Preparation and composition of mesophyll,epidermis and fibre cell walls from leaves of perennial ryegrass (lolium perenne) and italian ryegrass (lolium multiflorum)

Cells of mesophyll, epidermis and residual fibrous material were obtained from leaves of Italian and perennial ryegrass harvested at different stages of maturity by mechanical disruption of leaf tissue. Mesophyll cells were selectively removed by filtration through 0.045 mm nylon mesh and remaining non-mesophyll cells centrifuged in metrizamide solutions (56–58% wt to vol.) of known density (1.308–1.329 g cm³ at 5°C) to obtain a pure epidermis cell fraction and a residual fibre fraction. Whole mesophyll cells contributed 63–72%, epidermis 12–15% and the fibre fraction 15–24% to the total leaf dry matter. Fibre values were higher in late-cut samples. Cell walls were prepared from mesophyll and epidermis cells by disruption and washing to remove cell contents. Fibre cells were judged free of cell contents and received no further treatment. Examination of cell wall preparations by light and electron microscopy showed that both mesophyll and epidermis preparations were essentially free from contaminating material. Mesophyll cell walls were uniformly thin (200 nm) while those of epidermis ranged from 2000–3000 nm at the outer face, thinning to 300 nm or less at the inner surface. An electron-light layer (cuticle) of approximately 200 nm thickness was present covering the outer face of the epidermis. The fibre fraction largely consisted of sclerenchyma, but contained, in addition, other vascular cells, detached annular rings and heavily silicified leaf hairs. Analysis of cell walls accounted for 85–90% of dry matter. Cellulose was the major component of all cell walls examined (approximately 40% of dry matter) with xylose residues accounting for a further 11% of mesophyll, 13.5–17.5% of epidermis and 21–25% of fibre cell walls. Arabinose was low in fibre cells but was present in much higher proportions in mesophyll and epidermis walls. The ratio of arabinose to xylose was approximately 1:1.5 for mesophyll, 1:2.5 for epidermis and 1:7.0 for the fibre fraction. The molar ratio acetyl to xylose remained fairly constant at 1:4 regardless of the grass, cell type or maturity of the sample. The uronic acid content of epidermis was higher than that in other cell types and showed an increase with increasing maturity of the grass, reaching over 9% in late-cut samples. Total phenolic material represented 2–3% of mesophyll and epidermis cell walls and 6% of fibre walls. Ferulic acid alone was released from the primary cell walls by saponification and p-coumaric and ferulic acids from the secondary-thickened fibre walls. Crude protein values (NX6.25) were high in mesophyll cell wall preparations and low in epidermis and fibre cell walls. Amino acid patterns were similar for both grasses and cell types but hydroxyproline was found in greater amounts in fibre cell walls than in either epidermis or mesophyll.     

Chufa (cyperus esculentus): A new source of dietary fibre

Chufa (Cyperus esculentus var sativus Boeck) could be a new source of dietary fibre. The total dietary fibre content of chufa is very high: 19.0% (w/w) average (calculated on dry matter). The neutral sugar composition of the dietary fibre consists mainly of glucose and xylose. The average content of phytic acid is 724 mg per 100 g.     

In vitro evaluation of the fermentation of added‐value agroindustrial by‐products: cactus pear (Opuntia ficus‐indica L.) peel and pineapple (Ananas comosus) peel as functional ingredients

Agroindustrial by‐products derived from fruit processing are an important source of biocompounds that can be used as functional food ingredients. The objective of this work was to evaluate cactus pear and pineapple peel flours as an alternative carbon source during fermentation using bacteria with probiotic potential. The total fibre content of both flours was over 60%, with total soluble carbohydrate content around 20%, indicating a good carbon source for lactic acid bacteria. Kinetic parameters indicate that peel flours are a suitable carbon source because the lactic acid bacteria grow (mean growth rate constant, k, values close to glucose, 1.52 h) and acidify the culture media (maximum acidification rate, V_max, approximately 1.60 pH × 10^?3 min^?1). There was no difference in prebiotic potential or prebiotic activity score for both the peel flours. Pediococcus pentosaceus performs better during fermentation. In this respect, cactus pear and pineapple peel flours can be used as functional ingredients due to their fermentable properties.     

