TENSILE PROPERTIES OF BEEF SEMITENDINOSUS MUSCLE AS AFFECTED BY HEATING RATE AND END POINT TEMPERATURE

The effects of heating rate and end point temperature on tensile properties of beef semi-tendinosus muscle were studied. Samples of meat heated in glass tubes in a water bath to simulate oven roasting at 93 °C had lower (P < 0.01) shear values than those heated to simulate oven roasting at 149 °C. Samples heated to 60 and 70°C had lower (P < 0.001) shear values than samples heated to 50°C. Instron breaking strength values varied (P < 0.001) with end point temperature, but were not significantly affected by the rate of heating. Significant (P < 0.001) interactions between the end point temperature and heating rate, as well as between the end point temperature and fiber direction suggested that Instron breaking strength measurements may be more sensitive to changes in tenderness than Warner Bratzler shear measurements.     

Original article: Effect of sucrose and glycerol mixtures in the osmotic solution on characteristics of osmotically dehydrated mandarin cv. (Sai‐Namphaung)

This study investigated the effects of a series of osmotic solutions consisting of sucrose and glycerol on the quality of osmotically dehydrated mandarin, namely mandarin cv. (Sai‐Namphaung). Mandarin samples were peeled and osmotically dehydrated at 55 °C with agitation at 3.5776 × 10^?1g in five osmotic solutions containing various mixtures of 60% sucrose and 60% glycerol (9:1, 8:2, 7:3, 6:4 and 5:5 w/w, respectively). The osmotically dehydrated mandarin was further dried using hot‐air drying at 70 °C for 360 min. Increasing the glycerol ratio in the mixtures significantly (P ≤ 0.05) increased water loss and solid gain during osmotic dehydration, and significantly (P ≤ 0.05) affected kinetic rate constants during drying. An increase in the glycerol ratio in the mixtures caused a significant decrease in the quality factors of hardness, moisture content, water activity and reducing sugar. However, the increase resulted in an increase in the darkness of the dried mandarin, compared with increasing the sucrose ratio in the mixtures (P ≤ 0.05). The increase had an insignificant (P > 0.05) effect on vitamin C content.     

Effect of rice bran protein extract on enzymatic browning inhibition in potato puree

Effect of rice bran protein extract (RBPE) on enzymatic browning inhibition in potato puree was studied by colour measurement and polyphenol oxidase (PPO) inhibition. RBPE inhibited browning in potato puree and showed a higher per cent potato PPO inhibition at pH 4.0 and 5.0 than those at pH 3.0, 6.0 and 7.0 (P ≤ 0.05). RBPE heated to 40 and 60 °C had browning inhibition in potato puree and per cent potato PPO inhibition at a similar extent to unheated RBPE (P > 0.05). Browning inhibition and per cent potato PPO inhibition of RBPE were decreased when it was heated to 80 °C (P ≤ 0.05). RBPE inhibited browning in potato puree higher than 5, 10 and 20 mm ascorbic acid and 5 and 10 mm citric acid (P ≤ 0.05). Regarding the kinetics study, RBPE exhibited a mixed‐type inhibition for potato PPO. Therefore, RBPE has a potential to be used as a natural antibrowning agent in the potato industry.     

Hydrothermal treatments of two cowpea (Vigna unguiculata L. Walp) varieties: effect of micronisation on physicochemical and structural characteristics

