Metabisulfite Research Articles

Feasibility assessment and underlying mechanisms of metabisulfite pretreatment for enhanced volatile fatty acids production from anaerobic sludge fermentation

Employing chemical pretreatment for waste activated sludge (WAS) fermentation is crucial to achieving sustainable sludge management. This study investigated the feasibility of metabisulfite (MS) pretreatment for enhancing volatile fatty acids (VFAs) production from WAS. The results show that after 24-h MS pretreatment, the content of soluble organic matter and loosely bound extracellular polymeric substances (LB-EPS), especially proteins, increased significantly. During the fermentation, MS pretreatment under alkaline conditions was more efficient, with VFA peaking on the fifth day, showing a 140 % increase compared to the alkaline control group. Correlation analysis suggests that the dosage of MS, rather than pH, is closely related to the levels of soluble protein, polysaccharides, LB-EPS, and subsequential VFAs production, while alkaline conditions facilitate the dissolution of total organic carbon. Furthermore, sulfite radicals (SO3•−) are attributed to cell inactivation and lysis, while alkaline conditions initially reduce the size of the flocs, further promoting MS for attacking flocs, thereby improving the performance of fermentation. The study also found that MS pretreatment reduced microbial community diversity, enriched hydrolytic and fermentation bacteria (Actinobacteriota and Firmicutes), and suppressed methanogens (Methanobacteriaceae and Methanosaetaceae), making it a safe, viable, and cost-effective chemical agent for sustainable sludge management.

GOLD RECOVERY USING CITRUS SINENSIS PEELS AS BIOADSORBENT

The recovery of gold from electronic waste using locally available and environmentally friendly materials were investigated. Bio-adsorbent for gold recovery was prepared from Citrus sinensis peels through mechanical processing and chemical modification. Some ceramic computer processor units were leached using aqua-regia as lixiviant. Gold was recovered from the solution using the prepared bio-adsorbent and Sodium Meta Bisulphite (SMB). The recovery efficiency of the bio-adsorbent was determined and results compared to that of SMB. The adsorption of gold at different contact times was determined and the concentration of gold in solution was found using Agilent 4100 Micro Plasma Atomic Emission Spectroscopy (MP-AES). The results obtained showed that the bio-adsorbent has an adsorption capacity of 98.4% for gold and an adsorption kinetics correlation coefficient of 0.99989. This is comparable with SMB which has 95.4%. adsorption capacity and an adsorption kinetics correlation coefficient of 0.98597. The higher adsorption capacity of the bio-adsorbent is attributed to the binding sites and the chemical modification which increases the reducing properties of the functional groups present in the Citrussinensis peels.

Antisickling and Antihemolytic Mechanism of Spirulina platensis (Oscillatoriaceae): A Nutraceutical Commonly Used in Cameroon

Sickle cell anaemia (SCA) is a widespread genetic disease in Africa, associated with chronic hemolytic anaemia and vaso‐occlusive and infectious complications. The most commonly used means of management and treatment such as blood transfusions and allografting are expensive and predispose patients to the risk of infections. This research study aimed at evaluating the antisickling and antihemolytic activities of aqueous extracts of Spirulina platensis from Cameroon for optimising the management of this disease using natural substances. The Spirulina platensis harvested in Nomayos‐Yaounde was dried, crushed, and macerated for 24 h in distilled water and the filtrate was freeze dried. The determination of the inhibition rates of falciformation induced by 2% sodium metabisulfite (MBS) and the sickling reversibility rate was carried out at different concentrations (100, 200, 400, 800, and 1600 μg·mL−1) of the spirulina extract at different time intervals (2 h, 4 h, and 24 h). Aspirin, hypotonic solution, Triton X‐100, and hydrogen peroxide were used as hemolytic inducers and the antihemolytic activity of the extract was studied at 800 μg·mL−1 and 1600 μg·mL−1 using the colorimetric method. The extraction yield was 14.015%. The maximum duration of induced falciformation was 2 h 30 min and the percentage of falciformation increased from 27.99 ± 3.15% (at the initial time) to 91.44 ± 3.70%, giving a falciformation induction rate of 69.3%. The falciformation inhibition rate after 2 h 30 min ranges from 15.10 ± 0.60% to 66.09 ± 4.69% for the concentration of 100 μg·mL−1 to 1600 μg·mL−1 of the spirulina extract. This rate of inhibition of falciformation was found to be dose‐dependent. The best concentration of the extract was 1600 μg·mL−1. The reversibility rate of falciformation at 800 μg·mL−1 and 1600 μg·mL−1 varied from 37.54 ± 6.35% to 82.34 ± 5.63% as a function of time. 1600 μg·mL−1 was the most active concentration after 24 h. In addition, the extract improved the Fe2+/Fe3+ ratio with an increase in the rates of 69.78 ± 8.81 and 69.78 ± 13.82 at 800 μg·mL−1 and 1600 μg·mL−1, respectively. According to each inducer at 800 μg·mL−1 and 1600 μg·mL−1, respectively, of the spirulina extract, the following rates of inhibition of hemolysis were found: 53.03 ± 9.46% and 96.67 ± 5.77% (aspirin); 80 ± 8.66% and 71.25% (hypotonic solution); 36.56 ± 9.53% and 45.67 ± 22.55% (Triton X‐100); 24.26 ± 9.55% and 36.76 ± 1.27% (hydrogen peroxide). At the end of this study, the best antickling activities were obtained at the concentrations 800 μg·mL−1 and 1600 μg·mL−1. It also has antihemolytic properties on various hemolysis inducers at concentrations 800 μg·mL−1 and 1600 μg·mL−1 with inhibition rates varying from 36% to 96%.

