Effect Of Mild Heat Treatment Research Articles

Combined Effect of Mild Heat Treatment by Warm Sodium Hypochlorite Aqueous Solution and Active MAP on Browning of Fresh-Cut Celery

Combined Effect of Mild Heat Treatment by Warm Sodium Hypochlorite Aqueous Solution and Active MAP on Browning of Fresh-Cut Celery

A gas chromatography-mass spectrometry untargeted metabolomics approach to discriminate Fiore Sardo cheese produced from raw or thermized ovine milk

Thermization is a sub-pasteurization heat treatment of cheese milk (at 57-68°C for 15-30 s) aimed to reduce the number of undesirable microbial contaminants with reduced heat damage to the indigenous milk enzymes. In this work, the effects of milk thermization on the compositional parameters, proteolysis indices, free fatty acid levels, and low molecular weight metabolite profiles of ovine cheese were studied. Cheese samples at different ripening stages and produced in 2 different periods of the year were analyzed. While the effects of milk thermization on cheese macro-compositional parameters and free fatty acid levels were not evident due to the predominant effects of milk seasonality and cheese ripening stage, the gas chromatography-mass spectrometry based metabolomics approach of ovine cheese produced from raw and thermized milk highlighted strong differences at the metabolite level. Discriminant analysis applied to gas chromatography-mass spectrometry data provided an excellent classification model where cheese samples were correctly classified as produced from raw or thermized milk. The metabolites that mostly changed due to the thermization process belonged to the classes of free amino acids and saccharides. Gas chromatography-mass spectrometry-based metabolomics has proven to be a valid tool to study the effect of mild heat treatments on the polar metabolite profile in ovine cheese.

Effect of mild heat treatment on shelf life of fresh lotus root

Heat treatments of fresh lotus root (Nelumbo nucifera G.) at 40, 50 and 60 °C effectively prevented moisture loss, browning and microbial growth but increased soluble solids, total volatile compounds and firmness during storage at 25 °C for 15 d (p < 0.05). Polyphenol oxidase (PPO) and peroxidase (POD) activities and PPO electrophoretic band intensities (100 kDa) were minimally affected by the treatments. Results indicate that enzyme deactivation is not the dominant factor in the inhibition of browning that occurred during the storage of heat treated tubers and that other factors such as heat-induced substrate modifications could significantly contribute to this effect. Peroxidase heat shock proteins (Hsp) were detected at 60, 70 and 120 kDa in treated samples. The enhanced Hsp protective response and firmness retention in 60 °C treated samples indicate that this is the optimum treatment temperature for improving lotus root postharvest storage quality and shelf life.

Mild heat treatment inhibits the browning of fresh-cut Agaricus bisporus during cold storage

The effects of mild heat treatment (MHT 1 min and MHT 5 min at 40 °C) on inhibiting browning of sliced mushrooms were assayed during 6 d storage at 4 ± 0.5 °C. The results showed that the mushroom slices treated by MHT 5 min exhibited higher Lightness value and total phenolic content than that of MHT 1 min and control, and the activities of superoxide dismutase, catalase and phenylalanine ammonialyase were increased while polyphenol oxidase activity was suppressed. Furthermore, the increase of superoxide anion production rate, malondialdehyde content and hydrogen peroxide content were delayed in sliced mushrooms treated with MHT 5 min. No significant difference on ascorbic acid content and ascorbate peroxidase activity were found in sliced mushroom treated with MHT and control. The results shown that mild heat treatment (40 °C, 5 min) could delay the browning occurrence of sliced mushrooms by improving the activities of antioxidant enzymes and the contents of antioxidants, inhibiting the accumulation of reactive oxygen and the activities of browning related enzymes. And the appropriate heat treatment (40 °C, 5 min) can prolong the shelf-life of sliced mushrooms from 2 days to more than 6 days. The study suggests that MHT (40 °C, 5 min) could be a promising candidate to inhibit browning of sliced button mushrooms.

