Thermal inactivation kinetics parameters of browning enzymes in starfruit (Averrhoa carambola L.) juice

This study aimed to evaluate the thermal inactivation kinetics of polyphenol oxidase (PPO) and peroxidase (POD) in starfruit juice. It followed the Malaysia Food Regulations 1985 and CODEX STAN 247-2005. Glucose, fructose and sucrose were the main sugars in starfruit juice. The total soluble solids, pH, titratable acidity, and total phenolics content of the starfruit juice produced were 8.13 ± 0.25 °Brix, 3.80 ± 0.05, 0.43% ± 0.02% malic acid, and 93.67 ± 4.96 mg GAEL⁻¹, respectively. Thermal inactivation kinetics of PPO and POD followed the first-order kinetic model. The decimal reduction time at 83.6 °C (D_83.6) of PPO and POD was 198.48 and 98.4 s, respectively, while the thermal resistance constant (z value) of PPO and POD was 12.8 and 5.4 °C, respectively. In conclusion, PPO might be a suitable signal for thermal processing on starfruit juice since it has higher heat resistance than POD.     

Tannase improves gallic acid bioaccessibility and maintains the quality of mango juice

The effect of tannase on gallic acid (GA) bioaccessibility and auto-oxidative browning of mango juice was investigated. After 2 h of simulated gastric digestion, the concentration of bioaccessible GA increased (P < 0.05) 94.3 ± 7.0% in juice treated with 0.5 U mL⁻¹ tannase while juice not treated with tannase had only a 6.3 ± 3.4% increase in GA. During 2–10 h of simulated intestinal digestion, tannase treated juice continued to have a higher concentration (P < 0.05) of bioaccessible GA in comparison to juice that was not treated with tannase. The use of 167 U 100 mL⁻¹ tannase while processing mango juice did not result in any differences (P < 0.05) in browning measured at 420 nm, yet there was significantly higher (P < 0.05) GA in mango juice post-storage. Processing mango juice with tannase can help improve the bioaccessibility of mango polyphenols without hindering the quality of juice during storage.     

Viscosity of tangerine and lemon juices as a function of temperature and concentration

Viscosities of two fruit (lemon and tangerine) juices have been measured with a capillary flow technique. Measurements were made in the temperature range from 303 to 393 K. The range of concentration was between 15 and 40 °Brix for tangerine juice and between 17 and 45 °Brix for the lemon juice. The total uncertainty of viscosity and temperature measurements was estimated to be <0.5% at low concentrations and up to 1.5% at high concentrations and 0.025 K, respectively. The effect of temperature and concentration on viscosity of tangerine and lemon juices was study. The measured values of the viscosity were used to calculate the temperature, (? ln η/?T)_x, and concentration, (? ln η/?x)_T, coefficients for each juice. The Arrhenius type correlation equations for viscosity were used to represent the temperature dependence of viscosity. The values of the Arrhenius equation parameters (flow activation energy, E_a, and η_∞) were calculated for the measured viscosities of tangerine and lemon juices as a function of concentration. Different theoretical models for the viscosity of fruit juices were stringently tested with new accurate measurements on tangerine and lemon juices. The predictive capability of the various models was studied. The concentration and temperature dependence behavior of the viscosity of tangerine and lemon juices are discussed in light of the various theoretical models for viscosity of fruit juices. The applicability and predictive capability of the models used previously for aqueous solutions to represent the effect of temperature and concentration on viscosity of fruit juices was also studied. New model was developed to represent the combined effect of temperature and concentration on the viscosity of the juices. The average absolute deviation between measured and calculated values from this correlation equation for the viscosity was 0.8% and 2.1% for tangerine and lemon juices, respectively.     

Ascorbic acid,aroma compounds and browning of orange juices related to PET packaging materials and pH

The ascorbic acid content of orange juice made from concentrate was measured after 9 months of storage at 20 °C in glass, standard monolayer polyethylene terephthalate (PET₁), multilayer PET (PET₂) and plasma‐treated PET (PET₃) containers. Glass enabled the best preservation of ascorbic acid and, in plastic packaging materials, ascorbic acid losses were correlated with their oxygen permeability. PET₂ and PET₃, which exhibit oxygen permeability 10 times less than that of PET₁, enabled a gain of 100 mg L^?1 after 9 months of storage. Freshly hand‐squeezed orange juice samples were adjusted to various pH values using sodium hydroxide; a rise in the pH from 3.2 to 4.0 significantly reduced the amounts of off‐flavours (i.e., furfural and α‐terpineol) appearing during storage, by 79% and 65%, respectively. Moreover, an increase in the pH from 3.2 to 4.0 enabled the protection of ascorbic acid levels without detrimentally increasing non‐enzymatic browning. Copyright © 2006 Society of Chemical Industry     

