Feasibility of using dialysis for determining calcium ion concentration and pH in calcium-fortified soymilk at high temperature

Abstract: Dialysis was performed to examine some of the properties of the soluble phase of calcium (Ca) fortified soymilk at high temperatures. Dialysates were obtained while heating soymilk at temperatures of 80 and 100 °C for 1 h and 121 °C for 15 min. It was found that the pH, total Ca, and ionic Ca of dialysates obtained at high temperature were all lower than in their corresponding nonheated Ca‐fortified soymilk. Increasing temperature from 80 to 100 °C hardly affected Ca ion concentration ([Ca²⁺]) of dialysate obtained from Ca chloride‐fortified soymilk, but it increased [Ca²⁺] in dialysates of Ca gluconate‐fortified soymilk and Ca lactate‐fortified soymilk fortified with 5 to 6 mM Ca. Dialysates obtained at 100 °C had lower pH than dialysate prepared at 80 °C. Higher Ca additions to soymilk caused a significant (P≤ 0.05) reduction in pH and an increase in [Ca²⁺] of these dialysates. When soymilk was dialyzed at 121 °C, pH, total Ca, and ionic Ca were further reduced. Freezing point depression (FPD) of dialysates increased as temperature increased but were lower than corresponding soymilk samples. This approach provides a means of estimating pH and ionic Ca in soymilks at high temperatures, in order to better understand their combined role on soymilk coagulation.     

Effect of extrusion conditions on iron stability and physical and textural properties of corn snacks enriched with soybean ferritin

Soybean sprouts cultured in 20 mm FeSO₄ were introduced into corn snacks (1.75–3.50%) to supplement iron. The effect of extrusion process on the ferritin iron stability and on product quality was studied. Iron stability in these fortified snacks depended mainly on feed moisture levels, with the best results seen when the feed moisture and temperature were 12% and 110 °C, respectively. Lower feed moisture was beneficial to hardness, expansion ratio and bulk density, while lower temperature increased snack hardness and density, while worsening the expansion ratio. The snacks’ water absorption was strongly and directly dependent on the temperature, while their solubility mainly depended inversely on feed moisture. All of the variables tested altered the colour of the snacks. The conditions that were best for producing the ferritin‐fortified snacks – 12% feed moisture, and temperature equal than or less to 140 °C – may yield a product with the desired quality features.     

Vitamin A stability in triple fortified extruded,artificial rice grains containing iron,zinc and vitamin A

Multi‐micronutrient‐fortified rice could be an effective and sustainable approach to combat micronutrient deficiencies. We produced hot‐extruded artificial rice grains fortified with 10 mg iron (as micronised ground ferric pyrophosphate), 5 mg zinc (as oxide, sulphate or carbonate) and 750 μg vitamin A/g [as retinyl palmitate (RP)] and measured RP stability. The rice was designed to be mixed 1:200 with natural rice. Mean RP losses were 5.3% during extrusion, 28.5% during storage and 9.8% during cooking. Storage losses after 18 weeks at 30 °C in plastic packages exposed to light were ca 40% with iron and zinc causing no further losses. In aluminium packages (no light), mean RP losses were ca 20%. Iron, but not zinc, increased RP degradation. Zinc sulphate increased the negative effect of iron. The relatively good stability of RP during hot extrusion can be explained by the closed surface and dense nature of the artificial grain protecting RP from oxidation.     

Improvement in emulsifying properties of soy protein isolate by conjugation with maltodextrin using high‐temperature,short‐time dry‐heating Maillard reaction

Soy protein isolate (SPI)–maltodextrin (MD) conjugates were synthesised using Maillard reaction under high‐temperature (90, 115 and 140 °C), short‐time (2 h) dry‐heating conditions. The loss of free amino groups in proteins and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) profile confirmed that SPI‐MD conjugates were formed and higher dry‐heated temperatures could increase the glycosylation degree. The emulsifying properties of SPI and SPI‐MD conjugates were evaluated in oil‐in‐water emulsions. The emulsions stabilised with SPI‐MD conjugates synthesised at 140 °C exhibited higher emulsifying stability and excellent storage stability against pH, ionic strength and thermal treatment compared with those synthesised at 90 °C, 115 °C and SPI stabilised emulsions. This might be due to a greater proportion of conjugated MD in SPI‐MD conjugates synthesised at 140 °C because of the higher glycosylation degree, and more conjugated MD on the droplet surface could provide steric effect and enhance the stability of the droplets in the emulsions.     

