Studies on pasting and structural characteristics of thermally treated wheat germ

In order to utilize wheat germ, a nutrient-dense by-product of wheat milling industry, in various food products, different moist and dry heat treatments were used to stabilize and to investigate its influence on protein sub-unit composition, starch pasting characteristics and structural characteristics. The raw germ contained 11% moisture, 31.4% crude protein, 18.4% dietary fibre and 7% fat. Different heat treatments, except for fluidized bed drying, inactivated the lipase activity in germ completely. On the other hand, various heat treatments inactivated lipoxygenase activity to varying extents (78–92%). Extent of gelatinisation, as assessed in electron micrographs was least in steamed and fluidized bed dried samples, while steamed and oven-dried germ and drum dried germ samples exhibited greater extent of gelatinisation. The extent of gelatinisation seemed to be more in drum-dried sample as no intact starch granule was observed. Electrophoretic pattern and sub-unit composition of germ samples remained similar, irrespective of their nature of treatment. Raw germ showed a gelatinisation temperature of 67.9 °C as measured in visco-amylograph and increased to 80.3–88.3 °C for differently treated germ samples, except for drum-dried sample. Differently heated germ samples, depending on their extent of pre-gelatinisation, gave significantly lower peak viscosity (221–268 BU) and break down values (0–9 BU).     

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     

Survival of Lipase during Manufacture of Nonfat Dry Milk

Extracellular lipases from several strains of Pseudomonas fluorescens were active against milk fat. The activity of P. fluorescens strain B52 lipase in reconstituted NDM using β-naphthyl caprylate as substrate was 70% of that found with skim milk; however, hydration of the NDM at 4°C for 12 h resulted in 85% recovery of activity. As little as .0025% (vol/vol) of P. fluorescens spent media was detected in reconstituted skim milk powder using β-naphthyl caprylate. The process of freeze-drying or spray-drying without heating had little effect on either native or P. fluorescens B52 lipase. The bacterial lipase activity was reduced by 12 to 21% and 55 to 59% in NDM treated with low heat (72°C/16 s) and high heat (110°C/2 min), respectively, while the native lipases were completely inhibited by these treatments. Both native and bacterial enzymes were stable when stored in NDM for extended periods at 20°C. In a limited study of commercial NDM samples, microbial lipase was not detected, suggesting that the quality of the raw milk was sufficiently high to restrict the presence of heat-stable lipolytic enzymes.     

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.     

Microstructure and rheological properties of whipped cream as affected by heat treatment and addition of stabilizer

Whipping cream, 36% fat, was processed at 75°C for 16 s (high-temperature short time, HTST), and 140°C for 4 s, (ultra-high temperature, UHT) with and without added stabilizer. Following heat treatment and chilling for 24 h (5°C), cream samples were whipped to maximum overrun. Structural properties were assessed through low-temperature scanning electron microscopy (LTSEM) and dynamic oscillatory testing, using a controlled stress rheometer, immediately after the cream was whipped, and again after the foam was stored for 24 h at 5°C. No differences between fresh foam treatments were observed. However, aged foams exhibited changes in microstructure because of destabilization of the foam. Differences between aged foams resulted from the addition of stabilizers and the choice of heat treatment. Microstructural differences correlated well with measured changes in rheological properties.     

