首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Starch was isolated from unripe square banana (Musa balbisiana) fruit and its functional properties were determined. Square banana starch peak gelatinisation temperature was 79.8 °C and the transition enthalpy was 17.3 J/g. At 90 °C, the solubility was 16.8%, the swelling power was 17.1 g water/g starch and the water absorption capacity was 14.3 g water/g starch. The paste properties were: temperature, 81 °C; maximum viscosity, 326 BU; breakdown, 22 BU; setback, 40 BU and consistency, 18 BU. The clarity, expressed as transmittance, was 17.5%, and gel deformation was 32.4% with a 0.03 kgf maximum load. This starch had high syneresis and low stability in refrigeration and freezing cycles. Given its properties, square banana starch has potential applications in food systems requiring high temperature processing, such as jellies, sausages, bakery and canned products. It is inappropriate, however, for use in refrigerated or frozen foods.  相似文献   

2.
The starch of maca (Lepidium meyenii Walpers) presented oval and irregular morphology, with granule size between 7.4 and 14.9 μm in length and 5.8 and 9.3 μm in diameter. The isolated starch showed the following features: purity of 87.8%, with 0.28% lipids, 0.2% fibre and 0.12% fixed mineral residue, and no protein detected; the ratio between the amylose and amylopectin contents were 20:80; the solubility at 90 °C was 61.4%, the swelling power was 119.0 g water/g starch and the water absorption capacity was 45.9 g water/g starch; the gel turbidity rose 44% during the storing time; the gelatinization temperature was 47.7 °C and the transition enthalpy 6.22 J/g; the maximum viscosity reached 1260 UB at 46.4 °C, with breakdown, setback and consistence of 850, 440 and −410 UB, respectively. The low gelling temperature and the stability during gel refrigeration could be adequate for foods requiring moderate temperature process, but not for frozen food.  相似文献   

3.
Starch from palmyrah (Borassus flabellifer L.) seed-shoot flour was isolated and its composition, morphology, structure and physicochemical properties were determined. The yield of starch was 38.4% on a whole flour basis. The shape of the granule ranged from round to elliptical. Bound lipid, total lipid, apparent amylose, total amylose and resistant starch contents were 0.03%, 0.04%, 30.9%, 32.7% and 32.2%, respectively. The X-ray pattern was of the A-type and relative crystallinity was 34.1%. Palmyrah starch exhibited a high proportion (31.8%) of short amylopectin chains (DP 6–12) and a low proportion (1.2%) of long amylopectin chains (DP > 36). Gelatinization temperatures were 73.1–82.0 °C and enthalpy of gelatinization was 13.6 J/g. Pasting temperature, viscosity breakdown and set-back were 76.5 °C, 147 and 74 BU, respectively. Palmyrah starch exhibited high granular swelling, and restricted amylose leaching. Susceptibility towards in vitro α-amylolysis and retrogradation was low. The results showed that physicochemical properties of palmyrah starch were largely influenced by strong interactions between amylose–amylose and/or amylose–amylopectin chains within the granule interior.  相似文献   

4.
A novel probiotic product was developed, which was formulated as an oblea (wafer-type dehydrated traditional Mexican dessert) using goat sweet whey fermented with Bifidobacterium infantis or Lactobacillus acidophilus. To obtain the probiotic oblea, the fermented whey was formulated with prebiotic carbohydrates (inulin and resistant starch) and gelatin, and the preparation was poured onto a polytetrafluoroethylene-coated nonstick baking pan, dried in a convection oven, and finally dehydrated at a low relative humidity and room temperature (23 ± 2°C). The amounts of prebiotic carbohydrates and gelatin to be used in the formulation were determined by a factorial experimental design. An untrained sensory panel evaluated 3 quality characteristics (film formation, homogeneity, and smoothness) in the final product. Three different drying temperatures were tested, namely, 40, 55, and 70°C. Bacterial survival at each temperature was determined by viable plate-counting. The best formulation, based on the quality characteristics tested, consisted of 58.33% (vol/vol) of fermented whey, 8.33% (vol/vol) of 6% (wt/vol) resistant starch dispersion, 16.66% (vol/vol) of 15% (wt/vol) inulin solution, and 16.66% (vol/vol) of a 10% (wt/vol) gelatin solution. Drying at 55 ± 2°C for 2.66 ± 0.22 h allowed for concentrations of probiotic bacteria above 9 log10 cfu/g, which is above the minimum concentration required in a probiotic product.  相似文献   