The effects of a hydrothermal treatment consisting of tempering (to 41% moisture) and heating to 153 °C (micronisation) on the structural and physicochemical characteristics of two cowpea varieties were studied. The untreated varieties had similar cooking times, although cooked Bechuana white cowpeas were significantly (P ≤ 0.05) softer and had a higher incidence of splitting than Var. 462 cowpeas. This may be due in part to differences in cotyledon structure affecting water uptake during cooking. The hydrothermal treatment changed the physical structure and chemical properties of the cowpea seeds. This led to significant (P ≤ 0.05) reductions in the cooking time of micronised Bechuana white and Var. 462 cowpeas, by 47 and 36% respectively, as compared with control samples. Micronisation caused physical fissuring of the seed coat and cotyledon and significantly (P ≤ 0.05) reduced the bulk density of treated seeds. These changes in the physical structure significantly (P ≤ 0.05) improved the initial water uptake during soaking and cooking, increased the enzyme‐susceptible starch and reduced the protein solubility and hydration capacity of the cowpea seeds. Cooked (60 min) micronised cowpeas also had significantly (P ≤ 0.05) more splits and a significantly (P ≤ 0.05) softer texture than control samples. Copyright © 2005 Society of Chemical Industry     

Characterization of hot air drying and microwave vacuum drying of fingerroot (Boesenbergia pandurata)

Fingerroot (Boesenbergia pandurata) was subjected to hot air drying and microwave vacuum drying. Effective moisture diffusion coefficient during the hot air drying at 60 and 70 °C were 0.2073 × 10^?10 and 0.4106 × 10^?10 m² s^?1 respectively. By using the microwave vacuum drying (13.3 kPa) at the power of 2880 and 3360 W, the effective moisture diffusion coefficient were increased to 5.7910 × 10^?10 and 6.8767 × 10^?10 m² s^?1 respectively. Based on Lewis model, drying rate constants were 0.0002, 0.0004, 0.0061 and 0.0072 s^?1 for the hot air drying at 60 and 70 °C and the microwave vacuum drying at 2880 and 3360 W respectively. Compared with the hot air drying, the microwave vacuum drying decreased drying time by 90%. Rehydration ability of the microwave vacuum dried samples was also significantly improved (P ≤ 0.05), because of porous structure. In addition, the rehydrating water of the microwave vacuum dried samples contained higher b*‐value (yellowness) than that of the hot‐air‐dried samples (P ≤ 0.05).     

Physical,Functional, and Sensory Characteristics of Cereal Extrudates

Eleven cereals were processed in a twin-screw extruder to produce directly expanded extrudates. Physical and functional properties (gelatinization degree, bulk density, expansion ratio, water absorption index, water solubility index, and sensory characteristics (hardness, crispness, and bowl life) of cereal extrudates were determined. Relationships among different variables were analyzed by SPSS. Gelatinization degree positively and negatively correlated to starch and protein, respectively (p ≤ 0.01). The same relationship was observed with water absorption index at the same significance level. Water solubility index positively correlated to protein (p ≤ 0.05), negatively correlated to starch (p ≤ 0.01), amylose (p ≤ 0.01), and fat (p ≤ 0.05). Density and bowl life positively correlated to fat (p ≤ 0.01) and amylose (p ≤ 0.05), respectively. Gelatinization degree had a high correlation with water solubility index (p ≤ 0.05). As gelatinization degree increased, water solubility index decreased. Crispness positively correlated to bowl life (p ≤ 0.01).     

Physicochemical and sensory quality of wines from red sorrel/roselle (Hibiscus sabdariffa L.) calyces: effects of pretreatments of pectolase and temperature/time

The effects of pretreating red sorrel (Hibiscus sabdariffa L.) calyces on the physicochemical and sensory quality of wines were investigated. Sorrel calyces were processed at 60 °C for 3.5 h or 90 °C for 30 min at 0%, 0.5% and 1.0% w/w pectolase addition in fermentation of wines. Significant changes (P < 0.01) in all physicochemical parameters of sorrel wines were found during fermentation, but not (P > 0.05) because of temperature/time effects. Colour (P < 0.01) became redder with pectolase and on storage at 23 °C for 2 months. Significant differences (P < 0.01) were noted in sensory quality for taste and flavour, balance, duration and overall quality. Higher (P < 0.01) overall sensory quality scores were obtained for wines by pretreatment at 90 °C for 30 min (10.44–11.06/20) when compared with wines at 60 °C for 3.5 h (6.88–9.06/20). Colour of wines from 90 °C/30 min was most saturated and red than all wines and had pH 2.57 ± 0.01, 0.43 ± 0.07% citric acid, 10.53 ± 0.53 °Bx and 15.29 ± 0.71% alcohol.     

