Dried ground leaves ofPsidium guajava L. (guava) were extracted by water and aqueous ethyl alcohol 50%(1:10) ratio, and the total phenolic content in the extracts was determined spectrophotometrically according to Fol...Dried ground leaves ofPsidium guajava L. (guava) were extracted by water and aqueous ethyl alcohol 50%(1:10) ratio, and the total phenolic content in the extracts was determined spectrophotometrically according to FolinCiocalteu's phenol method and calculated as gallic acid equivalent (GAE). Remarkably high total phenolic content 575.3±15.5 and 511.6±6.2 mg of GAE/g of dried weight material (for ethanol guava leaf extracts and water guava leaf extracts,respectively) were obtained. The antioxidant activity of lyophilized extracts was determined at ambient temperature by means of a 2,2-diphenyl-1-picrylhydryzyl (DPPH') colorimetry with detection scheme at 515 nm. The activity was evaluated by the decrease in absorbance as the result of DPPH" color change from purple to yellow. The higher the sample concentration used, the stronger was the free radical-scavenging effect. The results obtained showed that ascorbic acid was a substantially more powerful antioxidant than the extracts from guava leaf. On the other hand, the commercial guava leaf extracts and ethanol guava leaf extracts showed almost the same antioxidant power whereas water guava leaf extracts showed lower antioxidant activity. The parameter EC50 and the time needed to reach the steady state to EC50 concentration (TEC50) affected the antiradical capacity of the sample. The antioxidant efficiency (AE) has been shown to be a more adequate parameter for selecting antioxidants than the widely used ECs0. This study revealed that guava leaf extracts comprise effective potential source of natural antioxidants.展开更多
Changes in tissue structures, rheological properties of cross- and vertical section boiled abalone meat were studied in relation to boiling time. The adductor muscle of abalone Haliotis discus which was removed from t...Changes in tissue structures, rheological properties of cross- and vertical section boiled abalone meat were studied in relation to boiling time. The adductor muscle of abalone Haliotis discus which was removed from the shell, was boiled for 1, 2, and 3 h, respectively. Then it was cut up and separated into cross- and vertical section meat. When observed by a light microscope and a scanning electron microscope, structural changes in the myofibrils were greatest in the cross section meat compared with the vertical section meat. When boiling time was increased from 1 h to 3 h, the instantaneous modulus E 0 and rupture strength of both section meat decreased gradually with increased boiling time, and no significant differences were observed between these two section meat for the same boiling time. When boiled for 1 h, the relaxation time of cross section meat was much longer than that of vertical section meat. There were no significant changes in the relaxation time of vertical section for different boiling time, but the relaxation time of cross section meat was reduced gradually with increasing boiling time. These results confirmed that the difference in rheological properties between the cross- and vertical section meat was mainly due to the denaturation level of myofibrils when heated for 1 h, as well as due to the changes in the amount of denatured proteins, and the manner in which the inner denatured protein components weve exchanged after boiling time was increased from 1 h to 3 h.展开更多
The chemical composition, total flavonoids and antioxidant capacity of 50% ethanolic extracts from raw and cooked buckwheat flour from southwest of China were determined. The heat treatment used to gelatinize the flou...The chemical composition, total flavonoids and antioxidant capacity of 50% ethanolic extracts from raw and cooked buckwheat flour from southwest of China were determined. The heat treatment used to gelatinize the flour starch significantly reduced the total flavonoids in the extract from 83.52 to 67.36 mg 100 g 1 of dry matter in the raw and cooked flour, respectively. The antioxidant capacity of the extracts was evaluated using autooxidation in a β carotene linoleate model system (AA or AAC), DPPH radical scavenging assay (IP) and oxygen radical absorbance capacity (ORAC) assay. Values for raw buckwheat flour extract were 97.84, 874.31, 76.45 and 94.92% for AA, AAC, ORAC and IP, respectively, while values in cooked buckwheat flour were 86.14, 842.88, 63.93 and 94.74% for AA, AAC, ORAC and IP, respectively. Values before cooked and raw buckwheat flour extracts were significantly different ( P <0.05) for AA, AAC, and ORAC.展开更多