Combination irradiation treatments for food safety and phytosanitary uses

Purpose of the review: Combination of irradiation treatment with other preservation techniques is of potential importance in enhancing the effectiveness and reducing the energy or dose requirement for destroying food borne illness and spoilage organisms while retaining or improving product quality. Phytosanitary irradiation to control quarantine pests, particularly insects, in traded fresh commodities may also benefit from combination with other disinfestation techniques to enhance effectiveness, and to reduce costs, treatment time, and product damage. Main findings: Combined preservation treatments can be beneficial to eliminate pathogenic bacteria due to the synergistic or additive effect of the treatments. It also permits less extreme use of a single treatment which may protect the sensory quality of the foods. Combination with modified atmosphere packaging (MAP), refrigeration, freezing or heating has great potential for improving the quality and the safety of fresh and processed foods. Irradiation and heat treatments reduce the numbers of pathogenic bacteria and the level of normal flora, while MAP and cold suppresses the growth of the survivors during subsequent storage. The use of natural antimicrobials at concentrations that do not affect the sensory qualities can increase the relative sensitivity of bacteria by >4-fold and can reduce the radiation dose necessary to eliminate pathogens. Natural antimicrobials are normally not stable over time; microencapsulation and the use of edible coatings can improve stability of antimicrobial formulations and prolong their bioactivity. Phytosanitary irradiation doses to control insects (50 to 400 Gy) are relatively low compared to doses for food safety and sterilization applications. Lowering doses further could save money on treatment costs by reducing treatment time, increasing the capacity of irradiation facilities, and reducing any problems with commodity quality. Combining irradiation with other insect disinfestation modalities such as cold, heat, fumigation, modified atmospheres, and chemical insecticides is a possible means to reduce the radiation dose, and the duration, level, or concentration of the companion treatment while meeting the technical objectives of the quarantine treatment. Irradiation in combination with cold is particularly promising, as it may be a means to reduce the duration and therefore costs of current cold treatment protocols. Irradiation may also allow use of higher cold temperatures that do not cause chilling injury in cold-sensitive fruits. Directions for future research: The efficacy of active edible coating and active biodegradable packaging in combination with irradiation for microbial control needs further investigation and should be demonstrated at the industrial level. The use of combined treatments to eliminate viruses and parasites in food is not well studied and should be investigated. The effects of mild heat treatment before irradiation on insect radiotolerance and bacteria radiosensitization should be investigated. The relationship between MAP packaging and insect radiation tolerance needs to be explored for a wider variety of quarantine pest species, including surface pests and inherently tolerant Lepidoptera and mites. Additional research is needed to demonstrate the efficacy of irradiation plus cold combination treatments against insects in fresh produce while assessing commodity quality and the potential for commercial application.

Effect of mild heat treatments on the antimicrobial activity of essential oils of Curcuma longa, Xylopia aethiopica, Zanthoxylum xanthoxyloides and Zanthoxylum leprieurii against Salmonella enteritidis

The antimicrobial activity of essential oils (EOs) from spices and medicinal plants or their constituents has gained increasing interest. However, studies on their use in combination with other antimicrobials or technologies are still scarce. In this paper, the survival of Salmonella enteritidis exposed to a combined effect of four EOs (from Xylopia aethiopica, Curcuma longa, Zanthoxylum leprieurii and Zanthoxylum xanthoxyloides) and mild heat treatments (55° and 60°C) were assessed. Salmonella enteritidis demonstrated a biphasic inactivation curve at 55°C in the absence of EOs, while in the presence of EOs the Weibull model was used. The combination of temperature and EOs reduced the treatment time needed to inactivate 7 log cfu/mL of S. enteritidis: this reduction ranged, with respect to the control, from 92.6% to 96.4% when the treatment was performed at 55°C, and from 20.5% to 27. 5% at 60°C. The efficiency of the interaction of the combination of EOs and mild thermal treatment is related to increased vapor pressure of EO constituents, which became more soluble in the membrane of stressed cells.

Enhancement of contractile force generation of artificial skeletal muscle tissues by mild and transient heat treatment.

