Cold‐triggered/heat‐destroyed emulsions composed of phospholipids and triacylglycerols as thermal history indicators for cold‐chain distribution systems

BACKGROUND: Recently, cold‐chain distribution systems have come to play important roles in worldwide food processing/storage/transportation networks. To ensure the maintenance of the quality and safety of foods, it is necessary to develop thermal history indicators for products involved in cold‐chain distribution systems. To provide a record of the occurrence of a high‐temperature event during a cold‐chain system, a temperature‐related phase change in a material within the indicator is needed to indicate that the high‐temperature event occurred. Preferentially, for safety, the materials of the indicators should be edible and easy to handle. It should be possible to store the indicators at ambient temperature before use, and they should be triggered automatically just by cooling at the start of a cold‐chain system. Furthermore, if the indicator is heated even once during the cold‐chain distribution system, its appearance must be irreversibly altered to provide evidence of the high‐temperature experience. RESULTS: Based on the edible materials composed of lyso‐lecithin (15 g), lecithin (2 g), triacylglycerol (150 g), and water, we successfully constructed a stable emulsion that could be triggered just by cooling to 4 °C or lower for more than 12 h. After triggering, it was immediately destroyed by heating up to 20 °C or higher. Furthermore, the mechanism of cold‐triggering and heat‐destruction has been studied by nuclear magnetic resonance. CONCLUSION: The cold‐triggered/heat‐destroyed emulsion should be applied as a new thermal history indicator that can be automatically triggered just by cooling down and irreversibly change its appearance after a high‐temperature experience in cold‐chain distribution systems. Copyright © 2008 Society of Chemical Industry     

Sensitivity analysis of a small‐volume objective heat stability evaluation test for recombined concentrated milk

To quantify the stability towards heat coagulation, an objective test method was developed. The combined use of emulsion preparation by microfluidisation and heat stress by immersion of capped samples in an oil bath enabled small‐volume heat stability evaluation of milk formulations. From experimental data, it became obvious that a heating period of about 9 min was necessary for the samples to acquire the requested temperature (i.e. 121 °C). Similarly, both viscosity and particle size analyses showed an increased aggregation tendency when samples were heated for longer than 10 min, whereby their positioning and the cooling medium seemed to have an insignificant effect.     

Oxidative stabilization of cold‐pressed sunflower oil using phenolic compounds of the same seeds

It is known that sunflower seeds are rich in phenols, constituting approximately 1–3 g per 100 g of seeds. The principal phenol is chlorogenic acid (CGA), followed by caffeic acid (CA) and lower quantities of several other compounds. On the contrary, it is known that phenols are present only in trace amounts in cold‐pressed sunflower seed oils. In this study, the possibility of improving the oxidative stability of cold‐pressed sunflower oil is evaluated using phenolic substances constitutive of seeds. Phenols, extracted from two different dehulled sunflower seed samples, were identified, measured and added to a cold‐pressed sunflower oil and compared with butylated hydroxyanisole (BHA), pure CGA and pure CA. Raw phenolic extract (RPE) was composed of CGA exclusively, whereas CA was present only in traces in its free form was not present. On the contrary, hydrolysable phenol acids (HPAs) were constituted prevalently from CA, released by CGA alkaline hydrolysis. The stabilization effect on oil oxidation at 110 °C was evaluated as 41% and 118% for RPE and HPAs respectively with respect to the control. At 30 °C, no significant differences were recorded between the two seed extracts. Their antioxidant effect was lower than that at 110 °C and evaluated to be, on average 13%. In comparison with BHA, at 30 °C, both seed extracts were more effective than this synthetic phenol; at 110 °C, the antioxidant effect of RPE and BHA was similar, whereas HPA was significantly more effective than BHA. In conclusion, this study demonstrates that the phenols present in sunflower seeds can be considered natural antioxidants suitable for stabilizing the oxidation of cold‐pressed sunflower oil, at both low and high temperatures. Copyright © 2003 Society of Chemical Industry     

