosity (Hv) and cold paste viscosity (Cv) decreased after oxidation but increased following acetylation. The setback tendency of the native starch was reduced significantly after chemical modification. However, the breakdown value of MNS, 65 BU (Brabender units), was lower than that of MOS (78 BU) but higher than that of MAS (40 BU). Differential scanning calorimetry studies of gelatinisation and retrogradation revealed that chemical modification reduced the onset temperature (T_o), peak temperature (T_p) and conclusion temperature (T_c). Oxidation and acetylation reduced the gelatinisation and retrogradation enthalpies of the native starch. The enthalpy of retrogradation of the starches increased as the length of storage increased. Copyright © 2003 Society of Chemical Industry     

Partial Leaching of Granule‐Associated Proteins from Rice Starch during Alkaline Extraction and Subsequent Gelatinization

Starch granule‐associated proteins, including granule‐bound starch synthase (GBSS), were found to be partially lost during alkaline extraction of rice starch. Variability in amount of loss of GBSS and other granule proteins was found among different rice lines. Also, part of the GBSS and other granule proteins leached out during gelatinization of the alkali‐extracted rice starch. Confocal laser scanning microscopy revealed that some protein still existed in gelatinized starch granules prepared from starch isolated using alkaline extraction. The starch that retained more GBSS and other granule proteins after alkaline extraction tended to have more protein in the isolated gelatinized starch granules, indicating that proteins resistant to alkaline extraction also tended to resist leaching during gelatinization. The study suggests that leaching of granule‐associated proteins may contribute to variations in paste properties of alkali‐extracted starches.     

Melting Properties and Lintnerisation of Potato Starch with Different Degrees of Phosphorylation

Lintner dextrins were prepared from size fractionated potato starch granules from two potato varieties (90BKG22 and Lady Rosetta) that contain high or low natural content of esterified phosphate, respectively. The time course of hydrolysis showed the typical two‐phase kinetics, with a maximal degree of hydrolysis of between 74% and 81% after 30 days of hydrolysis, except for the fraction of smallest granules of the low phosphorylated variety (low P), which was hydrolysed to 98%. The relative amount of retained glucose‐6‐P in the Lintner dextrins was 18.6% for the low P variety and 46.6% for the high P variety. However, when calculating the relative distribution of phosphate in the granules, it was shown that approximately 80% (low P) and 35.5% (high P) was located in the amorphous region. Melting characteristics were followed by differential scanning calorimetry (DSC). The DSC endothermic peak became low and broad during the time course of hydrolysis, with rise in enthalpy change, indicating a strong dependency on the amorphous region of the granules. After annealing the same fractions showed the typical raise in gelatinisation temperature and narrowing of gelatinisation peak. The values of the melting temperatures (T_o, T_m and T_c) are positively correlated to the degree of phosphorylation of the starch dextrin fractions both before and after annealing.     

Starch thermal transitions comparatively studied by DSC and MTDSC

The gelatinisation process of waxy starch was studied using both differential scanning calorimetry (DSC) and modulated temperature DSC (MTDSC). It was revealed that the results from the two techniques, especially the onset gelatinisation temperature, were slightly different, which may be due to the MTDSC principle and the mechanism of starch gelatinisation. Thus, it is suggested to avoid using MTDSC alone in the characterisation of starch thermal transitions especially in a quantitative way. However, MTDSC has the advantage in understanding the gelatinisation mechanism since it can separate the capacity change (reversible thermal event) from kinetic components (irreversible event). The stepwise change on reversible heat flow measured by MTDSC during gelatinisation was considered due to the phase transition of highly constrained starch polymer chains in granular packing. On the other hand, the glass transition of gelatinised starch (also thermoplastic starch) could not necessarily be detected by conventional DSC or MTDSC. However, by using a high‐speed DSC method, the extremely weak glass transition of the gelatinised starch with low moisture content could be enlarged and detected, which confirms the existence of glass transition of the gelatinised starch with low moisture content. This knowledge is helpful in the processing of starch‐based foods and polymeric materials.     

Physicochemical,crystallinity, pasting and thermal properties of heat‐moisture‐treated pinhão starch

The effect of heat‐moisture treatment (HMT) on the properties of pinhão starches under different moisture and heat conditions was investigated. The starches were adjusted to 15, 20 and 25% moisture levels and heated to 100, 110 and 120°C for 1 h. The X‐ray diffractograms, swelling power, solubility, gel hardness, pasting properties and thermal properties of the native and HMT pinhão starches were evaluated. Compared to native starch, there was an increase in the X‐ray intensity and gel hardness of HMT starches, with the exception of the 25% moisture‐treated and 120°C heat‐treated starch. HMT reduced the swelling power and solubility of the pinhão starches when compared to native starch. There was an increase in the pasting temperature, final viscosity and setback and a decrease in the peak viscosity and breakdown of HMT pinhão starches compared to native starch. HMT increases the gelatinisation temperature of native pinhão starch and reduces gelatinisation enthalpy.     