Artificial skeletal muscle tissues composed of cells are expected to be used for applications of regenerative medicine and drug screening. Generally, however, the physical forces generated by tissue-engineered skeletal muscle are lower than those of skeletal muscle tissues found in the body. Local hyperthermia is used for many diseases including muscle injuries. It was recently reported that mild heat treatment improved skeletal muscle functions. In this study, we investigated the effects of mild heat treatment on the tissue-engineered skeletal muscle tissues in vitro. We used magnetite cationic liposomes to label C2C12 myoblast cells magnetically, and constructed densely packed artificial skeletal muscle tissues by using magnetic force. Cell culture at 39°C promoted the differentiation of myoblast cells into myotubes. Moreover, the mild and transient heat treatment improved the contractile properties of artificial skeletal muscle tissue constructs. These findings indicate that the culture method using heat treatment is a useful approach to enhance functions of artificial skeletal muscle tissue.

Inactivation ofEscherichia coliby citral

The aim was to evaluate (i) the resistance of Escherichia coli BJ4 to citral in a buffer system as a function of citral concentration, treatment medium pH, storage time and initial inoculum size, (ii) the role of the sigma factor RpoS on citral resistance of E. coli, (iii) the role of the cell envelope damage in the mechanism of microbial inactivation by citral and (iiii) possible synergistic effects of mild heat treatment and pulsed electric fields (PEF) treatment combined with citral. The initial inoculum size greatly affected the efficacy of citral against E. coli cells. Exposure to 200 microl l(-1) of citral at pH 4.0 for 24 h at 20 degrees C caused the inactivation of more than 5 log(10) cycles of cells starting at an inoculum size of 10(6) or 10(7) CFU ml(-1), whereas increasing the cell concentration to 10(9) CFU ml(-1) caused <1 log(10) cycle of inactivation. Escherichia coli showed higher resistance to citral at pH 4.0 than pH 7.0. The rpoS null mutant strain E. coli BJ4L1 was less resistant to citral than the wild-type strain. Occurrence of sublethal injury to both the cytoplasmic and outer membranes was demonstrated by adding sodium chloride or bile salts to the recovery media. The majority of sublethally injured cells by citral required energy and lipid synthesis for repair. A strongly synergistic lethal effect was shown by mild heat treatment combined with citral but the presence of citral during the application of a PEF treatment did not show any advantage. This work confirms that cell envelope damage is an important event in citral inactivation of bacteria, and it describes the key factors on the inactivation of E. coli cells by citral. Knowledge about the mechanism of microbial inactivation by citral helps establish successful combined preservation treatments.

Enzymatic hydrolysis of granular native and mildly heat-treated tapioca and sweet potato starches at sub-gelatinization temperature

The effect of mild heat treatment (below gelatinization temperature) towards the susceptibility of granular starch to enzymatic hydrolysis was investigated. Tapioca and sweet potato starches were subjected to enzymatic hydrolysis with a mixture of fungal α-amylase and glucoamylase at 35 °C for 24 h. Starches were hydrolyzed in native (granular) state and after heat treatment below gelatinization temperature (60 °C for 30 min). The dextrose equivalent (DE) value of heat-treated starch increased significantly compared to native starch, i.e., 36–50% and 27–34% for tapioca and sweet potato starch, respectively. Scanning electron microscopy examination showed that enzymatic erosion occurred mainly at the surface of starch granules. Hydrolyzed heat-treated starch exhibited rougher surface and porous granules compared to native starch. X-ray analysis suggested that enzymatic erosion preferentially occurred in amorphous areas of the granules. The amylose content, swelling power and solubility showed insignificant increase for both starches. Evidently, heating treatment below gelatinization temperature was effective in enhancing the degree of hydrolysis of granular starch.