Cooking influences on the palatability of roasts from the beef hip

Two experiments were undertaken to obtain factual information to serve as a basis for guidance to consumers regarding optimal preparation and cooking procedures to be utilized with beef round cuts. Experiment I compared low temperature, dry beef cookery with moist beef cookery with a dry heat finish on five different roast cuts from the beef hip. Experiment II compared four different cookery methods for their influence on palatability attributes and cooking properties of eye of round (semitendinosus) roasts. Based upon results from Experiment I, low temperature, dry heat cookery should be recommended to consumers to improve the palatability of roasts from the beef hip, providing consumers are prepared to expend twice as long to prepare roast cuts. Results from Experiment II clearly indicate method C [high temperature, covered (oven turned on to 260 °C, with 250 ml of water added after 30 min)] should not be the method of choice. Although any of the other three methods could be recommended to provide a relatively palatable product, method D [high temperature initially, subsequently reduced, uncovered (roast brushed with 5 ml of Kitchen Bouquet™, placed into a cold oven turned on to 260 °C, with 250 ml of water added after 30 min and the oven temperature reduced to 140 °C)] appears to provide a more acceptable product based upon tenderness, particularly initial tenderness, than methods A [low temperature, dry heat (140 °C oven, uncovered with no moisture added)] and B [low temperature with moisture added (160 °C oven, uncovered with 250 ml of water added initially and 50 ml of water added every 30 minutes)]. In addition 46.4 min/kg less time was required to prepare roasts with method D than with method A. Consequently, the method of choice for recommendation to consumers is method D.     

Tolerance of Sitophilus zeamais (Coleoptera: Curculionidae) to heated controlled atmosphere treatments

Combination heat and controlled atmosphere (CA) postharvest phytosanitary treatments are environmentally friendly alternatives to chemical fumigants. A controlled atmosphere/heating block system (CA-HBS) was used to rapidly assess tolerances of adult maize weevil, Sitophilus zeamais, both under regular air (RA) and CA (1% O₂ and 15% CO₂) conditions. In the RA treatment, thermal death kinetics for S. zeamais adults were determined at temperatures between 46 °C and 52 °C at a heating rate of 5 °C/min. The results showed that thermal death curves of S. zeamais adults followed a 0th-order kinetic reaction model. The required holding times for achieving 100% mortality were 165, 40, 14, and 4 min at 46, 48, 50 and 52 °C, respectively. The activation energy for killing S. zeamais adults was 526.7 kJ/mol. The effects of CA at various temperature-time combinations and heating rates on insect mortality were evaluated. The mortality of S. zeamais adults was higher under CA treatment than in the heat treatment alone. The slowest heating rate (0.1 °C/min) achieved the highest insect mortality in CA treatments but lowest mortality in RA treatments. The information obtained from the CA-HBS can be used to develop combination heat and CA treatments against S. zeamais.     

Effects of Ultraviolet Light (UV‐C) and Heat Treatment on the Quality of Fresh‐Cut Chokanan Mango and Josephine Pineapple

The effects of ultraviolet (UV‐C) and medium heat (70 °C) treatments on the quality of fresh‐cut Chokanan mango and Josephine pineapple were investigated. Quality attributes included physicochemical properties (pH, titratable acidity, and total soluble solids), ascorbic acid content (vitamin C), antioxidant activity, as well as microbial inactivation. Consumers’ acceptance was also investigated through sensory evaluation of the attributes (appearance, texture, aroma and taste). Furthermore, shelf‐life study of samples stored at 4 ± 1 °C was conducted for 15 d. The fresh‐cut fruits were exposed to UV‐C for 0, 15, 30, and 60 min while heat treatments were carried out at 70 °C for 0, 5, 10 and 20 min. Both UV‐C and medium heat treatments resulted in no significant changes to the physicochemical attributes of both fruits. The ascorbic acid content of UV‐C treated fruits was unaffected; however, medium heat treatment resulted in deterioration of ascorbic acids in both fruits. The antioxidants were enhanced with UV‐C treatment which could prove invaluable to consumers. Heat treatments on the other hand resulted in decreased antioxidant activities. Microbial count in both fruits was significantly reduced by both treatments. The shelf life of the fresh‐cut fruits were also successfully extended to a maximum of 15 d following treatments. As for consumers’ acceptance, UV‐C treated fruits were the most accepted as compared to their heat‐treated counterparts. The results obtained through this study support the use of UV‐C treatment for better retention of quality, effective microbial inactivation and enhancement of health promoting compounds for the benefit of consumers.     

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.     

