Improving effect of xanthan and locust bean gums on the freeze-thaw stability of white sauces made with different native starches

The effect of adding xanthan gum and locust bean gum at low concentrations (0.15% w/w) on the freeze/thaw stability of white sauces prepared with native starches from four different sources (corn, waxy corn, potato, and rice) was investigated. Linear viscoelastic properties were taken as structural indicators and these and syneresis as indicators of the freeze/thaw stability of the sauces. The pasting properties of the starch in the sauce system were also studied. Both hydrocolloids reduced the structural changes occurring after thawing, xanthan gum being more effective than locust bean gum. In corn and potato sauces, the most affected by the freeze/thaw cycle, the appearance of syneresis and the increase in viscoelastic functions were significantly reduced by both hydrocolloids. In general, the addition of hydrocolloids affected peak, hot peak and cold peak viscosities and reduced relative total setback. The results regarding the possible effects of hydrocolloid addition to white sauce systems are discussed in molecular terms.     

Influence of corn starch type in the rheological properties of a white sauce after heating and freezing

The freeze/thaw and heating stability of white sauces prepared with two modified waxy corn starches (hydroxypropyl distarch phosphate and acetylated distarch adipate) and two native corn starches (waxy and normal) are compared.     

Effects of waxy maize and potato starches on the stability and physicochemical properties of model sauces prepared with fresh beef meat

Stability and physicochemical properties of model sauces containing 2.5 wt% fresh beef meat (related to raw material), 30 wt% rapeseed oil and native waxy maize starch (WMS) or potato starch (PS) at concentrations ranged from 0.5 to 4.0 wt% were assessed. Sauces thickened with WMS showed a significantly (P < 0.05) higher stability than respective ones made with PS. All studied systems exhibited non‐Newtonian, pseudoplastic behaviour. The Ostwald–de Waele and Herschel–Bulkley models were used to describe the flow properties of model sauces. In comparison with control sample (prepared without starch), addition of this polysaccharide (WMS or PS) increased consistency index, yield stress and apparent viscosity and decreased flow behaviour index of model sauces. The Arrhenius equation was used to determine the effects of temperature (20–50 °C) on the apparent viscosity. The activation energy values were in ranges 7.66–10.59 kJ mol^?1 and 8.87–11.82 kJ mol^?1 in sauces prepared with WMS and PS, respectively. The instrumentally detected changes in consistency and whiteness of model sauces were found, which may be used as the good predictors of the perceived sensory consistency and whiteness.     

Effects of non-starch hydrocolloids on the physicochemical properties and stability of a commercial béchamel sauce

The aim of this study was to investigate the effects of non-starch hydrocolloids (NSH) on the physicochemical properties and stability of a béchamel sauce. Three different NSH (guar gum, xanthan gum and carboxymethylcellulose) were added at two concentrations (0.10 wt.% and 0.25 wt.%) hereby replacing an equal amount of modified starch. Sauce batches were stored at refrigerated temperatures during four weeks and were rheologically characterized at day 2, 16 and 30 after preparation. The addition of all hydrocolloids caused a marked increase of the consistency index compared to the model system whereas this parameter decreased for all sauces during refrigerated preservation. The yield stress was also increased by the NSH. Furthermore all studied NSH reduced the amount of syneresis, with xanthan gum being the most effective. Besides, sensory tests demonstrated that there were no significant differences in taste and general preference between the hydrocolloid sauces and the model system.     

Gelatinization of waxy starches under high pressure as influenced by pH and osmolarity: Gelatinization kinetics, final structure and pasting properties

We investigated the influence of pH and osmolarity on the high-pressure-induced gelatinization of waxy corn and waxy rice starches in salt solutions, and the properties of the resulting gels. Gelatinization kinetics, the gel swelling power of starches, their structure and their rheological properties were studied for starch suspensions treated at 500 MPa. Gelatinization took place mostly in the first 15 min of the pressure treatment and both the gelatinization speed and the maximal level of gelatinized starch decreased with increasing osmolarity. pH had a minor influence on gelatinization kinetics differing from one starch to another. The resulting gels appeared as a mix of a gel and starch granules with a higher proportion of native granules with increasing osmolarity. Gel strength and swelling were positively correlated to their proportion of gelatinized starch. Thus, gels with different structures and gelatinization levels can be obtained under pressure depending on pH and osmolarity.     

