Impact of cell wall-degrading enzymes on water-holding capacity and solubility of dietary fibre in rye and wheat bran.

BACKGROUND: Rye and wheat bran were treated with several xylanases and endoglucanases, and the effects on physicochemical properties such as solubility, viscosity, water-holding capacity and particle size as well as the chemical composition of the soluble and insoluble fractions of the bran were studied. A large number of enzymes with well-defined activities were used. This enabled a comparison between enzymes of different origins and with different activities as well as a comparison between the effects of the enzymes on rye and wheat bran. RESULTS: The xylanases derived from Bacillus subtilis were the most effective in solubilising dietary fibre from wheat and rye bran. There was a tendency for a higher degree of degradation of the soluble or solubilised dietary fibre in rye bran than in wheat bran when treated with most of the enzymes. CONCLUSION: None of the enzymes increased the water-holding capacity of the bran or the viscosity of the aqueous phase. The content of insoluble material decreased as the dietary fibre was solubilised by the enzymes. The amount of material that may form a network to retain water in the system was thereby decreased.

Rheological characterization of dilute acid pretreated softwood.

Large-scale bioethanol production from lignocellulosic biomass will require high solids loading in the enzymatic hydrolysis step. However, slurries of pretreated lignocelluloses are complex fluids due to the fibrous nature, especially at high concentrations of water insoluble solids (WIS). A prerequisite for dealing with transport issues and for developing efficient full-scale processes is a fundamental understanding of the flow properties of pretreated lignocellulose. A comprehensive rheological characterization of dilute acid pretreated spruce has been carried out in this study, accounting for the effects of WIS concentration, particle size distribution (PSD), and the degree of enzymatic hydrolysis. The rheology of pretreated spruce slurries was found to be strongly dependent on the WIS concentration. The storage modulus (G'(LVR)) and yield stress showed typical power-law dependencies on volume fraction and WIS content. Milling of the pretreated material resulted in significantly higher yield stress and viscosity, likely due to narrower PSD, which suggests that the strength of the network of the coarsest fibers determines the rheology of these materials to a large extent. During enzymatic hydrolysis, yield stress and viscosity decreased dramatically, partly due to decreasing WIS content, but possibly also due to changes in fiber properties such as the chemical composition.

Processed meat products with added plant antioxidants affect the microbiota and immune response in C57BL/6JRj mice with cyclically induced chronic inflammation.

Epidemiological studies have found that there is a correlation between red and processed meat consumption and an increased risk of colorectal cancer. There are numerous existing hypotheses on what underlying mechanisms are causative to this correlation, but the results remain unclear. A common hypothesis is that lipid oxidation, which occurs in endogenous lipids and phospholipids in consumed food, are catalyzed by the heme iron in meat. In this study, five pre-selected plant antioxidant preparations (sea buckthorn leaves and sprouts, summer savory leaves, olive polyphenols, onion skin and lyophilized black currant leaves) were added to a meatball type prone to oxidize (pork meat, 20 % fat, 2% salt, deep-fried and after 2 weeks of storage). Pro-inflammatory markers, neutrophil infiltration and microbiota composition were studied after four months in a chronic inflammation model in C57BL6/J female mice. We found that the bacterial diversity index was affected, as well as initial immunological reactions.

Lipid oxidation inhibition capacity of plant extracts and powders in a processed meat model system.

A meat model system was used for screening lipid oxidation inhibiting capacity of diverse horticultural plant materials. In the model, heme-containing sarcoplasmic proteins from the meat water-phase were homogenized with linoleic acid and thiobarbituric reactive substances (TBARS) were measured. 23 Plant materials were investigated at three high (50, 100, and 200 ppm) concentrations and five plant extracts were tested at three low (5, 10, and 20 ppm) concentrations over time. In the high concentration sets, summer savory freeze-dried powder, beetroot leaves extracted with 50% ethanol, and an olive polyphenol powder extracted from wastewater, inhibited oxidation the most effectively. After two weeks and at 200 ppm concentration, oxidation was reduced to 17.2%, 16.6% and 13.5% of the blank sample with no added antioxidants respectively. In the low concentration set, spray dried rhubarb juice inhibited oxidation the most after two weeks at 5 ppm where oxidation was reduced to 68.3% of the blank sample with no added antioxidants.

Lipid Oxidation Inhibition Capacity of 11 Plant Materials and Extracts Evaluated in Highly Oxidised Cooked Meatballs.