Effects on microbial inactivation and quality attributes in frozen lychee juice treated by supercritical carbon dioxide

In this paper, we described the use of high-pressure carbon dioxide (HPCD) for the inactivation of natural microbes in lychee juice and evaluated its effects on lychee juice quality, compared to a conventional high-temperature, short-time (HTST) method. The HPCD treatments were carried out using a HPCD unit (8 MPa, 36 °C, 2 min), and the HTST was performed at 90 °C for 60 s. The results showed that five log reduction for yeasts and molds and total aerobic microorganisms occurred at 8 MPa for 2 min. And effects of the treatments on pH and concentrations of microbes, organic acids, titratable acidity (TA), total soluble solid (TSS), sugars, polyphenols, color, and free amino acids were also investigated. HPCD could efficiently maintain the concentration of polyphenols and original color at 8 MPa, 36 °C for 2 min. Insignificant differences in colors were observed between unprocessed and HPCD juices, while significant differences were observed between unprocessed and HTST juices. Furthermore, HTST decreased the total free amino acids, whereas HPCD caused a significant increase (increased by 45.92% at 8 MPa) (p < 0.05). The increase in total amino acids induced by HPCD treatment is beneficial for nutritional value of commercial ready-to-drink lychee juice. In general, HPCD treatment had less influence on the measured quality parameters of lychee juice than HTST treatment. Therefore, HPCD treatment could be a useful alternative to traditional heat treatment.     

Nutritional changes in maize (Zea mays) during storage at three temperatures

Nutritional changes in maize grains stored at 10, 25 and 45 °C for 6 months were studied. Significant decrease in pH and increase in titratable acidity was observed during storage of maize grains at 25 and 45 °C. Moisture contents of maize grains decreased by 25% at 25 °C and 38% at 45 °C after six months of storage. Total soluble sugars increased by 10.7% at 10 °C and 17.3% at 25 °C, whereas a 39.5% decrease was observed after 6 months storage at 45 °C. Total available lysine and thiamine contents in maize grains decreased by 13 and 9.26% at 25 °C, 16 and 20.4% at 45 °C, respectively, after 6 months of storage. Protein digestibility decreased by 5.19 and 9.0% at 25 and 45 °C, respectively, whereas decrease in starch digestibility was 9.86% at 25 °C and 15.1% at 45 °C on storage of maize grains for 6 months. However, no significant nutritional changes occurred during storage of maize grains at 10 °C.     

Effect of Infrared Blanching on Enzyme Activity and Retention of β‐Carotene and Vitamin C in Dried Mango

The objectives of this work were to evaluate infrared (IR) dry blanching in comparison with conventional water blanching prior to hot air drying of mango to inactivate polyphenol oxidase (PPO) and ascorbic acid oxidase (AAO) enzymes, and to study its effect on color change and retention of vitamin C and β‐carotene. Mango cylinders were blanched under similar temperature–time conditions either by IR heating or by immersion in a water bath during 2 min at 90 °C (high‐temperature‐short‐time—HTST) or for 10 min at 65 °C (low‐temperature‐long‐time—LTLT). After blanching mango was hot air dried at 70 °C. PPO was completely inactivated during the blanching treatments, but AAO had a moderate remaining activity after LTLT treatment (～30%) and a low remaining activity after HTST treatment (9% to 15%). A higher retention of vitamin C was observed in mango subjected to IR dry blanching, 88.3 ± 1.0% (HTST) and 69.2 ± 2.9% (LTLT), compared with water blanching, 61.4 ± 5.3% (HTST) and 50.7 ± 9.6% (LTLT). All‐trans‐β‐carotene retention was significantly higher in water blanched dried mango, 93.2 ± 5.2% (LTLT) and 91.4 ± 5.1% (HTST), compared with IR dry blanched, 73.6 ± 3.6% (LTLT) and 76.9 ± 2.9% (HTST). Increased levels of 13‐cis‐β‐carotene isomer were detected only in IR dry blanched mango, and the corresponding dried mango also had a slightly darker color. IR blanching of mango prior to drying can improve the retention of vitamin C, but not the retention of carotenoids, which showed to be more dependent on the temperature than the blanching process. A reduction of drying time was observed in LTLT IR‐blanching mango.     

