Physical texture as an indicator of processing conditions for canning low-acid artichoke hearts

Kramer shear cell measures of texture of artichoke hearts were used to establish thermal loss parameters. A D₁₂₁= 25.5 min. and a z = 27°C for texture were obtained, with a high correlation between texture and treatment time. Maximum conservation of texture, in canned low-acid artichoke hearts in 0.5 kg cans (71.5 × 117 mm) whilst still ensuring microbiological stability, was obtained by heating at 121°C for 15 min.     

采收期及贮存方法对菊芋多糖含量的影响研究

通过热水法提取菊芋多糖,研究同一贮存方法下不同采收期内的菊芋多糖含量变化及同一采收期内不同贮存方法下菊芋多糖含量的变化。以葡萄糖为标准物,采用3,5-二硝基水杨酸法测定还原糖含量,标准曲线表明葡萄糖含量在测定范围内成良好线性,以葡萄糖为对照采用苯酚-硫酸法测定水解后的总糖含量,最大吸收波长为490 nm。结果表明,采收期对菊芋多糖含量有影响但其影响波动与贮存方法相比较小,贮存方法对菊芋多糖含量的影响较大。结论为10月27日前后是菊芋采收的最佳时期。其中沸煮2 min直接阴干方法是菊芋的最适宜贮存方法。     

诱变选育以菊芋为原料高产甘露醇的乳酸菌

以短乳杆菌为出发菌株,采用大气压冷等离子体介质阻挡放电法和离子束对乳酸菌进行诱变。以菊芋作为筛选培养基,摇瓶筛选得到高产甘露醇的菌株。之后对筛选出的高产甘露醇菌株进行遗传稳定性实验,证实该菌株遗传稳定。在5L发酵罐中进行发酵,该菌株可有效地将果糖转化为甘露醇,产率达到62%。这株诱变菌可作为高产甘露醇的优良菌株。     

Study of the impact of a new hurdle technology composed of electro‐activated solution and low heat treatment on the canned pea and corn quality and microbial safety

The objective of this work was to evaluate the quality of sterilised canned pea and corn in electro‐activated brine solutions at moderate temperatures. The lowest change in vitamin C was associated with the lowest heat treatment, while the short treatment time resulted in significant changes in texture and colour of vegetables. Best texture profile was obtained with the acid electro‐activated brine solution for pea and corn. The neutral electro‐activated brine solution resulted in a less firm texture for pea and corn. The green colour and brightness of canned pea were higher when neutral solution was used (a* = ?8.4 ± 0.3) than for the acidic one (a* = ?3.7 ± 0.6). The yellowness of corn was better with the neutral electro‐activated brine solution (b* = 36.32 ± 1.24) than with the acidic one (b* = 28.44 ± 2.39). Thirty‐three percent decrease of energy consumption was obtained using the electro‐activation technology.     

Commercially sterilized mussel meats (Mytilus chilensis): a study on process yield

The processing steps most responsible for yield loss in the manufacture of canned mussel meats are the thermal treatments of precooking to remove meats from shells, and thermal processing (retorting) to render the final canned product commercially sterile for long-term shelf stability. The objective of this study was to investigate and evaluate the impact of different combinations of process variables on the ultimate drained weight in the final mussel product (Mytilu chilensis), while verifying that any differences found were statistically and economically significant. The process variables selected for this study were precooking time, brine salt concentration, and retort temperature. Results indicated 2 combinations of process variables producing the widest difference in final drained weight, designated best combination and worst combination with 35% and 29% yield, respectively. Significance of this difference was determined by employing a Bootstrap methodology, which assumes an empirical distribution of statistical error. A difference of nearly 6 percentage points in total yield was found. This represents a 20% increase in annual sales from the same quantity of raw material, in addition to increase in yield, the conditions for the best process included a retort process time 65% shorter than that for the worst process, this difference in yield could have significant economic impact, important to the mussel canning industry.     

Thermal treatment of common beans (Phaseolus vulgaris L.): Factors determining cooking time and its consequences for sensory and nutritional quality

Over the past years, the shift toward plant-based foods has largely increased the global awareness of the nutritional importance of legumes (common beans (Phaseolus vulgaris L.) in particular) and their potential role in sustainable food systems. Nevertheless, the many benefits of bean consumption may not be realized in large parts of the world, since long cooking time (lack of convenience) limits their utilization. This review focuses on the current insights in the cooking behavior (cookability) of common beans and the variables that have a direct and/or indirect impact on cooking time. The review includes the various methods to evaluate textural changes and the effect of cooking on sensory attributes and nutritional quality of beans. In this review, it is revealed that the factors involved in cooking time of beans are diverse and complex and thus necessitate a careful consideration of the choice of (pre)processing conditions to conveniently achieve palatability while ensuring maximum nutrient retention in beans. In order to harness the full potential of beans, there is a need for a multisectoral collaboration between breeders, processors, and nutritionists.     

