We are searching data for your request:
Upon completion, a link will appear to access the found materials.
At the level of molecular structure, can the dietary fibres be regarded as polymers?
Dietary fibers are the indigestible portion of food derived from plants.
Most of these are indeed polymers of sugars (that is, a chain of repeated basic unit of carbohydrate), for example cellulose, alginate or pectin. They have glycosidic bonds that cannot be broken down by enzymes found in humans, and are thus indigestible.
But there are exceptions, for example raffinose, a trisaccharide found in beans & cabbage, is also categorised as a dietary fiber, as it is not breakable by human enzymes.
Dietary fibre in foods: a review
Dietary fibre is that part of plant material in the diet which is resistant to enzymatic digestion which includes cellulose, noncellulosic polysaccharides such as hemicellulose, pectic substances, gums, mucilages and a non-carbohydrate component lignin. The diets rich in fibre such as cereals, nuts, fruits and vegetables have a positive effect on health since their consumption has been related to decreased incidence of several diseases. Dietary fibre can be used in various functional foods like bakery, drinks, beverages and meat products. Influence of different processing treatments (like extrusion-cooking, canning, grinding, boiling, frying) alters the physico- chemical properties of dietary fibre and improves their functionality. Dietary fibre can be determined by different methods, mainly by: enzymic gravimetric and enzymic—chemical methods. This paper presents the recent developments in the extraction, applications and functions of dietary fibre in different food products.
This is a preview of subscription content, access via your institution.
The importance of food fibres has led to the development of a large and potential market for fibre-rich products and ingredients and nowadays there is a trend to find new sources of dietary fibre (DF), such as agronomic by-products that have traditionally been undervalued. Although there have been great achievements in this research field, further investigations are needed for designing ‘new food systems’ that consider the precise functionality of DF from both technological and physiological points of view.
Present knowledge about different aspects of DF and future potential applications of fibres and/or its components as functional foods or ingredients will be the focus of this report.
10 - Bioengineered natural textile fibres
Cellulose is a biological renewable resource whose biomass can be used in the production of paper, textiles, biofuels and chemical compounds. Cellulose rarely occurs in its pure form and is usually found in the form of lignocellulosic biomass. Recently bacterial cellulose (BC) of microbiological origin, synthesised by microorganisms, has also been developed. The transformation of lignocellulosic biomass is not a simple task and typically involves two stages: first, pre-treatment, and second, hydrolysis of the pre-treated cellulose and hemicellulose to form simple sugars (saccharification). Further understanding of the complex mechanisms that allow termites to decompose cellulose-based material of this type may make it possible to apply similar solutions on an industrial scale. One potential future direction in this area is the development of modified natural fibres and biomaterials such as biosilk and fibres based on polylactic acid (PLA) and polyhydroxybutyric acid (PHB), but this is very much in the early stages at present.
Meat and meat products, in spite of having high biological value protein and essential nutrients required for human sustenance, are highly susceptible to lipid oxidation and also deficient in complex carbohydrates like dietary fibre (DF). This deficiency of DF is often associated with increased occurrence of some chronic diseases such as risk of cardiovascular diseases, type 2 diabetes and colorectal cancer. Besides, development of oxidative changes in meat and meat products needs to be readdressed to prevent the quality deterioration during storage.
Scope and Approach
A wide range of plant-derived materials and their by-products are potentially rich sources of DFs and bioactive compounds (phytochemicals) with inherent antioxidant properties, commonly known as antioxidant dietary fibres (ADFs). ADF holds the promise to act as functional ingredient to ameliorate the deficiency in DF as well as oxidative changes in meat products, besides offering health benefits. So, fortification of meat and meat products with functional ingredients (ADFs) having dual properties, therefore, assumes significance.
Key Findings and Conclusions
This comprehensive review focuses on the present knowledge in the literature about the sources of ADFs and their potential application as functional ingredients to improve the physico-chemical characteristics, oxidative stability, sensory attributes and shelf life of meat and meat products. Considering the positive health effects of ADF, its incorporation in meat products opens up new possibilities for the industry to improve its ‘‘image” and opportunity to address consumer demands.
Chemical Fiber Analysis
Hair is the fine threadlike strands growing from the skin of humans, mammals, and some other animals, while fibers are defined as the smallest part of a textile material. Both come under the heading of "trace evidence" in an investigation.
Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime. It can provide a link between the criminal and the act.
From hair you can determine:
- Human or animal
- Manner in which hair was removed
- Treated hair
- Drugs ingested
Hair is composed of the protein keratin, which is also the primary component of finger nails.