Influence of blanching and guar gum pretreatments on total phenolic content and antioxidant activity of cabinet-dried white bitter gourd Momordica charantia L.

Currently, the global food industry is experiencing a shift in consumer preference towards natural sources of antioxidants derived from edible fruits and vegetables. In view of this, white skinned bitter gourd with bioactive properties has great potential. Additionally, guar gum has the characteristic ability to form strong hydrogen bonds with water molecules, thereby reducing shrinkage during dehydration. Thus, the present investigation was carried out to study the influence of blanching and guar gum pretreatment on the retention of the total phenolic content (TPC) stability and antioxidant activity (AA) of white Momordica charantia L. when cabinet dried at 60±5 °C. The results are indicative of a significant (P values of < 0.05) impact of using guar gum along with blanching before dehydration of white Momordica charantia. The findings obtained clearly show the positive impact of guar gum on the stability and retention of TPC (Folin Ciocalteau) and AA (percentage of 2,2-diphenyl-1-picrylhydrazyl DPPH scavenging activity) in the dried product in comparison to the untreated control. Water Blanching + 1% Guar gum (T5) and 2%Salt Blanching + 0.2% Potassium meta bisulphite + 1%Sodium carbonate + 1% Guar gum (T16) showed higher AA [20.29% (T5) and 40.13% (T16)] and TPC [30.8 (T5) and 39.5 (T16) GAE per 100 g of dried weight (DW)]. Therefore, the application of guar gum as a pretreatment with blanching turns out to be beneficial for higher retention of TPC and AA, thereby maintaining product quality as a whole.

Comparative assessment of guar gum for enhancing qualitative properties of dehydrated white skinned bitter gourd (Momordica charantia L.)

The enhancement of physical qualitative properties of a dehydrated product is a highly desirable aspect in processing fresh vegetables. This study compared the use of guar gum (GG) as pre-treatment for enhancing physical qualitative properties of dehydrated white skinned bitter gourd (WSBG). The experiment primarily focused on comparing GG as solo pre-treatment or in combination with other pre-treatment viz. salt solution (SS) or potassium meta bisulphite (KMS) or sodium carbonate (SC) along with water blanching (Wat Blanch) or salt blanching (Sal Blanch). The results are indicative of a significant (P values of < 0.05) impact of using guar gum along with blanching before dehydration of WSBG at 60±5ºC in a mechanical dehydrator, in comparison to untreated control. The findings clearly exhibit solo GG sample T5 (Wat Blanch+1%GG) and combination GG sample T16 (2%Sal Blanch+0.2%KMS+1%SC+1%GG) as most superior with highest RR [9.23 (T5) & 11.30 (T16)] and BD [0.50 g/cm3 (T5) & 1.08 g/cm3 (T16)] in final dried product. The higher retention of RR and BD indicates that GG pretreated samples have better reconstitution than the control (T1). Hence, application of GG as a pre-treatment with blanching is beneficial for developing a quality product with good storage dynamics.

