Kinetic analysis of volatile formation in milk subjected to pressure-assisted thermal treatments

Volatile formation in milk subjected to pressure-assisted thermal processing (PATP) was investigated from a reaction kinetic analysis point of view to illustrate the advantages of this technology. The concentration of 27 volatiles of different chemical class in milk subjected to pressure, temperature, and time treatments was fitted to zero-, 1st-, and 2nd-order chemical reaction models. Temperature and pressure effects on rate constants were analyzed to obtain activation energy (E(a)) and activation volume (deltaV*) values. Hexanal, heptanal, octanal, nonanal, and decanal followed 1st-order kinetics with rate constants characterized by E(a) values decreasing with pressure reflecting negative deltaV* values. Formation of 2-methylpropanal, 2,3-butanedione, and hydrogen sulfide followed zero-order kinetics with rate constants increasing with temperature but with unclear pressure effects. E(a) values for 2-methylpropanal and 2,3-butanedione increased with pressure, that is, deltaV* > 0, whereas values for hydrogen sulfide remained constant, that is, deltaV* = 0. The concentration of all other volatiles, including methanethiol, remained unchanged in pressure-treated samples, suggesting large negative deltaV* values. The concentration of methyl ketones, including 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, 2-nonanone, 2-decanone, and 2-undecanone, was independent of pressure and pressure-holding time. PATP promoted the formation of few compounds, had no effect on some, and inhibited the formation of volatiles reported to be factors of the consumer rejection of "cooked" milk flavor. The kinetic behavior observed suggested that new reaction formation mechanisms were not likely involved in volatile formation in PATP milk. The application of the Le Chatelier principle frequently used to explain the high quality of pressure-treated foods, often with no supporting experimental evidence, was not necessary.     

High-Pressure Processing Technologies for the Pasteurization and Sterilization of Foods

The food-processing industry has made large investments in processing facilities relying mostly on conventional thermal processing technologies with well-established reliability and efficacy. Replacing them with one of the novel alternatives recently developed is a decision that must be carefully approached. Among them, high-pressure processing (HPP), at room or refrigerated temperature, is now a well-established option experiencing worldwide commercial growth. Surveys have shown an excellent consumer acceptance of HPP technology. For financial feasibility reasons, HPP treatments must be kept short, a challenge that can be met by some of the alternatives here reviewed such as the use of the hurdle technology concept. Although HPP technology is limited to pasteurization treatments, the combination of high pressure and high temperature used in pressure-assisted thermal processing (PATP) can be used to sterilize foods. An analysis of alternatives to achieve the inactivation of bacterial spores at the lowest temperature possible highlights the need for additional research on the use of germinants. Because of incomplete research, PATP presents several implementation challenges, including the modeling of food temperature, the determination of inactivation kinetics particularly for bacterial spores, and the prediction of chemical changes including the potential formation of toxic compounds.     

Combined pressure–temperature effects on the chemical marker (4-hydroxy-5-methyl- 3(2H)-furanone) formation in whey protein gels

Chemical markers, such as furanone, are intrinsically formed in foods at elevated process temperatures, and have been successfully used as indirect indicators of heating patterns in advanced thermal proces-ses such as aseptic processing, microwave sterilization and ohmic heating. However, very limited information is available on suitability of these chemical markers during combined pressure–heat treatment. The present study was conducted on the formation and stability of chemical marker M-2 (4-hydroxy-5-methyl-3(2H) furanone, a by-product of Maillard reaction) as a function of pressure, temperature and pH. Whey protein gels (containing 1g ribose/100g gel mix) at pH 6.1 and 8.3 were subjected to pressure assisted thermal processing (PATP; 350 and 700 MPa, 105 °C), high pressure processing (HPP; 350 and 700 MPa, 30 °C) and thermal processing (TP; 0.1 MPa, 105 °C) for different holding times. Unprocessed gel was used as control. The marker yield was quantified using HPLC. The initial concentrations of M-2 in the gels were 9.17 and 6.1 mg/100 g at pH 6.1 and 8.3, respectively. As expected, heat treatment at 105 °C, 0.1 MPa increased M-2 concentration. The marker yield increased with increase in holding time, following a first order kinetics and decreased with increasing pH. Pressure treatments from 350 to 700 MPa at 30 °C reduced the chemical marker formation for both pH values investigated. Marker formation during combined pressure-temperature (105 °C, 350 and 700 MPa) was influenced by both heat (which favored the marker formation) and pressure (which hindered marker formation). The net final concentration of the marker formed during PATP was higher than HPP, but lower than thermal treatments. This study suggests that 4-hydroxy, 5-methyl, 3(2H) furanone may not be a suitable marker for evaluating pressure–heat uniformity during PATP.     