Enrichment of stirred yogurt with soluble dietary fiber from Pachyrhizus erosus L. Urban: Effect on syneresis, microstructure and rheological properties

Yam soluble fiber (YSF) extracted from Pachyrhizus erosus was added (1 g per 100 mL) to a stirred yogurt (SY_YSF). Its syneresis and microstructure properties were evaluated and compared to those of a stirred yogurt (SY_C) without added YSF. The SY_C yogurt exhibited a more compact casein micelle aggregates network than that of the SY_YSF yogurt which was more open, relaxed and covered with fibrous structures attributed to the YSF components. The rheological analysis showed that the SY_YSF yogurt had lower storage modulus (G′) and loss modulus (G″) values in the linear viscoelastic region than the SY_C yogurt, but its flow behavior was characterized by a lower flow index (n), higher consistency index (k), and higher yield stress (τ₀) than the SY_C yogurt. Incorporation of the YSF reduced significantly the syneresis and produced a more acceptable mouthfeel in the SY_YSF yogurt in comparison to the SY_C yogurt, indicating the viability of the process to obtain a commercial product.     

Rheological properties of Lepidium sativum seed extract as a function of concentration, temperature and time

The seeds of Lepidium sativum (Garden Cress) were selected as a new source of hydrocolloid and its chemical composition and molecular parameters were determined. The macromolecular component of the extract had a molecular weight of 540 kDa, and was nearly as rigid as xanthan with regard to chain conformation. The main rheological features were investigated as a function of shear rate, concentration and temperature. The extract exhibited strong shear-thinning behaviour, which was even more pronounced than for xanthan. An increase in concentration or temperature led to an increase in pseudoplasticity. The Arrhenius model was applied to the temperature dependence of viscosity, and the activation energy (E_a) was found to decrease with increasing concentration. The extract solutions showed thixotropic behaviour at all the concentrations and temperatures studied, and the first-order stress decay model with a non-zero equilibrium stress fairly described the time-dependent behaviour. The rheological characteristics found indicated a potential application of the extract as a novel thickener.     

Physico-chemical properties of jackfruit seed starch (Artocarpus heterophyllus) and its application as a thickener and stabilizer in chilli sauce

This study investigates the possible utilization of starch extracted from jackfruit seed waste from the jackfruit frying industry. We first compared the physico-chemical properties of jackfruit seed starch (JFSS) with cornstarch (CS) and potato starch (PS) and then compared JFSS with CS as a thickener and stabilizer in chilli sauce. JFSS had a higher amylose content and its granules were much smaller than CS and PS granules; in addition, JFSS had a higher pasting temperature and final viscosity than CS and PS. JFSS experienced lower breakdown than CS and PS pastes which indicates that JFSS paste is more resistant to thermal and mechanical shear during cooking. The XRD patterns showed JFSS to be Type A starch, similar to corn starch. JFSS is suitable as a thickener and stabilizer in chilli sauce because chilli sauce with JFSS had the lowest serum separation and highest viscosity during storage compared with control chilli sauce and sauce containing CS. In addition, sensory evaluation demonstrated that chilli sauce containing JFSS received the highest score in terms of color, mouth feel, homogeneity and overall quality.     