The moisture loss degree is important in determining the quality of post-harvest mushroom (Agaricus bisporus (Lange) Sing). Quantitative roughness analyzed by atomic force microscopy (AFM) was proposed to denote the d...The moisture loss degree is important in determining the quality of post-harvest mushroom (Agaricus bisporus (Lange) Sing). Quantitative roughness analyzed by atomic force microscopy (AFM) was proposed to denote the degree of shrinkage, with arithmetic average roughness (Ra) and root mean square roughness (Rq) as parameters, The initial value of Ra was (30.035±1.839)nm, while those of 2℃, 25℃ and dynamic temperature on the 2nd day were (40.139±3.359) nm, (54.393±13.534) nm and (41.197±6.555) nm, respectively. There is a similar tendency for the results of Ra and Rq Both values of roughness increased in duration of storage and with increasing temperatures. The three-dimensional profile of the pileus epicutis could signify the process of water evaporation intuitionally. The tendency was in accordance with the roughness results, especially for the earlier stage of the storage (0-2 d). The outcome of roughness analysis could signify the differences of storage conditions. It was shown that the roughness measured by atomic force microscopy effectively reflected the moisture loss degree of the mushroom pileus epicutis during post-harvest storage.展开更多
The stability of porphyra-334 in solutions of different pH values at different temperatures was studied. In high acidic conditions, below pH 3, the absorption maximum, λ max, of porphyra-334 shows hypsochromic shift ...The stability of porphyra-334 in solutions of different pH values at different temperatures was studied. In high acidic conditions, below pH 3, the absorption maximum, λ max, of porphyra-334 shows hypsochromic shift towards lower wavelength and the absorbance also has a light decrease. In high alkaline conditions of over pH 12, the absorbance of porphyra-334 decreases and an unknown compound with a peak maximum at 225 nm appears. The peak height of the unknown compound increases with the decrease of absorbance of porphyra-334. This might be related to the decomposition of porphyra-334. At room temperature, porphyra-334 solutions, except high alkaline solutions, are stable. Increasing the temperature, especially higher than 60℃, promotes the decomposition of porphyra-334 and causes the absorbance decrease both in basic and acidic solutions.展开更多
The physiological mechanism of maintaining the green colour of pak choy leaves (Brassicarapa var chinensis) with heat-shock treatment was studied. Chlorophyll in the outerleaves of pak choy degraded rapidly during sto...The physiological mechanism of maintaining the green colour of pak choy leaves (Brassicarapa var chinensis) with heat-shock treatment was studied. Chlorophyll in the outerleaves of pak choy degraded rapidly during storage at ambient temperature (20±2℃), aslight yellow appeared. Heat-shock treatment (46-50℃) had a mild effect on maintainingthe green colour of outer leaves. Normal chlorophyll degradation was associated with abinding of chlorophyll with chlorophyll-binding-protein preceding chlorophyll breakdown.Heat-shock treatment was found to reduce the binding-capacity between chlorophyll-binding-protein and chlorophyll. In the chlorophyll degradation pathway, pheide dioxygenasewas synthesized during leaf senescence which was considered to be a key enzyme inchlorophyll degradation. Activity of this enzyme was reduced following heat-shocktreatment, which might explain the observed reduction in chlorophyll breakdown. Twogroups of heat-shock proteins were detected in treated leaves, the first group containingproteins from 54KDa to 74Kda, and the second group contained proteins from 15KDa to29KDa. Heat-shock treatment was also found to retard the decline of glucose and fructose(the main energy substrates) of outer leaves.展开更多
The effect of application of cellulose-based edible coating, hydroxypropyl methylcellulose (HPMC) to mature-green tomatoes on the firmness and color was investigated. Tomatoes were stored at 20℃ for up to 18 days. Fi...The effect of application of cellulose-based edible coating, hydroxypropyl methylcellulose (HPMC) to mature-green tomatoes on the firmness and color was investigated. Tomatoes were stored at 20℃ for up to 18 days. Firmness decreased as storage time increased in all treatments. However, application of HPMC edible coating delayed softening of tomatoes during 18 days of storage at 20℃ . At days 7, 13 and 18,the firmness of tomatoes coated with HPMC was significantly ( P ≤ 0.05) greater than the firmness of uncoated tomatoes. The study also confirmed that HPMC coatings could significantly (P≤0.05) delay the changes in color of tomatoes stored at 20℃ . The ripening of tomatoes from the pink stage to the red stage was successfully retarded. HPMC coating could extend the shelf life of fresh tomatoes. The retardation of the rate of loss of firmness could reduce the economic loss that would result from spoilage by mechanical injury during transportation of tomatoes.展开更多