Controlling denaturation and aggregation of whey proteins during thermal processing by modifying temperature and calcium concentration

Whey protein isolate solutions (8.00 g protein/100 g; pH 6.8) were treated for 2 min at 72, 85 or 85 °C with 2.2 mM added calcium Ca to produce four whey protein systems: unheated control (WPI‐UH), heated at 72 °C (WPI‐H72), heated at 85 °C (WPI‐H85) or heated at 85 °C with added Ca (WPI‐H85Ca). Total levels of whey protein denaturation increased with increasing temperature, while the extent of aggregation increased with the addition of Ca, contributing to differences in viscosity. Significant changes in Ca ion concentration, turbidity and colour on heating of WPI‐H85Ca, compared to WPI‐UH, demonstrated the role of Ca in whey protein aggregation.     

The influence of enzymatic cross‐linking of proteins on the Maillard reaction in milk

The influence of transglutaminase (TGase) on the Maillard reaction was investigated in skimmed milk samples during heat treatment. TGase‐treated and control samples were heated at 80, 120 and 140 °C for 1, 5, 15, 30, 40 and 60 min. Compared with the TGase‐treated samples heated at 80 and 120 °C, the sample heated at 140 °C showed a larger decrease in furosine concentration. It was also found that TGase did not affect the formation of hydroxymethylfurfural and lactulose at 120 °C, whereas their concentrations increased in the presence of TGase at 140 °C. It was concluded that blockage of lysine residues via enzymatic cross‐linking of milk proteins had a limited effect on the Maillard reaction.     

A preliminary study about the influence of high hydrostatic pressure processing on the physicochemical and sensorial properties of a cloudy wheat beer

High hydrostatic pressure (HHP) (400 MPa/15 min, 500 MPa/10 min, 600 MPa/5 min at 20 °C) and heat (60 °C/15 min) processing of wheat beers were evaluated by examining their impacts on microorganisms, colloidal haze, flavour, foam stability and shelf‐life prediction during 84 days of storage at 20 °C. The results obtained showed that the microbiological stability of HHP beers was comparable with heat‐treated samples, and the development of both aerobic bacteria and lactic acid bacteria was inhibited for 84 days of storage. The main parameters of the wheat beer, such as ethanol content, original extract, pH, bitterness and viscosity, were scarcely affected by either treatment compared with the control samples; however, heat pasteurization increased the colour value. Heat‐pasteurized beer resulted in an increase in the phenethyl alcohol concentration and a decrease in isoamyl acetate and ethyl acetate levels compared with the HHP samples. These treatments did not affect the amount of 4‐vinylguaiacol and 4‐vinylphenol in the beer. The HHP‐treated beers had higher colloidal haze and foam stability values than the heat‐pasteurized beers. Dynamic light scattering analysis showed that HHP treatments at 500 MPa/10 min resulted in smaller and more uniform particle sizes, which had a positive effect on beer haze stability during storage. Copyright © 2016 The Institute of Brewing & Distilling     

Evaluation of the effect of Ultra Rice® EDTA supplementation on the soluble iron,visual acceptance and vitamin A stability of commercial milled rice blends

The addition of NaFeEDTA at only 5% of total iron to ferric pyrophosphate‐fortified Ultra Rice^® increased the in vitro soluble iron ten‐fold. Ultra Rice^® formulated with NaFeEDTA at 2–7% of total iron, or with Na₂EDTA·2H₂O at 0.5× the total iron equivalents, increased the soluble iron seven‐ to thirty‐fold. The colour of the batches was acceptable through 20 weeks at 21 °C, but colour stability needs to be evaluated under authentic storage conditions. Although only 34–46% of the initial vitamin A remained after extrusion, 18‐week storage at 30 °C/70% relative humidity, and simulated cooking, there were indications that losses could be decreased by raising the pH (to ~5) and/or using a better protected vitamin A ingredient. The enhancement of soluble iron afforded by low‐level NaFeEDTA or Na₂EDTA·2H₂O supplementation suggests that this fortification strategy may merit further study as a means of increasing absorbable iron in Ultra Rice^®.     