Tooth whitening, oxidation or reduction? Study of physicochemical alterations in bovine enamel using Synchrotron based Micro-FTIR

ObjectivesTooth whitening demand formulations have not evolved significantly over years being hydrogen peroxide (HP) or carbamide peroxide (CP) the main active agents used. These oxidizing compounds need high concentrations and long application times to achieve the desired whitening results, leading to painful secondary effects. A novel treatment based on a reducing agent, sodium metabisulphite (MBS) encapsulated in liposomes, demonstrated significant whitening results in just 3 minutes. The aim is to provide information about the chemical interactions of the encapsulated MBS with the enamel structure compared with CP’s and to study their penetration in the hydroxyapatite (HAP). MethodsChemical imaging is performed by synchrotron-based micro Fourier transformed infrared spectroscopy (SR-µFTIR). Continuous Stiffness Measurements (CSM) were used to determine the depth reached by the treatments in order to delimitate the area of study. ResultsPrincipal component analysis (PCA) showed that the main differences between treatments were found in the intensity of the ν3 PO3-4 peak related with tooth demineralization produced by the acidic nature of MBS; these changes were observed in deeper regions of the enamel when MBS was encapsulated. SignificanceThe obtained results indicated that CP and MBS promote different changes in the HAP mineral, and that liposomes favour the diffusion of MBS into the enamel. It is the first time that synchrotron light is used to map chemically the bovine incisor’s enamel, and to determine the effect of a whitening treatment in terms of chemical HAP modifications, and the extent in deep of these effects.

Effects of the combination of some essential oils with methylparaben and sodium metabisulfite against pathogenic foodborne bacteria

In this work, the antimicrobial and antioxidant activity of some essential oils (EOs) and their synergistic effects with synthetic preservatives against foodborne pathogenic bacteria were evaluated. Nine EOs were screened against Bacillus cereus, Staphylococcus aureus, Escherichia coli, and Salmonella enterica serotype Typhi, and six of these were associated with methylparaben (MTP) and sodium metabisulfite (MTBS). Essential oils of cinnamon and oregano showed potential antibacterial activity. The combinations of cinnamon + MTP, coriander + MTP, and oregano + MTP, showed synergism against S. enterica ser. Typhi, E. coli, and S. aureus, respectively. Clove oils exhibited higher radical scavenging activity against DPPH. Moreover, clove leaves + MTP presented a synergistic antimicrobial interaction against E. coli and S. enterica ser. Typhi. These findings showed a reduction in the minimal inhibitory concentration (MIC) of the synthetic preservative with a low concentration of EOs, highlighting an alternative source as preservatives in embedded foods and derivatives for the food industry. Novelty impact statement The use of essential oils in combination with the synthetic preservative methylparaben (MTP) promoted synergistic antimicrobial effects against foodborne bacteria. The clove leaf oil showed synergism with MTP against Gram-negative bacteria (FICI = 0.49) and high antioxidant activity (IC50 = 8.06 μg/ml), and this can be used as an alternative source for delaying the oxidative process and for the preservation of food products.

Effect of Sodium Metabisulfite on Selective Flotation of Chalcopyrite and Molybdenite

Sodium metabisulfite (MBS) was used in this study for selective flotation of chalcopyrite and molybdenite. Microflotation tests of single and mixed minerals were performed to assess the floatability of chalcopyrite and molybdenite. The results of microflotation of single minerals showed that MBS treatment significantly depressed the floatability of chalcopyrite and slightly reduced the floatability of molybdenite. The results of microflotation of mixed minerals demonstrated that the MBS treatment could be used as a selective chalcopyrite depressant in the selective flotation of chalcopyrite and molybdenite. Furthermore, the addition of diesel oil or kerosene could significantly improve the separation efficiency of selective flotation of chalcopyrite and molybdenite using MBS treatment. A mechanism based on X-ray photoelectron spectroscopy analysis results is proposed in this study to explain the selective depressing effect of MBS on the flotation of chalcopyrite and molybdenite.