Partial characterization of white cabbages (Brassica oleracea var. capitata f. alba) from different regions by glucosinolates, bioactive compounds, total antioxidant activities and proteins

Glucosinolates (GLS), antioxidative compounds, total radical scavenging activities (TRSAs) and proteins of white cabbage samples derived from different regions of Europe, collected in the spring and autumn, were studied. Glucobrassicin and sinigrin were the dominating GLS in all analyzed cabbage samples. Depending on origin, these two GLS accounted for ∼30% to ∼70% of the total. The total GLS content ranged from 3.3 to 7.7 μmol/g dw in lyophilized vegetables. Assays based on electron transfer [total phenols by Folin-Ciocalteu reagent (FCR), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] radical cation (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH)] were used to compare the TRSAs and the main bioactive compounds in cabbage. Total polyphenols varied from 2.4 to 4.9 GAE/g dw. The TRSAs ranged from 2.7 to 8.2 μmol TE/g dw in ABTS test and from 2.4 to 5.4 μmol TE/g dw in DPPH assay. The maximum amount of polyphenol compounds, antioxidant activity, as well as total GLS content, were recorded in Belgian cabbage harvested in the autumn and the lowest ones were found for Poland 2 cabbage harvested in the spring. In extracted and separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) proteins from cabbage leaves only in samples from England and Belgium some differences in patterns were found in the regions of 60 and 97 kDa. The calculated correlations between antioxidative potency and the abundance of bioactive compounds were highly statistically significant. This suggests that TRSA could serve as a means of standardization of natural mixtures, at least in the case of cabbage, necessary to compare results of biological studies carried out for vegetable derived samples.     

In vitro digestibility of starch in cooked potatoes as affected by guar gum: Microstructural and rheological characteristics

Potatoes from different New Zealand cultivars (Nadine, Moonlight, Red Rascal, Agria) were analysed for starch digestibility in vitro (under simulated gastric and small intestinal conditions). The extent of starch hydrolysis (%) for all the potato cultivars ranged between 85% and 95% at the end of in vitro digestion. Nadine potatoes, which were waxy in texture, showed higher starch hydrolysis (%) whereas these levels did not differ significantly among the other three cultivars. Confocal laser scanning microscopy and scanning electron microscopy were performed on the digests in order to study the microstructural changes occurring during digestion in cooked potatoes. The micrographs clearly showed that starch was quickly hydrolysed by the enzymes present in simulated intestinal fluid (SIF) whereas the cell walls remained intact during simulated digestion process. Addition of guar gum (0.5%) to cooked potatoes reduced their starch hydrolysis (%) by ∼15% during the in vitro digestion. Online viscosity measurements were also performed on the cooked potatoes during simulated small intestinal digestion using a dynamic rheometer. Cooked potato viscosity dropped considerably upon the action of enzymes from SIF on starch as the digestion progressed. The presence of 0.5% guar gum facilitated the cooked potato matrix to maintain viscosity similar to undigested cooked potato sample throughout the in vitro digestion, which might have resulted in lower starch hydrolysis (%).     

Changes in carbohydrate and glucosinolate composition in white cabbage (Brassica oleracea var. capitata) during blanching and treatment with acetic acid

The effect of blanching and treatment with white vinegar containing acetic acid on dietary fibre, low-molecular-weight carbohydrates and glucosinolates was studied in two cultivars of white cabbage (Heckla and Predikant). The total content of dietary fibre and low-molecular-weight carbohydrates was similar in both cultivars (24 and 60 g/100 g DM, respectively), while the distribution between soluble and insoluble fibre differed (19% was soluble in Heckla versus 26% in Predikant, P < 0.01). Further, Heckla contained higher amounts of glucose and sucrose, while the content of fructose and total glucosinolates was lower than in Predikant. The content of individual glucosinolates differed between the two cultivars. During blanching there was a loss of dry substance (30–34 g/100 g DM), where low-molecular-weight carbohydrates primarily explained the loss (82–90%), but some of the loss was also dietary fibre (about 8%), both soluble fibre containing uronic acids (mainly Predikant) and insoluble ones containing glucose (mainly Heckla). The glucosinolate levels decreased substantially in both cultivars, although the total loss was higher in Predikant (74%) than in Heckla (50%). The individual glucosinolates were affected to different degrees (15–91%). During souring with acetic acid, the content of dietary fibre (primarily insoluble ones) decreased further, while the content of low-molecular-weight carbohydrates was less affected. The total content of glucosinolates was not affected in Heckla but was further reduced in Predikant. There was, however, a substantial increase in 4-methoxyglucobrassicin in both cultivars. It is concluded that blanching and souring decrease the content of carbohydrates and glucosinolates to a great extent and both cultivars behaved similarly. However, individual components were affected differently in the two cultivars.     