Evaluation of the instrumental quality of pressure-assisted thermally processed carrots

ABSTRACT:  This study was conducted to compare the effectiveness of pressure-assisted thermal processing (PATP) in preserving the texture, color, and carotene content of carrot cylinders in the pressure range of 500 to 700 MPa and the temperature range of 95 to 121 °C. The effectiveness of PATP was compared with that of conventional thermal processing (TP) by matching carrot preprocess temperature history. Results indicated that under comparable process temperatures (up to 105 °C), PATP retained the carrot quality attributes such as color and carotene content better than TP. However, process and preprocess thermal history at 121 °C greatly influenced carrot textural change and pressure protective effects were less pronounced. This study demonstrated that PATP has the potential to produce low-acid foods with a relatively better quality than TP.     

Reaction Kinetics at High Pressure and Temperature: Effects on Milk Flavor Volatiles and on Chemical Compounds with Nutritional and Safety Importance in Several Foods

Consumers demand, in addition to excellent eating quality, high standards of safety and nutrition in ready-to-eat food. This requires a continuous improvement in conventional processing technologies and the development of new alternatives. Prevailing technologies such as thermal processing can cause extensive and undesirable chemical changes in food composition while minimal processing strategies cannot eliminate all microbial pathogens. This review focuses on pressure-assisted thermal processing, a new alternative for shelf-stable foods. Its implementation requires an analysis of reaction kinetics at high pressure and elevated temperature. Acceleration of the inactivation of bacterial spores by the synergistic effect of pressure and temperature is expected to allow processing at lower temperature, shorter process time, or a combination of both. Therefore, thermal degradation of quality is expected to be lower than that of conventional thermal processes. However, few studies have focused on the effect of the conditions required for the inactivation of bacterial spores on the kinetics of chemical reactions degrading food quality, particularly at the high temperatures required for the processing of low-acid foods.     

Phytochemicals: nutraceuticals and human health

Phytochemicals, as plant components with discrete bio‐activities towards animal biochemistry and metabolism are being widely examined for their ability to provide health benefits. It is important to establish the scientific rationale to defend their use in foods, as potential nutritionally active ingredients. Phytochemicals could provide health benefits as: (1) substrates for biochemical reactions; (2) cofactors of enzymatic reactions; (3) inhibitors of enzymatic reactions; (4) absorbents/sequestrants that bind to and eliminate undesirable constituents in the intestine; (5) ligands that agonize or antagonize cell surface or intracellular receptors; (6) scavengers of reactive or toxic chemicals; (7) compounds that enhance the absorption and or stability of essential nutrients; (8) selective growth factors for beneficial gastrointestinal bacteria; (9) fermentation substrates for beneficial oral, gastric or intestinal bacteria; and (10) selective inhibitors of deleterious intestinal bacteria. Such phytochemicals include terpenoids, phenolics, alkaloids and fiber. Research supporting beneficial roles for phytochemicals against cancers, coronary heart disease, diabetes, high blood pressure, inflammation, microbial, viral and parasitic infections, psychotic diseases, spasmodic conditions, ulcers, etc is based on chemical mechanisms using in vitro and cell culture systems, various disease states in animals and epidemiology of humans. However, it must be emphasized that a distinction needs to be drawn between the types of information that can be obtained from studies in vitro, in animals and in humans. Mechanisms of action must certainly be established in vitro; however, the efficacy of these same ingredients with their mechanisms of action, must also be demonstrated in vivo. The rapid growth in the use of phytochemicals in nutraceutical and functional foods requires that the food and pharmaceutical industries face new challenges: in addressing worldwide public concern over the efficacy and safety of supplements and foods claimed to be health‐promoting; in government regulations related to safety, labeling and health claims for products that contain phytochemicals; in the manufacturing of foods with different qualities and stabilities; and in marketing issues, particularly as they relate to consumers' recognizing added value. © 2000 Society of Chemical Industry     