Variation in 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and fructo‐oligosaccharide (FOS) status in onion bulbs. Influence of temperature and storage time

Effects of storage temperature and duration on 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and trisaccharide (Tri) and fructo‐oligosaccharide (FOS) status in onion bulbs var Tenshin kept for 24 weeks at 10 and 20 °C were investigated. 1‐FEH activity peaked sharply after 10 weeks and seemed to be triggered by a decrease in sucrose content. 1‐KH activity increased during the first 8 weeks and remained stable during the last 8 weeks. Contents of Tri, FOS and total FOS decreased abruptly during the first 8 weeks; however, at 10 °C, contents of Tri, FOS (DP 3–12) and total FOS were lower than those at 20 °C. The consumption rate of fructo‐oligosaccharides also appeared to be higher at 20 °C than at 10 °C, despite the slight degradation in activities observed at this low temperature. 1‐FEH seems to be under the control of a triggering signal which induces its activity, and sucrose seems to be this biochemical signal which initiates dormancy release and the onset of sprouting, as found previously. Thus changes in carbohydrates seem to be a strong indicator of the end of the dormant state of the bulb and the beginning of the sprouting period. Copyright © 2004 Society of Chemical Industry     

Effect of a cold‐active pectinolytic system on colour development of Malbec red wines elaborated at low temperature

The effect of a new cold‐active pectinolytic system on colour of Malbec wines was studied under the following winemaking conditions: (i) fermentation at low temperature (20 °C) and (ii) prefermentative cold maceration (PCM) (5 °C–7 days) followed by traditional fermentation (28 °C). The pectinolytic system was mainly composed of polymethylgalacturonase and pectin lyase activities, detected under similar conditions to those in winemaking (pH 3.6–20 °C). The results show that the enzyme system significantly accelerated colour extraction by reducing the maceration time necessary for vinification at low temperature and shortening the PCM stage. Enzyme‐treated wines exhibited better chromatic parameters than their controls at devatting and after 6 months of storage. The cold‐active enzyme compensated the decrease in colour extraction due to the low maceration temperature, achieving high‐quality wines with chromatic characteristics similar to those of traditional wines.     

Effect of cold‐shock treatment on chilling injury in mango (Mangifera indica L. cv. ‘Wacheng’) fruit

To investigate how cold shock may affect chilling injury in mango fruit (Mangifera indica L. cv. ‘Wacheng’), the fruit were treated for 3, 4 or 5 h at 0 °C, or treated for 8, 10 or 12 h at 4 °C, respectively, then transferred to 20 °C for 20 h prior to being stored at 2 °C, 85–95% RH. The chilling injury index of mango treated at 0 °C for 4 h was 59.7% lower than that of the control fruit directly stored at 2 °C, 85–95% RH. Some attributes were assayed in the fruit treated at 0 °C for 4 h. Ion leakage of the cold‐shock fruit at 0 °C for 4 h was 16% or 10% lower than that of the control on day 9 or day 12 of storage, respectively. Malondialdehyde content of the cold‐shocked fruit was 70% or 50% lower than that of the control on day 6 or day 12 of storage at 2 °C, respectively. Activities of catalase, ascorbate peroxidase, and contents of glutathione and phenolic compounds in the fruit during storage were all markedly enhanced by the cold‐shock treatment, whereas activities of superoxide dismutase, glutathione reductase and content of ascorbic acid in the mango were slightly influenced by the cold‐shock treatment. These results suggest that cold‐shock treatment may hold promise as an alternative approach to reduce chilling injury in mango fruit during cold storage. Copyright © 2006 Society of Chemical Industry     

Optimization of Microencapsulation of Fish Oil with Gum Arabic/Casein/Beta‐Cyclodextrin Mixtures by Spray Drying