Effects of Mild Heat Treatment on Microbial Growth and Product Quality of Packaged Fresh‐Cut Table Grapes

The changes in packaged fresh-cut grape quality and microbial growth as affected by mild heat treatments and the retention of grape cap stems during 5 degrees C storage were evaluated. Each individual grape was either manually pulled off (stemless) from the stems, or cut (cut stem) to allow for a 1- to 2-mm cap stem remaining on the berry. The samples were sanitized in 100 mg/L chlorine solution for 1 min, followed by a mild heat treatment in a water bath (45 degrees C, 8 min) or an oven (55 degrees C, 5 min). After cooling, the berries were packaged in rigid trays sealed with a gas permeable film and stored at 5 degrees C. Product quality and decay rate were evaluated periodically during storage. The results indicate that in the package headspace for hot water treatment of stemless grapes, partial pressures of O(2) declined significantly (P < 0.05) less and C(2)H(4) increased significantly (P < 0.001) less than for the control and hot air treatment. Stem removal and heat treatment had significant (P < 0.05) effects on the decay rate of grapes during storage. Hot water treatment maintained a significantly lower decay rate than the control and hot air treatment throughout the entire storage. Color and texture were not significantly (P > 0.05) affected by either heat treatment or stem removal. Grapes that retained the cap stems and received hot water treatment had the lowest decay rate and lowest microbial growth with the absence of any negative impact on grape color, texture, and flavor.

Influence of moderate heat pre-treatments on physical and chemical characteristics of kiwifruit slices

The effect of mild heat treatments, applied to whole kiwifruit, on physical characteristics and chemical composition of minimally processed fruit was studied. Fruits were subjected to heat treatments at 45 °C for 25 and 75 min, cooled for 24 h, minimally processed and stored at 4 °C for 12 days. Heat-treated fruits showed increased respiration rates in the first 2 days of storage. Samples colour was marginally affected either by heat treatments or by minimal processing. The application of heat treatments leads to an increment of slices firmness due to cross linking between demethylated galacturonic acid chains and endogenous calcium. An increment in sucrose, L-malic, citric, quinic and ascorbic acids was observed as a consequence of applied heat treatments. Heat treatment at 45 °C for 25 min applied to whole fruits allows quality retention of minimally processed fruit during 9 days at 4 °C.

Mild Whole-Body Heat Stress Alters Retinoid Metabolism in the Rat Small Intestine

Mild heat treatment can modulate metabolism and prevent stress-induced alterations in cells and tissues. Retinoids are known to influence cellular metabolism and are essential for growth and differentiation, particularly of epithelial tissue. This study examines the effect of mild heat treatment on retinoid alterations in enterocytes in the rat small intestine. Heat treatment changed the differentiation pattern of enterocytes along the villus-crypt axis, accompanied by increases in retinol, retinaldehyde, and retinoic acid in proliferating crypt cells. Activities of retinoid metabolizing enzymes such as retinaldehyde oxidase and retinaldehyde reductase were also increased. These results suggest that mild heat treatment can alter retinoid metabolism in the small intestine, which might influence epithelial cell proliferation and differentiation.

Combining heat treatment and subsequent incubation temperature to prevent growth from spores of non-proteolytic Clostridium botulinum.

Refrigerated processed foods of extended durability rely on a mild heat treatment combined with refrigerated storage to ensure microbiological safety and quality. The principal microbiological safety risk in foods of this type is non-proteolytic Clostridium botulinum. In this article the combined effect of mild heat treatment and refrigerated storage on the time to growth and probability of growth from spores of non-proteolytic Cl. botulinum is described. Spores of non-proteolytic Cl. botulinum (two strains each of type B, E and F) were heated at 90 degrees C for between 0 and 60 min and subsequently incubated at 5 degrees, 10 degrees or 30 degrees C in PYGS broth in the presence or absence of lysozyme. The number of spores that resulted in turbidity depended on the combination of heat treatment, incubation time and incubation temperature they received. Heating at 90 degrees C for 1 or more min ensured a 10(6) reduction when spores were subsequently incubated at 5 degrees C for up to 23 weeks. Heating at 90 degrees C for 60 min ensured a 10(6) reduction over 23 weeks when subsequent incubation was at 10 degrees C in the presence of added lysozyme. The same treatment did not reduce the spore population by 10(6) when subsequent incubation was at 30 degrees C.