5.
Enterobacter aerogenes was studied for its growth, and promoting the formation of total volatile base nitrogen (TVBN) and histamine in tuna dumpling stuffing stored at various temperatures from −20 °C to 37 °C. The bacterial number rapidly increased in low (2.0 log CFU/g) or high (5.0 log CFU/g) inoculated concentrations at temperature above 15 °C and reached the highest bacterial count at 37 °C. In addition, the low spiked sample stored at 37 °C for 12 h and the high spiked sample stored at 25 and 37 °C for 12 h, formed histamine at above 50 mg/100 g of the potential hazard level in most illness cases. However, bacterial growth was controlled by cold storage of the samples at 4 °C or below, but histamine formation was stopped only by frozen storage. Once the frozen stuffing samples were thawed and stored at 25 °C, histamine started to accumulate rapidly.  相似文献   

6.
The functionality of starch from chestnut (Castanea sativa Mill.) fruits isolated by alkaline and enzymatic methods were assessed. The studied properties included: solubility, swelling power, pasting properties, synaeresis, turbidity, and thermal and rheological behaviours. In addition amylose and resistant starch content were also evaluated. Results showed that the starch isolation method induced changes in most of those properties. Extracted starches (with high contents of amylose and resistant starch) showed low and similar swelling solubility values for all of the samples. Gelatinisation temperatures were also similar (61.5-63.0 °C), but the enzymatic method induced lower consistencies at 95 °C and after holding at this temperature. High values of setback were found, which were clearly affected by the isolation method. This parameter presented lower values for starches isolated by alkaline method (160 BU and 235 BU, respectively for Martainha and Longal). Starches did not present a peak consistency during pasting. Turbidity and synaeresis values were low at room temperature. Synaeresis increased when pastes were stored at low temperatures. This effect was more evident for the material isolated by enzymatic method. All of the isolation starches presented low enthalpy values (3.0-3.5 J/g), but the activation energy was higher for Martainha starches and for starches isolated by A3S method. Pastes showed viscoelastic behaviour, with a predominance of elastic property, forming strong gels after cooling. Longal variety seems to be less resistant to the effect of isolation method. In general starches isolated by the alkali method present the best functional properties as a food ingredient.  相似文献   

7.
Ca-independency with potential activity and stability at low pH are among the most interesting characteristics of α-amylase in starch industry. In this attempt the synergetic effect of low pH on activity of crude Ca-independent α-amylase isolated from a native Bacillus sp. KR-8104 in solid-state fermentation (SSF) was studied using wheat bran (WB) as a substrate. The effects of different parameters including moisturizing agents, solid substrate to moisture ratio, particle size, incubation temperature and period, inoculum (v/w) and supplementation with 1% (w/w) different carbon and nitrogen sources on enzyme production were investigated. Maximum enzyme production of 140 U/g dry fermented substrate was obtained from wheat bran moistened with tap water at a ratio of 1:1.5 and supplemented with 1% (w/w) NH4NO3 and 1% (w/w) lactose after 48 h incubation at 37 °C. Even though the production of α-amylase was lower at 40 and 45 °C, the viable cell count was higher. In addition response surface methodology (RSM) was applied to find optimum conditions of temperature and pH on crude amylase activity. Using central composite design (CCD) a quadratic mathematical model equation was derived for the prediction of enzyme activity. The results showed that the model was in good agreement with experimental results, with R2 = 0.90 (p < 0.0001) and the low pH has a synergetic effect on enzyme activity at higher temperature.  相似文献   