Fish oil was encapsulated with gum arabic/casein/beta‐cyclodextrin mixtures using spray drying. The processing parameters (solids concentration of the barrier solutions, ratio of oil to barrier materials, emulsifying temperature, and air inlet temperature) were optimized based on emulsion viscosity, emulsion stability, encapsulation efficiency, and yield. A suitable viscosity and high emulsion stability could increase encapsulation efficiency and yield. Encapsulation efficiency and yield were significantly affected by all the 4 parameters. Based on the results of orthogonal experiments, encapsulation efficiency and yield reached a maximum of 79.6% and 55.6%, respectively, at the optimal condition: solids concentration of 35%, ratios of oil to barrier materials of 3:7, emulsifying temperature of 55 °C, and air inlet temperature of 220 °C. Scanning electron microscopy analysis showed that fish oil microcapsules were nearly spherical with a smooth surface with droplet size ranging from 1 to 10 μm.     

The loss of OSA‐modified starch emulsifier property during the high‐pressure homogeniser and encapsulation of multi‐flavour bergamot oil by spray drying

The encapsulation of bergamot oil by spray drying was investigated by using octenyl succinylated waxy maize starch as wall material and bergamot oil as core. The bergamot oil is majorly composed of d‐limonene, linalool and linalyl acetate. High‐speed and high‐pressure homogenisers were used as major tools of emulsification process. The results indicated that some chemical functional groups were lost during the high‐pressure homogenisation. Moreover, larger emulsion droplet size (5–10 μm) was observed when emulsion passed through high‐pressure homogeniser. Meanwhile, the saturation of carrier solution before preparing the emulsion was also important to produce the encapsulated flavour powder by spray drying. The optimal value of air inlet temperature at 160 °C to give the highest flavour retention and the lowest surface oil content was observed. Furthermore, the retention of linalool after spray drying was higher than 100%. The transformation of each flavour might occur.     

Stability of oil‐in‐water emulsions as influenced by thermal treatment of whey protein dispersions or emulsions

Properties of whey protein concentrate stabilised emulsions were modified by protein and emulsion heat treatment (60–90 °C). All liquid emulsions were flocculated and the particle sizes showed bimodal size distributions. The state and surface properties of proteins and coexisting protein/aggregates in the system strongly determined the stability of heat‐modified whey protein concentrate stabilised emulsions. The whey protein particles of 122–342 nm that formed on protein heating enhanced the stability of highly concentrated emulsions. These particles stabilised protein‐heated emulsions in the way that is typical for Pickering emulsions. The emulsions heated at 80 and 90 °C gelled due to the aggregation of the protein‐coated oil droplets.     

Inverse Emulsion of Starch‐graft‐Polyacrylamide

An inverse emulsion of cationic starch‐graft‐polyacrylamide was prepared by inverse emulsion polymerization and a subsequent Mannich reaction. The copolymerization was carried out using potassium persulfate as initiator. The reaction conditions and factors affecting emulsion stability were studied. Experiments showed that a high solids content, a high cationic degree and a stable latex can be obtained under the following condition: A molar ratio starch/acrylamide/formaldehyde/dimethylamine of 0.11:1:1:1.2; a stable inverse emulsion system; graft copolymerization of starch and acrylamide for 2‐3 h at 50 °C; pre‐formation of an aldehyde‐amine adduct, which is subsequently dropped into an inverse emulsion of starch‐graft‐polyacrylamide. The reaction temperature was 45 °C, the reaction time was 3‐4 h, and the pH was 5.5.     

Processing and storage effects on the oxidative stability of hemp (Cannabis sativa L.) oil‐in‐water emulsions

Hempseed oil was used to form oil‐in‐water emulsions, and the effect of heating, storage and light on the oxidative stability of the dispersed phase was investigated. Lipid oxidation rate increased following thermal processing and light exposure, whereas oxidation markers remained relatively unaffected during emulsions storage at 4 °C for 10 days. Induction times of the emulsions were reduced up to 26% and the concentration of thiobarbituric acid reactive substances increased up to 4.5‐fold, depending on the processing conditions. Selected berries as potential sources of natural antioxidants were screened for polyphenol and anthocyanin content in order to investigate their ability to retard lipid oxidation in comparison with a commercially available synthetic counterpart. Raspberry powder extract significantly improved the oxidative stability of hemp‐based emulsion compared with the control and was even more effective compared to a synthetic antioxidant when samples were subjected to heat treatment.     