The Accumulation of α- and β-Carotene in Serum and Tissues of Preruminant Calves Fed Raw and Steamed Carrot Slurries

The preruminant calf model was used to evaluate the effects of mild heat treatment on the serum and tissue accumulation of alpha- and beta-carotene from carrots. Twenty-four 1-wk-old Holstein male calves were assigned to one of four groups and fed a milk replacer diet. Negative control animals received no additional supplement. The three remaining groups received an additional 20 mg beta-carotene/d from either water-soluble beadlets, homogenized raw carrots or homogenized steamed carrots. Serum samples were obtained daily, and calves were killed after 7 d and samples of serum, liver and adrenal collected. Tissue and serum alpha- and beta-carotene concentrations were not significantly higher in steamed carrot-fed animals than in raw carrot-fed animals. The molar ratios of beta-carotene to alpha-carotene in both raw carrot-fed and steamed carrot-fed groups were highest in adrenal tissues, intermediate in serum and lowest in the diets. None of these differences were statistically significant. When the serum, liver and adrenal beta-carotene data were pooled, the mean relative accumulation of beta-carotene, expressed as a percentage of the mean response of calves receiving water-soluble beadlets, was 46.8% for calves fed raw carrots and 74.0% for calves fed steamed carrots. These results suggest a small enhancing effect of mild heat treatment of carrots on the serum and tissue accumulation of carotenoids.

Effect of mild heat treatment on actin and nucleotide binding of myosin subfragment 1.

Chymotryptic subfragment 1 (S-1) prepared from rabbit skeletal myosin has lost its ATPase activity upon incubation at 35 degrees C for 3 h. The loss in ATPase activity was accompanied by the perturbation of the structure of the 50K domain as indicated by a dramatic increase in the tryptic susceptibility of this domain without any change in the susceptibility of the other domains of S-1. The perturbation starts at the C-terminal region of the domain as suggested by the appearance of a 29K intermediate protein band in the tryptic peptide pattern of the heat-treated S-1. The heat-treated molecule essentially retained its actin and polyphosphate binding ability, and the actin binding was still sensitive to the presence of ATP or pyrophosphate. However, as opposed to native S-1, in heat-treated S-1 the addition of ATP does not induce an increase in tryptophan fluorescence, and, in the case of the treated species, the fluorescence of 1,N6-ethenoadenosine 5'-diphosphate added to the mixture is quenchable by acrylamide. This latter observation suggests that the binding of the adenine ring of the nucleotide has been altered following the heat treatment. The results indicate that the actin and polyphosphate binding sites of S-1 are distinct and that they are relatively independent of the adenine ring binding site.

Effect of mild heat treatment on the ATPase activity and proteolytic sensitivity of myosin subfragment-1

The K +-EDTA-activated ATPase activity of chymotryptic myosin subfragment-1 (S-1) decreased by 85–90% when S-1 was incubated over a 2-h period at 35 °C. Addition of F-actin, ATP, or ATP analogs, such as ADP or PP i, to S-1 before incubation at 35 °C prevented the loss of ATPase activity. The decrease in ATPase activity was also accompanied by changes in tryptic sensitivity. Instead of the normal peptide pattern—which is comprised of three heavy chain fragments (27K, 50K, and 20K)—only two fragments (27K and 20K) appeared on the sodium dodecyl sulfate-gel electrophoregram after limited tryptic digestion of thermally treated S-1. Addition of any ligand—e.g. ATP, ADP, pyrophosphate, or actin—which prevented the loss of ATPase activity during incubation at 35 °C also prevented the observed change in the tryptic peptide pattern of S-1. Tryptic digested S-1, whose heavy chain has been cleaved to 27K, 50K, and 20K fragments, also lost its ATPase activity upon mild heat treatment. The heat-treated trypsin-digested S-1 was subjected to a second tryptic digestion, which resulted in the disappearance of the 50K fragment, while the 50K fragment of tryptic S-1 not subjected to heat treatment was not susceptible to additional tryptic hydrolysis. The results indicate that the structural changes, that take place specifically in the 50K region of S-1 upon mild heat treatment, lead to both the loss of the ATPase activity and the changed tryptic sensitivity of S-1.