Gallic Acid Grafted Chitosan Has Enhanced Oxidative Stability in Bulk Oils

Gallic acid (GA) was grafted in chitosan and the effects of GA grafted chitosan (GA‐g‐CS) on the oxidative stability in bulk oil was tested at 60 and 140 °C. To text oxidative stability in oils, headspace oxygen content, conjugated dienoic acid (CDA) value, p‐anisidine value (p‐AV), and acid value were determined. Chitosan itself did not show antioxidative or prooxidative effects in oils at 60 °C. However, GA‐g‐CS and GA acted as antioxidants at 60 °C. At 140 °C heating with moisture supplied condition, different results were observed. GA‐g‐CS acted as antioxidants based on the results of CDA and p‐AV. However, chitosan showed the highest oxidative stability based on results of acid value and brown color formation at 140 °C. This could be due to reduction of moisture content by chitosan. GA was continuously released from GA‐g‐CS in bulk oil. This might have provided extra antioxidant activities to oils.     

Degradation kinetics of rebaudioside A in various buffer solutions

Rebaudioside A is a noncaloric high‐intensity sweetener extracted from Stevia rebaudiana. For it to be used in foods, rebaudioside A needs to be stable during processing and storage. This study evaluated the kinetics of rebaudioside A degradation in 0.02 and 0.1 m citrate and phosphate buffer solutions at pH 3, 5 and 7 stored at 20, 30 and 40 °C for 9 months. At pH 3 and temperatures less than 30 °C, degradation was slow (i.e. less than 6% loss in 6 months) and not affected by buffer type or buffer concentration. At pH 7, the degradation of rebaudioside A increased dramatically in phosphate buffer (losses of up to 25% in 6 months at 30 °C), while remaining relatively slow in citrate buffer (less than 5% loss). The degradation rates at pH 7 increased 2.6 times as the concentration of phosphate buffer increased. For optimum stability of beverages containing rebaudioside A, formulations with lower concentrations of citrate buffer stored at lower temperatures are recommended.     

L-Ascorbic Acid and Its 2-Phosphorylated Derivatives in Selected Foods: Vitamin C Fortification and Antioxidant Properties

Two carbonated beverages fortified with 30 mg L-ascorbic acid (AsA) equivalents/250 mL in the form of L-ascorbate 2-monophosphate (AsMP) and stored at 25–35°C retained more vitamin C than those with added AsA or L-ascorbate 2-polyphosphate (AsPP). Breads enriched with ferrous iron and fortified with 560 AsA eq./100g flour in the form of AsPP and AsA retained 40% and 5% vitamin C, respectively, after 6 davs at 25°C. Bran (40%) flakes fortified with 0.19% AsA ea. as AsMP and AsPP gave much improved retention of vitamin C during storage for 7 mo at 25–40°C and 7–11% moisture levels. The sodium salts of AsA, AsMP, and AsPP, when injected into whole eye of round beef at 0.18% AsA eq., inhibited hexanal formation after the meat was roasted and stored for 5 days at 5°C. Those sodium salts did not prevent accumulation of peroxides in peanut paste.     

The effect of protein profile and preheating on denaturation of whey proteins and development of viscosity in milk protein beverages during heat treatment

The effect of preheat temperature (63 or 77 °C for 30 s; final heat 120 °C for 30 s) and casein to whey protein ratio on the physical characteristics of 3.3%, w/w, dairy protein beverages was investigated. Dispersions preheated at 77 °C had lower viscosity than dispersions preheated at 63 °C. Casein‐containing dispersions had significantly lower levels of α‐lactalbumin denaturation than whey protein‐only dispersions. A higher proportion of casein improved the thermal stability of protein dispersions. Overall, alteration of preheat temperature and casein to whey protein ratio can influence dairy beverage quality, with increasing levels of casein reducing physical changes due to heat treatment.     