The underlying mechanism(s) behind the potential carcinogenicity of processed meat is a popular research subject of which the lipid oxidation is a common suspect. Different formulations and cooking parameters of a processed meat product were evaluated for their capacity to induce lipid oxidation. Meatballs made of beef or pork, containing different concentrations of fat (10 or 20 g 100 g-1), salt (2 or 4 g 100 g-1), subjected to differing cooking types (pan or deep frying), and storage times (1, 7, and 14 days), were evaluated using thiobarbituric reactive substances (TBARS). The deep-fried meatball type most susceptible to oxidation was used as the model meat product for testing the lipid oxidation inhibiting capacity of 11 plant materials and extracts, in two concentrations (100 and 200 mg kg-1 gallic acid equivalent (GAE)), measured after 14 days of storage using TBARS. Summer savory lyophilized powder was the most efficient plant material, lowering lipid oxidation to 13.8% and 21.8% at the 200 and 100 mg kg-1 concentration, respectively, followed by a sea buckthorn leaf extract, lowering lipid oxidation to 22.9% at 100 mg kg-1, compared to the meatball without added antioxidants. The lipid oxidation was thus successfully reduced using these natural antioxidants.

Antioxidant capacity and major phenol compounds of horticultural plant materials not usually used.

Horticultural plant materials not usually used from onion, carrot, beetroot, sea buckthorn, black and red currants as well as a wastewater powder from olive oil production were analyzed for total phenols content (FC), ferric reducing ability of plasma (FRAP), radical scavenging capacity (ABTS), and for major phenolic compounds by HPLC-MS. Antioxidant capacity and phenol content varied significantly between species and cultivars, with extracts of sea buckthorn leaves being superior. In different species, different phenolic compounds were closely associated with FRAP, ABTS and FC. For instance, hydrolysable tannins were major antioxidants in sea buckthorn whereas quercetin was the major antioxidant in onion peel and skin. This study shows that horticultural plant materials usually left in the field or waste materials from processing may have high antioxidant properties, and that extracts of these materials therefore could be of potential interest for development of antioxidant food additives.

Possible mechanism for the effect of the RN(-) allele on pork tenderness.

The effect of the dominant RN(-) allele on rigor development, ageing and tenderness was studied in M. longissimus dorsi (LD) from 11 heterozygous carriers and five non-carriers of the RN(-) allele. Rigor development was followed by measurements of muscle shortening, isometric tension, pH and FOP. During ageing the myofibrillar length and Warner-Bratzler shear force were measured in the meat. Sensory analysis was performed at 4 days post-mortem using a trained expert panel. It was found that the decrease in pH was faster for RN(-) carriers than non-carriers during the first 5 h post-mortem, after which the pH-time slope was similar for the two groups. This resulted in a significantly lower mean ultimate pH in LD from RN(-) carriers than non-carriers. During rigor development the isometric tension was lower in RN(-) carriers than in non-carriers, while contraction (shortening and sarcomere length) did not differ significantly between the two genotypes. The myofibrillar length, which is an indirect measure of the proteolytic activity that has occurred in the meat, was shorter for the RN(-) carriers than for the non-carriers. The difference in myofibrillar lengths between the genotypes was significant at 1 and 4 days post-mortem but not at 7 days post-mortem, which indicates that the RN(-) carriers have a higher proteolytic activity earlier post-mortem. The results from the Warner-Bratzler shear force measurements showed that the meat from the RN(-) carriers was significantly more tender, 1 and 4 days post-mortem, than the meat from the non-carriers. The meat from non-carriers needed 7 days to reach the tenderness attained by that from the RN(-) carriers 4 days post-mortem. The greater tenderness in LD from RN(-) carriers than that from non-carriers was also confirmed by a sensory panel at 4 days post-mortem. In conclusion, differences observed in the course of rigor and ageing in muscle from carriers and non-carriers of the RN(-) allele suggest that proteolytic action, as initiated by a more rapid fall in pH, is the most important factor governing the variation in tenderness of the two genotypes.

Sensory and meat quality traits of pork in relation to post-slaughter treatment and RN genotype.