Optimization of medium constituents for ε-poly-L-lysine fermentation with response surface methodology

Abstract: ɛ-Poly-L-lysine (ɛ-PL) is a novel food biopreservative with broad antimicrobial activity. In the present study, single-factor experiments were applied to screen optimal carbon and nitrogen sources that affect the yield of a ɛ-PL-producing strain, Streptomyces violaceusniger, which was obtained in our laboratory recently. Box-Behnken design and response surface methodology (RSM) were adopted to derive a statistical model for optimizing the composition of the fermentation medium. The results showed that the main factors that affect ɛ-PL production were glucose, carbon source; peptone, organic nitrogen source; and (NH₄)₂SO₄, inorganic nitrogen source. The optimum fermentation medium for ɛ-PL production of S. violaceusniger consisted of (g/L) glucose, 62.49; peptone, 5.71; (NH₄)₂SO₄, 11.19; MgSO₄, 0.5; FeSO₄, 0.03; ZnSO₄, 0.04; KH₂PO₄, 1.36; and Na₂HPO₄.12H₂O, 3.58. When cultured in the optimum medium, the ɛ-PL production was an average of 0.349 ± 0.025 mg/mL, which was 1.75 times higher than the initial medium. Practical Application: The present study illustrated the potential use of response surface methodology with the Box-Behnken design in biotechnology. Results from this work suggested that ɛ-PL production was increased greatly with the optimal medium constituents by the potential organism, S. violaceusniger, which may be a good resource for the industrial production of ɛ-PL in future.     

Slight Fermentation with Lactobacillus fermentium Improves the Taste (Sugar:Acid Ratio) of Citrus (Citrus reticulata cv. chachiensis) Juice

The aim of this study was to evaluate the hypothesis that fermentation with Lactobacillus fermentium, which can metabolize citric acid, could be applied in improving the taste (sugar:acid ratio) of citrus juice. During fermentation, the strain of L. fermentium can preferentially utilize citric acid of citrus (Citrus reticulata cv. Chachiensis) juice to support the growth without the consumption of sugar. After 6 h of fermentation with L. fermentium at 30 °C, the sugar:acid ratio of citrus juice increased to 22:1 from 12:1, which resulted in that the hedonic scores of sweetness, acidity and overall acceptability of fermented‐pasteurized citrus juice were higher than the unfermented‐pasteurized citrus juice. Compared with unfermented‐pasteurized citrus juice, the ORAC value and total amino acid showed a reduction, and no significant change (P > 0.05) in the L*, a*, b*, total soluble phenolics and ascorbic acid (Vc) content in the fermented‐pasteurized citrus juice was observed as compared with unfermented‐pasteurized citrus juice. Hence, slight fermentation with L. fermentium can be used for improving the taste (sugar:acid ratio) of citrus juice with the well retaining of quality.     

The properties and molecular structures of gusiljatbam starch compared to those of acorn and chestnut starches

The properties and molecular structures of starch from gusiljatbam (GS) (Castanopsis cuspidate), a pine nut‐type fruit with a chestnut taste, compared to starches from an acorn (AS) and a chestnut (CS) were investigated. The starches were isolated using an alkaline steeping method, and analyzed. The TAM contents of GS, AS, and CS were 44.09, 30.56, and 29.55%, respectively. The GS showed the highest water binding capacity (110.83%) and solubility at 80°C (10.00%). The initial pasting temperature of GS was the lowest, but its pasting viscosity was the highest among them. Trough, cold, and setback viscosities and particle sizes were in the following order: GS>AS>CS. The XRD patterns of GS, AS, and CS revealed B, A, and C_b type crystals, respectively. HPSEC showed the MW distribution patterns of the starches as AP, intermediate materials (IM), and AM peaks. However, the MW of AM as well as AP peak intensity and IM patterns were different. According to the branched chain length distribution of AP at DP 13–24 and DP 25–36, DP_n, and DP_w decreased in the following order: GS>AS>CS, but DP 6–12 and DP ≥ 37 were distributed in reverse order.     