Hair is produced from a structure called the hair follicle. Hair color is mostly the result of pigments, which are chemical compounds that reflect certain wavelengths of visible light. Hair shape (round or oval) and texture (curly or straight) is influenced heavily by genes. The physical appearance of hair can be affected by nutritional status and intentional alteration (heat curling, perms, straightening, etc.). The body area (head, arm, leg, back, etc.) from which a hair originated can be determined by the sample's length, shape, size, color, and other physical characteristics. In order to test hair evidence for nuclear DNA, the root must be present. The hair may also be tested using mitochondrial DNA present in the shaft of the hair whether or not the root is present.
The medulla is the hair core that is not always present. The medulla comes in different types and patterns. Human medulla may be continuous, fragmented or absent.
The Medulla Index is used to compare hairs and to determine the type of hair found. The index value is calculated by measuring the diameter of the medulla and dividing it by the diameter of the hair. Human hair has an index value around ⅓ while animal hairs have an index value of around &half.
Almost all fibers are some form of chemical polymer. Polymers are chemical molecules with repeating units of structure.
Fibers are separated into two general categories: Natural and Synthetic. And then further classified based on their origin: animal, vegetable or mineral.
Cotton is a vegetable fiber. Strong, tough, flexible moisture absorbent not shape retentive. When ignited it burns with a steady flame and smells like burning leaves. The ash left is easily crumbled. Small samples of burning cotton can be blown out as you would a candle.
Linen is also a plant fiber but different from cotton in that the individual plant fibers which make up the yarn are long where cotton fibers are short. Linen takes longer to ignite. The fabric closest to the ash is very brittle. Linen is easily extinguished by blowing on it as you would a candle.
Silk is a protein fiber and usually burns readily, not necessarily with a steady flame, and smells like burning hair. The ash is easily crumbled. Silk samples are not as easily extinguished as cotton or linen.
Wool is also a protein fiber but is harder to ignite than silk as the individual "hair" fibers are shorter than silk and the weave of the fabrics is generally looser than with silk. The flame is steady but more difficult to keep burning. The smell of burning wool is like burning hair.
Acetate is made from cellulose (wood fibers), technically cellulose acetate. Acetate burns readily with a flickering flame that cannot be easily extinguished. The burning cellulose drips and leaves a hard ash. The smell is similar to burning wood chips.
Acrylic technically acrylonitrile is made from natural gas and petroleum. Acrylics burn readily due to the fiber content and the lofty, air filled pockets. A match or cigarette dropped on an acrylic blanket can ignite the fabric which will burn rapidly unless extinguished. The ash is hard. The smell is acrid or harsh.
Nylon is a polyamide made from petroleum. Nylon melts and then burns rapidly if the flame remains on the melted fiber. If you can keep the flame on the melting nylon, it smells like burning plastic.
Polyester is a polymer produced from coal, air, water, and petroleum products. Polyester melts and burns at the same time, the melting, burning ash can bond quickly to any surface it drips on including skin. The smoke from polyester is black with a sweetish smell. The extinguished ash is hard.
Rayon is a regenerated cellulose fiber which is almost pure cellulose. Rayon burns rapidly and leaves only a slight ash. The burning smell is close to burning leaves.
Blends consist of two or more fibers and, ideally, are supposed to take on the characteristics of each fiber in the blend. The burning test can be used but the fabric content will be an assumption.
Generally fiber analysis is completed by many of the same methods used to analyze hair. That is to say most of the testing is simply examination using a microscope and comparison. The chart below lists many of the examinations used on fibers. Note how many of the processes are microscopy.
One of the simplest ways to identify fabric fibers that are unknown, is a simple burn test. This test can be done to determine if the fabric is a natural fiber, manmade fiber, or a blend of natural and manmade fibers. The burn test is to crude to be used to determine the exact fiber content. However, it can still determine the difference between many fibers to "narrow" the choices down to natural or manmade fibers. The advantage of this test for forensic purposes is the amount of time it takes to complete it.
Potato (Solanum tuberosum L.) is the most important vegetable crop, with a global production of around 368 million tonnes and more than 5000 known varieties. Tubers are the edible part of the plant, which can be eaten in various forms e.g. boiled, cooked, fried, crisped, etc. Processing of raw tubers usually involves peeling that generates a great amount of bulky waste which is usually discarded or used as animal feed.
Scope and approach
The present review aims at deeply discussing the current knowledge on the nutritional value, chemical composition and potentially related bioactivities of potato peels. Moreover, an overview on the reutilization of this bio-residue by the food industry is presented, by discussing the reported applications/incorporations into different food matrices, along with the potential technological properties.
Key findings and conclusions
Considering the nutritional value and chemical composition of potato peels, along with the bioactivity and technological properties of their extracts, the sustainable valorization of potato processing by-products presents great interest for the food and pharmaceutical industries that could increase the overall added value and minimize the environmental impact of this food crop.