The effects on eating quality and meat quality of two different forms of post-slaughter treatment, performed in an abattoir, were studied in carriers and non-carriers of the RN(-) allele. Carcasses were subjected to rapid and slow chilling, and pelvic and Achilles suspension in a factorial experimental design. A temperature of 10 °C was achieved in the centre of M. longissimus dorsi (LD) within 3.5 h in rapidly chilled carcasses and within 8 h in slowly chilled carcasses. In deep M. semimembranosus (SM) a temperature of 10 °C was achieved within 11.5 h in rapidly chilled carcasses and within 14 h in slowly chilled carcasses. LD from slowly chilled RN(-) carriers suspended by the pelvis exhibited the greatest tenderness, while LD from rapidly chilled non-carriers suspended from the Achilles tendon exhibited the lowest tenderness. Pelvic suspension or slow chilling of non-carriers produced the same improvement in tenderness, and when combined the tenderness increased further. However, the tenderness of the RN(-) carriers was already high, and no significant improvement was seen following any of the studied post-slaughter treatments. Pelvic suspension prevented shortening of muscle fibres, as seen by longer sarcomeres in LD from pelvic-suspended sides. However, longer sarcomeres were associated with greater tenderness only in LD from non-carriers of the RN(-) allele. The presence of the RN(-) allele and a slow chilling regime increased the rate of pH decline in LD. Achilles suspension also increased the rate of pH fall in SM, in addition to the RN(-) allele and slow chilling. The overall tenderness of LD was mainly related to the course of pH decline during rigor; lower pH values between 3 and 7 h post-mortem contributing to greater tenderness. The myofibrillar length was predominantly related to RN genotype and was shorter in RN(-) carriers than in non-carriers. The RN(-) allele and slow chilling contributed to higher evaporation losses and RN(-) carriers exhibited increased frequency of PSE meat in the ham muscles. The use of pelvic suspension appears advantageous over slower chilling, since it improved tenderness without any negative influence on drip loss, evaporation or cooking loss.

Sensory quality and the incidence of PSE of pork in relation to crossbreed and RN phenotype.

The effects of crossbreed and of RN phenotype on pork and its eating quality were evaluated in four different pig crossbreeds [involving Swedish Landrace (L) × Yorkshire (Y) sows and Hampshire (H), Duroc (D), Yorkshire (Y) or Hampshire × Yorkshire (HY) as the terminal sire]. Pigs from the LYH crossbreed were also classified as either carriers or non-carriers of the RN(-) allele. In the crossbreeds investigated, M. longissimus dorsi (LD) and M. semimembranosus (SM) from LYH were found to have the lowest pH as measured 24h post-mortem (pH(24h)). The low pH in the LYH crossbreed was due to the large proportion of RN(-) carriers it had (approximately 70%). The non-carriers of the RN(-) allele in the LYH crossbreed had a pH(24h) close to that of LYD, LYY and LYHY. In a selected group of pigs (N=50), the ultimate pH in the ham muscles M. biceps femoris (BF), M. quadriceps femoris (QF), M. gluteus medius (GM) and M. semitendinosus (ST) was also found to be lower in RN(-) carriers of LYH than in the other crossbreeds. As determined visually, LYD had the highest frequency (2%) of pale, soft and exudative meat (PSE), in LD. Ham from RN(-) carriers of LYH had the highest frequency (23%) of PSE meat around the femur, indicating that when the pH is low, the deep musculature, in which the chilling rate can be slow, is particularly sensitive to the development of PSE. According to assessments by members of a trained sensory panel, tenderness was significantly greater in LD from carriers of the RN(-) allele in LYH than in LD from LYD, LYHY and non-carriers of LYH. The tenderness of LD from LYY was rated as intermediate. The intramuscular fat content was found to be highest in LD from LYD, no relationship between intramuscular fat content and tenderness being found. The RN(-) carriers of LYH received the highest ratings in terms of juiciness. In conclusion, the sensory ratings demonstrated the great eating quality of LD from carriers of the RN(-) allele, indicating that abandoning the Hampshire crossbreed or eliminating the RN(-) allele from it, would result in the meat being less tender.

The effects of cereal additives in low-fat sausages and meatballs. Part 1: Untreated and enzyme-treated rye bran.

Rye bran was added to frankfurter-type sausages and meatballs with the aim of producing low-fat products with increased dietary fibre content. The addition of untreated rye bran to sausages was detrimental, causing a substantial increase in frying loss (20% compared to 13.2%). The addition of rye bran treated with hydrolytic enzymes reduced the frying loss to 15.2-16.4%. The firmness was also improved by the treatments (12.8-14.2 N compared to 8.8 N). Enzymatic treatment of rye bran did not however improve the water-holding capacity or the texture of sausages compared to the rye bran that had only been soaked in water. The reason could be that enzymes degraded the solubilized fraction of the dietary fibre, leaving small fragments that cannot contribute to the water-holding capacity and the texture of the sausages. The benefits of treating rye bran in water were not seen in meatballs, probably due to the more particulate structure of meatballs, which is not as sensitive to additives.

The effects of cereal additives in low-fat sausages and meatballs. Part 2: Rye bran, oat bran and barley fibre.

Rye bran, oat bran and barley fibre have been compared as additives in low-fat sausages and meatballs. The water/protein ratio and starch content were constant to allow direct comparisons. Oat bran was the best alternative in low-fat sausages due to its gelling ability upon heating. These sausages exhibited low process (0.9%) and frying losses (10.9%), and high values of firmness (11.0 N) and sensory acceptance. The sausages containing barley fibre, with the highest amount of soluble ß-glucan, had high losses (3.8% and 19.6%) and the lowest firmness (4.6 N). Rye bran was suitable in meatballs, probably due to its particulate nature, which is more acceptable in this type of meat product, where the gelling properties are not as important as in sausages. There was no significant difference between the firmness of meatballs containing rye bran (6.1 N) and the reference (7.5 N), after pan-frying. Meatballs with oat bran or barley fibre were less firm (3.6 N and 2.0 N).