文摘Dried ground leaves ofPsidium guajava L. (guava) were extracted by water and aqueous ethyl alcohol 50%(1:10) ratio, and the total phenolic content in the extracts was determined spectrophotometrically according to FolinCiocalteu's phenol method and calculated as gallic acid equivalent (GAE). Remarkably high total phenolic content 575.3±15.5 and 511.6±6.2 mg of GAE/g of dried weight material (for ethanol guava leaf extracts and water guava leaf extracts,respectively) were obtained. The antioxidant activity of lyophilized extracts was determined at ambient temperature by means of a 2,2-diphenyl-1-picrylhydryzyl (DPPH') colorimetry with detection scheme at 515 nm. The activity was evaluated by the decrease in absorbance as the result of DPPH" color change from purple to yellow. The higher the sample concentration used, the stronger was the free radical-scavenging effect. The results obtained showed that ascorbic acid was a substantially more powerful antioxidant than the extracts from guava leaf. On the other hand, the commercial guava leaf extracts and ethanol guava leaf extracts showed almost the same antioxidant power whereas water guava leaf extracts showed lower antioxidant activity. The parameter EC50 and the time needed to reach the steady state to EC50 concentration (TEC50) affected the antiradical capacity of the sample. The antioxidant efficiency (AE) has been shown to be a more adequate parameter for selecting antioxidants than the widely used ECs0. This study revealed that guava leaf extracts comprise effective potential source of natural antioxidants.
文摘Changes in tissue structures, rheological properties of cross- and vertical section boiled abalone meat were studied in relation to boiling time. The adductor muscle of abalone Haliotis discus which was removed from the shell, was boiled for 1, 2, and 3 h, respectively. Then it was cut up and separated into cross- and vertical section meat. When observed by a light microscope and a scanning electron microscope, structural changes in the myofibrils were greatest in the cross section meat compared with the vertical section meat. When boiling time was increased from 1 h to 3 h, the instantaneous modulus E 0 and rupture strength of both section meat decreased gradually with increased boiling time, and no significant differences were observed between these two section meat for the same boiling time. When boiled for 1 h, the relaxation time of cross section meat was much longer than that of vertical section meat. There were no significant changes in the relaxation time of vertical section for different boiling time, but the relaxation time of cross section meat was reduced gradually with increasing boiling time. These results confirmed that the difference in rheological properties between the cross- and vertical section meat was mainly due to the denaturation level of myofibrils when heated for 1 h, as well as due to the changes in the amount of denatured proteins, and the manner in which the inner denatured protein components weve exchanged after boiling time was increased from 1 h to 3 h.
文摘The chemical composition, total flavonoids and antioxidant capacity of 50% ethanolic extracts from raw and cooked buckwheat flour from southwest of China were determined. The heat treatment used to gelatinize the flour starch significantly reduced the total flavonoids in the extract from 83.52 to 67.36 mg 100 g 1 of dry matter in the raw and cooked flour, respectively. The antioxidant capacity of the extracts was evaluated using autooxidation in a β carotene linoleate model system (AA or AAC), DPPH radical scavenging assay (IP) and oxygen radical absorbance capacity (ORAC) assay. Values for raw buckwheat flour extract were 97.84, 874.31, 76.45 and 94.92% for AA, AAC, ORAC and IP, respectively, while values in cooked buckwheat flour were 86.14, 842.88, 63.93 and 94.74% for AA, AAC, ORAC and IP, respectively. Values before cooked and raw buckwheat flour extracts were significantly different ( P <0.05) for AA, AAC, and ORAC.