Effects of cultivar,root weight,storage and boiling on carbohydrate content in carrots (Daucus carota L)

The effects of cultivar (n = 4), root weight (n = 4), storage (5 months) and boiling (7 min) and their interactions on the content of dry matter and carbohydrates were studied and ranked in carrots. Boiling had the greatest effect and had an influence on all variables except the ratio between sucrose and the monosaccharides glucose and fructose. The choice of cultivar was also of great importance as regards glucose, fructose and sucrose content, while dietary fibre and dry matter were much less affected, or even unaffected, by this factor. Root weight and storage were consistently of less significance than boiling and cultivar. Thus dietary fibre solubility, fructose content and the ratio between sucrose and the monosaccharides glucose and fructose were independent of the root weight, while storage had no impact on the dry matter content. After storage the cultivar Lonto had lost more dry matter than the other cultivars (10% versus mean 1% for the others, P = 0.009) and the sugar ratio between sucrose and the monosaccharides glucose and fructose had increased in the cultivar Amarant, while it decreased in the other cultivars (P < 0.001). Furthermore, Amarant had a lower loss of sugars (35%) following boiling than the other cultivars (mean 39%, P = 0.002). Storage and boiling interacted concerning soluble and insoluble dietary fibre, fibre solubility and glucose content. It is concluded that the various factors (especially boiling and cultivar) gave rise to such differences in carbohydrate content and composition that they might be of nutritional importance. The results may thus provide a basis for selecting raw material when studying possible health effects of carrots. Copyright © 2004 Society of Chemical Industry     

Effect of the addition of soluble (nutriose,inulin and polydextrose) and insoluble (bamboo,potato and pea) fibres on the quality of sugar‐snap cookies

Dietary fibre intake can help to improve the health of the population. Cookies are one of the most consumed bakery products. The aim of this study was to investigate the influence of different fibres on cookie quality. Soluble fibres (nutriose, inulin and polydextrose) decreased dough consistency favoured cookie spread during baking and produced wider and thinner cookies. In contrast, insoluble fibres (elongated and rounded) showed an opposite trend increasing dough consistency and giving rise to cookies with higher moisture, lower spread factor and higher hardness. Long insoluble fibres gave rise to harder cookies and with lower spread factor. Cookies made with soluble fibres were darker than the control cookie and cookies containing insoluble fibres. Therefore, solubility and shape of insoluble fibres play an important role in cookie quality. Fibre selection will be key to enriched cookies development.     

The effect of linseed and psyllium fibre on the gelling properties of unwashed mince from farmed meagre (Argyrosomus regius)

The gelling properties of farmed meagre (Argyrosomus regius) mince mixed with linseed and/or psyllium fibres (up to 4.0%, w/w) were studied. The effects of chilled storage time (15 days vs. 1 day) and cold gelling (setting at 2 ± 2 °C) were measured. Linseed addition increased ω3 PUFA content and worsened the gel products' texture. Psyllium functional fibre addition had only a negative effect upon breaking force and deformation, not affecting the remaining textural properties and improving water‐holding capacity (WHC) from 61–77 to 70–85%. The incorporation of 4.0% (w/w) psyllium seems to be advisable. Quality of heat‐induced meagre gels was unaffected by chilled storage time. Production of an acceptable cold set gel is feasible provided that enough time is allowed for completion of the setting process. Overall results showed a potential for combining small‐sized meagre (<2 kg) and psyllium fibres to produce high added‐value functional foods.     

Cauliflower (Brassica oleracea L), globe artichoke (Cynara scolymus) and chicory witloof (Cichorium intybus) processing by-products as sources of dietary fibre

By-products arising from vegetable processing activities have been assessed in relation to their potential application as sources of dietary fibre supplements in refined foods. Sources used were fresh cauliflower, globe artichoke and chicory witloof. Non-starch polysaccharide (NSP) content and composition of selected parts of each plant source have been measured from alcohol insoluble residues (AIR) and by fibre analysis, complemented by methylation analysis to characterise structural features of component polysaccharides. Results indicate that cauliflower upper stem NSP was similar to the floret (∽25 g kg⁻¹ fresh weight) and each was rich in pectic polysaccharides. Cauliflower lower stem was enriched in NSP (∽66 g kg⁻¹) due mainly to cellulose and xylan deposition, which resulted in a proportionate decrease in pectic polysaccharides. Artichoke stem (∽38 g NSP kg⁻¹) was similar to the receptacle (∽34 g NSP kg⁻¹) but bracts were heavily lignified. Chicory root and leaf bud were each rich in pectic polysaccharides but NSP content was much higher in the root (∽46 g kg⁻¹) than the leaf (∽8 g kg⁻¹). Results indicate that processing by-products, eg cauliflower upper stem, artichoke stem and chicory root, could prove useful as sources of pectic polysaccharide-rich supplements. However, polysaccharide composition and glycosidic linkage pattern also identified important structural differences between sources. The importance of ‘fibre type’ when considering development of food supplements is discussed. © 1998 SCI.     