Heat stability of radio frequency dielectric heat treated low heat and high heat nonfat dry milk

The heat stability of low (LH) and high heat (HH) nonfat dry milk (NDM) that received a radio frequency dielectric heat (RFDH) treatment at 75, 80 or 85 °C for different periods of time (between 43 and 125 min) was assessed. NDM was reconstituted at 3.5% (w/w) protein. Heat stability was assessed at 140 °C by recording the heat coagulation time. Samples were evaluated at native pH, and adjusted pH from 6.4 to 7.2. LH samples heated to 75 °C or 80 °C showed greater heat stability than non-treated LH at pH 6.4 to 6.8. Data suggest that RFDH treatment of LH induced associations between whey proteins and casein micelles, which increased the heat stability in this pH region. The same effect was not observed in the HH samples, suggesting different reactions may be induced. Dry heating NDM may affect protein associations differently from liquid systems, depending upon the conditions.     

Increasing the oxidative stability of soybean oil through fortification with antioxidants

Vegetable oils high in polyunsaturated fatty acids (PUFA), like soybean oil (SO), are known for lowering the risk of consumers for contracting cardiovascular disease as well as improving cognitive health. However, they are more susceptible to lipid oxidation than recently introduced high‐oleic cultivars like high‐oleic sunflower oil (HOSFO). Thus, the objective of this study was to increase the stability of PUFA oils to maintain the aforementioned health benefits by supplementing them with industrially relevant antioxidant compounds that prevent or delay oxidation during food production and storage. Herein, a variety of synthetic and natural antioxidants tested alone or in mixtures was screened to bring the stability of SO closer to that of HOSFO. Oils were stored under accelerated conditions (35 °C) in the dark for 28 weeks, and the evolution of primary (hydroperoxides) and secondary (hexanal) lipid oxidation products was monitored. Oxidative stability index data showed that addition of 300 ppm of ascorbyl palmitate (AP) stabilised SO to the greatest magnitude. Further, a combination of AP (300 ppm) and M‐TOC (1000 ppm) was able to limit hydroperoxide and hexanal formation in SO at 35 °C for 12 weeks. It was demonstrated that assessing multiple quality parameters for lipid stability are a necessary undertaking.     

Gelation enhancement of soy protein isolate by sequential low‐ and ultrahigh‐temperature two‐stage preheating treatments

The effects of combined two heating steps with low (LT, 60 °C for 1 h) and ultrahigh (UHT, 130 or 140 °C for 4 s) temperatures on the thermal gelation of soy protein isolate (SPI) were studied. UHT pretreatments significantly increased protein solubility and enhanced the gelling potential of SPI. Yet, the two‐stage preheating treatment with LT and then UHT‐130 °C had a most remarkable effect: the gel strength of the SPI₆₀₊₁₃₀ sample was, respectively, 1.45‐, 1.64‐ and 3.19‐fold as strong as those of SPI₆₀, SPI₂₅₊₁₃₀, and SPI₂₅. In comparison with single LT or UHT treatments, this two‐stage heating also produced greater amounts of soluble protein aggregates stabilised predominantly by disulphide bonds and hydrophobic forces, contributing to the improved gel network structure.     

Improved physical stability of docosahexaenoic acid and eicosapentaenoic acid encapsulated using nanoliposome containing α‐tocopherol

This study aimed to develop a nanoliposomal formulation containing α‐tocopherol loaded with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and to characterise the formulation by its physical stability. For this purpose, different nanoliposomal formulations with dipalmitoyl phosphocholine were prepared using a modified thin‐film hydration method and evaluated by particle size, polydispersity index (PDI), transmission electron microscopy, differential scanning calorimetry and determining the encapsulation efficiencies of DHA and EPA. A physical stability study was conducted by investigating the change in the vesicle encapsulation efficiency, particle size, PDI and shape when stored at 4, 30 and 40 °C for 3 months. High encapsulation efficiency of DHA and EPA (89.1% ± 0.6% and 81.9% ± 1.4%) and appropriate particle size (82 ± 0.8 nm) were obtained for liposomes composed of α‐tocopherol. The optimum formulation was stable for 90 days when kept at 4 °C. This study demonstrated that α‐tocopherol had a protective effect on the physical stability of the nanoliposomes containing DHA and EPA.     