8.
The morphological, thermal and pasting properties of starch separated from potatoes of three varieties (Kufri Chandramukhi, Kufri Jyoti and Kufri Chipsona-2), treated either with CIPC (isopropyl N-(3 chlorophenyl) carbamate) or γ-irradiation (Co60, 0.1 and 0.5 kGy) and subsequently stored at 8, 12 and 16 °C for 90 days, were studied. Scanning electron microscopy (SEM) showed the presence of oval and irregular shaped starch granules with a diameter range of 15–16 μm. Mean granule size of starch separated from potatoes stored at 12 °C ranged from 18–25 μm and irradiation treatment resulted in an increase in the proportion of small size granules. The irradiation of potatoes with 0.5 kGy resulted in starch with significantly lower peak-, trough- and breakdown-viscosity as compared to starch from potatoes treated with either CIPC or 0.1 kGy irradiation. The irradiation of potatoes with 0.5 kGy caused a significant increase in setback and pasting temperature. Pasting temperature of starch was observed to vary with the storage temperature. Starch separated from potatoes stored at higher temperature showed lower pasting temperature and vice versa. The starch from potatoes stored at 8 °C showed higher peak-, trough- and breakdown-viscosity and lower setback. Peak viscosity increased and swelling volume decreased with increase in storage temperature. FTIR spectra showed that the starch from irradiated potatoes displayed a significant decrease in the intensity of the C–H stretch region between 2800 and 3000 cm−1, which was observed to be irradiation dose-dependent, and higher with 0.5 than 0.1 kGy. However, a slight broadening of O–H stretch (3000–3600 cm−1) in starches from irradiated potatoes was observed. The spectral changes caused by γ-irradiation were apparent in the O–H stretch (3000–3600 cm−1), C–H stretch (2800–3000 cm−1) and bending mode of water (1600–1800 cm−1).  相似文献   

9.
Effects of the type and amount of fatty acid (0-2.0 mmol/g-starch of lauric, myristic, palmitic, stearic, oleic, and linoleic acids) on the complex formation, thermal properties, and in-vitro digestibility of gelatinized potato starch-fatty acid mixtures were investigated. Complex index (CI) evaluated by the reduction in the iodine binding capacity of starch increased with an increase in the amount of fatty acids, and reached a plateau depending on the type of fatty acid. The maximum CI value was higher in the order of lauric (49.9%), linoleic (47.6%), myristic (42.4%), oleic (36.7%), stearic (35.3%), and palmitic acid (30.9%). From the calorimetric study, it was demonstrated that melting temperature of the complexes was higher in the order of stearic (96.7 °C) > lauric, myristic, palmitic, and oleic (89.6-92.1 °C) > linoleic acid (78.3 °C). Melting enthalpy for complexes was roughly related to the CI value (R2 = 0.667). From the in-vitro digestibility measurement, it was found that a certain amount of fatty acid reduced the starch content hydrolyzed at a given condition. Among them, 0.50 mmol/g-starch lauric and oleic acid samples showed the largest reduction in the hydrolyzed starch content. This result was related to the extent of complex formation characterized by CI value and its helical order characterized by melting temperature. In addition, there was a possibility of the complex formation between amylose and unsaturated fatty acid during the hydrolysis of gelatinized starch.  相似文献   

10.
The Australian lentils, Lens culinaris: Matilda (Green Lentil) and Digger (Red Lentil) contain 44–45% starch (HPLC method) and 30–33% protein (LECO Analyser). This paper describes, first, the identification of optimum starch extraction conditions where yield is high and starch and protein damage is acceptable and, second, the properties of the starch and protein recovered. Starch was extracted from the flour of each variety with water at four temperatures (ambient 22, 30, 35 and 40 °C) and at five pH conditions (distilled water and pH adjusted with NaOH to 8, 8.5, 9.0 and 9.5). Extraction at pH 9.5, for all temperatures, achieved the maximum starch yield (85–95%) for both varieties. Digger gave a lower starch yield than Matilda when extracted in distilled water at all four temperatures. The yields of Digger starch were not significantly different at the four alkaline pHs. Matilda flour showed gradual increase in % starch yield with increase in extraction temperatures and pH (significant to 95% confidence level). Protein yield achieved, from both Digger and Matilda flour, was relatively low: 43–60% of the analysed protein content for Digger and 48–63% for Matilda. No significant difference was observed for extracted Digger protein at the various extraction pHs and temperatures. Matilda protein yields were significantly different between the various extraction conditions. The % starch damage was high for both varieties when extracted at higher temperature and pH. The DSC ΔH value increased with increasing pH and temperature. Extraction at higher pH resulted in a smoother and more symmetrical peak, denoting the absence of protein adhering to the starch surface. Even though low pH and low temperature caused less starch damage, these conditions were undesirable because they resulted in lower starch and protein yields. Taking all factors into account, pH 9.0 at 30 °C was chosen as an optimum extraction condition for Matilda while pH 8.5 at 35 °C was chosen for Digger.  相似文献   