Effects of enzymatically-extracted purple rice bran fiber as a protectant of L. plantarum NRRL B-4496 during freezing,freeze drying,and storage

This study investigated purple rice bran fiber (PRF) as a protectant for Lactobacillus plantarum NRRL B-4496 (LP) during freezing, freeze drying and storage. PRF was enzymatically extracted from purple rice bran. L. plantarum NRRL B-4496 was grown in MRS broth, centrifuged, and immobilized on PRF suspension. LP cells immobilized on PRF (LP-PRF) and free LP cell (control) samples were frozen in either air blast (AF) or cryogenic freezing (CF) before freeze drying. Freeze-dried (FLP) samples were stored either at room temperature or at refrigerated temperature. For either freezing method, PRF protected cells had less than one log reduction of viable cells while the control had reductions greater than six logs after freeze drying. The log reductions of viable LP cells protected with PRF after freeze drying and 12 weeks storage at 4° C for AF and CF treatments were 0.7 and 1.3 log cycle, respectively. The viable LP-PRF cell count for CF was significantly lower than for AF after 12 weeks at room temperature. PRF improved LP survival in both AF and CF samples in bile. This study demonstrated that freezing methods affected LP viability during storage and that PRF could protect at both refrigerated and room temperatures.     

Seasonal variation in red deer (Cervus elaphus) venison (M. longissimus dorsi) drip loss,calpain activity,colour and tenderness

Sixty four young red deer (Cervus elaphus) stags (< 2 years old) were slaughtered at four different times (December (Group 1); n = 17, March (Group 2); n = 8, July (Group 3); n = 20 and September (Group 4); n = 19) to evaluate seasonal effects on venison quality. M. longissimus dorsi samples for calpain analysis were collected on the slaughter line and the rest of these muscles were collected at 1 day post-slaughter. Loins were divided into four parts and randomly allocated to storage for 1 day, 3, 9 or 14 weeks at −1.5 °C and then vacuum packaged. Seasonal variation was demonstrated in venison pH. Highly significant positive regressions were found for shear force (P < 0.001) and colour display life (P < 0.001) on pH, where higher pH values were associated with tougher venison and longer colour display life. A clear trend of increasing fluid loss during storage, calculated as amount of purge at 14 weeks of storage minus the amount of drip loss at 1 day post-slaughter, was evident, averaging 2.5% (SEM 0.17) over the four groups. The relative activities of the calpastatin-bound calpain, μ-calpain and m-calpain all exhibited a seasonal pattern although there was no evidence (P > 0.05) that this affected tenderness. There was a highly significant (P < 0.001) negative regression for the average over the four storage times of drip and purge on calpastatin-bound calpain activity.     

Thermal destruction kinetics of Bacillus licheniformis spores in carrot juice extract as influenced by pH,type of acidifying agent and heating method

The combined effects of different heating methods (conventional (CH) vs. Ohmic (OH)), types of acidifying agent (citric vs malic acid) and pH levels (pH 4.5, 5.5 and 6.2) were investigated to study their influence on destruction kinetics of spores of Bacillus licheniformis. The ultimate aim to generate relevant kinetic data on an indicator microbial spore is useful for assessing the efficacy of thermal processes for acid or acidified low acid foods. Kinetic parameters were evaluated according to the first-order kinetic model. Temperature and pH showed a highly significant (p < 0.01) effect on the spore destruction kinetics. Ohmic heating showed marginally better rate of bacterial destruction than conventional heating. The overall range of D and z values were 1.1–11.2 min and 12.6–17 °C, respectively, depending up on the pH and temperature levels, method of heating as well as the type of acidulate used. The shortest D_97°C = 1.1 min was obtained at pH of 4.5 when citric acid was used as an acidifying agent in OH. No significant difference (p > 0.05) was observed with respect to D and z values between the two types of acidifying agents.     

