Simultaneous lactic acid and xylitol production from vine trimming wastes

Hemicellulosic hydrolyzates from vineshoot trimmings obtained by dilute sulfuric acid hydrolysis were evaluated for xylitol production by Debaryomyces hansenii NRRL Y‐7426. Bioconversion was not efficient, however, since a mixture of products (mainly ethanol) was achieved. Taking into account that hexoses (such as glucose or mannose) can inhibit xylose metabolism by repression and inactivation of the xylose transport system or catabolic enzymes and that these hemicellulosic hydrolyzates are characterized by a high glucose concentration, a novel technology was developed, sequentially transforming glucose into lactic acid by Lactobacillus rhamnosus followed by fermentation of xylose into xylitol by Debaryomyces hansenii after L. rhamnosus removal by microfiltration. Optimal conditions were achieved using detoxified concentrated hemicellulosic hydrolyzates, after CaCO₃ addition in both stages of fermentation and using nitrogen purges after sampling in order to reduce the oxygen dissolved. Under these conditions 31.5 g lactic acid L^?1 (Q_LA = 1.312 g L^?1 h^?1 and Y_LA/S = 0.93 g g^?1) and 27.5 g xylitol L^?1 (Q_Xylitol = 0.458 g L^?1 h^?1 and Y_Xylitol/S = 0.53 g g^?1) were produced. Finally, lactic acid was selectively recovered using the resin Amberlite IRA 400 (0.0374 g of lactic acid g^?1 of dry resin), allowing a further recovery of xylitol by sequential stages of adsorption, concentration, ethanol precipitation, concentration and crystallization to obtain food‐grade xylitol according to a developed process. Copyright © 2007 Society of Chemical Industry     

Effect of Blanching and Drying Temperature on Polyphenolic Compound Stability and Antioxidant Capacity of Apple Pomace

The effects of blanching and drying treatments on stability, physical properties, and antioxidant activity of apple pomace polyphenols were evaluated. Blanched and unblanched apples were extracted, and the pomace was dried in a cabinet dryer at a speed of 3 m/s at 50 °C, 60 °C, 70 °C, and 80 °C. The color, total phenolics, flavonoids, individual polyphenolic compounds, anthocyanins, and total antioxidant activity were analyzed. The blanching process caused a major retention in color, total polyphenolic content, and total flavonoid content for fresh apple pomace when compared with fresh unblanched pomace. Drying of either fresh blanched or fresh unblanched pomace caused a significant reduction (P < 0.05) in total polyphenol and flavonoid content leading to a reduction in the total antioxidant activity. When compared with the unblanched treatment, drying the blanched pomace at 80 °C resulted in a product with significant amounts of total phenolics, flavonoids, and antioxidant activity. The individual phenolic compounds were significantly increased (P < 0.05) in blanched pomace that was not dried when compared with unblanched samples. Drying blanched apple pomace did not cause a significant change in the concentration of individual polyphenolic compounds, but drying unblanched apple pomace caused a reduction in the concentrations of epicatechin and caffeic acid, with an important reduction in p-coumaric acid at temperatures higher than 60 °C. However, the drying process caused a significant reduction in the antioxidant capacity. Therefore, a combination of blanching and drying processes for apple pomace results in a product that maintains antioxidant capacity.     

Proanthocyanidin metabolites associated with dietary fibre from in vitro colonic fermentation and proanthocyanidin metabolites in human plasma

Proanthocyanidins (PAs) or condensed tannins, a major group of dietary polyphenols, are oligomers and polymers of flavan‐3‐ol and flavan‐3, 4‐diols widely distributed in plant foods. Most literature data on PAs' metabolic fate deal with PAs that can be extracted from the food matrix by aqueous‐organic solvents ( extractable proanthocyanidins). However, there are no data on colonic fermentation of non‐extractable proanthocyanidins (NEPAs), which arrive almost intact to the colon, mostly associated to dietary fibre (DF). The aim of the present work was to examine colonic fermentation of NEPAs associated with DF, using a model of in vitro small intestine digestion and colonic fermentation. Two NEPA‐rich materials obtained from carob pod (Ceratonia siliqua L. proanthocyanidin) and red grapes (grape antioxidant dietary fibre) were used as test samples. The colonic fermentation of these two products released hydroxyphenylacetic acid, hydroxyphenylvaleric acid and two isomers of hydroxyphenylpropionic acid, detected by HPLC‐ESI‐MS/MS. Differences between the two products indicate that DF may enhance the yield of metabolites. In addition, the main NEPA metabolite in human plasma was 3,4‐dihydroxyphenyl acetic acid. The presence in human plasma of the same metabolites as were detected after in vitro colonic fermentation of NEPAs suggests that dietary NEPAs would undergo colonic fermentation releasing absorbable metabolites with potential healthy effects.     