Physicochemical properties and in vitro digestibility of flours and starches from taro cultivated in different regions of Thailand

This research aimed to study physicochemical properties and in vitro digestibility of flours and starches from taro cultivated in different regions of Thailand, that is, Kanchanaburi (KB), Chiang Mai (CM), Phetchaburi (PB) and Saraburi (SB). Taro starches were extracted from taro flours using either water or alkaline extraction. The taro flours had significantly (P ≤ 0.05) larger particle size, higher pasting and gelatinisation temperatures, and resistant starch content but lower total starch content, whiteness (L* value), paste viscosities and clarity than their corresponding extracted starches. All the taro starches exhibited polygonal and irregular granules and gave A-type X-ray diffraction pattern. The alkaline-extracted taro starches had significantly (P ≤ 0.05) higher extraction yield, total starch content, L* value, pasting and gelatinisation temperatures, and paste clarity but lower granular size, amylose content, resistant starch content, paste viscosities and relative crystallinity than their water-extracted counterparts.     

Effect of Hydrothermal Treatment on Formation and Structural Characteristics of Slowly Digestible Non‐pasted Granular Sweet Potato Starch

The formation and structural characteristics of slowly digestible non‐pasted granular starch in sweet potato starch were investigated under various hydrothermal treatment conditions. The moisture content of the sweet potato starch was adjusted to 20, 50 or 90%, and the starch was heated at 40, 55 or 100°C for 12 h in a dry oven. The relative crystallinity of the hydrothermally treated samples was decreased with increasing temperature, and the X‐ray diffraction patterns of the samples were altered from C_b‐type to A‐type. Microscopic observations did not reveal any changes in the starch granules of any samples except those with moisture contents of 50 and 90% that were heated at 100°C. When gelatinization parameters were examined, samples with moisture contents of 50 and 90% that were heated at 55°C and samples of all moisture contents that were heated at 100°C had peak temperatures higher than that of raw starch but gelatinization enthalpies lower than that of raw starch. The swelling factor of the samples heated at 40°C did not change significantly, whereas that of samples heated at 55 and 100°C was decreased at increased moisture levels. The sweet potato starch with 50% moisture content that was heated at 55°C had the highest content of granular slowly digestible starch, about 200% that of raw starch, although our study did not involve further hydrothermal treatment conditions. Further study is required to complete a process for more efficient production of heat stable and slowly digestible starch.     

Effect of heat treatment on quality, thermal and pasting properties of sweet potato starch during yearlong storage

BACKGROUND: Proper postharvest handling and storage of sweet potato is an important link in the chain from producer to consumer or manufacturing industry. Heat treatments have been used as a non‐chemical means to modify the postharvest quality and reduce pathogen levels and disease development of a wide variety of horticultural products. The objective of this study was to investigate the effects of hot water treatment (HWT) on the quality, gelatinisation enthalpy and pasting properties of sweet potato starch during long‐term storage. The weight loss, sprouting, spoilage and sugar content of sweet potato were also determined. RESULTS: HWT significantly inhibited the sprouting and decay of sweet potato during the storage period. There were no significant differences (P < 0.05) in the pasting properties and onset (T_O), peak (T_P) and endset (T_E) temperatures of gelatinisation of sweet potato starch among all treatments, especially between heat‐treated and non‐heat‐treated samples. HWT also had no significant impact on the quality of the internal components of the roots. Less than 4% of the yearlong‐stored roots were discarded owing to spoilage. HWT supplied a lethal dose of heat to surface pathogens and black spot without damaging the nutritional and processing qualities of sweet potato. CONCLUSION: HWT was an effective method to reduce root sprouting and deterioration without significant impact on the quality of the internal components of sweet potato. This novel technique will open a new avenue to extend the storage life of sweet potato with good quality and minimal waste. Copyright © 2011 Society of Chemical Industry     

Characteristics of pressurised pork meat batters as affected by addition of plasma proteins,apple fibre and potato starch

Pork meat (low‐fat) batters were prepared without and with the addition of three non‐meat ingredients: (blood) plasma proteins, (dietary) apple fibre and potato starch. The batters were processed by cooking‐alone (70 °C) and by high‐pressure/temperature combination (400 MPa/70 °C). Protein denaturation and starch gelatinisation through the different processings were followed by differential scanning calorimetry. Batter characteristics such as water holding (weight loss) and different texture parameters (texture profile analysis) were used as quality criteria for comparisons among different formulations and processes. Plasma proteins and apple fibre behaved as inert fillers in both kinds of processed batters. Potato starch effects depended on processing conditions to the extent that these influenced the degree of gelatinisation. In pressurised batters (pressure and heating in sequence), regular preservation effects against subsequent thermal denaturation of proteins were observed. Differential scanning calorimetry revealed that starch was also pressure‐preserved from subsequent thermal gelatinisation, which was confirmed by scanning electron microscopy. The presence of native‐like proteins and ungelatinised starch produced cumulative softening effects in pressurised batters. © 2000 Society of Chemical Industry     