Enhanced chemical stability,chromatic properties and regeneration of betalains in Rivina humilis L. berry juice

Betalains are hydrophilic colorants containing chromophore betalamic acid. Owing to poor stability, its usage is limited to low acidic short shelf-life, and frozen foods. In this report, effect of metals (inorganic Se⁴⁺, Zn²⁺, and Cu²⁺) on stability of betalains in Rivina humilis L. berry juice (RBJ) was studied in presence of 10 and 40 μg metal/mL with/without ascorbic acid (AA; 0.25 and 0.5 g/100 mL). Se bleached RBJ betacyanins mildly, whereas Zn, and Cu bleached the pigments significantly. AA protected the pigments from metal-induced bleaching, and stabilizing effect of 0.25 g AA/100 mL was higher (P < 0.05) than 0.5 g AA/100 mL. AA (0.25 g/100 mL) + Se (40 μg/mL) enhanced (five-fold) the half-life time of betacyanins. RBJ betacyanins degraded up to 95% and 96% on treatment for 36 min at 90 °C and storage for 48 days at 25 °C, respectively, whereas only 15% pigment was lost on storage (5 °C, 90 days). AA (0.25 g/100 mL) + Se (40 μg/mL) regenerated the pigments on storage at 5 °C after thermal degradation. Color values of AA (0.25 g/100 mL) + Se (40 μg/mL) containing samples indicated an orange tinge, whereas other samples turned brown yellow after thermal treatment.     

Survival of Lactobacillus acidophilus, Lactobacillus paracasei subsp. paracasei, Lactobacillus rhamnosus, Bifidobacterium animalis and Propionibacterium in cheese-based dips and the suitability of dips as effective carriers of probiotic bacteria

The suitability of cheese-based dips as a delivery vehicle for probiotic bacteria including Lactobacillus acidophilus, Lactobacillus paracasei subsp. paracasei, Lactobacillus rhamnosus, Bifidobacterium animalis, and Propionibacterium freudenreichii subsp. shermanii was studied by evaluating the survival of these organisms in dips. Effects of organic acids, oils and gums, -cysteine and NaHCO₃ on the survival of probiotics in cheese-based dips were also studied. Eight different combinations and five individual bacteria as controls of these probiotic bacteria were added to 21 batches of French onion dip and selective enumeration of these probiotic bacteria was carried out over a period of 10 weeks of storage. The population of L. acidophilus and B. animalis reduced by 1 log and 2 log per g, respectively. However, when the inoculation level of these bacteria were increased to 8 log per g, they maintained a population of more than 6 log over the shelf life. L. paracasei subsp. paracasei and L. rhamnosus remained at the inoculated level or increased slightly during the storage. A rapid increase in the population of P. freudenreichii subsp. shermanii occurred to attain more than the inoculation level following reduction in their number by 3 log. Except bacterial interaction, no other factors showed significant effect on the survival of individual probiotic bacteria. Each of L. acidophilus, B. animalis, L. paracasei subsp. paracasei, and L. rhamnosus showed varied levels of antogonism, while P. freudenreichii subsp. shermanii showed no effect. Any combination of these bacteria can be used as probiotics in cheese-based French onion dip. However, the inoculation level should be 8 log per g for L. acidophilus and B. animalis and 7 log per g for L. paracasei subsp. paracasei, and/or L. rhamnosus to obtain greater than 6 log of individual bacterial population at the end of shelf life.     

Prediction of Listeria spp. growth as affected by various levels of chemicals, pH, temperature and storage time in a model broth