Effect of lipid oxidation and frozen storage on muscle proteins of Atlantic mackerel (Scomber scombrus)

The effect of storage on the lipids and proteins in Atlantic mackerel stored for up to 24 months at ?20 and ?30 °C was studied. Traditional methods including the peroxide value, thiobarbituric acid‐reactive substances (TBARS) and a reverse phase HPLC method were used to determine the primary and secondary lipid oxidation products. All tests showed an increase in lipid oxidation products with storage time and at a higher storage temperature of ?20 °C compared with samples stored at ?30 °C. Antioxidants had a significant effect (P < 0.01) on the inhibition of lipid oxidation, as shown by the reduction in peroxide value and hydroxides, and malondialdehyde formation. Similarly, deterioration of protein structure and functionality in mackerel stored for 3, 6, 12 and 24 months was greater at ?20 than ?30 °C. ATPase activity in the myosin extract of Atlantic mackerel showed a significant decrease (P < 0.01) with progressive frozen storage. Protein solubility in high salt concentration (0.6 M NaCl) decreased (P < 0.01) during storage at both ?20 and ?30 °C but was greater at ?20 °C. Interestingly, antioxidants BHT, vitamin C and vitamin E protected the proteins against complete loss of ATPase activity and protein solubility to a significant level (P < 0.01) for up to 1 year at ?20 °C compared with samples stored without antioxidants. This study confirms the deleterious effect of lipid oxidation products on protein structure and function in frozen fatty fish. © 2002 Society of Chemical Industry     

Improvement of rheological and physicochemical properties of longan honey by non‐thermal magnetic technique

A non‐thermal technology using magnetic field (MF) can improve flowability of honey while maintaining its physicochemical quality. Effects of MF treatment on rheological and physicochemical properties of longan honey exposed to MF for 2 h at 15 °C and 28 °C were investigated and compared with those of non‐MF samples. Increasing MF strength at 28 °C caused a reduction in firmness (P ≤ 0.05), but not in consistency, index of viscosity and cohesiveness. The effects at 15 °C were greater. Newtonian behaviour was observed for all samples. Shear stress and viscosity were significantly reduced with increasing MF strength at 15 °C (P ≤ 0.05), but less at 28 °C. pH was also decreased. Total soluble solids content was increased at both temperatures (P ≤ 0.05). Colour index was not significantly affected by MF, whereas optical density was slightly increased at high MF strengths (P > 0.05). L* values for the MF treated samples were increased (P ≤ 0.05), giving lighter and more pleasant colour to the honey. MF treatment improved overall qualities of honey.     

Steeping‐induced physicochemical changes of milled waxy rice and their relation to the quality of yukwa (an oil‐puffed waxy rice snack)

The influence of water‐steeping periods (0 to 15 days, 25 °C) on the physicochemical properties of raw waxy rice in relation to the yukwa quality was investigated. The moisture contents in waxy rice and reducing sugar in its steeping medium were increased, while contents of protein and minerals of raw waxy rice were decreased in proportion to the water‐steeping duration. With longer steeping periods, swelling power, solubility and peak viscosity were increased, while grain hardness was decreased with apparent kernel structural change. Depending on the water‐steeping duration of raw waxy rice, the hardness decreased from 26.0 to 1.8 g, and the expansion ratio of yukwa increased from 762 to 1539%. Correlations between the physicochemical properties and yukwa quality indicated that variables having the most positive influential on expansion ratio were reducing sugar (γ = 0.961, P < 0.01) and peak viscosity (γ = 0.897, P < 0.01), and those for hardness of yukwa were crude protein (γ = 0.875, P < 0.01) and hardness (γ = 0.887, P < 0.01) of the steeped waxy rice. It is suggested that steeping‐induced physicochemical changes of raw waxy rice had a significant influence on the final quality of yukwa in terms of hardness and expansion ratio. Copyright © 2004 Society of Chemical Industry     