Use of time–temperature superposition to study the rheological properties of cheese during heating and cooling

The objective of this study was to investigate the time–temperature superposition behaviour of the rheological properties of cheese during heating and cooling. A standard part‐skim Mozzarella cheese and a fat‐free cheese were used for the study. Fourier transform mechanical spectroscopy was used to simultaneously study the rheological properties over a range of frequencies from 0.08 to 8 Hz while samples were being heated from 10 to 90 °C or cooled from 90 to 10 °C at the rate of 1 °C min^?1. Master curves of storage modulus (G′), loss modulus (G′′) and loss tangent were obtained using a reference temperature of 70 °C.     

On the temperature reversibility of the viscoelasticity of acid-induced sodium caseinate emulsion gels

Viscoelastic properties of acid-induced sodium caseinate emulsion gels have been investigated using a controlled shear stress rheometer. Gelation was introduced by addition of acidulant glucono-δ-lactone (GDL) at three different temperatures (5, 25 and 45°C). It was found that the gelation temperature has a significant effect on the rate of gelation and on the dynamic moduli of the emulsion gels. The rheology of these emulsion gels was investigated over the temperature range 5–45°C. The viscoelasticity of the emulsion gel prepared at 45°C was temperature reversible, suggesting that the temperature change only affects the strength of physical bonding within the network and not the gel microstructure. In contrast, the temperature-dependent viscoelasticity of the emulsion gel prepared at 5°C exhibited a highly irreversible character. This implies significant structural reorganization of the network during the heating stage from 5°C. Analogous temperature irreversibility has been observed in emulsion electrophoretic mobility measurements and in solution surface tension measurements of the corresponding caseinate systems at pH values near the isoelectric point of the protein.     

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.     

Mathematical modelling of the heat inactivation of trypsin inhibitors in soymilk at 121–154 °C

Response surface methodology (RSM) was used to investigate the effects of processing temperature and time on the inactivation of trypsin inhibitors (TI) in soymilk. The factorial experimental design consisted of four levels of temperature and six levels of time in a temperature range of 121–154 °C and a time interval of 10–90 s. A quadratic polynomial equation, relating log(% TI retained) as a function of heating time and temperature, was satisfactorily fitted to the experimental data by least squares regression with r² (correlationcoefficient) = 0.959. Within the range of heating times investigated, TI in soymilk was satisfactorily destroyed to 10% retained at 143 and 154 °C with 62 and 29 s heating time respectively. © 2002 Society of Chemical Industry     

Effects of CO2 and O2 shocks at high temperature on postharvest quality of cold‐stored citrus fruit

The effect of CO₂ or O₂ shocks at high temperature on the quality of citrus fruits stored at 5 °C for up to 6 weeks followed by shelf life of 1 week at 20 °C was investigated. ‘Ortanique’ and ‘Nadorcott’ mandarins exposed to 95 kPa CO₂ at 33 °C for 24 h showed apparent rind physiological disorders and a global loss of fruit quality. Exposure to CO₂ concentrations up to 50 kPa at 33 °C for 24 h did not adversely affect mandarin quality. Moreover, the treatment of mandarins and ‘Valencia’ oranges with 15 kPa CO₂ and 30 kPa O₂, respectively, both at 33 °C for 48 h, reduced weight and rind firmness loss and prevented the accumulation of fermentative volatiles on cold‐stored fruit.     