Quality of shelf-stable low-acid vegetables processed using pressure–ohmic–thermal sterilization

Pressure ohmic thermal sterilization (POTS) involves ohmic heating of foods by applying an electric field under elevated pressure. Experiments were conducted using a custom made POTS apparatus using carrot as the model food. The samples were processed at a target temperature of 105 °C at 600 MPa and treated for 0, 1, 3, and 5 min by regulating the electric field (30 V/cm). POTS treated carrot sample quality attributes were compared against those processed using ohmic heating (0.12 MPa, 30 V/cm, 105 °C) and pressure-assisted thermal processing (PATP; 600 MPa, 0 V/cm, 105 °C). Within the experimental conditions of the study, the thermal come-up time of the POTS, Ohmic and PATP were 1.45 min, 3.58 min and 6.84 min respectively. PATP come-up time also included the pre-heating time (≈6 min). Results indicate the POTS samples had the least textural damage due to minimal thermal exposure. POTS samples had higher crunchiness index (CI) of 0.76 compared to PATP (CI = 0.57) and ohmic heated (CI = 0.62) carrots. All the technologies investigated had minimal impact on product color. This study demonstrates the potential to produce high quality shelf stable low-acid vegetable products using POTS.     

Effects of thermal food processing on the chemical structure and toxicity of fumonisin mycotoxins

Fumonisins are Fusarium mycotoxins that occur in corn and corn-based foods. They are toxic to animals and at least one analogue, fumonisin B1, is carcinogenic to rodents. Their effect on human health is unclear, however, fumonisins are considered to be risk factors for cancer and possibly neural tube defects in some heavily exposed populations. It is therefore important to minimize exposures in these populations. Cleaning corn to remove damaged or moldy kernels reduces fumonisins in foods while milling increases their concentration in some and reduces their concentration in other products. Fumonisins are water-soluble and nixtamalization (cooking in alkaline water) lowers the fumonisin content of food products if the cooking liquid is discarded. Baking, frying, and extrusion cooking of corn at high temperatures ( > or = 190 degrees C) also reduces fumonisin concentrations in foods, with the amount of reduction achieved depending on cooking time, temperature, recipe, and other factors. However, the chemical fate of fumonisins in baked, fried, and extruded foods is not well understood and it is not known if the reduced concentrations result from thermal decomposition of fumonisins or from their binding to proteins, sugars or other compounds in food matrices. These possibilities might or might not be beneficial depending upon the bioavailability and inherent toxicity of decomposition products or the degree to which bound fumonisins are released in the gastrointestinal tract. In this review the affects of cooking and processing on the concentration and chemical structure of fumonisins as well as the toxicological consequences of known and likely fumonisin reaction products are discussed.     

Kinetics of Strecker aldehyde formation during thermal and high pressure high temperature processing of carrot puree

Strecker aldehydes have been negatively associated to flavor of heat sterilized plant-based foods. The present study demonstrated the importance of processing conditions (temperature, pressure and time) as a strong means for the control of Strecker aldehyde formation in vegetables purees. A kinetic study was set up (at isothermal and isothermal-isobaric conditions) to quantify the effects of single process parameters on the changes of 3-methylbutanal (3-MB) in carrot puree as a case study. The increase in 3-MB concentrations was best described by an empirical, logistic model. During the isothermal treatment at atmospheric pressure, the maximum reaction rate constant of 3-MB formation was increased as a function of processing temperature. However, the formation rate was clearly slower at high pressure (600 MPa) compared to the process at 0.1 MPa. Hence, the reduced formation of Strecker aldehydes under high pressure could open a new possibility for process control and optimization of the formation of these compounds.Industrial relevanceHigh pressure high temperature (HPHT) processing is a relatively young technology and its effect on important quality-related chemical reactions is not as well understood as is the case for conventional thermal processing. The present work investigates the impact of processing conditions (e.g. pressure, temperature) on Strecker aldehydes formation, volatiles that have been negatively associated to flavor of heat sterilized plant-based foods. Based on the kinetic study, the formation rate of the Strecker aldehyde (3-methylbutanal) was clearly slower at high pressure (600 MPa) compared to the process at 0.1 MPa in carrot puree. Considering the fact that these compounds are often linked to off-flavor development, their reduced formation under high pressure could open a new possibility for process control and optimization.     