南瓜叶浓缩蛋白制品的食用安全性初步评价

采用我国《食品安全性毒理学评价程序》中所规定的标准方法和实验模型,对南瓜叶浓缩蛋白制品的食用安全性进行评价。结果显示,该产品小鼠经口LD50值大于21.501g/kg·bw,属无毒级;小鼠30d喂养未显示任何毒副作用。因此,该产品对实验动物不具有急性毒性作用。      

Effects of harvest time and storage on dietary fibre components in various cultivars of white cabbage (Brassica oleracea var capitata)

The effect of harvest time and storage on dietary fibre content and composition was investigated in six cultivars of white cabbage (Brassica oleracea var capitata). Three cultivars were of early maturity type (SW Nordpol, Rolly and Balbro) and three of late maturity type (Predikant, Hanna and Lion). The average total dietary fibre (TDF) content was 241 g kg^?1 dry matter (DM) (CV = 13), of which approximately 25% was soluble (CV = 15). The main dietary fibre components were glucose (37%), uronic acid (32%), arabinose (12%) and galactose (8%) residues. Early cultivars generally had a lower TDF content than late maturity types, due to a lower amount of both insoluble (arabinose, galactose and glucose) and soluble (arabinose) polymers. An early cultivar, Rolly, had the highest solubility, 33%, versus 25 ± 4% for the other cultivars. The early cultivar SW Nordpol had a similar TDF content and proportion of soluble dietary fibre (SDF) to the late cultivar Hanna, but the dietary fibre composition was different, with the early cultivar having a lower proportion of arabinose residues. Storage for 6 weeks had minor effects on the dietary fibre. After further storage of the late maturity cultivars, there was an increase in insoluble dietary fibre (IDF) (glucose and uronic acid residues) and a decrease in SDF (arabinose and galactose residues). As a consequence the solubility of TDF decreased from 29 to 19% on average. Harvesting before physiological maturity was reached resulted in a somewhat lower content of TDF and IDF for two cultivars (Predikant and Hanna), while SDF was more or less unaffected for all cultivars. Long‐term storage had fewer effects on cabbage harvested prior to maturity than when harvested at the right physiological maturity. It is concluded that the observed differences between cultivars and after long term storage are of such magnitude that they may affect nutritional properties of the dietary fibre. © 2002 Society of Chemical Industry     

Physicochemical characterisation and in vitro Starch digestion of Avocado Seed Flour (Persea americana V. Hass) and its starch and fibrous fractions

The avocado seed is considered a by-product of their pulp exploitation and today it does not present relevant food or industrial applications. In this study, we evaluate the potential use of its flour, their isolated starch and fibre fractions. After processing, the flour yielded 46.28%, and showed 6.7% of protein and low fat and ash contents (3.4, and 2.71% respectively). The starch yielded 27.28% with low-fibre content that influenced its viscosity properties; as well as their water absorption index (WAI), water solubility index (WSI) and oil absorption index (OAI), that were 2.43%, 11.22% and 0.16% respectively. The in vitro starch digestion of the different obtained fractions showed higher amounts of rapidly digestible starch (56.8%–75.36%, flour and starch respectively). The functional properties of the materials were correlated with strong molecular interactions with their apparently unique amylose structure; for this, this by-product may have different potential for food applications.     