Dietary fibers, major phenolics, main minerals, and trace elements in persimmons and apples were analyzed and compared in order to choose a preferable fruit for an antiatherosclerotic diet. Fluorometry and atomic absorption spectrometry following microwave digestion were optimized for the determination of major phenolics and minerals. Total, soluble, and insoluble dietary fibers, total phenols, epicatechin, gallic and p-coumaric acids, and concentrations of Na, K, Mg, Ca, Fe, and Mn in whole persimmons, their pulps, and peels were significantly higher than in whole apples, pulps, and peels (P < 0.01−0.0025). Conversely, the contents of Cu and Zn were higher in apples than in persimmons. In persimmons and apples all of the above components were higher in their peels than in whole fruits and pulps. The relatively high contents of dietary fibers, total and major phenolics, main minerals, and trace elements make persimmon preferable for an antiatherosclerotic diet.
Keywords: Persimmons apples fibers phenolics minerals trace elements
Humans lack the enzyme necessary to digest cellulose. Hay and grasses are particularly abundant in cellulose, and both are indigestible by humans (although humans can digest starch). Animals such as termites and herbivores such as cows, koalas , and horses all digest cellulose, but even these animals do not themselves have an enzyme that digests this material. Instead, these animals harbor microbes that can digest cellulose.
The termite, for instance, contains protists (singlecelled organisms) called mastigophorans in their guts that carry out cellulose digestion. The species of mastigophorans that performs this service for termites is called Trichonympha, which, interestingly, can cause a serious parasitic infection in humans.
Animals such as cows have anaerobic bacteria in their digestive tracts which digest cellulose. Cows are ruminants, or animals that chew their cud. Ruminants have several stomachs that break down plant materials with the help of enzymes and bacteria. The partially digested material is then regurgitated into the mouth, which is then chewed to break the material down even further. The bacterial digestion of cellulose by bacteria in the stomachs of ruminants is anaerobic, meaning that the process does not use oxygen . One of the by-products of anaerobic metabolism is methane, a notoriously foul-smelling gas. Ruminants give off large amounts of methane daily. In fact, many environmentalists are concerned about the production of methane by cows, because methane may contribute to the destruction of ozone in Earth's stratosphere.
Although cellulose is indigestible by humans, it does form a part of the human diet in the form of plant foods. Small amounts of cellulose found in vegetables and fruits pass through the human digestive system intact. Cellulose is part of the material called "fiber" that dieticians and nutritionists have identified as useful in moving food through the digestive tract quickly and efficiently. Diets high in fiber are thought to lower the risk of colon cancer because fiber reduces the time that waste products stay in contact with the walls of the colon (the terminal part of the digestive tract).
We know that humans ingest microplastics. Considering the totality of research findings on microplastics to date, we know that shellfish and other marine organisms consumed with intact GI tracts pose particular concern because they accumulate and retain microplastics. The toxicity associated with consuming microplastics is likely dependent on size, associated chemicals, and dose. Our collective understanding is limited regarding the sources, fate, exposure, bioavailability, and toxicity of microplastics and their associated chemicals in the marine environment. Current knowledge is mostly based on research conducted within the last decade however, interest in studying microplastics is growing. The following are key research needs for microplastics and their effects on human health:
Assess microplastics’ impact on ecological systems and food safety and improve understanding of potential toxicological mechanisms and public health effects.
Identify, if possible, lower risk species, production methods, or regions, and interactions of microplastics with nutrients and various seafood processing and cooking methods, in order to promote adjustments rather than consumer avoidance of seafood.
Standardize data collection methods for microplastic occurrence in the environment and food stuffs, followed by exposure assessment for dietary intake.
Standardize data collection assessing major seafood production types and seafood producing countries.
Collect data on presence, identity and quantity of degraded plastic in food, and data on the translocation of microplastics through the aquatic food web and human food system.
Develop methods to assess physical and chemical changes of micro- and nanoplastics when interacting with biological systems.
Collect toxicity exposure data evaluating mixtures of various additives/monomers.
Collect toxicological data on the most common polymers and their relative contributions to microplastic contamination.
Develop specific biomonitoring processes and body burden measurements for additives and monomers.
Research the toxicokinetics and toxicity of micro- and nanoplastics and their associated chemical compounds, to determine local gastrointestinal (GI) tract effects in animals and humans.
While much remains to be learned, filling these gaps is essential for advancing the dual goals of promoting seafood consumption and protecting consumers from negative health effects from microplastics in the marine environment.
Support for D.C.L. and R.A.N. was provided by the Johns Hopkins Center for a Livable Future (CLF) with a gift from the GRACE Communications Foundation, which had no role in study design, analysis, findings, or development of recommendations. The authors thank Jillian Fry, Shawn McKenzie, Jim Yager, Keeve Nachman, Mardi Shoer, and Marc Weisskopf for their insightful feedback.