Measurement of High‐Pressure Carbon Dioxide Solubility in Orange Juice,Apple Juice,and Model Liquid Foods

ABSTRACT: An experimental system to measure the carbon dioxide (CO₂) solubility in liquids at different pressures was designed and tested. Pressure and temperature were controlled in the system, and the design assured an accurate measurement of solubility. Experimental measurements of CO₂ solubility were performed in pure water, model solutions (ascorbic acid–sugars–water, citric acid–sugars–water), and in commercial orange juice (OJ) and apple juice (AJ), as a function of pressure (7.58 to 15.86 MPa) at constant temperature (40 °C). Aspen simulation software was used to predict the solubility in simple cases. All experimental results and predictions from simulations were compared with literature data. Measurements of CO₂ solubility in pure water were not significantly different than the literature. CO₂ solubility (g/100 g of liquid) results in the model liquids and in the juices were lower than for pure water, due to the presence of solutes. The software simulation was able to predict the CO₂ solubility in the model systems at low pressures.     

Kiwifruit Juice Clarification using a Fungal Proteolytic Enzyme

A commercial fungal proteolytic enzyme from Aspergillus niger was used in kiwifruit juice as a replacement for conventional fining agents to produce a stable clarified juice. Reductions in detectable protein levels of 73% and 82% were achieved using 500 mg/kg of enzyme and incubating at 60°C for 20 and 60 min respectively. Concentrates prepared from proteolytic enzyme-treated juice had reduced browning and haze formation compared to a control, without affecting ascorbic acid level. When stored at 20°C, proteolytic enzyme treated concentrates (60 min) remained clear up to 90 days and had minimal haze (A_{650 nm}= 0.047) and browning (A_{420 nm}= 0.93) after 6 mo storage. The molecular size of the protein as well as protein concentration are important factors in haze formation.     

Laboratory evaluation of previously fermented juice as a fermentation stimulant for lucerne silage

The potential use of forage juice anaerobically stored for 2 days (previously fermented juice, PFJ) as a silage additive was investigated. Lucerne (450 g) was ensiled in laboratory‐scale silos (900 ml capacity) with or without sucrose (20 g kg⁻¹) or PFJ (2.5 ml kg⁻¹). Silages treated with both additives were also made and fermentation quality, in vitro dry matter digestibility and in vitro ruminal NH₃ production were determined. The control silage showed very poor quality with high butyrate and NH₃‐N concentrations. Addition of sucrose significantly increased lactate but failed to inhibit the deterioration by clostridial fermentation. Use of PFJ further increased lactate and greatly reduced butyrate and NH₃‐N production during storage. The combination of sucrose and PFJ was more effective in improving fermentation than either additive on its own. In vitro digestibility appeared to be higher when lucerne was well preserved. Ruminal NH₃ production in vitro was decreased in silages with sucrose and PFJ added at ensiling. This result indicates that use of PFJ can be a promising way to stimulate lactate production in some difficult direct cut silage. The potential of improving fermentation may be comparable to conventional sugar additives. © 1999 Society of Chemical Industry     

Mixed fermentation of jujube juice (Ziziphus jujuba Mill.) with L. rhamnosus GG and L. plantarum-1: effects on the quality and stability

This study was conducted aiming at improving the quality of jujube juice by mixed fermentation of lactobacilli. Selection of favourable lactobacilli and addition of nitrogen sources were explored as an efficient method to improve the viability of probiotic in jujube juice. After fermentation, the viability increased to 9.15 ± 0.10 Log CFU mL⁻¹, while the content of lactic acid increased to 5.61 ± 0.03 mg mL⁻¹. The total phenolic and total flavonoid content were 2663.03 ± 11.95 μg mL⁻¹ and 163.95 ± 0.47 μg mL⁻¹ respectively. Moreover, the stability of fermented jujube juice during refrigeration was investigated, which showed that the viability dropped to 8.84 ± 0.6 Log CFU mL⁻¹ and the concentration of lactic acid slowly increased to 6.51 ± 0.04 mg mL⁻¹; the ABTS value showed a 4.26% reduction and FRAP value did not significantly (P < 0.05) change during refrigerated storage. In addition to the existing knowledge, our data aid to the future applications of the jujube as a potential ingredient in novel probiotic foods formulation.     

Polyphenol content and antioxidative activity in apple purées with rhubarb juice supplement