蔗渣膳食纤维化学结构的研究(Ⅰ)──细胞壁物质(膳食纤维)的分离与分级

蔗渣含88．3％（干基）的膳食纤维，是一种良好的膳食纤维新资源。本文利用简化的CNDF法从蔗渣中提取出纯净的细胞壁物质（膳食纤维），分析其单糖组成为4．08％Ara，36．54％Xy1，31．68％Glc和3．29％UA。通过80℃H2O，NaClO2—HOAc，1mol／LNaOH和4mol／LNaOH4种溶剂将细胞壁物质分级成7种聚合物组分，并分析它们的单糖组成。     

蔗渣膳食纤维化学结构的研究(Ⅳ)──挤压蒸煮对化学结构的影响

蔗渣细胞壁物质（膳食纤维）整体的化学成分与单糖组成不随双螺杆挤压蒸煮而发生变化。细胞壁物质中80℃H2O分级组分的相对含量会因挤压蒸煮处理而由原来的24％提高到13．3％，且分子的Xyl：Ara比值由原来的6．2减小到4．2；1mol／LNaOH分级组分的相对含量则由原来的189％减少到11．2％，分子Xal：Ara比值由原来9．3增加至11．4。挤压蒸煮对这2种分级组分的聚合物基本结构没有影响，但会使lmol／LNaOH分级组分发生增溶作用或断裂部分连接键，导致其分子量下降，分子更趋于直线型，分支程度减小，其中有部分转变成80℃H2O分级组分。     

Human Colonic Bacterial Degradability of Dietary Fibres from Sea-Lettuce (Ulva sp)

Sea-lettuce (Ulva sp) is one of the commonly consumed seaweeds which contains 16·5% of water-soluble and 13·3% insoluble dietary fibres. Since physiological effects of fibres are partly related to their colonic bacteria fermentability, Ulva sp and its constitutive soluble and insoluble fibres were incubated with faecal bacteria in an in vitro batch fermenter system. After 24 h of incubation, 32·0±0·4%, 25·9±0·4% and 50·9±7·4% of Ulva, soluble and insoluble fibres constitutive sugars, respectively, were degraded. Consequently, Ulva and its soluble fibre, ulvan, are poorly fermented by colonic bacteria. The constitutive sugars, rhamnose and glucuronate and the aldobiouronate β-D -glucuronosyluronate-(1,4)-L -rhamnose of the glucuronoxylorhamnan sulphate present in the soluble fibre are highly fermented. Chemical desulphation and/or carboxyl group reduction did not modify this fermentation behaviour. Thus, the particular chemical structure of ulvan is responsible for the resistance of this polysaccharide and of Ulva to colonic bacterial fermentation. As a physiological consequence of this particular behaviour, consumption of dietary fibres from sea-lettuce could be expected to act mainly as bulking agents with little effect on nutrient metabolism due to colonic bacterial fermentation products (short-chain fatty acids). © 1997 SCI.     

Protein quality of parched immature durum wheat (Frekeh)

The protein quality of parched immature Durum wheat (frekeh) produced from Deir Alla-2 variety was evaluated. Frekeh from two maturity stages was used: one at the end of the milk stage (F1) and the other at the end of the dough stage (F6). Two animal experiments were carried out in which net protein utilisation (NPU) was determined for the two samples and for mature wheat using Sprague Dawley rats, the first for 12 and the second for 11 days. Additionally, the chemical scores for these cereals were calculated. The results indicated that the protein of F1 was of higher quality than that of F6 or mature wheat; the protein efficiency ratio adjusted values for F1, F6 and wheat were respectively 2.70, 1.93 and 1.45, and the NPU_op values were 53, 46 and 44 respectively. There was agreement between these results and the chemical score values as they were 54, 41 and 42 for F1, F6 and wheat respectively. There was a significantly higher voluntary intake of cereal-based diets in comparison with the casein-based diet (P <0.05). Thus it is shown that frekeh produced from wheat harvested at an early stage of maturity was of higher protein quality than that produced at a late stage of maturity or mature wheat.     

Physicochemical and sensory characteristics of cookies containing residue from king palm (Archontophoenix alexandrae) processing

The aim of this study was to evaluate the chemical properties of the flours prepared with residues from organic king palm processing, and also to determine the cookie-making performance of residue blends from organic king palm processing and wheat flour, as well as the effect of the blends on the consumers' acceptance and purchase intent of high-fibre cookies. The king palm flours (PFs) contained high contents of total dietary fibre and total ash. Blends containing 0%, 10%, 15%, 20% and 25% of either PF or sieved king-palm flour (SPF) replacing wheat flour were prepared. The total dietary fibre content of the cookies ranged from 4 to 7 g (100 g)⁻¹ on a dry-matter basis. The level of these components improved with increased amounts of PF and SPF in the blends. All the cookies were acceptable and approved in relation to purchase intent.