X-ray Diffraction Pattern and Functional Properties of <Emphasis Type="Italic">Dioscorea hispida</Emphasis> Dennst Starch Hydrothermally Modified at Different Temperatures

Starch from Thai yam Dioscorea hispida Dennst was hydrothermally modified at its original moisture content (∼13%, w/w) and 90 °C to 130 °C for 10 h. X-ray diffraction analysis of the modified starch showed that the crystallographic pattern of the starch was altered from type B in native starch to type C in the starch modified at 90 °C and to type A in those modified at 100–130 °C. Along with the change in crystallographic pattern, decreases in granule swelling, starch solubility, and amylose leaching were observed. Up to the modification temperature of 100 °C, a reduction in the estimated degree of crystallinity and an increase in peak viscosity were noted. Seven percent starch gel of all modified starches, except for that modified at 130 °C, showed higher complex moduli over 0.001 to 10 Hz in dynamic shear test when compared with 7% native starch gel.     

Genetic diversity in the physicochemical properties of waxy rice (Oryza sativa L) starch

The genetic diversity in the physicochemical properties of starches from 56 waxy rice (Oryza sativa L) genotypes (34 of indica and 22 of japonica) was studied. The parameters included thermal and retrogradation properties tested by differential scanning calorimetry (DSC), pasting viscosity tested by rapid viscoanalyser (RVA), and flour swelling volume (FSV). Wide diversity was found in all the parameters. According to their gelatinisation temperature (GT), the waxy rice genotypes could be divided into two groups, a high‐GT group and a low‐GT group. A total of 15 genotypes were identified as high‐GT, all belonging to the indica subspecies. There was about a 5 °C difference within each group and a 10 °C difference between groups. Many parameters were correlated with each other in all 56 waxy rices, but some correlations were also consistent and significant when comparing the high‐GT group and the low‐GT group separately. For example, hot paste viscosity (HPV) was positively correlated with onset temperature (T_o) and enthalpy of gelatinisation (ΔH_g). The results suggested that initial screening in waxy rice breeding programmes for varieties with desirable starch properties for specific food uses could be efficiently accomplished using pasting profiles from the RVA. Copyright © 2004 Society of Chemical Industry     

Cooking qualities of parboiled rices produced at low and high temperatures

The cooking characteristics of parboiled rice are related to (i) its hydration behaviour at temperatures above and below the gelatinisation point; (ii) to kernel elongation on cooking; and (iii) to the extent of amylose solubility. These properties differ among samples, depending on the parboiling conditions. Samples were prepared by parboiling paddy at 70, 80, 90, 100, 110 and 120°C. The kernel elongation on cooking and the amount of soluble amylose in the gruel were then determined. The water uptake values for raw and parboiled rice samples were determined by hydrating them at room temperature (25-30), 60 and 98°C (boiling temperature) for optimal cooking times. The rate of hydration at temperatures below the gelatinisation point increased on parboiling and, conversely, a reverse pattern above this point. Close correlations existed between the temperature of parboiling and the properties studied. The different properties studied also correlated well. The temperature of parboiling influenced the linear elongation of the kernel after cooking. The soluble amylose content was negatively correlated with the temperature of parboiling. Though the hydration properties of different parboiled samples differed among themselves, depending on the degree of parboiling, they fell into two distinct classes, viz. the samples parboiled at a temperature close to the gelatinisation point having cooking qualities similar to raw rice, and above this point qualities differing from raw rice. The water uptake values at room temperature and at 60°C, and the ratio of water uptake at 98°C and optimum cooking time to that at 60°C were found to be useful in differentiating the parboiled rices into the two classes.     