Use of microbial transglutaminase and sodium alginate in the preparation of restructured fish models using cold gelation: Effect of frozen storage

Changes in physicochemical properties of raw-appearing restructured models made from hake (Merluccius capensis) muscle, using cold gelation technology by addition of sodium alginate and microbial transglutaminase (MTGase), were studied during frozen storage at ? 15 °C.Among the more interesting results, addition of MTGase produced more protein aggregation in models processed by muscle homogenization and thus the protein network that formed in the gel was better than in samples with added sodium alginate. All samples presented enhanced changes in mechanical properties such as gel strength in the course of frozen storage. The protein network that formed was better organized as shown by the ultrastructure analysis and by protein aggregation data from the beginning of storage, and as a result Water Binding Capacity was greater in restructured models processed by muscle homogenization. Some of the models studied presented lipid oxidation during frozen storage, slightly more in the ones with MTGase added.Industrial RelevanceThe industrial relevance of the present work is to establish bases for using fish fillet trimmings and minced muscle to prepare restructured products that can be commercialized in a raw state and that could also support frozen storage in order to prolong the self-life in the market. The models studied here are not final products but the base with which to prepare them. One possibility of them is to process this kind of products with technologies normally used in whole fish muscle such as smoked fish fillets, carpaccios or marinated products. In addition, these raw restructured products can be commercialized to be cooked as a normal fresh fish fillet or pieces of fillet in a variety of preparations, and also products that contain a high amount of salt. Samples elaborated by binding larger muscle fragments imitate well the original fibrousness of the muscle so that it could be used to elaborate products similar to hamburgers or others that will be fried in batter.     

Uptake of Tritiated Liquids by Individual Breakfast Cereal Flakes

ABSTRACT: Surface liquid adhesion (SLA) and liquid absorption (LA) of tritiated liquids, including water and skim, low-fat, whole, and fat-enriched milks, by cornflakes (CF) and frosted flakes (FF) were determined by scintillation counting using water-[³H] at 0.5 μCi/mL. SLA or the liquid adhering to individual flakes after a short immersion period was the same for CF and FF in the case of water (approximately 0.011 μL mm⁻² of flake) but were always higher for CF than for FF and increased as the fat content in milks augmented. LA of individual flakes, followed for 300 s of soaking, increased with time and was always higher for CF than for FF (for the same liquid), however, data did not follow a regular pattern. Flakes showed quite compact outer surfaces and an internal porous matrix composed of air cells of various sizes separated by dense walls of different thicknesses. This heterogeneous microstructure of individual flakes may be the cause of the lack of a simple kinetics during the soaking process. Previous results obtained by soaking a mass of flakes overestimated the uptake of fluid by individual because they included the liquid occluded between the flakes.     

Physicochemical properties of ready‐to‐eat extruded nixtamalized maize‐based snacks enriched with grasshopper

The aim of this research was to prepare an extruded snack based on nixtamalized maize flour (Zea mays L.) (NMF) enriched with grasshopper meal (Sphenarium purpurascens Ch.) (GM) using a single screw extruder with a compression screw ratio of 3:1. A central experimental design comprising three independent variables, namely, extrusion temperature (T = 120–180 °C), feed moisture content (FMC = 18–22 g/100 g) and the grasshopper meal proportion (GMP = 0–40 g/100 g), was used. Increasing T decreased (P < 0.05) the expansion index (EI), bulk density (BD) and hardness (H). Increasing the FMC increased (P < 0.05) the EI. Increasing the GMP decreased (P < 0.05) the EI, H and water absorption index (WAI) and increased (P < 0.05) the BD and total colour difference (ΔE). The treatments that resulted in better general acceptability were those that contained a lower GMP. An extruded snack acceptable to the consumer can be obtained from a blend of NMF and GM, and up to 8.11 g/100 g of GM can be incorporated without affecting the physicochemical properties and acceptance of the snack.     

Effects of a citrus based juice on biomarkers of oxidative stress in metabolic syndrome patients

Bioactive substances found in numerous foods can be successfully and safely used to modify various cellular functions and affect the oxidative stress. The aim of this study was to analyze the effect of a citrus-based juice (juice citrus (95%) with 5% of aronia extract (Aronia melanocarpa)) on biomarkers of oxidative stress in patients with metabolic syndrome compared with healthy individuals. The study comprised 20 healthy subjects and 33 patients with metabolic syndrome. Eighteen patients consumed daily 300 mL of a citrus-based juice during 6 months and 15 patients consumed 300 mL of a placebo beverage. The control group consumed a citrus-based juice (CJ). Before, and at sixth months after consuming of a citrus-based juice the following parameters were determined: 15-isoprostane F₂, 8-hydroxydeoxyguanosine (8-OHdG), reduced and oxidized glutathione (GSH/GSSH), carbonyl groups and oxidized LDL (ox-LDL). After consuming CJ during 6 months the values of 8-OHdG, carbonyl groups and LDL-ox decreased in both analyzed groups and the values of GSH/GSSH increased. Significant differences were observed in both groups. Thus consumption of citrus-based juice improved the biomarkers of oxidative stress in metabolic syndrome patients.