Effects of temperature,pH and light on the stability of aloin A and characterisation of its major degradation products

This study explored the stability and degradation products of aloin A under varying pH, temperature and light conditions usually encountered in processing. The stability of aloin A was significantly affected by temperature and pH. The content of aloin A decreased by more than 90% within 12 h at 50 °C and within 6 h at 70 °C, respectively. A significant decrease in stability was also observed at higher pHs. At pH 8.0, less than 2% of aloin A remained within 12 h. However, aloin A exhibited good stability at acidic pH levels with 94% remaining at pH 2.0 for 14 days. Light exerted no influence on the stability during the experimental period (14 days). Aloe‐emodin, elgonica‐dimers A and B were characterised as major degradation products of aloin A at pH 5.0 or below, and elgonica‐dimers were mainly formed at 4 °C as well. 10‐hydroxyaloins A and B were found under any condition except at pH 2.0 and 3.0, and they were mainly formed under high temperature, neutral‐basic and any light conditions.     

Effects of Calcium Addition on Stability and Sensory Properties of Soy Beverage

Pasteurized or thermally processed soy beverages (6% soy solids) were fortified to a comparable level of cow's milk with 25 mM (or 30 mM) calcium using mixtures of calcium citrate and tricalcium phosphate. These fortified pasteurized products had acceptable sensory properties. Addition of these calcium salts did not adversely affect protein stability of the beverage. Calcium citrate addition caused a decrease in beverage pH and viscosity. Thermally processed (still retort and agitort) canned beverages containing calcium salts were stable for 6 months when stored at 1°C or at room temperature.     

The stability of vitamin A in fortified palm olein during extended storage and thermal treatment

The stability of vitamin A in Refined Bleached Deodorised Palm Olein (RBDPOL) was studied for 24 months. Vitamin A decreased with time, temperature and thermal treatment (frying/cooking). RBDPOL fortification was observed over several temperature ranges, using PET, nylon and HDPE commercial packaging materials. After 24 months, the following vitamin A contents of 39–43 IU g^?1 (39–45%) at 16–20 °C; 35–40 IU g^?1 (43–49%) at 24–29 °C; and 28–39 IU g^?1 (45–73%) at 24–45 °C were detected at the respective temperature ranges. Results showed stability of vitamin A fortified RBDPOL vegetable oil was not stable over typical shelf life (12 months). Depletion of vitamin A accelerated when the RBDPOL vegetable oil was subjected to high temperature thermal treatment.     

Effect of additives on mesophilic α-amylase and its application in the desizing of cotton fabrics

An investigation was carried out on thermal stability of α-amylase. The influence of various additives (calcium acetate, sodium lactate, L-histidine, and water-soluble chitosan) on the stability of α-amylase was studied. Results showed the inactivation behavior of α-amylase with or without additives all followed the first-order kinetics. All additives (Ca2+, sodium lactate, L-histidine, and water-soluble chitosan) displayed good stabilizing effect on α-amylase lower than 80 °C, and only water-soluble chitosan had an efficient stabilizing effect on α-amylase when the treatment temperature exceeds 80 °C. All additives improved the catalytic activity of α-amylase at 70–90 °C, and the appearance of water-soluble chitosan increased the catalytic activity of α-amylase at 90 °C sharply. A desizing ratio of 68.42% was obtained by treating the cotton fabrics in the buffer solution at 100 °C without α-amylase. To obtain a desizing ratio exceed 95% when fabrics were treated at 100 °C for 10 min, the addition of water-soluble chitosan saves 2/3 α-amylase dosage. Moreover, water-soluble chitosan showed a further improvement in desizing effect than the additive of calcium acetate.