A study of the effect of the drying process on the composition and physicochemical properties of flours obtained from durian fruits of two ripening stages

Durian cv. Monthong with two ripening stages (unripe and fully ripe) was subjected to microwave vacuum drying (MWD) at 5.49 W g^?1 and hot air drying (HAD) at 60 °C. With an increase in ripening degree, the starch content was significantly (P ≤ 0.05) decreased from 40.08–40.42% to 9.44–11.76%. X‐ray diffraction indicated that the crystalline pattern was changed from starch to sucrose. The starch granule morphology of durian flour was conserved for both drying conditions. Peak gelatinisation temperatures of MWD and HAD flours were increased significantly (P ≤ 0.05) from 56.71–57.32 to 60.71–61.23 °C. Using different drying methods, MWD flour had less a*‐value (P ≤ 0.05) than HAD flour. The peak viscosity and trough of the HAD unripe durian flour (5.92 RVU and 3.45 RVU, respectively) were significantly (P ≤ 0.05) lower than those of the MWD unripe durian flour (34.32 RVU and 11.57 RVU, respectively).     

ISOLATION AND CHARACTERIZATION OF LIMA BEAN (PHASEOLUS LUNATUS) STARCH

Starch from large lima beans (Phaseolus lunatus) was isolated and some of the important characteristics determined. The yield of starch was 22% on a whole seed basis. The shape of the starch granules was round to oval to elliptical, with granules 15–36 μm diameter. Scanning electron micrographs revealed presence of smooth surfaces. Gelatinization temperature range was 70–75–80°C and amylose content was 34.5%. The starch exhibited high single stage swelling and moderate solubility in water. The x-ray diffraction pattern was of the C-type. The viscoamylographic examination on starch paste (6%, w/v) showed the absence of a peak viscosity, a high 95°C viscosity (700 BU) and a breakdown in consistency (60 BU) during the 95°C holding cycle. Scanning electron microscopy showed that native starch granules were very resistant to attack by porcine pancreatic α-amylase. However, defatting slightly increased the extent of hydrolysis. The gel showed poor stability towards refrigerated storage and freeze-thaw cycling. The starch granules were highly resistant to acidic hydrolysis.     

Physicochemical and Functional Characterization of Baby Lima Bean (Phaseolus lunatus) Starch

One potential source of starch is the tropical legume baby lima bean (Phaseolus lunatus) that contains around 56—60% of starch. The objectives of this work were to evaluate this starch's physicochemical and functional properties and compare it with the properties of other starches. The chemical composition of lima bean starch was: 10.16% moisture, 0.20% protein, 0.67% fiber, 0.14% ash, 0.54% fat, 98.43% starch and 0.013% phosphorus. The amylose content was higher (32.7%) than that of other cereal and tuber starches but similar to other legume starches. The average granule size (diameter 17.9 μm) was comparable to that of corn starch and of other legume starches. The granule was heterogeneous, presenting an oval shape. The gelatinization temperature was 80.16 °C (range 75—87 °CC), which is similar to other legume starches but higher than that of corn starch. The molecular size (alkali number 3.22), was smaller than that of potato starch but similar to that of corn starch. Compared to corn starch, the gels were firmer and presented a higher degree of retrogradation even at high concentrations. The water solubility was positively correlated with the temperature: i.e., 1.8, 3.4, 8.5 and 12.3% at 60, 70, 80 and 90 °C, respectively. The swelling power had the same behaviour: 2.6, 3.3,12.8 and 19.9 g of water/per gram of starch at 60, 70, 80 and 90 °C, respectively. The amylogram showed that the viscosity (680 Brabender units) and stability were higher than those of commercial corn starch (252 Brabender units). The use of this starch in the preparation of syrups with high glucose contents, as well as in baked and canned products that require heating, is suggested.     