Evaluating the impact of thermal and pressure treatment in preserving textural quality of selected foods

A study was conducted to evaluate the efficacy of various combinations of pressure and thermal treatments in preserving textural quality of selected foods. Carrot, zucchini, apricot, red radish, and jicama were used as test samples. Pressure-assisted thermal processing (PATP; 600 MPa, 105 °C), high-pressure processing (HPP; 600 MPa, 25 °C), and thermal processing (TP; 105 °C, 0.1 MPa) experiments were conducted. Role of pressure (600 MPa) in preserving product quality while simultaneously (PATP) or sequentially (HPP-TP) exposed to elevated process temperature (105 °C) was also compared. Instrumental puncture, shear force, color and sensory analyses were utilized to compare the influence of the various process treatments. A crunchiness index (CI), relating product puncture force and stiffness, was able to characterize the severity of the process treatments on various products tested. Among the treatments, TP was the worst at retaining texture, but HPP-TP improved texture retention. In comparison to TP alone, PATP better retained texture and color. Jicama was least influenced by the treatments as compared to products tested. Process treatments investigated degraded the textural quality of zucchini and apricot. Instrumental CI results were also in agreement with the sensory data of carrot, red radish and jicama samples.     

Chemistry and Reaction of Singlet Oxygen in Foods

Singlet oxygen is a highly reactive, electrophilic, and nonradical molecule. It is different from diradical triplet oxygen in its electron arrangement. Photosensitizers can form singlet oxygen from triplet oxygen in the presence of light. The reaction rate of singlet oxygen with foods is much greater than that of triplet oxygen due to the low activation energy. Singlet oxygen oxidation produces undesirable compounds in foods during processing and storage. However, carotenoids and tocopherols in foods can minimize singlet oxygen oxidation. The in‐depth scientific knowledge on the formation, reactions, quenching mechanisms, and kinetics of singlet oxygen can greatly improve the quality of foods by minimizing the oxidation during processing and storage. The single oxygen oxidation of foods has contributed to the explanation of several important chemical reactions in the reversion flavor in soybean oil, sunlight flavor in milk products, and the rapid losses of vitamin D, riboflavin, and ascorbic acid in milk under light storage.     

Review: Pulsed Electric Fields Processing of Protein-Based Foods

Pulsed electric fields (PEF) processing is a promising nonthermal food preservation technology, which is ongoing from laboratory and pilot plant scale level to the industrial level. Application of PEF processing may be a good alternative treatment to thermal methods in protein-based foods. A large number of literatures have fully demonstrated that small molecule compounds in plant-based foods, mainly aroma compounds and health-related phytochemicals, were not significantly affected by PEF. However, there was a lack of knowledge on the effects of PEF on proteins and qualities of protein-based foods. This review focuses on effects of PEF processing on endogenous enzymes, safety, and quality of protein-based foods. Finally, the ways to achieve food quality assurance and food safety in PEF processing of protein-based foods are proposed.     

水产加工品中N-亚硝胺形成影响因素及变化规律的研究进展

N-亚硝胺(N-nitrosamines, NAs)是一类化学结构多样, 具有致畸性、致突变性和致癌性的强毒性化合物。NAs不仅在自然界中广泛存在，而且在水产品在的腌渍、烤制、烟熏、油炸等加工过程中均较易生成NAs, 。其中，市售干制动物性水产加工品中N-二甲基亚硝胺(N-nitrosodimethylamine, NDMA)污染水平较高。NAs是目前影响水产品安全性的重要因素。众多水产品生产企业因产品不合格, 导致企业信誉受损严重, 经济损失巨大, 已经受到生产企业和消费者的高度关注。因此, 明确水产品加工过程中NAs的变化规律和影响因素和对促进水产品加工行业健康发展至关重要 。本文以水产加工品的安全性为出发点, 介绍了NAs的种类、毒性、各国家和地区建立国内外规定食品中NAs的限量值，和指导值及我国市售水产加工品中NAs的污染情况,。 重点通过分析NAs的形成机理，了从水产加工工艺角度入手，对水产加工品中NAs生成的影响因素及变化规律进行综述，影响NAs生成的因素, 并初步探讨了水产品加工过程中NAs的变化规律, 以期为后续制定水产品在实际加工过程中有效控制措施和开发NAs形成的阻断技术提供理论基础, 对保障我国水产品的质量安全和保护消费者健康具有重要意义。     

