Chemical composition of the Egyptian dry dates

Paper chromatographic analysis is applied to detect the sugars in both the flesh and the seeds of the dry dates (Balady variety). The analysis revealed the presence of fructose, glucose and sucrose. Poly, saccharides in the flesh and seeds were hydrolysed and analysed chromatographically. Xylose, arabinose, glucose and galactose were located and quantitatively determined. Protein hydrolysates showed the presence of 13 amino acid in the flesh and the seeds and the amino acid content of each were determined.     

Dietary fibre in sweet potatoes

The dietary fibre content of sweet potatoes grown in southwestern Ontario was found to be equivalent to that in roots produced in the United States. Based on a 3-year survey (1989, 1990, 1992) of three cultivars (Beauregard, Georgia Jet and Jewel), the total dietary fibre ranged from 9·07–12·16% for cured roots. Soluble and insoluble dietary fibre averaged 5·30% and 5·43%, respectively. Five cultivars were analysed, of each in green, cured and stored states, from the 1989 crop-year. With the exception of Southern Delite, whose fibre increased over 3% when stored, the analyses showed very little change in each cultivar's total dietary fibre in any state.     

Cell wall modifications during cooking of potatoes and sweet potatoes

Sweet potato (Ipomoea batatas L) tissue, when cooked at 70 °C to activate β‐amylase and break down starch, takes on a distinctive firm, brittle texture and does not show the cell separation that occurs in, for example, cooked potato (Solanum tuberosum L). Similar cooking conditions increase firmness in other plants by activating pectin methyl esterase which de‐esterifies pectic polysaccharides and protects them from thermal depolymerisation. We therefore isolated cell walls from both potatoes and sweet potatoes cooked at 70 °C and 100 °C and determined the remaining degree of methyl esterification of their pectins. Pectins from both species were demethylated to a similar extent at 70 °C and 100 °C. Since cooking sweet potato at 100 °C induced cell separation and softening, it is concluded that β‐amylase is rapidly inactivated at that temperature and swollen starch distends and separates the cells, whereas the firm texture obtained by cooking that species at 70 °C is not the result of pectin demethylation but is caused by the breakdown of starch to oligomers that can escape from the cell. © 2000 Society of Chemical Industry     

加工过程中紫薯汁化学成分变化分析

为探讨加工过程对紫薯汁品质的影响,对紫薯汁加工中护色、烫漂、酶解、灭菌过程中游离氨基酸、游离糖、花青素、可溶性蛋白含量变化进行了测定。结果表明:护色和烫漂可导致游离氨基酸、游离糖、花青素损失,但是酶解过程会使紫薯汁中的游离氨基酸、游离糖、花青素增加。杀菌过程中,无论是巴氏杀菌还是高压蒸汽灭菌均可造成花青素、游离糖、游离氨基酸含量降低,但高压蒸汽灭菌造成的损失高于巴氏杀菌。水溶性蛋白在加工过程中整体呈下降趋势,尤其是热烫处理后降低为护色后的20%。     

Microbiological quality of fresh-cut sweet potatoes

Sweet potato roots were dipped in various concentrations of chlorine for 5 min at 1 or 20 °C before and after slicing, and then stored at 2 or 8 °C for 14 days to evaluate the effects of different chlorine treatments and storage temperatures on the microbiological quality of fresh‐cut sweet potato slices. The microflora of fresh‐cut sweet potato slices was dominated by mesophiles, followed by psychrotrophs and fungi initially and during storage. The 2 °C storage was necessary to keep the microbial load at a low level. No spoilage was observed in fresh‐cut sweet potatoes at both storage temperatures for 14 days. Chlorination of sweet potatoes before slicing was not effective in ensuring acceptable microbiological quality of fresh‐cut sweet potatoes. Dipping slices in 200 ppm chlorine at 1 °C reduced the population of all micro‐organisms during storage.     

Chemical composition of hulls of the sweet almond (Prunus amygdalus)

Determination of moisture, crude fibre, fat, ash, total nitrogen and carbohydrates was carried out on almond hulls. The contents of P, K, Mg, Cu, Zn, Fe, Mn, NO₃- and B were also determined. Amino acid composition was established. The results are compared with analytical data on almond nuts.     