Effects of microwave and hot‐air drying methods on colour, β‐carotene and radical scavenging activity of apricots

The effects of drying by microwave and convective heating at 60 and 70 °C on colour change, degradation of β‐carotene and the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) scavenging activity of apricots were evaluated. Microwave heating reduced significantly the drying time (up to 25%), if compared with convective one, also owing to the higher temperature reached during the last phase of the process, as monitored by infrared thermography. Colour changes of apricot surface, described with lightness and hue angle, in both drying methods followed a first‐order reaction (0.927 ≤ R² ≤ 0.996). The apricots dried by microwave were less affected by the darkening phenomena. The evolution of β‐carotene in fresh apricots (61.2 ± 5.6 mg kg^?1 d.w.) during the drying highlighted a wider decrease (about 50%) when microwave heating was employed for both the temperatures used. Radical scavenging activity increased (P < 0.05) in all dried samples except for hot‐air dried apricots at 60 °C.     

Effect of Heat Processing of Dried Egg White on In Vitro Iron Bioavailability

Egg white (EW) was desugared, adjusted to either pH 7 or pH 9, and freeze-dried. Portions were held at 25°, 50°, 60°, 70° or 80°C for 1 wk. In vitro iron bioavailability (IVIB) was estimated by the method of Kane and Miller (1984) and no differences in IVIB were observed due to EW pH. IVIB of EW held at 50°, 60°, or 70°C was not different (P>0.05) than that of EW held at 25°C [9.87% dialyzable iron (DI)]; only the 80°C treatment led to IVIB lower (6.76% DI, P<0.05) than the 25°C control. Differential scanning calorimetry and nondissociating electrophoresis showed that native protein structure, including that of the iron-binding protein ovotransferrin, was maintained after the 70°C treatment but not after the 80°C treatment.     

A transgressive brown rice mediates favourable glycaemic and insulin responses

BACKGROUND: We evaluated glycaemic response of a brown rice variant (BR) developed by cross‐breeding. Subjects (n = 9) consumed 50 g carbohydrate equivalents of BR, white rice (WR) and the polished brown rice (PR) in comparison to 50 g glucose reference (GLU) in a cross‐over design. Plasma glucose and insulin at 0, 15, 45, 60, 90, 120 and 180 min were measured and incremental area under the curve (IAUC) and indices for glucose (GI) and insulin (II) calculated. RESULTS: BR compared to PR or WR produced the lowest postprandial glycaemia (GI: 51 vs 79 vs 86) and insulinaemia (II: 39 vs 63 vs 68) irrespective of amylose content (19 vs 23 vs 26.5%). Only BR was significantly different from GLU for both plasma glucose (P = 0.012) and insulin (P = 0.013) as well as IAUC_glu (P = 0.045) and IAUC_ins (P = 0.031). Glycaemic and insulinaemic responses correlated positively (r = 0.550, P < 0.001). Linear trends for IAUC_glu and IAUC_ins indicated a greater secretion of insulin tied in with a greater glycaemic response for WR (r² = 0.848), moderate for PR (r² = 0.302) and weakest for BR (r² = 0.122). CONCLUSION: The brown rice variant had the lowest GI and II values but these advantages were lost with polishing. Copyright © 2011 Society of Chemical Industry     

Gel and Molecular Properties of Waxy Rice Starch

The differences in the physicochemical properties of starch (amylopectin) from waxy rices from the Philippines, Japan, and Thailand differing in processed rice quality were investigated. Samples of waxy rice starch showed final birefringence end-point temperature (BEPT) between 58 and 78°C. None of the samples showed BEPT values between 70 and 72°C. The gel viscosity values (measured with a Wells-Brookfield viscometer) of samples with BEPT values above 70°C were higher than those of samples with BEPT values below 70°C. Sedimentation coefficient and intrinsic viscosity were positively correlated and showed a U-shaped relationship with BEPT with minima at a BEPT of about 68°C. Differences in viscosity properties were mainly due to differences in the molecular weight of amylopectin, since the samples studied had similar mean chain lengths. BEPT was a useful index of amylopectin molecular weight in the waxy rice starch samples studied.