Effect of Lenient Steam Injection (LSI) heat treatment of bovine milk on the activities of some enzymes,the milk fat globule and pH

This study investigated the effects of Lenient Steam Injection (LSI) treatment at temperatures 70–150 °C on the enzymatic activities of the indigenous milk enzymes alkaline phosphatase, lactoperoxidase (LPO), xanthine oxidase (XO), lipoprotein lipase (LPL) and plasmin in comparison with two reference heat treatments of 63 °C for 30 s and of 72 °C for 15 s by indirect heating. Milk fat globule (MFG) size distributions and pH were also monitored. Alkaline phosphatase, LPO, XO and LPL activities decreased with increasing LSI temperature. Plasmin activity was increased at temperatures <80 °C and decreased at temperatures above 90 °C. Milk fat globule homogenisation was observed at temperatures above 110–130 °C.     

Effect of dry heat stabilisation on the functional properties of rice bran proteins

Rice bran was stabilised by dry heat method at 120 °C for 10–60 min, and then, protein was extracted from stabilised rice bran using weak alkali method. The storage characteristics of stabilised rice bran and the influences of dry heat pretreatment on the physicochemical properties of rice bran protein isolate were also evaluated. The results indicated that dry heat pretreatment could not only prevent rancidity of rice bran effectively, but also improve some functional properties of rice bran proteins, such as emulsifying properties, oil holding capacity, and water holding capacity. However, foaming properties and protein solubility were slightly destroyed because of heating. Rice bran was pretreated at 120 °C for 10 or 20 min and then extracted at pH 9.5, and the protein yields were 50.09% and 46.98%, respectively. Therefore, the dry heat treatment at 120 °C for 10 or 20 min was a suitable alternative process in stabilisation of rice bran.     

Combined high pressure and heat treatment effectively disintegrates spore membranes and inactivates Alicyclobacillus acidoterrestris spores in acidic fruit juice beverage

The commercial potential of high pressure and thermal processing (HPTP) was investigated against Alicyclobacillus acidoterrestris spores in commercial acidic apple juice beverage and in acidified and neutral potassium buffers. With starting spore counts prior to treatments being 6.5 and 7.2 log₁₀ respectively for strains AJA 66 (D_90°C 15.4 min) and ATCC 49025 (D_90°C 8.5 min), HPTP at 600 MPa at 80 °C for 3 min provided an optimal treatment with spore viability reduced below the detection limit for both strains. HPTP at 80 °C for 1 min and HPTP at 70 °C for 3 min achieved 4.1–4.5 log₁₀ CFU/mL reduction. HPTP at 70 °C for 1 min reduced the number of viable spores by 2.0–2.5-log₁₀ CFU/mL. Flow cytometry revealed the presence of membrane-compromised spores among culturable spores following HPTP and heat alone treatments at different temperatures. Electron microscopy clearly showed the efficiency of HPTP with crushed or hollow spores predominating after treatments. No correlation between HPTP susceptibility and genetic diversity was observed for two genotypes of A. acidoterrestris spores. The treatment combination provides a promising option for industrial utility since it requires lower heat and processing time.     

The effect of heat treatment of caprine milk on the composition of cheese whey

In three independent trials, caprine milk from the same batch was divided into three lots, which were heated at 65 °C for 30 min, 80 °C for 5 min or 90 °C for 5 min. Representative whey samples collected during the whole cheese making process were analysed for fat, protein and dry matter contents, which decreased as the heating temperature of milk increased. Percentages of serum albumin and β-lactoglobulin in the total proteins of whey decreased as the heating temperature of milk increased, while α-lactalbumin and glycomacropeptide increased, particularly in the 90 °C whey. Lactoferrin and the immunoglobulin-heavy chain were only detected in the 65 °C whey.     