Solvent retention capacity: Supplemental solvents for evaluation of gluten quality

Solvent retention capacity (SRC) is a solvation test for wheat flour in which functional contributions of different polymeric components are predicted based on their swelling behavior with different diagnostic solvents. To assess the functionality of individual gluten components, four solvents have been proposed: 1) 55% aqueous ethanol for gliadins; 2) 0.75% sodium dodecyl sulfate (SDS) for glutenin macropolymer; 3) 0.006% sodium metabisulfite (MBS) for gluten strength; and 4) 0.75% SDS + 0.006% MBS for glutenin macropolymer without disulfide network. This research aimed to study the gluten functionality of commercial wheat flour samples by the four proposed supplemental diagnostic solvents. Commercial wheat samples were purchased in 2020 at a grocery store in Fargo, North Dakota. Four different brands from three flour types (bread flour, all-purpose flour, and cake flour) were analyzed. These flour types represent wheat flour from three different U.S. wheat classes, hard spring wheat, hard winter wheat, and soft wheat. SRC was measured according to the AACC-approved method 56–11.02 with modifications. The supplementary solvents 55% aqueous ethanol, 0.75% SDS, 0.006% MBS, and 0.75% SDS +0.006% MBS were used instead of the traditional SRC solvents. Highly significant (p ≤ 0.001) and positive correlations between SDS SRC, MBS SRC, and SDS + MBS SRC solvents and the analyzed rheological and baking quality traits, especially water absorption and loaf volume. Additionally, when protein composition was assessed, the three previously mentioned supplementary SRC solvents denoted a significant (p ≤ 0.01) and positive correlation with the glutenin polymers fraction, which is associated with dough functionality. These results highlight the importance of assessing specific flour polymers' functional contributions to predict each flour type's end-use potential.

The depression of molybdenite flotation by sodium metabisulphite in fresh water and seawater

Sodium metabisulfite (MBS) has been widely applied to depress pyrite in copper-molybdenum flotation plants in particular when seawater is used as the main water resource. However, whether MBS depresses molybdenite flotation is unknown. In this study, the flotation of molybdenite at 106 and 53 µm was carried out in the absence and presence of MBS in DI water and seawater to determine the depression role of MBS. Then the products formed on molybdenite faces and edges were detected by cryogenic X-ray photoelectron spectroscopy to understand the reactions involving MBS. This study confirmed the depression of MBS on molybdenite flotation especially for fine particles in DI water. The depression was caused by the adsorption and oxidation of sulphite ions on molybdenite edges, forming sulphate complexes which provided a steric barrier to collector adsorption on molybdenite faces. This study also confirmed little effect of MBS on the flotation of molybdenite at 106 and 53 µm in seawater. This is because sulphite ions preferentially combined with calcium and magnesium ions in water rather adsorbed on molybdenite edges.

Sodium metabisulfite hypersensitivity in urticaria

Background: Sodium metabisulfite is a recognized, but rare, trigger of urticaria, wherein the IgE mechanism has been sporadically proven. The aim of this study was to identify the potential reaction to sodium metabisulfite (MBS) based on a placebo-controlled oral challenge in patients with urticaria and suspected hypersensitivity to food additives. Materials and Methods: A total of 110 adult patients (76 females and 34 males with a mean age of 46 years) were included in the study between 2017 and 2019. All subjects underwent MBS skin prick tests (SPT) and patch tests (PT). Patients with a positive skin test or suspected MBS hypersensitivity were qualified for a placebo-controlled oral challenge (OC). Results: Skin testing was positive in 24 patients: SPT in 20% (n = 22), PT in 5% (n = 6). Out of 64 oral challenges, 13 positive results were obtained. Patients with a positive challenge typed sulfite foods twice as often as a culprit compared to those with a negative OC. Conclusions: In patients with urticaria, both the IgE and non-IgE mechanism of MBS hypersensitivity has been demonstrated. Skin tests with a detailed medical history of potentially guilty foods may be helpful in determining sulfite hypersensitivity.