The purpose of the present study was to evaluate the effect of rhubarb juice addition and peeling in apple purée production and storage on its phenolic composition, antioxidant activity and colour. The apple material used in this study was of two varieties: Sampion and Idared. The apple purées prepared in three variants (control purées, peeling purées and purées with 5% of rhubarb juice) were stored for 3 and 6 months at 30 °C. Apple purées were investigated for their antioxidant activity, change of colour and contents of phenolic compounds plus the polymer procyanidins and degree of polymerization (DP). The preparation of purées from apples without peeling and the addition of rhubarb juice during purée preparation had significant influence on polyphenol content. The purée prepared from peeled apples of Idared variety had phenolic content 2.2 times lower than the control sample (non‐peeled apples). The highest level of total polyphenols was found in Idared + rhubarb sample (129.82 mg 100 g^?1 purée). The content of this compound in Idared control sample was more than 2.8 times lower than in Idared purées with rhubarb. The use of non‐peeled Idared apples and 5% of rhubarb juice in purée preparation significantly increased polymeric procyanidins from 11.68 to 75.20 mg 100 g^?1 and other phenolics from 9.23 to 54.62 mg/100 g. This effect for Sampion apples was smaller. The procyanidins during purées storage were more stable in samples with rhubarb juice addition. The purée samples with the addition of rhubarb juice had higher antioxidant activity measured using ABTS (2,2′azinobis‐(3‐ethylbenzthiazoline‐6‐sulphonic acid)) than purée samples without the addition (two times higher for Idared variety) of rhubarb juice. After 3 and 6 months of storage at temperature 30 °C, the antioxidant capacity decreased in all purées. Rhubarb juice had only high and positive effect on L* value in the case of Idared variety. The results showed that all Sampion apple purées had higher L* values than Idared.     

The effect of lemon juice on bonito (Sarda sarda,Bloch, 1793) preserved by sous vide packaging

This study examined the effect of lemon juice on sensory, biochemical and microbiological quality of sous vide (SV)‐packaged bonito. Bonitos were salted (0.2%) and divided into two groups. The first group (SV) was vacuum‐packaged in a gas barrier plastic pouch, pasteurised (70 °C, 10 min) and stored at 4 ± 1 °C. The second group [(lemon juice‐treated sous vide (LSV)] was treated with lemon juice, vacuum‐packaged, pasteurised and stored similarly. LSV samples had lower pH, mesophilic and psychrophilic aerobic counts than SV samples (P < 0.05), and they had better sensory quality. SV samples spoiled on the 35th day, while the LSV samples were acceptable until 49th day of storage. This result shows that treatment with lemon juice increased the acceptability and shelf life of SV packaged bonito for 2 weeks (40%). When compared to several other mild preservation procedures, addition of lemon juice to SV fish is inexpensive and uncomplicated method.     

EFFECTS OF CETYLPYRIDINIUM CHLORIDE, LACTIC ACID AND SODIUM BENZOATE ON POPULATIONS OF LISTERIA MONOCYTOGENES AND STAPHYLOCOCCUS AUREUS ON BEEF

The effects of cetylpyridinium chloride (CPC), lactic acid (LA) and sodium benzoate (SB) on the Listeria monocytogenes and Staphylococcus aureus populations on beef were evaluated. Samples of longissimus dorsi beef muscle inoculated with L. monocytogenes and S. aureus were dipped into 0.5, 2.0 and 0.3% of CPC, LA and SB, respectively, or an equal mix of any two solutions for 15 s at 35C ± 1. CPC demonstrated 1.93 and 2.15 log reductions of L. monocytogenes and S. aureus, respectively, on the fifth day of refrigerated storage, whereas LA reduced L. monocytogenes and S. aureus by 1.72 and 0.99 log, respectively. Results indicated that the single intervention of CPC and LA solutions were more effective than mixed solutions of these decontaminants to reduce the pathogens of concern on beef.     

Citrus Tissue Extracts Affect Juice Cloud Stability

Salt extractable proteins were isolated from hand expressed juice, rag and peel of Valencia oranges. Each tissue extract was divided into dialysis supernatant (DS) and precipitate (DP) (forms during dialysis). DP, DS and DS heated for 2 min at 80°C (HDS) were added to pasteurized, reconstituted frozen concentrated orange juice at 5 U · mL^?1 of pectinmethylesterase. Samples were incubated either at 25°C for 14 days or 4°C for 28 days and periodically sampled to determine the effects of tissue extracts on juice cloud stability. Tissue specific differences were observed for the rate of juice cloud precipitation and among the HDS, DS, and DP fractions of a given tissue. HDS fractions destabilized juice cloud more rapidly than DS or DP at both 25 and 4°C.     

Enhanced Hyaluronic Acid Production of Streptococcus zooepidemicus by Shifting Dissolved Oxygen Level Based on Broth Rheology and Oxygen Mass Transfer Characteristics

This research focused on a dissolved oxygen (DO)-shifting strategy to enhance the production of hyaluronic acid (HA) by Streptococcus zooepidemicus. In this strategy, DO was controlled at above 10 ± 1% during 0–8 h and at 5 ± 0.5% during 8–18 h. The DO-shifting strategy increased the consistency index and oxygen mass transfer coefficient and decreased the flow behavior index n. With the proposed DO-shifting strategy, HA production increased from 5.0 ± 0.1 g/L to 6.3 ± 0.1 g/L. The enhanced HA production was attributed to the alleviation of carbon and energy competition between cell growth and HA synthesis.     