Effect of varying starch properties and mashing conditions on wort sugar profiles

The aim of this research was to investigate the relationship between starch composition in barley and its malted counterpart alongside malt enzyme activity and determine how these factors contribute to the fermentable sugar profile of wort. Two Australian malting barley varieties, Commander and Gairdner, were sourced from eight growing locations alongside a commercial sample of each. For barley and malt, total starch and gelatinisation temperature were taken, and for malt, α‐ and β‐amylase activities were measured. Samples were mashed using two mashing profiles (infusion and Congress) and the subsequent wort sugar composition and other quality measures (colour, original gravity, soluble nitrogen) were tested. Variety had no significant (<0.05) effect on any barley, malt, enzyme or wort characteristics. However, growing location impacted gelatinisation temperature, colour, malt protein content and original gravity. The gelatinisation temperature in malt samples was higher, by ~0.8°C, than in the equivalent barley sample. Several malt samples, even with protein contents <12.0%, had gelatinisation temperature >65°C. The fermentable sugars measured in the malt prior to mashing showed a higher proportion of maltose than glucose or maltotriose. In addition, there were significant differences in the amount of sugar produced by each mashing method with the high temperature infusion producing a higher amount of sugar and proportionally more maltose. There is scope for further research on the effect of genetics and growing environment on gelatinisation temperature, mash performance and fermentable sugar development. Routinely measuring gelatinisation temperature and providing this information on malt specification sheets could help brewers optimise performance. © 2019 The Institute of Brewing & Distilling     

Effects of Growth Temperature on Some Structural Properties of Crystalline Lamellae in Starches Extracted from Sweet Potatoes (Sunnyred and Ayamurasaki)

Thermodynamic characteristics defining gelatinisation (modelled as ‘melting’) processes for starches extracted from two sweet potato cultivars (Ayamurasaki and Sunnyred) grown in soil at different temperatures (15, 21, 27 or 33 °C) were studied using high sensitivity differential scanning calorimetry (DSC). The gelatinisation temperatures for all starches were elevated significantly with increasing growth temperature. A linear correlation between growth temperature and gelatinisation temperature of extracted starches was found for both cultivars. The increase of gelatinisation temperatures was associated with almost constant or slightly increased enthalpy (Ayamurasaki) but with moderate elevation of crystalline lamellae thickness (Sunnyred). Elevation of gelatinisation temperatures by 8‐9 °C by DSC for starches heated in 1.5 M aqueous KCl were found in comparison with aqueous starch dispersions. The crystalline polymorphic form was confirmed as A‐type using wide angle X‐ray scattering (WAXS). The values of the thermodynamic surface parameters characterising the faces of crystalline lamellae of these starches were calculated. Two endothermic peaks were observed by DSC for starches grown at 15 °C when suspended in 1.5 M KCl solution. The first peak was ascribed to the melting of B‐type structure while the second one was attributed to the melting of A‐type structure. As a conclusion it was suggested that these starches contain C‐type polymorphic structures.     

Extracted Lipids and Carbohydrates During Washing and Boiling of Milled Rice

Washing and cooking of waxy and nonwaxy milled rice and rice flour resulted in extraction of lipids, and carbohydrates, principally starch and nonstarch polysaccharides. Lipids, nonstarch polysaccharides and amylose contributed to hardening of waxy rice (IR 29) starch gel consistency in H₂O. Lipids extracted were mainly nonstarch lipids, principally free fatty acids. Nonstarch polysaccharides extracted in cold water were rich in glucose, galactose and arabinose, but those extracted in hot water were mainly glucans. Hot water extractable starch was more in waxy than in nonwaxy rice but complexed less with IR 29 amylopectin.     

Physicochemical properties of the starchy flour extracted from sweet potato tubers through lactic acid fermentation

The efficiency of starch extraction from sweet potato tubers was improved by lactic acid fermentation using a mixed culture inoculum. Study of the properties of the starchy flour showed that there was a significant reduction in the starch content and consequently the soluble and apparent amylose contents of fermented samples from all six varieties used. A fall in peak viscosity and viscosity breakdown was observed for fermented samples, while the pasting temperature was enhanced significantly. The fermented flour showed greater solubility and reduced swelling. Differential scanning calorimetry studies indicated a delay in gelatinisation and a fall in enthalpy of gelatinisation of the starch on fermentation. Unlike cassava, all the properties of the starch from sweet potato tubers, ie viscosity, swelling, solubility, gelatinisation temperature, amylose content and starch content, were affected by fermentation, and variation was also observed among cultivars. Copyright © 2005 Society of Chemical Industry