Carbohydrates moisture determination

Samples to be analyzed can be of very complex nature (dairy products, fruit juice, etc.). Therefore, and provided that the preliminary steps—namely, sampling and moisture determination— have been properly attended to, the first important stage is sample preparation, which comprises extraction and cleanup. Once a sufficiently clean extract has been obtained, the carbohydrates therein may be separated prior to their detection and quantitation. 

Table 3 shows some physicochemical properties used as international GA quality parameters, for example moisture, total ash content, volatile matter and internal energy, with reference to gums taken from Acacia Senegal species in Sudan (FAO, 1990, Larson Bromley, 1991). The physicochemical properties of GA may vary depending on the origin and age of trees, the exudation time, the storage type, and climate. The moisture content facilitates the solubility of GA carbohydrate hydrophilic and hydrophobic proteins. The total ash content is used to determine the critical levels of foreign matter, insoluble matter in... 

In order to define this variety of food matrices, chemical composition differences that primarily influence chemical analytical measurements have to be considered. Major food components determining basic chemical make-up are the proximate composition of fat, protein, carbohydrate, ash, and moisture. Variations in ash content in general have a minor influence on analytical methods for other constituents and impact of moisture content can be controlled. Thus the major components influencing analytical performance are the relative levels of fat, protein, and carbohydrate. 

The complete analysis comprises determinations of the moisture, ash, gluten, nitrogen, fat, cellulose, digestible carbohydrates and acidity. All these determinations are made on the finely powdered material by the methods described for flour. The following investigations are also of importance. 

Although studies on potato structure had been carried out previously using conventional SEM, van Marie et al [70] used cryo-SEM to advantage in this high moisture material. The fracture planes of cooked and uncooked samples were used to help characterize cell wall adhesion in the four potato cultivars. In particular, differences in cell wall contact area and surface detail were used to explain the mealy versus firm textural attributes in the cultivars. By determining the parameters which contributed to the texture of potatoes, processing conditions and selection of suitable raw materials could be facilitated. Such information would be difficult to obtain with conventional, chemically fixed material due to the high moisture content and the inability of standard chemical fixation to retain carbohydrate-based structures. 

Proximate (approximate) analysis is a scheme developed originally in 1865 by Henneberg and Stohmann of the Weende Experiment Station in Germany to analyse the main components. It is often referred to as the Weende System and has been refined over time. The system consists of determinations of water (moisture), ash, crude fat (ether extract), CP and crude fibre (CF). It attempts to separate carbohydrates into two broad classifications CF (indigestible carbohydrate) and N-free extract (NFE, or digestible carbohydrate). NFE is measured by difference rather than by direct analysis. 

The physical/chemical states and the thermal transitions of food materials determine the process conditions, functionality, stability and overall quality, including the texture, of the final food products. Carbohydrates and proteins— two major biopolymers in various food products—can exist in an amorphous metastable state that is sensitive to moisture and temperature changes (Cocero and Kokini 1991 Madeka and Kokini 1994, 1996). The physical states of components in a biopolymer mixture determine the transport properties, such as viscosity, density, mass and thermal dif-fusivity, together with reactivity of the material. 

Sensory characteristics (texture, flavor, aroma, and color) of a food product are the most important attributes for the consumer (Aktas and Kaya, 2001b). The texture of food is mostly determined by moisture and fat content, as well as the types and amounts of structural carbohydrates and proteins. There are several physical and chemical methods of tenderizing meat. However, the mechanism of muscle tissue tenderization in solutions... 

The carbohydrate composition and lignin were determined using the NREL laboratory analytical procedures (http //wwwl.energy.gov/biomass/analytical procedures.html). The moisture content of the bagasse samples was determined using a moisture analyzer (Computrac MAX 1000, Arizona Instrument Corporation, Tempe, AZ, USA). 

The second food sample was a rice mixture which contained seaweed, egg, rice, imitation crab, and spinach. LC analysis was used to determine sugars and glycerol. Relative moisture, protein, lipid, ash, and carbohydrates were calculated based on USDA National Nutrient Database [2], Theoretical ethanol yield for a 100 g/1 sample was 34.6 g/1. Pictures of the dried, homogenized PRE mixture and the rice mixture are shown in Fig. 2a and b, respectively. Compositions of the two food mixtures are seen in Fig. 3. The PRE mixture (Fig. 3a) has less... 

Composition analysis of the treated/untreated biomass was done according to the NREL Laboratory Anal)dieal Procedures Preparation of samples for compositional analysis and determination of structural carbohydrates and lignin in biomass (draft version) [32]. The moisture content in biomass was measured by an inftared moisture balance (Denver Instrument, IR-30). Sugar content in compositional analysis and enzymatic digestibility was determined by HPLC using a Bio-Rad Aminex HPX-87P. 

In the case of comminuted meat (e.g., burgers), the purpose of analysis is to characterize the main constituents (moisture, protein, fat, ash) and also to determine to what extent it differs from the intact meat. For example, typical analyses applied to comminuted meat samples might include meat species identification and determination of collagen and carbohydrate content. As the meat products move further away from the original entire meat, a range of analyses is used to characterize the food, particularly assays for nonmeat proteins, for additives such as salts, and for preservatives. In the case of cured meat and cured meat products, the important analyses are for salt, nitrite and nitrate, and other additives such as sugars and phosphorus (polyphosphates). 

According to the glass transition theory, lipids are dispersed in the free volume of the food matrix composed of carbohydrates and protein polymers. In the rubbery state, the lipids react readily with oxygen and become oxidized. In the glassy state, however, the lipids are stable to oxidation because they are encapsulated and there is no free volume. The glass transition temperature, which determines when the food matrix changes from one state to the other, increases with a decrease in moisture and water activity. In many foods the... 

The Atwater procedure, in brief, was to adjust the heats of combustion (gross calories) of the fat, protein, and carbohydrate in a food to allow for the losses in digestion and metabolism found for human subjects, and to apply the adjusted caloric factors to the amounts of protein, fat, and carbohydrate in the food. The contents of protein and fat were determined by chemical analysis, and the percentage of carbohydrate was obtained by difference that is, it was taken as the remainder after the sum of the fat, protein, ash, and moisture had been deducted from 100. This so-called total carbohydrate, therefore, included fiber (an all-inclusive term for carbohydrates that are not digested by people) as well as any noncarbohydrate residue present... 

A high grain moisture content and environmental temperature increase both fungi growth and activity of most enzymes. The hydrolysis of fats occurs at a faster rate than carbohydrates or proteins. Therefore, measurements of lipid damage via titrat-able acidity, pH, or free fatty acids are the most sensitive indexes to determine grain condition or soundness. These tests correlate with the evaluation of off-odors widely practiced by federal grain inspectors (Anonymous 1992) (Chapter 2). 

The proximate composition of the dialyzed EPS of Lactobacillus sp. CFR-2180 was determined. It had a moisture content of 2% with negligible amount of protein (0.7%), as an impurity, which was also confirmed with the presence of a peak at 289 nm in UV spectrum (data not shown). The total carbohydrate and uronic acid contents of the sample were found to be 65 and 10%, respectively and the remaining might be the minerals or other impurities. Similarly, presence of glucuronic acid in the EPS produced b by Lact. acidophilus LMG 9433 was reported (Robjin et al, 1996). The sugar composition of the dialyzed EPS was found to... 

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