文摘The moisture loss degree is important in determining the quality of post-harvest mushroom (Agaricus bisporus (Lange) Sing). Quantitative roughness analyzed by atomic force microscopy (AFM) was proposed to denote the degree of shrinkage, with arithmetic average roughness (Ra) and root mean square roughness (Rq) as parameters, The initial value of Ra was (30.035±1.839)nm, while those of 2℃, 25℃ and dynamic temperature on the 2nd day were (40.139±3.359) nm, (54.393±13.534) nm and (41.197±6.555) nm, respectively. There is a similar tendency for the results of Ra and Rq Both values of roughness increased in duration of storage and with increasing temperatures. The three-dimensional profile of the pileus epicutis could signify the process of water evaporation intuitionally. The tendency was in accordance with the roughness results, especially for the earlier stage of the storage (0-2 d). The outcome of roughness analysis could signify the differences of storage conditions. It was shown that the roughness measured by atomic force microscopy effectively reflected the moisture loss degree of the mushroom pileus epicutis during post-harvest storage.
基金supported by the Natural Science Foundation of Qingdao(No.04-2-JZ-110).
文摘The stability of porphyra-334 in solutions of different pH values at different temperatures was studied. In high acidic conditions, below pH 3, the absorption maximum, λ max, of porphyra-334 shows hypsochromic shift towards lower wavelength and the absorbance also has a light decrease. In high alkaline conditions of over pH 12, the absorbance of porphyra-334 decreases and an unknown compound with a peak maximum at 225 nm appears. The peak height of the unknown compound increases with the decrease of absorbance of porphyra-334. This might be related to the decomposition of porphyra-334. At room temperature, porphyra-334 solutions, except high alkaline solutions, are stable. Increasing the temperature, especially higher than 60℃, promotes the decomposition of porphyra-334 and causes the absorbance decrease both in basic and acidic solutions.
文摘The physiological mechanism of maintaining the green colour of pak choy leaves (Brassicarapa var chinensis) with heat-shock treatment was studied. Chlorophyll in the outerleaves of pak choy degraded rapidly during storage at ambient temperature (20±2℃), aslight yellow appeared. Heat-shock treatment (46-50℃) had a mild effect on maintainingthe green colour of outer leaves. Normal chlorophyll degradation was associated with abinding of chlorophyll with chlorophyll-binding-protein preceding chlorophyll breakdown.Heat-shock treatment was found to reduce the binding-capacity between chlorophyll-binding-protein and chlorophyll. In the chlorophyll degradation pathway, pheide dioxygenasewas synthesized during leaf senescence which was considered to be a key enzyme inchlorophyll degradation. Activity of this enzyme was reduced following heat-shocktreatment, which might explain the observed reduction in chlorophyll breakdown. Twogroups of heat-shock proteins were detected in treated leaves, the first group containingproteins from 54KDa to 74Kda, and the second group contained proteins from 15KDa to29KDa. Heat-shock treatment was also found to retard the decline of glucose and fructose(the main energy substrates) of outer leaves.
文摘The effect of application of cellulose-based edible coating, hydroxypropyl methylcellulose (HPMC) to mature-green tomatoes on the firmness and color was investigated. Tomatoes were stored at 20℃ for up to 18 days. Firmness decreased as storage time increased in all treatments. However, application of HPMC edible coating delayed softening of tomatoes during 18 days of storage at 20℃ . At days 7, 13 and 18,the firmness of tomatoes coated with HPMC was significantly ( P ≤ 0.05) greater than the firmness of uncoated tomatoes. The study also confirmed that HPMC coatings could significantly (P≤0.05) delay the changes in color of tomatoes stored at 20℃ . The ripening of tomatoes from the pink stage to the red stage was successfully retarded. HPMC coating could extend the shelf life of fresh tomatoes. The retardation of the rate of loss of firmness could reduce the economic loss that would result from spoilage by mechanical injury during transportation of tomatoes.