肉制品中杂环胺的研究进展

杂环胺是富含蛋白质的食品在热加工和风味形成过程中产生的有毒化合物,这些有毒化合物对人体健康产生不利的影响,并且可能具有致突变性和致癌性.随着科技的发展及人们对食品安全的重视,肉制品中杂环胺越来越受到人们广泛的关注.本文主要对肉制品中杂环胺的形成、影响因素、危害、检测方法及控制等方面进行了综述,并对未来的研究方向进行了展...     

Efficacy of Pressure-Assisted Thermal Processing, in Combination with Organic Acids, against Bacillus amyloliquefaciens Spores Suspended in Deionized Water and Carrot Puree

ABSTRACT:  Effect of organic acids (acetic, citric, and lactic; 100 mM, pH 5) on spore inactivation by pressure-assisted thermal processing (PATP; 700 MPa and 105 °C), high pressure processing (HPP; 700 MPa, 35 °C), and thermal processing (TP; 105 °C, 0.1 MPa) was investigated.  Bacillus amyloliquefaciens  spores were inoculated into sterile organic acid solutions to obtain a final concentration of approximately 1.3 × 10⁸ CFU/mL.  B. amyloliquefaciens  spores were inactivated to undetectable levels with or without organic acids after 3 min PATP holding time. At a shorter PATP treatment time (approximately 2 min), the inactivation was greater when spores were suspended in citric and acetic acids than in lactic acid or deionized water. Presence of organic acids during PATP resulted in 33% to 80% germination in the population of spores that survived the treatment. In contrast to PATP, neither HPP nor TP, for up to 5 min holding time with or without addition of organic acids, was sporicidal. In a separate set of experiments, carrot puree was tested, as a low-acid food matrix, to study spore recovery during extended storage following PATP. Results showed that organic acids were effective in inhibiting spore recovery in treated carrot puree during extended storage (up to 28 d) at 32 °C. In conclusion, addition of some organic acids provided significant lethality enhancement ( P  < 0.05) during PATP treatments and suppressed spore recovery in the treated carrot puree.     

外源物质在食品加工过程中的变化与安全性

许多农药、兽药、毒素、食品添加剂、重金属、环境污染物等外源物质不但本身有一定毒性, 污染食品后对人体造成危害, 而且在食品加工过程中也会发生变化而导致食品的二次污染, 可能分解为毒性更强的物质, 或与食品内源组分发生反应产生新的有害物质, 或与其他物质之间存在毒性协同增强作用等。实际上, 大量的外源物质在食品加工过程中的变化与安全性问题尚未研究。本文对该领域的研究进展进行了综述, 期望引起相关研究者的重视。     

Headspace components that discriminate between thermal and high pressure high temperature treated green vegetables: Identification and linkage to possible process-induced chemical changes

For the first time in literature, this study compares the process-induced chemical reactions in three industrially relevant green vegetables: broccoli, green pepper and spinach treated with thermal and high pressure high temperature (HPHT) processing. Aiming for a fair comparison, the processing conditions were selected based on the principle of equivalence. A comprehensive integration of MS-based metabolic fingerprinting techniques, advanced data preprocessing and statistical data analysis has been implemented as untargeted/unbiased multiresponse screening tool to uncover changes in the volatile fraction. For all vegetables, thermal processing, compared to HPHT, seems to enhance Maillard and Strecker degradation reaction, triggering the formation of furanic compounds and Strecker aldehydes. In most cases, high pressure seems to accelerate (an)aerobic thermal degradation of unsaturated fatty acids leading to the formation of aliphatic aldehydes and ketones. In addition, both thermal and HPHT processing accelerated the formation of sulfur-containing compounds. This work demonstrated that the approach is effective in identifying and comparing different process-induced chemical changes, adding depth to our perspective in terms of studying a highly complex chemical changes occurring during food processing.     