11.
Synthesised E- and Z-ajoene were used to determine their amounts in food oils containing various fresh garlics. The best yield of E-ajoene (172.0 μg/g of garlic) and Z-ajoene (476.0 μg/g of garlic) was obtained from freshly prepared Japanese garlic with rice oil which was heated at 80 °C. Determination of E- and Z-ajoene from soybean oil containing 15% Japanese garlic samples prepared at 80 °C for 0.5 h gave the amount of E-ajoene (170.0 μg/g of garlic) and Z-ajoene (127.0 μg/g of garlic). After 9-month storage, 54.0% E- and 11.0% Z-ajoene remained in Japanese garlic with rice oil. Ajoene (0.1 mM) in ethyl acetate was incubated under UV-light (253.7 nm) for 3 days, 81.7% E- and 56.9% Z-ajoene remained. 4.3% and 0.5% E- and Z-ajoene remained when ajoene (0.1 mM in ethyl acetate) was incubated at 100 °C.  相似文献   

12.
Flavanones including hesperidin and narirutin constitute the majority of the flavonoids that occur naturally in citrus fruits. The main purpose of this study was to extract valuable natural flavanones from agricultural by-products such as citrus peels using subcritical water extraction (SWE). Thus, the application of SWE to extraction of flavanones hesperidin and narirutin from Citrus unshiu peel was evaluated, and the effect of key operating conditions was determined by varying the extraction temperature (110–200 °C) and time (5–20 min) under high pressure (100 ± 10 atm). The maximum yields of hesperidin (72 ± 5 mg/g C. unshiu peel) and narirutin (11.7 ± 0.8 mg/g C. unshiu peel) were obtained at an extraction temperature of 160 °C for an extraction time of only 10 min. These yields accounted for approximately 99% of the total amount of these flavanones in the original material. The SWE was compared with three conventional extraction methods in terms of the extraction time and recovery yields for hesperidin and narirutin. The hesperidin yield by SWE was more than 1.9-, 3.2-, and 34.2-fold higher than those obtained by extraction methods using ethanol, methanol, or hot water, respectively, and the narirutin yield was more than 1.2-, 1.5-, and 3.7-fold higher.  相似文献   

13.
Thermus thermophilus HB-8 is a source of trehalose synthase (GTase), which catalyses conversion of maltose into trehalose. Specific activity of maltose transglucosylation by cell-free extracts of the bacteria was about 0.1 U mg−1 protein and precipitation at 28% saturation of ammonium sulphate caused 3.5-fold enzyme purification. The optimum temperature for conversion of maltose into trehalose was 65 °C with about 27% of maximum activity at 85 °C. The highest GTase productivity was achieved at cultivation temperature over 60 °C and at NaCl concentration range of 0.1–0.5% (w/v). However, larger concentrations of sodium chloride in the growth media caused a remarkable decrease of GTase synthesis. The results, of ammonium sulphate fractionation and activity towards maltotriose (0.028 U mg−1), maltotetraose (0.16 U mg−1) and GlcαpNp (0.27 U mg−1), show that trehalose synthase and α-glucosidase activities reside in separate protein fractions of cell-free extracts from T. thermophilus cells.  相似文献   

