Preparation and physicochemical properties of modified jackfruit starches

Modifications of jackfruit starch, extracted from the cotyledons of Artocarpus heterophyllus Lam. (Thong Prasert cultivar), were carried out to obtain a pregelatinized starch, three (m-, n- and i-) carboxymethyl starches, a hydroxypropyl starch and a phosphate cross-linked starch. Physicochemical properties of native and modified jackfruit starches were comparatively investigated. Pregelatinized, hydroxypropyl, and cross-linked starches were insoluble or partially soluble in water at room temperature, while carboxymethyl starches were soluble with good overall water uptake. Scanning electron microscopic images revealed that granules of most modified jackfruit starches retained the native appearance and crystal structure, with the exception of pregelatinized starch and two (n- and i-) carboxymethyl starches, which showed significant breakage of granules. X-ray diffraction patterns corroborated to suggest the loss of crystallinity in these modified starches. Thermal analysis showed a significant decrease in the gelatinization temperature of hydroxypropyl starch with no change in enthalpy, while higher gelatinization temperature and less enthalpic value were observed for pregelatinized starch. Pregelatinized and hydroxypropyl starches showed temperature-dependent improvement on swelling and solubility, while cross-linked starch exhibited less solubility. Aqueous solution of m-carboxymethyl starch yielded the highest apparent viscosity with improved heating-cooling stability.     

挤压改性对菠萝蜜种子淀粉精细结构的影响

以菠萝蜜种子为原料提取淀粉,利用双螺杆挤压机通过控制挤压操作参数对淀粉进行改性,并对挤出物进行分子量分布和链长分布实验。结果表明:挤压改性后的菠萝蜜种子淀粉对比原淀粉重均分子量和数均分子量均降低,平均回旋半径减少,链长分布中A链和B1链的比例变大,B2链和B3+链比例变小;随着机筒温度和螺杆转速的增加,重均分子量和数均分子量显著降低,A链比例显著增加,B1、B2和B3+链比例显著减少,表明挤压改性菠萝蜜种子淀粉精细结构受挤压操作参数影响显著。     

菠萝蜜果实挥发物的热脱附-气相色谱/质谱(TCT-GC/MS)联用分析

采用热脱附-气相色谱/质谱(TCT-GC/MS)联用技术,对动态顶空密闭循环吸附捕集的菠萝蜜果肉及果皮挥发物分别进行检测。结果表明,菠萝蜜果皮与果肉挥发物中富含酯类化合物,果皮挥发物中的乙酸正丙酯和乙酸正己酯相对含量高于果肉中的,果肉挥发物中的异戊酸甲酯、戊酸丁酯、丁酸乙酯相对含量高于果皮挥发物中的,二者中的戊酸乙酯相对含量接近;二者中的其他酯和醇、羧酸(酐)、含氮及含硫类化合物均无共同成分;果皮挥发物中未检出而果肉挥发物中检出的化合物类型还有醛、醚、萜烯类。     

Storage stability of jackfruit (Artocarpus heterophyllus) powder packaged in aluminium laminated polyethylene and metallized co-extruded biaxially oriented polypropylene during storage

Total colour difference (ΔE), rates of adsorbed moisture and sensory attributes of drum-dried jackfruit powder packaged in aluminium laminated polyethylene (ALP) and metallized co-extruded biaxially oriented polypropylene (BOPP/MCPP) pouches stored at accelerated storage (38 °C, with 50%, 75% and 90% relative humidity (RH)) were determined over 12 weeks period. The changes in total colour followed zero order reaction kinetics. Packaging materials, storage temperature and RH values significantly (p < 0.05) influenced the rates of adsorbed moisture of jackfruit powder. There was a significant (p < 0.05) decrease in the intensities of the fruity odour, taste and increase in the lumpiness of the jackfruit powder stored at 38 °C with 90% RH. The shelf life of jackfruit powder stored at 38 °C and 90% RH was limited by overall acceptability and the intensity of fruity odour, taste and lumpiness at week 8 of storage. Jackfruit powder stored at 28 °C remained stable and acceptable throughout the storage period for all RH values. The powder packaged in ALP significantly (p < 0.05) reduced total colour change, rates of adsorbed moisture, lumpiness intensity of jackfruit powder and was rated higher in terms of overall acceptability over BOPP/MCPP. Results of this study suggested that ALP packaging with storage conditions of 28 °C and RH less than 75% was better suited for keeping jackfruit powder.     

Effect of Artocarpus communis Extract on UVB Irradiation-Induced Oxidative Stress and Inflammation in Hairless Mice

Administration of antioxidants and anti-inflammatory agents is an effective strategy for preventing ultraviolet (UV) irradiation-induced skin damage. Artocarpus communis possesses several pharmacological activities, such as antioxidant, anticancer and anti-inflammation. However, the photoprotective activity of methanol extract of A. communis heartwood (ACM) in ultraviolet irradiation-induced skin damage has not yet been investigated. The present study was performed using ultraviolet absorption, histopathological observation, antioxidant and anti-inflammation assays to elucidate the mechanism of the photoprotective activity of ACM. Our results indicated that ACM displayed a UVA and UVB absorption effect and then effectively decreased scaly skin, epidermis thickness and sunburn cells during ultraviolet irradiation in hairless mice. ACM not only decreased ultraviolet irradiation-mediated oxidative stress, including lowering the overproduction of reactive oxygen species and lipid peroxidation (p < 0.05), but also reduced the levels of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α) and interleukin 1β. Additionally, ACM can decrease the synthesis of cytosolic phospholipase A2, cyclooxygenase, inducible nitric oxide synthase and vascular cell adhesion molecular-1 via inhibiting TNF-α-independent pathways (p < 0.05) in UVB-mediated inflammation and formation of sunburn cells. Consequently, we concluded that ACM extract has a photoprotective effect against UVB-induced oxidative stress and inflammation due to its sunscreen property, and its topical formulations may be developed as therapeutic and/or cosmetic products in further studies.     

Characterisation of a trypsin/chymotrypsin inhibitor from jack fruit (Artocarpus integrifolia) seeds

Jack fruit seed (Artocarpus integrifolia Hook f) trypsin inhibitor (JSTI) was found to be rich in acidic amino acids and devoid of free thiol groups. The N-terminal and C-terminal amino acids of JSTI were aspartic acid and scrine, respectively. The inhibitor was stable under conditions of extremes of pH (3·0–12·0), at high temperatures and in the presence of denaturing agents. JSTI showed a non-competitive type of inhibition with K_i values of 0·48 ± 0·17 nM and 0·16 ± 0·04 nM for trypsin and chymotrypsin, respectively. The JSTI–trypsin complex exhibited chymotrypsin inhibitory activity suggesting the ‘double-headed’ nature of the inhibitor. Chemical modification of lysine residues resulted in loss of trypsin and chymotrypsin inhibitory activities of JSTI indicating that amino groups are essential for activity.     

菠萝蜜蛋白酶提取方法的比较研究

分别用乙醇法、硫酸铵沉淀法和氯化钠沉淀法提取菠萝蜜蛋白酶,以酶的比活力为指标,采用正交实验得出各方法的最佳处理组合。三种方法的实验结果表明,硫酸铵沉淀法提取得率和酶活力较高,酶活回收率为57.18%。