The effects of concentration of NaCl (0.5 to 12.5%), methyl paraben (0.0 to 0.2%), sodium propionate (0.3%), sodium benzoate (0.1%), potassium sorbate (0.3%), pH (>5.9) temperature (4 to 30°C), storage time (up to 58 d) and inoculum (>10⁵ to >10⁻² per ml) on the log₁₀ probability percentage of one cell of Listeria spp. to initiate growth in a broth system were evaluated in a factorial design study. At pH 5.96 and temperature ranging from 4 to 30°C the concentrations of sodium propionate, potassium sorbate, and sodium benzoate examined allowed growth of L. monocytogenes with lag phases at 4°C of 18, 27 and 21 days, respectively. For 0.1 and 0.2% methyl paraben growth of all Listeria spp. was initiated at 8°C and 30°C, respectively. At pH 6, concentration of 12% NaCl supported the growth of L. monocytogenes at 8 to 30°C, whereas 12.5% inhibited all Listeria species. Four regression equations were derived relating probability of growth initiation to temperature, concentrations of NaCl and preservatives storage time, and Listeria species specific effects. From these equations, the number of cells needed for growth initiation can be calculated. The impact of this type of quantitative study and its possible application on the development of microbial standards for foods is discussed.     

Development of dry fermented sausages rich in docosahexaenoic acid with oil from the microalgae Schizochytrium sp.: Influence on nutritional properties,sensorial quality and oxidation stability

Significant enrichment of dry fermented sausages in n−3 polyunsaturated fatty acids (PUFA) was achieved by incorporating algae oil from Schizochytrium sp. into an emulsion that partially substituted pork backfat from the traditional formulation. Two different levels of substitution were initially tested, both including BHA and BHT as antioxidants: (15% and 25%). A triangular test showed that products with 25% substitution were not sensorially acceptable. Sausages with 15% substitution supplied 1.30 g/100 g product of docosahexaenoic acid (DHA), with an interesting n−6/n−3 ratio of 2.62. No signs of oxidation were detected at the end of the ripening process, with low values of TBARs (<0.2 mg/kg), peroxides (<2 meq O₂/kg fat) and volatile aldehydes. Storage of these sausages under vacuum during 30 days totally guaranteed their stability, whereas after 90 days certain degree of oxidation was detected, only by means of aldehydes analysis. Hexanal, nonanal and dienals increased, whereas no increment in TBARs or peroxides were observed. Aerobical storage of these sausages was not viable due to a high oxidation susceptibility of the new formulation, despite the use of antioxidants.     

Application of thermal inactivation of enzymes during vitamin C analysis to study the influence of acidification,crushing and blanching on vitamin C stability in Broccoli (Brassica oleracea L var. italica)

The effectiveness of heat inactivation of oxidative enzymes e.g., ascorbic acid oxidase (AAO) to stabilise vitamin C during extraction and analysis was evaluated. The influence of different sequences of performing treatments including acidification (pH 4.3 vs. pH 6.5), crushing, high temperature short time (90 °C/4 min–HTST) and low temperature long time (60 °C/40 min–LTLT)) blanching on vitamin C stability in broccoli florets and stalks was also investigated. Heat inactivation of enzymes prior to matrix disruption resulted in higher vitamin C values mainly in L-ascorbic acid (L-AA) form, while lack of enzyme inactivation resulted in high vitamin C losses resulting from conversion of L-AA to dehydroascorbic acid. Various treatments and their sequence of application influenced vitamin C stability as follows: (i) crushing prior to blanching reduced vitamin C stability and (ii) in the absence of heating, acidification increased vitamin C stability (iii) blanching prior to crushing resulted in higher vitamin C retention, with HTST blanching retaining more vitamin C than LTLT blanching.     

Effects of heat-processing regime, pH, water activity and their interactions on the behaviour of Listeria monocytogenes in ground pork. Modelling the boundary of the growth/no-growth areas as a function of pH, water activity and temperature

The influence of four heat‐processing regimes and a storage phase on the behaviour of Listeria monocytogenes in ground pork was studied. The effects of pH and water activity (a_w) were also tested. During the heat process phase, a_w, the heat‐processing regime and its interactions with pH or a_w, had a significant effect on the behaviour of L. monocytogenes. During the storage phase, all parameters tested and their interactions had significant effects. Nevertheless, the area in which the growth of L. monocytogenes was observed at the end of the experiment was not influenced by the heat‐processing regime tested. On the contrary, pH, a_w and their interactions had significant effects on Listeria behaviour. The boundary of the growth area delimited by environmental conditions where growth was higher than 1.0 Log CFU g^?1 from those where growth was lower than this limit was correctly predicted by Augustin's model.