14.
Corn-broad bean spaghetti type pasta was made with a corn/broad bean flour blend in a 70:30 ratio, through an extrusion-cooking process (Brabender 10 DN single-screw extruder with a 3:1 compression ratio). The effect of temperature (T = 80, 90 and 100 °C) and moisture (M = 28%, 31% and 34%) on the extrusion responses (specific consumption of mechanical energy and pressure) and the quality of this pasta-like product (expansion, cooking-related losses, water absorption, firmness and stickiness) was assessed. The structural changes of starch were studied by means of DSC and XRD. The extrusion-cooking process, at M = 28% and T = 100 °C, is appropriate to obtain corn-broad bean spaghetti-type pasta with high protein and dietary fibre content and adequate quality. The cooking characteristics and resistance to overcooking depended on the degree of gelatinisation and formation of amylose–lipid complexes. The critical gelatinisation point was 46.55%; beyond that point, the quality of the product declines.  相似文献   

15.
The effect of high-temperature fluidized-bed heating on some properties of an amaranth high-starch fraction obtained from Amaranthus cruentus grains was evaluated. A two-factor at three levels factorial experimental design (32) was adopted, one factor being the heating temperature (190, 200 and 210 °C) and the other, the moisture content of the high-starch fraction (12%, 16% and 20% wet basis). The effects on the responses water solubility, swelling power, amylographic and dynamic responses, crystallinity degree and gelatinization enthalpy were established by using response surface methodology. A partial loss of starch crystalline structure was observed but most of their granular integrity was preserved. As temperature and moisture increased, loss of crystalline structure and degree of gelatinization also increased. The obtained amaranth high-starch flours were of a solid character at low temperature, with high consistency when cooked and low water solubility, which make them suitable for industrial applications.  相似文献   

16.
Water uptake behavior of three cultivars of lentils (Boomer, French-green and Nugget) was studied at three different hydration temperature regimes (room temperature, 50 °C and 85 °C). Boomer had the highest amount of water uptake capacity (74.60 g water/100 g of seeds) at room temperature (20 °C) which can be linked with its pore properties. French-green lentils imbibed the largest amount of water at elevated soaking temperatures (50 °C and 85 °C) and can be attributed to its higher seed surface area to volume ratio, high protein content and relatively thinner seed coat. Water uptake at elevated temperatures (50 °C and 85 °C) were predicted by a two parameter Mitscherlich model (R2 > 0.99, χ2 < 0.5) within 1.36–3.07% average absolute error. At room temperature, only the water uptake of Boomer was reasonably predicted by this model. The texture (hardness) of the soaked lentils was found to be related the amount of water uptake and soaking temperature used rather than seed size or seed mass alone. The hardness values of Boomer, French-green and Nugget at 85 °C after 75 min soaking were reduced to 5.66%, 3.53% and 6.77%, respectively compared to their respective initial seed hardness values. The water uptake capacity of the aged Boomer was found to be significantly reduced compared to the fresh seeds (p < 0.01) while French-green and Nugget do not exhibit significant change (p < 0.05). During 72 h of germination, hardness of all lentil cultivars showed a typical pattern which decreased in the first 24 h followed by an increase compared to the hydrated seeds. A peak hardness value was obtained within 36–48 h before finally declining in all types of lentils. Structural changes within the cotyledon, such as depletion of starch granules, new nuclei formation and development of tissues in vascular bundles and rupture of the seed coat were observed during germination.  相似文献   

17.
The goal of this study was to develop a general model of inactivation of salmonellae in commercial liquid egg yolk for temperatures ranging from 58 °C to 66 °C by studying the inactivation kinetics of Salmonella in liquid egg yolk. Heat-resistant salmonellae (three serovars of Enteritidis [two of phage type 8 and one PT 13] and one Oranienburg) were grown to stationary phase in Tryptic Soy Broth and concentrated 10-fold by centrifugation. Each inoculum was added to liquid egg yolk and mixed thoroughly, resulting in a final population of ca. 7 log CFU/ml egg yolk. Inoculated yolk was injected into sterile glass capillary tubes, flame-sealed and heated in a water bath at 58, 60, 62, 64, and 66 °C. Capillary tubes were ethanol sanitized, rinsed, and contents were extracted. Yolk was diluted, surface plated onto Tryptic Soy Agar + 0.1% sodium pyruvate and 50 μg/ml nalidixic acid and incubated at 37 °C for 24 h before colonies were enumerated. Decimal reduction values were calculated from survivor curves with a minimum inactivation of 6 log CFU/ml at each temperature. Survival curves (except for 66 °C) featured initial lag periods before first order linear inactivation. Estimated asymptotic D-values were 1.83 min at 58 °C, 0.69 min at 60 °C, 0.26 min at 62 °C, 0.096 min at 64 °C and 0.036 min at 66 °C. The estimate of the asymptotic z-value was ca. 4.7 °C with standard error of 0.07 °C. A linear relationship between the log10 of the lag times and temperature was observed. A general kinetic model of inactivation was developed. The results of the study provide information that can be used by processors to aid in producing safe pasteurized egg yolk products and for satisfying pasteurization performance standards and developing industry guidance.  相似文献   