The Effects of Garlic Oil and Tartaric Acid on the Quality of Shrimp Stored at 4°C

The objectives of this study were to determine the effects of garlic oil (GO) and tartaric acid (TA) on microbiological, pH, and Thiobarbituric Acid Reactive Substances (TBARS) (lipid peroxidation) of shrimp stored at 4°C. Shrimp of 2 kg were dipped in GO and TA solutions at 1:2 shrimp/treatment solutions (w/w) for 30 mins under 25ºC. Sodium metabisulfite (MBS) and sterile distilled water (dH20) were used as positive and negative controls, respectively. Shrimp were drip-dried for 5 mins, packaged, and stored in a chiller (4°C) for 10 days. The shrimp were analysed on days 0, 3, 5, 7, and 10. Total aerobic plate count, psychotropic bacteria count, Listeria monocytogenes, Salmonella enterica serovar Typhimurium (S. Typhimurium) and Vibrio parahaemolyticus counts ranged from 3.52-8.73 log CFU/g, <3.30-5.16 log CFU/g, 3.48-7.60 log CFU/g, 3.42-6.34 log CFU/g and 3.48-5.55 log CFU/g, respectively. The pH of shrimp ranged from 6.64 to 8.03. The pH of shrimp dipped in MBS (7.70) and TA+GO (7.70) was lowest at the end of storage period. TBARS values ranged from 0.70-2.66 and TBARS values for shrimp treated with MBS (1.83) were lowest at day 10. In general, microbiological counts, pH and TBARS values of sample treated with TA+GO increased with storage time, however comparable to MBS. Treatment of shrimp with GO and TA could inhibit the growth of foodborne pathogens. The pH of the test and control shrimp were similar on day 10. Lipid peroxidation was lowest for TA and MBS treated shrimp by day 10.

The Effects of Garlic Oil and Tartaric Acid on the Quality of Shrimp Stored at 4°C

The objectives of this study were to determine the effects of garlic oil (GO) and tartaric acid (TA) on microbiological, pH, and Thiobarbituric Acid Reactive Substances (TBARS) (lipid peroxidation) of shrimp stored at 4°C. Shrimp of 2 kg were dipped in GO and TA solutions at 1:2 shrimp/treatment solutions (w/w) for 30 mins under 25ºC. Sodium metabisulfite (MBS) and sterile distilled water (dH20) were used as positive and negative controls, respectively. Shrimp were drip-dried for 5 mins, packaged, and stored in a chiller (4°C) for 10 days. The shrimp were analysed on days 0, 3, 5, 7, and 10. Total aerobic plate count, psychotropic bacteria count, Listeria monocytogenes, Salmonella enterica serovar Typhimurium (S. Typhimurium) and Vibrio parahaemolyticus counts ranged from 3.52-8.73 log CFU/g, <3.30-5.16 log CFU/g, 3.48-7.60 log CFU/g, 3.42-6.34 log CFU/g and 3.48-5.55 log CFU/g, respectively. The pH of shrimp ranged from 6.64 to 8.03. The pH of shrimp dipped in MBS (7.70) and TA+GO (7.70) was lowest at the end of storage period. TBARS values ranged from 0.70-2.66 and TBARS values for shrimp treated with MBS (1.83) were lowest at day 10. In general, microbiological counts, pH and TBARS values of sample treated with TA+GO increased with storage time, however comparable to MBS. Treatment of shrimp with GO and TA could inhibit the growth of foodborne pathogens. The pH of the test and control shrimp were similar on day 10. Lipid peroxidation was lowest for TA and MBS treated shrimp by day 10.

Effect of different drying method on the chemical and microstructural properties of Loquat slices

This study reported the effect of different drying methods, that is, T.D (tray drying) (55°C), V.D (vacuum drying) (55°C), at 500 mm Hg) and F.D. (freeze-drying) (−40°C, 0.006 bar) on microstructural changes, chemical composition changes and sensory parameter (Taste, flavor, color, overall acceptance) of Indian loquat fruit slices. In this research, loquat fruits cut in thin slices (approx. 0.5 cm) and dried by different drying methods. To prevent undesirable browning reaction pre-treatment is carried out by treating 1% potassium meta bisulfite solution for 15 min. Scanning electron microscopy (SEM) was used to analyze the changes in dried fruit structure. Chemical properties of dried products including flavonoids, titratable acidity, Total phenol, ascorbic acid content, β-Carotene, and total sugar were also measured. The result reflected a decrease in chemical properties when compared to fresh loquat fruits. Freeze-dried slices showed significantly higher retention in most of the quality attributes studied in this study. Freeze-dried slices have a porous structure, whereas the tray died and vacuum dried samples showed a compact structure. The sensory analysis resulted that all dried samples accepted by panellists but freeze-dried samples scored a maximum. Practical applications Due to high moisture content (more than 80%) loquat fruit is highly perishable and susceptible to spoilage. Drying techniques preserve this fruit by reducing water activity and extend the shelf life of the fresh fruit making it available throughout the year. Novel drying techniques like freeze-drying help to develop dehydrated and good quality shelf-stable products. The dried slices developed using these techniques may be used by industries for the development of various functional foods, confectionery, and food supplements for children and infants as fruits in dried form also retain high health-promoting nutrition.