The influence of different processing stages on particle size, microstructure, and appearance of dark chocolate.

UNLABELLED: The effect of different process stages on microstructural and visual properties of dark chocolate was studied. Samples were obtained at each phase of the manufacture process: mixing, prerefining, refining, conching, and tempering. A laser light diffraction technique and environmental scanning electron microscopy (ESEM) were used to study the particle size distribution (PSD) and to analyze modifications in the network structure. Moreover, colorimetric analyses (L*, h°, and C*) were performed on all samples. Each stage influenced in stronger way the microstructural characteristic of products and above all the PSD. Sauter diameter (D [3.2]) decreased from 5.44 µm of mixed chocolate sample to 3.83 µm, of the refined one. ESEM analysis also revealed wide variations in the network structure of samples during the process, with an increase of the aggregation and contact point between particles from mixing to refining stage. Samples obtained from the conching and tempering were characterized by small PS, and a less dense aggregate structure. From color results, samples with the finest particles, having larger specific surface area and the smallest diameter, appeared lighter and more saturated than those with coarse particles. PRACTICAL APPLICATION: Final quality of food dispersions is affected by network and particles characteristics. The deep knowledge of the influence of single processing stage on chocolate microstructural properties is useful in order to improve or modify final product characteristics. ESEM and laser diffraction are suitable techniques to study changes in chocolate microstructure.

Heat-treated and homogenised potato pulp suspensions as additives in low-fat sausages.

Differently homogenised and heat treated potato pulp, used as a dietary fibre additive in low-fat sausages, gave rise to an enhanced instrumentally and sensory measured firmness and compactness, respectively. This is believed to be due to the high content of insoluble fibre, which creates a fibrous network that enhances the texture of the sausage, while not interfering with the meat protein network. The process and frying losses of the sausages, using potato pulp as an additive, were not significantly different compared to the reference. Comparing the different potato pulp sausages using various kinds of heat treatment of the potato pulp significantly lowered the frying loss and increased the firmness. An explanation to these observations could be that the potato pulp exposed to shorter heat treatment compared with longer gave rise to a lower amount of amylase-leakage from the swelling starch granules caught in the potato pulp matrix.

A proposed mechanism of tenderising post-rigor beef using high pressure-heat treatment.

Tenderness of beef M. Sternomandibularis was tough when cooked from both raw, and when previously heated (60 degrees C, 20 min), whereas a significant improvement in tenderness was achieved when pressure-heat (P-H) treated muscle (200 MPa, 60 degrees C, 20 min) was cooked. In order to determine the mechanism for this improvement, connective tissue, myofibrillar and sarcoplasmic proteins, were separated into three fractions and studied with regard to their solubilisation, denaturation and aggregation, degradation and strengthening of protein structures for the three treatments (raw, heated and H-P treated). Measurements included DSC, SDS-PAGE, surface hydrophobicity, and the appearance, length and width of myofibres (light microscopy). For the connective tissue fraction, heat solubility was determined. It is suggested that the mechanism for this improvement in tenderness is the formation of a strengthened myofibrillar structure that, when sheared by mastication, allows the crack to pass through the meat rather than dissipate into a more visco-elastic structure. In this way a more brittle fracture is achieved and the meat is perceived as more tender. The pre-requisite is that adequate enzymatic activity has occurred. It is suggested that cathepsins are responsible.

The effects of presalting methods from injection to pickling, on the yields of heavily salted cod (Gadus morhua).

The production of heavy-salted cod (Bacalao) has changed from being a single-step process (kench) salting to a multistep procedure varying between producers and countries. Presalting by injection, brining, or pickling is increasingly applied prior to pile (dry) salting. This article describes the effects of different presalting methods (injection and brining, brining only, and pickling) on yield and chemical composition of salted cod fillets, in comparison to a single-kench salting step. The procedures used influenced the weight yields and chemical composition of the products. Injection was significantly different from other methods in increasing weight yields throughout brining, dry salting, and rehydration. The yield of nitrogenous compounds tended to be lower for injected and brine-salted fillets, mainly due to higher losses of nonprotein nitrogen. Practical Application: Salting procedures for cod have changed rapidly in recent years. Injection is increasingly used as a presalting method. It has been suggested to have strong effects on weight yields of salted cod products. This article describes the effects of injection on weight yields on products in salted, rehydrated, and cooked stage.