Protein isolates from Egyptian sweet potato leaves

The optimum conditions for protein extraction from sweet potato leaves were studied. The results obtained led to the following conclusions: pH 10 was found to be the best pH for maximum protein recovery after 4 h of extraction using distilled water in a ratio of 20:1 (v/w) solvent to sweet potato leaf powder; to increase the yield of the extractable protein (leaf protein concentrate, LPC) it was necessary to double the extraction steps. After extraction, the protein was precipitated according to its isoelectric point which was found at pH 4. The LPC yielded from sweet potato leaves had less value of antinutritional factors than found initially in the leaves. Also, the functional properties of the isolated LPC were studied: Oil holding capacity of LPC was higher than water holding capacity of the same protein, also it was higher than oil holding capacity of the albumin. The coagulated protein value of the LPC was much lower than that of albumin. The foaming capacity of LPC at pH 7 was higher than that found at pH 4 and both were much lower than those of albumin. On the other hand the foam of LPC was more stable at pH 7 than that found at pH 4.     

紫薯色素的研究进展

紫薯色素主要含花青素类色素,它具有抗氧化、抗突变、减轻肝机能障碍与心血管疾病等作用。综述近年来国内外对紫薯色素植物来源、分离纯化、化学组成、分子结构、稳定性、生物活性及其应用前景等方面的研究进展。     

紫薯在肉制品中的应用前景

自紫薯引入中国,其产品开发类型主要围绕着色素提取和功能性食品进行的;其中功能性食品包括紫薯全粉、冻干食品、紫薯饮料、茎尖蔬菜和休闲食品。结合紫薯的营养价值和紫薯淀粉的理化性质,本文对紫薯在肉制品行业的应用前景进行了探讨,同时为新品研发提供可行性依据。     

甘薯的不同收获日期对其淀粉产量的影响

对河北省甘薯集中产区秦皇岛市卢龙县主要甘薯品种进行了 2年的生长期采样动态研究表明 ,甘薯的收获时间不同 ,其淀粉的产出率和淀粉公顷产量也不同。如在最佳的收获时间段内 ,加工甘薯制取淀粉 ,就能提高甘薯淀粉的公顷产量 ,增加农民的收入和提高甘薯的社会经济效益     

添加剂对熟制甘薯抗老化作用的研究

为了抑制熟制甘薯在贮藏期间的老化,以优质甘薯为原料,经烘烤、熟制、搅拌成泥,加入抗老化剂制成熟制甘薯食品,并进行冷冻储藏。研究了添加不同抗老化剂对熟制甘薯的保水力、糊化性质和老化程度的影响。结果表明,添加了抗老化剂的熟制甘薯保持了其特有的口感风味,且保水力较大,糊化特性和老化度都不同程度地优于不添加抗老化剂的熟制甘薯。      

酶法水解不同品种甘薯制备甘薯多糖

甘薯经酶解、高温糊化、离心分离、酒精沉淀等工艺制备甘薯多糖。研究结果表明,经酶解后甘薯液在30℃、甘薯液酒精度达81.2度时沉淀,甘薯多糖沉淀最多。在此条件下,不同品种甘薯多糖制备率分别为:苏薯8号0.87%;日本黄薯0.73%;京薯6号1.88%;香蕉薯1.77%;金海2号1.58%;水果薯2.57%;美国黑薯2.41%;德国黑薯3.59%;花心薯1.24%。其中德国黑薯甘薯多糖制备率最高,是宜于制备甘薯多糖品种。     

酶法水解甘薯提取三种紫甘薯色素

甘薯俗称地瓜,是我国四大主要粮食作物之一,具有丰富营养价值,是我国人民喜爱的粮、菜兼用,物美价廉大众食品。自19世纪中期第一个人工合成有机色素问世以来,合成色素被大量应用于食品工业中,此后,由于合成色素安全性受到质疑,并确认部分合成色素具有潜在致畸、致癌及其它毒副作用,人们便把注意力转向天然色素。甘薯经冷冻、打浆、加酶、离心、浓缩、酒精沉淀等过程可得到甘薯色素,最适酶解条件为:α-淀粉酶添加量200U/mL,温度40℃,pH5,酶解时间20min;果胶酶和纤维素酶添加会破坏紫甘薯色素,碱性条件下紫甘薯色素会分解;酶法水解三种紫甘薯色素提取率分别为:美国黑薯1.25%,德国黑薯0.82%,花心薯1.09%。     

Chemical composition and nutritive value of lantana and sweet pepper seeds and nabak seed kernels