Influence of Heating and Cooling Rates on Bacillus cereus Spore Survival and Growth in a Broth Medium and in Rice

Survival, spore germination, and growth of emetic and diarrheal type strains of Bacillus cereus were evaluated in broth and rice media during heating and cooling. Samples were heated to 80°C (20C°/hr or 40C°/hr) or 90°C (ca. 900C°/hr), prior to cooling to 10°C (5C°/hr or 10C°/hr). Following heating to 80°C, growth occurred during 5C°/hr cooling. After heating to 90°C, inactivation of three strains occurred during cooling from 90 to 80°C and again from 50 to 40°C. Great variability was observed among the responses of the four strains. Emetic strains exhibited greater survival than diarrheal strains. Rice reduced low temperature inactivation, and did not favor emetic strains. Significant two and three way interactions existed among media, strains, heating and cooling rates.     

Heat‐induced coagulation of whole milk by high levels of calcium chloride

This study investigated the interaction of calcium ions and milk proteins during heat‐induced coagulation of milk. Addition of 20–200 mM calcium chloride to milk caused coagulation on heating to 70 °C. Preheating milk at 90 °C for 10 min or ultra‐high temperature treatment at 140 °C for 6 s increased the sensitivity of milk proteins to coagulation. The former treatment was more effective than the latter in coagulating proteins. A maximum of 98% of the protein in milk preheated at 90 °C for 10 min was coagulated by 50 mM added calcium chloride at 70 °C with holding for 5 min.     

Optimisation of process conditions for lactose hydrolysis in paneer whey with cold‐active β‐galactosidase from psychrophilic Thalassospira frigidphilosprofundus

The present study was conducted to analyse the physiochemical properties of Indian paneer whey. High concentration of minerals such as potassium, calcium, zinc and sodium, as NaCl, were observed which indicates the suitability of paneer whey in the preparation of beverages. A central composite rotatable design (CCRD) of response surface methodology (RSM) was employed to optimise the hydrolysis of lactose from whey using cold‐active β‐galactosidase of Thalassospira frigidphilosprofundus. Results indicated that 80% of lactose was hydrolysed at pH of 6.5 at 20 °C in 40 min in comparison with 40% at 30 °C. This emphasises the potential use of cold‐active β‐galactosidase in dairy industry.     

Preparation of Recombined Milk Using Modified Butterfats Containing α‐Linolenic Acid

Abstract: Modified butterfats (MBFs) were produced by lipase‐catalyzed interesterification with 2 substrate blends (6:6:8 and 4:6:10, by weight) of anhydrous butterfat (ABF), palm stearin, and flaxseed oil in a stirred‐batch type reactor after short path distillation. The 6:6:8 and 4:6:10 MBF contained 21.7% and 26.5%α‐linolenic acid, respectively. Total saturated fatty acids of the MBFs ranged from 41.4% to 47.4%. The cholesterol contents of the 6:6:8 and 4:6:10 MBFs were 21.0 and 12.1 mg/100 g, respectively. In addition, the melting points of the 6:6:8 and 4:6:10 MBFs were 32 °C and 31 °C, respectively. After preparation of recombined milks (oil‐in‐water emulsions) with MBFs, the stability of emulsions prepared with the MBFs (6:6:8 and 4:6:10) was compared to those with ABF during 10‐d storage at 30 °C. Skim milk powder (containing 1% protein) was added to prepare emulsions as an emulsifier. Microstructures of emulsions freshly prepared with the ABF and the MBFs consisted of uniform fat globules with no flocculation during 10‐d storage. With respect to fat globule size distribution, the volume‐surface mean droplet diameter (d₃₂) of the 6:6:8 and 4:6:10 MBF emulsions ranged between 0.33 and 0.34 μm, which was similar to the distribution in ABF emulsion. Practical Application: Milk, an expensive dairy food, has been widely used in various milk‐derived food products. Modified butterfats (MBFs) contain α‐linolenic acid as an essential fatty acid. Emulsion stability of recombined milks (oil‐in‐water emulsions) with MBFs was similar to that in anhydrous butterfat emulsion during 10‐d storage. They may be a promising alternative for reconstituted milks to use in processed milk‐based products.