Effect of mild heat treatment on the nutritive value of low glucosinolate–low erucic acid rapeseed meals

AbstractHeat treatment (dipping seeds in boiling water) of two cultivars of Brassica napus, 1788 and 940, low in glucosinolates and erucic acid produced improved weight gains and lower thyroid weights in rats who received these meals as the only source of protein. Unheated cv 940 meal on autolysis did not produce detectable amounts of nitriles and increased weight gains were observed in rats ingesting the autolysed meal. Steaming of unheated meal similarly gave increased weight gains and the effects of steaming and autolysis were additive. The rates of weight gain of rats who ingested unheated and heated meals were different for the first ten days of feeding the meals but subsequently were similar, indicating the possibility of palatability factor(s) or another appetite depressing factor(s) being present in unheated meals. Trypsin inhibitor activities determined for various rapeseed meals were low as compared to soybean. Chlorogenic acid and myrosinase, both known constituents of rapeseed, did not show any trypsin inhibitor activity. In vitro digestibility measurements with pancreatin and pepsin didnot show significant differences between heated and unheated meals nor did an in vivo digestibility trial, although the rats consumed less of the feed containing unheated meal.

THERMAL INJURY AND RECOVERY OF Saccharomyces cerevisiae

ABSTRACTThis investigation was undertaken to determine the effect of mild heat treatments on the survival, injury and recovery of Succharomyces cerevisiae. Cells of S. cerevisiae strain Y‐25 were grown in yeast extract‐malt extract, harvested, by centrifugation, washed 2X, and suspended in 0.1M phosphate buffer at pH 7.0. Cell suspensions were heated in a water bath at various temperatures and survivors were determined by plating on Plate Count Agar (PCA) and Potato Dextrose Agar (PDA) with or without acidification. The heated suspensions were stored at room temperature (20–22°C) and sampled at various periods to monitor the recovery of injured cells. Using the system described above, heat‐injured cells of S. cerevisiue were not recovered when plated on PCA or PDA immediately after heating. Heat‐injured cells were recovered on the plating media after storage in buffer at room temperature, but 5–7 days were required for maximum recovery. Initially, the rate of recovery on PCA was greater than on PDA; this was not attributable to the differences in pH of the media, but apparently was due to nutritional factor(s). Resting cells of S. cerevisiae did not undergo a comparable recovery when heated and stored in either water or buffer.

Photooxidase Activity of Heated Chromatophores of Rhodospirillum rubrum

\Tan Niel's classical (listinction between bacterial andl green plant photosyntheses is based on the differences in the metabolism of the photooxidant (16). But direct measurement of the oxidizing power in bacterial photosynthesis is, at best, difficult with the -usual spectrophotometric equipment. Light-induced oxidations of endogenous cytochromes have been demonstrated in whole cells and extracts of Rhodospirillini rubruzn (2, 4, 15), but special spectrophotometers were always require(l. The oxidizing power generated by light was easily measured by Vernon and Kamen using as the assay the photooxidation of re(luced indophenol or exogenous mammalian cytochrome c (18,19). However, this photooxidation of exogenous indicators was oxygen dependent and heat resistant causing Smith to doubt its physiological significance (14). The photooxidation of reduced indophenol could merely represent a manifestation of the wvell-known ability of bacteriochlorophyll to mediate a sensitized photooxidation (7). Mild heat has been shown to destroy two absorption bands characteristic of the spectrum of bacteriochlorophyll in the chromatophore of R. rubrumn (3. 8) while the photooxidase assay is relatively heat insensitive (10, 18). By comparing the effect of mild heat treatments on both the spectrum and on the photoxidase activity of the chromatophore, a validation was sought of the photooxidase assay using reduced indophenol. The rate of photooxidation of indophenol was not related to the strength of any absorption peak of bacteriochlorophyll. This participation of other heatlabile factors suggested that this in vitro assay is related to the in vivo metabolism of the oxidant.

Growth failure caused by mild heat treatment of the diet.

Summary.The effect of mild heat treatment on the nutritional value of a diet composed to correspond to the average composition of the diet of the Finnish people has been investigated. The test diet was dried and then kept at 140° C for 30—40 minutes. Rats were used as test animals.The heated diet caused a total cessation of the growth of the rats. The growth was restored by the addition of casein or lysin. Leucine, methionine, histidine, vitamin B12 and sucrose were without effect.