Abstract: Chemical analysis was carried out on lantana (Lantana camara) and sweet pepper (Capsicum annuum L.) seeds and nabak (Zizyphus spina‐christi) seed kernels. The proximate analysis (on dry weight basis) of sweet pepper seeds, lantana seeds, and nabak seed kernels showed the following composition: moisture 70.95%, 17.27%, and 4.22%; ash 4.88%, 1.81%, and 3.51%; fat 19.57%, 11.0%, and 30.19%; crude protein 19.28%, 6.3%, and 38.2%; and carbohydrate 56.3%, 80.9%, and 28.1%, respectively. For minerals, potassium was the most abundant element, followed by phosphorus and sodium. Also, zinc, iron, copper, and manganese were detected. Analysis of amino acids revealed that the first limiting amino acid was valine, for both lantana and sweet pepper seeds, but it was threonine for nabak seed kernels. Antinutritional compounds, including, phytic acid, trypsin inhibitor, and tannins, were detected in all seeds. Results of fatty acid compositions showed that the major fatty acid was oleic acid in both lantana (48.73%) and nabak oils (53.25%), but it was linoleic acid in sweet pepper oil (71.55%). Moreover, the degree of unsaturation of these oils was close to that of common vegetable oils. In all oils, there was absorbance in the ultraviolet (UV)‐B and UV‐C ranges with potential for use as broad spectrum UV protectants. It can be inferred that the seeds investigated are good sources of crude fat, crude protein, ash, carbohydrate, and some minerals. Furthermore, the oil extracts could be useful as edible oils and for industrial applications. Practical Application: The nutritional composition of the investigated seeds suggested that they could be used to meet part of the nutritional requirements of animal feeds. Also, they could be regarded as good sources of food ingredients and as new sources of edible oils.     

鲜切甘薯酶促褐变调控的研究

采用不同浓度的D-异抗坏血酸钠和柠檬酸分别处理鲜切甘薯,研究其在10℃贮藏过程中的酶促褐变反应,揭示不同褐变抑制剂对鲜切甘薯酶促褐变的调控机制。结果表明,0.5%～1.5%D-异抗坏血酸钠和低浓度(0.01%～0.03%)柠檬酸均延缓了鲜切甘薯酶促褐变的发生,有效抑制了PPO和POD的活性,降低了总酚含量;但高浓度(≥0.05%)柠檬酸处理反而加速了酶促褐变反应的进行。比较两种褐变抑制剂,D-异抗坏血酸钠抑制效果更好,其最佳浓度为1.0%。     

甘薯粉丝加工技术

阐述了甘薯加工的意义及其开发的途径 ,说明了甘薯粉丝加工的方法和工艺流程。认为甘薯加工是广大农村“节本增效”的好途径 ,对促进山区经济发展有着重要意义。     

Effects of drying and extrusion on colour,chemical composition,antioxidant activities and mitogenic response of spleen lymphocytes of sweet potatoes

Antioxidative and physiological property changes of freeze-dried, hot air-dried and extruded products made from two different colours of sweet potatoes (yellow and orange) were investigated. The results showed that there were no significant differences of dietary fibre content amongst all the treatments, except that the extruded products of orange sweet potatoes had higher dietary fibre contents. However, the water solubility index (WSI) values and antioxidant content were significantly different between yellow and orange sweet potatoes, and significantly different amongst freeze-dried, hot air-dried and extruded samples. The WSI values of the extruded samples were significantly higher than those of the hot air- and freeze-dried samples. The freeze-dried samples of orange sweet potatoes had more total phenolic compounds, β-carotene, and anthocyanin and had better scavenging effect on DPPH radicals than had freeze-dried yellow sweet potatoes. However, the scavenging effect on DPPH radicals was appreciably greater for hot air-dried than freeze-dried yellow sweet potatoes, but this trend was opposite for orange sweet potatoes. The extrusion process significantly increased the WSI values, scavenging effect on DPPH radicals and total phenolic compounds but decreased the β-carotene and anthocyanin for both yellow and orange sweet potatoes. At lower concentration (25–50 μg/ml), the methanolic extract of freeze-dried yellow sweet potatoes possessed a greater capacity of increasing the mitogenic response than did freeze-dried orange sweet potatoes; at higher concentration (100–200 μg/ml), the proliferation of the lymphocytes increased when stimulated with mitogen Con A for all the samples. This suggests that mitogen Con A selectively promotes T-cell-dependent proliferative activity.