Role of mercaptans on acrylamide elimination

The reaction between acrylamide and mercaptans (benzyl mercaptan and N-acetylcysteine) was studied in an attempt to clarify some of the reaction pathways by which amino acids affect the acrylamide content in foods. The obtained results showed that, in the absence of oxygen, mercaptans reacted very rapidly with acrylamide producing the corresponding addition product. The activation energy of this reaction was 28–30 kJ/mol. The produced adduct was stable and only trace amounts of acrylamide were formed by thermal heating of 3-(benzylthio)propanamide. In the presence of oxygen, the addition product was not observed but a higher amount of acrylamide disappeared, more likely as a consequence of radical reactions. These last reactions could be inhibited by antioxidants, which prevented acrylamide losses. All these results constitute a new proof of the complexity of the reactions involved in the formation and elimination of acrylamide in foods, which are also going to depend on the food composition and the presence of oxygen. Potential toxicities of the compounds formed between acrylamide and mercaptans still remain to be analysed.     

The effect of pressure on the kinetics of polyphenolics degradation – Implications to hyperbaric storage using Epigallocatechin-gallate as a model

Understanding reaction kinetics at elevated pressures is of importance for the development of pressure-based technologies and especially for hyperbaric storage (HS), a potential alternative for the energy-consuming refrigeration. The effect of pressure on degradation kinetics of a polyphenol, Epigallocatechin-gallate (EGCG), was explored at pressures up to 200 MPa (HS levels) for several hours, with and without fructose. In a baroresistant buffer, pressure enhanced EGCG degradation, due to a negative activation volume, while in phosphate buffer the pH decreased (as is also expected to occur in many foods) resulting in a superposition of accelerating and protective effects. A previously undescribed protective, pressure-level dependent, effect of fructose was identified. Novel in situ spectroscopy and HPLC analysis revealed that in addition to the effect on EGCG degradation rate, pressure also modifies the ratios between the numerous degradation products, likely due to a varying effect on the different steps involved in the degradation pathway.Industrial relevanceThe effect of pressure on reaction kinetics in food systems can be of great importance in processing conditions combining thermal and high pressure, and critical for the emerging concept of hyperbaric storage, where the food is exposed to high pressures for long duration of time, allowing a plethora of reactions to take place, all varyingly affected by pressure. Yet the effects of pressure on kinetics are often overlooked. Polyphenolic compounds are a large group of molecules responsible for both sensorial and health-promoting functionality in plant-based foods. Those compounds are known to undergo degradation by several mechanisms during processing and storage and their successful conservation is often considered of significant industrial importance. The presented work provides fundamental information regarding the effects of pressure on the kinetics of EGCG (Epigallocatechin-gallate) degradation, as a model for relatively unstable, polyphenolic compound, (taking into account pressure-induced pH shifts, and the presence of co-solutes). EGCG is also of specific importance in many products where it naturally occurs (green tea drinks etc.) and where it is externally added as a valuable supplement.     

Volatiles from interactions of Maillard reactions and lipids.

This article provides current information on the production of volatile compounds from interactions of Maillard reactions and lipids. It includes a brief introduction outlining the Maillard reactions, the Strecker degradation of amino acids, and the oxidation of lipids. It highlights those compounds derived from these reactions that could interact to form volatile flavor components during the processing or cooking of food. The article discusses results obtained from model systems involving interactions between (1) Maillard reaction products and carbonyl compounds, (2) amino acids and carbonyl compounds, (3) amino acids and derivatives of fatty acids, and (4) Maillard reaction products, triglycerides and phospholipids. The qualitative and quantitative effects that triglycerides and phospholipids have on the formation of volatile Maillard products are also discussed. Particular attention is given to those long-chain alkyl heterocyclic compounds formed during these reactions, proposed methods for their formation, and their aromas. The role that such compounds play in food flavors is discussed with reference to those volatile compounds identified in certain cooked foods, such as meat (beef, lamb, and pork), chicken, potatoes (baked, French-fried, and crisps), and beverages (coffee, tea, and cocoa).