Radio frequency heating against Sitophilus zeamais Motschulsky in white maize

Radio frequency treatments were evaluated for the control of Sitophilus zeamais Motschulsky in white maize, and their effects on physiological and biochemical properties were evaluated. A 12 kW, 27.12 MHz radio frequency machine was used with an electrode gap of 20 cm; batches of 10 and 20 kg of white maize (11.8% moisture content, w.b.) were treated. Radio frequency heating treatments at 50 °C for 3 min or 60 °C in white maize were effective to achieve 100% mortality of Sitophilus zeamais 4th instar larvae. Significant changes were observed in the moisture content, water activity and color in the corn kernels after the treatments (P < 0.05); however, they were within the range established by the Mexican Standard. As an advantage, the viability and germination of the grain were not affected by the treatments (P > 0.05). Radio frequency has potential to be a postharvest treatment against this pest without damage to white maize.     

Comparison of the effects of novel processing technologies and conventional thermal pasteurisation on the nutritional quality and aroma of Mandarin (Citrus unshiu) juice

Conventional thermal pasteurisation (90 °C and 30 s), high pressure processing (HPP: 600 MPa, 4 °C and 300 s), ultrasound processing (US: 50 °C, 750 W and 36 min) and microwave processing (MW: 800 W, 80 °C and 70 s) were evaluated by examining their effects on the sensory and nutritional qualities of mandarin juice. The treated samples had <2 log CFU/mL total aerobic bacteria, which is equivalent to microorganism inactivation. Sugar and acid components were almost constant for all the treated mandarin juices, and no differences between treatments were perceptible. However, the mandarin juice treated with novel technologies maintained better colour (L*, a* and b*), nutritional value (ascorbic acid, total phenolic, total carotenoid content and phenolic components) and aroma than the thermally pasteurised one. This study showed that US, MW and HPP are good novel processing techniques to inactivate microorganisms and maintain the sensory and nutritional quality of mandarin juice.     

Thermal Inactivation Kinetics of Tulane Virus in Cell‐Culture Medium and Spinach

Human noroviruses (HNoVs) cause significant gastrointestinal disease outbreaks worldwide. Tulane virus (TV) is a cultivable HNoV surrogate widely used to determine control measures against HNoVs. The objective of this study was to determine the heat inactivation kinetics (D‐ and z‐values) of TV in cell‐culture media and on spiked homogenized spinach using the first‐order and Weibull models. TV in cell‐culture media at approximately 7 log PFU/mL (PFU—plaque forming unit) in 2‐mL glass vials was heated at 52, 54, and 56 °C for up to 10 min in a circulating water bath. Survivors were enumerated using confluent host LLC‐MK2 cells in six‐well plates by plaque assay. Data from three replicate treatments assayed in duplicate were analyzed statistically. D‐values by the first‐order model for TV in cell‐culture media at 52, 54, and 56 °C were 4.59 ± 0.05, 2.91 ± 0.05, and 1.74 ± 0.07 min, respectively, with a z‐value of 9.09 ± 0.01 °C (R² = 0.997). The Weibull model showed t_d = 1 values of 2.53 ± 0.08, 1.99 ± 0.10, and 0.57 ± 0.64 min, respectively, at the same temperatures. The D‐values for TV in spinach were 7.94 ± 0.21, 4.09 ± 0.04, and 1.43 ± 0.02 min and the z‐value was 10.74 ± 0.01 °C (R² = 0.98) by the first‐order model and 4.89 ± 0.02, 3.21 ± 0.45, and 0.25 ± 0.38 min for the Weibull model at 50, 54, and 58 °C, respectively. In comparison to previously reported results for the cultivable HNoV surrogate, murine norovirus ‐1, TV in cell‐culture media and spiked on spinach homogenates showed lower D‐ and z‐values. TV may not be an ideal HNoV surrogate for heat inactivation studies in cell‐culture media or homogenized spinach in vacuum bags.