Selectively Depress Copper-Activated Pyrite in Copper Flotation at Slightly Alkaline pH

Pyrite depression in the flotation of copper ores is difficult due to the activation of Cu2+ ions on pyrite surface. In this study, the radical chain reaction involving the redox cycling of Cu(I/II) induced by sodium metabisulphite (MBS) was exploited to selectively depress the flotation of copper-activated pyrite at pH 8.0. Electrochemical measurements revealed that the presence of Cu2+ and O2 was essential to the formation of $$ {\mathrm{SO}}_5^{\bullet -} $$ through sulphite oxidation, the main entity to convert the activating species Cu(I)S on pyrite to Cu(II)-hydroxide/sulphate, causing deactivation of pyrite. The depression role of MBS on pyrite flotation was closely associated with the type of grinding media which affected the electrochemical conditions of flotation. When forged steel was used as the grinding media, a high dosage of MBS was required to depress pyrite, but a low dosage of MBS could almost completely depressed pyrite when high chrome steel grinding media was used. This is because high chrome steel produced a stronger oxidation condition with a higher amount of Cu2+ and O2 which promoted the formation of $$ {\mathrm{SO}}_5^{\bullet -} $$ .

Avaliação sensorial de ketchup adicionado de amido de semente de pitomba

O ketchup é um molho popular em diversos países, caracterizado pela cor forte, sabor adocicado e consistência espessa. Variações nessas características podem interferir na aceitação do produto, assim, objetivou-se com este estudo analisar a aceitação dos parâmetros sensoriais (aroma, cor, sabor, aparência) e intenção de compra de ketchup adicionado de amido de pitomba e com isso comparar com os atributos sensoriais de ketchup adicionado de amido de milho comercial. A extração do amido foi realizada por trituração da semente da pitomba em solução de metabissulfito de sódio (0,2%) seguida de secagem à 50 °C. Os ketchups foram formulados com adição de 0,5 e 1% de amido de pitomba, 0,5 e 1% de amido de milho, e uma formulação controle. As formulações foram avaliadas microbiologicamente quanto coliformes termotolerantes e Salmonella e submetidos a avaliação de aceitação sensorial quanto aos parâmetros de cor, aparência, aroma, sabor e intenção de compra. Os resultados revelaram que as formulações apresentaram bom padrão microbiológico e os ketchups não apresentaram diferença significativa (p ≤ 0,05) entre os parâmetros de cor, aparência, aroma e sabor, indicando que as porcentagens e os tipos de amido utilizado não causaram interferência nas características sensoriais avaliadas. As maiores intenções de compra foram registradas para as formulações adicionadas de amidos, sugerindo a preferência dos consumidores por formulações consistentes.

Sesame Meal and Moringa oleifera Leaves Ready to Cook Curry Mix: An Ethnic Food of Godavari Districts in Andhra Pradesh, India

Sesame meal was widely consumed in Godavari districts of Andhra Pradesh, India which was not known to most of the people and under-utilized. Moringa leaves were another nutritious food that is also under-utilized and not available in urban areas. The aim of this work was to develop the sesame meal and dried Moringa leaves as a ready to cook curry mix by assessing the ratio of sesame meal and dried Moringa leaves as to determine the best closer fresh leaves and sesame meal blend. The Moringa leaves were treated with citric acid, and potassium meta bisulphite to retain the colour and dried by different techniques such as shade drying, solar drying and drying in Ezidri food dehydrator at 60, 50, 35ºC. The leaves dried in Ezidri food dehydrator retained more colour and nutrients. The dried leaves were used to prepare curry with sesame meal taking fresh leaves as a control in the ratio 1:2. The dried leaves and sesame meal were taken in the ratio 0.1:1, 0.12:1 and 0.14:1, prepared samples were evaluated for sensory characteristics and compared with the control sample. The curry prepared in the ratio 0.12:1 is best accepted and close to the control sample. The nutritive value shows Sesame meal and Moringa leaves were the best cheapest sources of protein, calcium, iron, potassium and vitamin A.