Industrial orange juice debittering: Impact on bioactive compounds and nutritional value

The impact of an industrial debittering process (DP) on nutritional and bioactive compounds in orange juice (OJ) was studied. The DP was aimed at removing bitter components in OJ by physical adsorption in a resin. The levels of bioactive compounds (carotenoids, ascorbic acid and phenolics), total antioxidant activity and the colour in the fresh orange juices (non-debittered) and in the debittered counterparts were measured. The results demonstrated that the carotenoid contents were not significantly affected by the treatment. However, the debittered orange juices showed a reduction (p < 0.001) of 26% in ascorbic acid, 32% in hydroxycinnamic acids, 28% of flavones and 41% of flavanones in comparison with the non-treated juices. The antioxidant activity of the hydrophilic fraction (HF) was significantly higher (p < 0.05) in untreated juice than in debittered juices. Some colour parameters (L^∗, a^∗ and h_ab) were also affected. Discriminant analysis revealed that the canonical function related to the levels of HF compounds allowed a 100% correct classifications of the different types of juices.     

Selection of lactic acid bacteria for acidification of brown juice (grass juice), with the aim of making a durable substrate for L‐lysine fermentation

BACKGROUND: Brown juice is a waste product from the green crop‐drying industry. Heating and pressing of green crops prior to drying produces a juice rich in nutrients, which can be converted to a stable universal fermentation medium by lowering its pH to 4.0–4.5 via lactic acid fermentation. The aim of this study was to select a strain of lactic acid bacteria for industrial acidification of brown juice. RESULTS: Several strains were tested in fermentation experiments and Lactobacillus salivarius ssp. salivarius DSM 20555 was found to be the best choice. It showed high growth rates at temperatures ranging from 40 to 48 °C, with an optimum temperature of 46 °C (µ_max = 2.2 h^?1), and maintained a high productivity at pH 4.0 in continuous fermentation. The highest productivity of 7.23 g L^?1 h^?1 was found at a dilution rate of 1.0 h^?1. CONCLUSION: With today's increased focus on utilisation of residues from food and agro‐industry, coupled with restrictions on their use as fertiliser for farmlands, lactic acid fermentation could play a significant role in conservation of these nutrient‐rich liquids. This study shows that Lb. salivarius ssp. salivarius DSM 20555 is a very promising micro‐organism for use in such a process. Copyright © 2008 Society of Chemical Industry     

Identification of Natural Antimicrobial Substances in Red Muscadine Juice against Cronobacter sakazakii

ABSTRACT: Red muscadine (Vitis rotundifolia Michx.) juices with natural organic, phenolic acids and polyphenol compounds were tested against Cronobacter sakazakii. The concentration of total phenolic compounds of commercial baby juices ranged from 176.7 to 347.7 mg/mL. Commercial baby juices showed poor antimicrobial activity, reducing less than 1-log of C. sakazakii in juice samples for 2 h at 37 °C. Red muscadine juices, regardless of processing methods (filtration, pasteurization, and sterilization), achieved a 6-log reduction of C. sakazakii in the same time period (2 h). The mixture of synthetic organic acids (malic and tartaric acids) and polyphenolic acid (tannic acid) showed strong antimicrobial activity against C. sakazakii. Among synthetic organic acids, tannic acid was undetected in commercial baby juices. Tannic acid showed the highest antimicrobial activity (1.4- to 3.8-log reduction) against C. sakazakii, while malic and tartaric acids showed less than 0.5-log reduction. These results suggest that red muscadine juice could be utilized as a natural antimicrobial in baby food formulations to inhibit C. sakazakii.     

Temperature–time relationships for thermal inactivation of pectinesterases in orange juice

The first‐order kinetic model of a two‐component system was applied to calculate the necessary parameters using the commercial Mathcad program package during the experimental thermal pasteurisation of Valencia orange juice. Thermostable and thermolabile pectinesterases, accounting for 6.6 and 93.4% of the total enzyme population in the juice respectively, showed a 5.63 °C Z_s value and a 9.54 °C Z_l value respectively from the thermal destruction curves at temperatures ranging from 75 to 90 °C. The calculated Z_s values were consistent with the literature values for Valencia orange juice. The calculated and experimental non‐linear thermal pasteurisation curves for orange juice were also in good agreement at temperatures between 75 and 90 °C. © 2003 Society of Chemical Industry