18.
There is a great variability in cooking time and final texture among cassava cultivars and one factor in determining these characteristics is the age of roots at harvest. Final texture after cooking is an important attribute for the acceptability of cassava and starch gelatinization has a role in softening the tissue. Two cassava cultivars at two different harvest maturities were cooked at 90 °C and at boiling water temperature (98 °C) and the extent of gelatinization was determined using an iodine colorimetric method. A generalized model for starch gelatinization, considering temperature and cooking time as continuous variables and age at harvest as qualitative variable, was used to model the cooking process and applied for each cultivar. At 90 °C IAPAR-19 Pioneira reached maximum gelatinization in 32 min for the 12 month old sample and 88 min for the 25 month old sample, while double the time was needed for Catarina Amarela. At 98 °C Pioneira gelatinized in 12 min for the 12 month and 32 min for the 25 month old sample while Catarina Amarela needed 28 and 56 min. Calculated activation energy for starch gelatinization was 122.3±5.2 and 98.6±4.7 kJ/mol for cultivar IAPAR-19 Pioneira and Catarina Amarela, respectively.  相似文献   

19.
The objective of this research was to verify the effect of drying conditions on thermal properties and resistant starch content of green banana flour (Musa cavendishii). The green banana flour is a complex-carbohydrates source, mainly of resistant starch, and quantifying its gelatinization is important to understand how it affects food processing and the functional properties of the flour. The green banana flour was obtained by drying unripe peeled bananas (first stage of ripening) in a dryer tunnel at 52 °C, 55 °C and 58 °C and air velocity at 0.6 m s−1, 1.0 m s−1 and 1.4 m s−1. The results obtained from differential scanning calorimetry (DSC) curves show a single endothermic transition and a flow of maximum heating at peak temperatures from (67.95 ± 0.31) °C to (68.63 ± 0.28) °C. ANOVA shows that only drying temperature influenced significantly (P < 0.05) the gelatinization peak temperature (Tp). Gelatinization enthalpy (ΔH) varied from 9.04 J g−1 to 11.63 J g−1 and no significant difference was observed for either temperature or air velocity. The resistant starch content of the flour produced varied from (40.9 ± 0.4) g/100 g to (58.5 ± 5.4) g/100 g, on dry basis (d. b.), and was influenced by the combination of drying conditions: flour produced at 55 °C/1.4 m s−1 and 55 °C/1.0 m s−1 presented higher content of resistant starch.  相似文献   

20.
The effects of post-resting temperature (5 °C, 15 °C and 25 °C) and drying level (low and high, corresponding to final water contents (w/w) of 57% and 50%, respectively) were evaluated in restructured dry-cured hams. The reduction of NaCl content, with and without the addition of K-lactate as NaCl substitute was also evaluated. Physicochemical and instrumental colour and texture (Stress Relaxation test) parameters and sensory attributes were measured. The main effects of reducing the NaCl addition from 30 g/kg to 15 g/kg in restructured dry-cured hams were the reduction of saltiness and the increase of aw, proteolysis and softness. The addition of K-lactate (19.7 g/kg) contributed to reduce these effects. Hams from high drying level had a longer processing time and a higher proteolysis index, but lower water content and harder texture. The increase of post-resting temperature to above 5 °C reduced the processing time and the metallic flavour, but at 25 °C restructured hams were spoiled. Therefore, the problems due to the reduction of NaCl to 15 g/kg in restructured dry-cured hams can be reduced by adding K-lactate and drying at 15 °C (after 3.5 months of resting at 5 °C) until a final weight loss of around 45% is reached.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号