Shelf Life and Sensory Evaluation of Hill Lemon (Citrus pseudolimon Tan.) Juice using Organic and Inorganic Preservatives

Hill lemon (Citrus pseudolimonTan.) is a hardy plant and grown well in low and mid hills of Himachal Pradesh. Its juice is preserved and being used as souring agent in many food preparations, pickles and chutneys. The shelf life of Hill lemon juice was assessed by using organic and inorganic preservatives. Boiling of juice till the end of formation of foam/leather and adding organic source of preservative (Salt @ 20gm/L of juice + top dressing of mustard oil @ 20ml/L of juice) was found best and received highest rating on various sensory attributes especially colour and flavour under nine point hedonic scale. This treatment not only enhanced the shelf life of the juice up to 10 months but also retained original flavour and colour of juice. Under inorganic preservatives, Potassium meta bisulphite @0.7 gm/L of juice and Sodium benzoate @ 0.5gm/L of juice, six and five months shelf life was observed respectively. Hence use of organic method for preserving the juice can be a better substitute of inorganic preservatives in many food processing industries.

Breaking the rules: tooth whitening by means of a reducing agent.

It is widely accepted that current tooth whitening treatment effect is based on the oxidizing action of peroxides, even if the mechanism of action remains still unclear. Treatments are claimed to be safe, but several secondary effects have been described, since long application times and high concentrations are needed. A faster whitening ingredient which permits the use of lower concentrations and shorter application times could potentially overcome this problem. In this work, a different approach based on a reducing agent, sodium metabisulfite (MBS), is explored. The reaction between tannic acid (TA) with carbamide peroxide (CP), MBS, and potassium persulfate (PS), as an oxidizing agent, was monitored for 48 hours by measuring its absorbance, comparing their different whitening effects. The reduction process between TA and MBS was confirmed by cyclic voltammetry. An in vitro test was used to observe if MBS whitens also stained teeth. It is shown that MBS bleaching effect is faster and higher than CP's effect over time. PS produced a darkening effect after the 3rd hour because of the strong absorbance of the oxidation metabolite. Cyclic voltammetry showed a progressive increase in the intensity of the TA anodic peak when MBS was present, demonstrating that a reduction is taking place. In vitro, MBS showed a faster whitening performance than CP, using lower concentrations. Using a TA solution as a staining model, it was possible to show that MBS has a visible bleaching effect through a reduction reaction, faster than CP, both in solution and in vitro. Low concentrations of MBS are effective in whitening. This work shows MBS as a promising candidate to develop novel whitening treatments, which is acting by reducing mechanism instead of oxidation.

The role of sodium metabisulphite in depressing pyrite in chalcopyrite flotation using saline water

In response to the high pyrite recovery in copper flotation using seawater, this study investigated the role of sodium metabisulphite (MBS), a widely used pyrite depressant, in depressing the flotation of copper-activated pyrite to identify a solution to maximising pyrite rejection. It started with chalcopyrite flotation against pyrite with MBS added in the mill before grinding and in the conditioning cell before flotation. The surface properties of pyrite exposed to different reagent schemes were investigated by X-ray photoelectron spectroscopy (XPS) analysis. The reactions on pyrite surface responsible for different flotation results were then investigated by cyclic voltammogram (CV) measurements and discussed in terms of a radical chain mechanism involving the redox cycling of Cu(I/II) induced by sulphite species. It was found that the addition of MBS during the conditioning stage was more efficient in depressing the flotation of copper-activated pyrite. This is because the combination of sulphite ions and oxygen may form a strongly oxidising radical SO5·- which can oxidise Cu(I)S, the copper activation product on pyrite surface, to form hydrophilic Cu(OH)2/CuSO4. The addition of MBS at low dosages in the mill depressed pyrite flotation to a less extent due to the less oxygen available, while its depression effect was even weakened at high dosages due to the consumption of dissolved oxygen and a strongly reducing environment which favoured copper activation on pyrite surface.