Food process innovation through new technologies: Use of ultrasound

The use of new or non-conventional technologies widens the food processing innovation possibilities. Among technologies with a potential application, high intensity ultrasonics has emerged. Ultrasound is a mechanical wave that can affect transport phenomena. Accordingly, the effect associated to ultrasonic application will be dependent on the medium where ultrasound is travelling and on the material to be affected. In this work, ultrasonic applications in different media, such as liquid, gas and supercritical fluid, are addressed as innovative alternatives to enhance transport phenomena and highlight the main factors affecting the process.     

Processing factor for a selected group of pesticides in a wine-making process: distribution of pesticides during grape processing

The processing factors (the pesticide concentration found in the wine/pesticide concentration found in grapes) of acetamiprid, azoxistrobin, carbaril, carbendazime, cyprodinil, dimethoate, dimethormorf, imazalil, imidacloprid, kresoxim methyl, penconazole, procymidone and thiabendazole were determined in a wine-making process. Pesticide analysis was performed using a multi-residue method for the determination of different pesticides both in wine and in grapes by extraction with acetonitrile followed by LC/MS. The pesticide distribution was studied for each step of the process, and the pesticide processing factors were calculated and found to vary among the different pesticides studied. pK_ow was found to affect a pesticide’s processing factor; a linear correlation was obtained for all pesticide processing factors, except for dimethoate, which was the most water soluble. However, no correlation was found between the processing factor and the water solubility of pesticides.     

Simulation and experimental validation of simultaneous heat and mass transfer for cooking process of Mortadella Bologna PGI

In this study, Protected Geographical Indication (PGI) Mortadella Bologna cooking process was investigated for heat and mass transfer. Apparent mass and heat transfer coefficient functions as well as apparent thermal diffusivity and mass diffusion coefficients were experimentally estimated. These thermo‐physical properties were used to develop a mathematical model for the simulation of simultaneous heat and mass transfer during Mortadella Bologna PGI cooking. The developed method was successfully validated for both heat and mass transfer by means of experimental cooking tests: maximum errors of about 3.5% and 4% were found for final product temperature and cooking time experimentally obtained respectively. Simulated weight loss values were also found not to differ significantly from those experimentally obtained. In addition, the developed model was successfully validated during a Mortadella cooking process carried out in an industrial plant proposing itself as a predictive tool to forecast and optimise cooking time and weight loss of this type of meat product. The proposed approach may be also used to design air cooking processes of other food products.     

Development and characterization of a prototype of a lactic acid–based time–temperature indicator for monitoring food product quality

Temperature is a crucial factor affecting the quality and safety of food products during both distribution and storage. The difficulty in controlling and monitoring the temperature history of food products makes it difficult to precisely predict shelf life. Time–temperature indicators (TTIs) provide a visual summary of a product’s accumulated chill-chain history, recording the effects of both time and temperature. Attempts have been made to develop a prototype of a time–temperature indicator based on the diffusion of lactic acid, which is temperature-dependent. Four lactic acid-based TTIs were made in different substrate concentrations. Color changes associated with the diffusion of lactic acid were monitored. In the vapor diffusion of lactic acid, an irreversible color change of a chemical chromatic indicator (from green to red) clearly and progressively occurred due to the pH reduction. The temperature dependence of these TTIs kinetics was characterized isothermally in the range of 4–45 °C, yielding activation energy (E_a) of, approximately, 50 kJ mol⁻¹. The mathematical models of each TTI were established according to the relationships between color changes and time and temperature. The differences between the E_a values of the TTIs and the E_a associated with food quality losses – including enzymatic loss, hydrolysis, lipid oxidation, nutrient loss and microbial growth – were less than 40 kJ mol⁻¹, and therefore these TTIs could be considered as good candidates to monitor food quality losses. Although these TTIs do not cover the whole range of food quality losses, they could be applied to show the time–temperature history of some foods, especially fruits and vegetables, and to indicate food quality associated with time–temperature exposure.     

Evaluation of a new time temperature integrator in pilot plant conditions

 Pilot plant studies were carried out to evaluate the accuracy and general performance of a new Time Temperature Integrator based on a gelled mixture of alginate-starch and mushroom puree over a temperature range of 115 to 125°C. New thermal resistance data were also obtained for Bacillus stearothermophilus spores heated to high temperatures (121–135°C), which are necessary for calculating the theoretical and experimental sterilization levels reached in the Integrator during pilot plant experiments. The results indicate that the decimal reduction coefficient (D) value of the gelled samples was higher than that of double-distilled water and ungelled samples under the same conditions. A mathematical model, improved by the use of recently measured D values, was able to predict the ability of the new Integrator to kill microorganisms extremely well, such that there were no significant differences between predicted and measured values. The number of microorganisms surviving in the Time Temperature Integrator when heated in an acidified brine was less than that surviving when heated in unacidified brine, for all the conditions studied. This result indicates that there is a good exchange capacity between the integrator and the surrounding medium, with the spores immobilized in the Integrator being subjected to stress conditions similar to those found in real food. Received: 26 May 1997 / Revised version: 3 September 1997     

AKD施胶新工艺应用

以浙江某纸厂生产定量140g／m2的挂面箱纸板为试验研究对象,详细探讨了AKD施胶应用的新工艺配比。试验表明：15％含量的AKD乳液配合阴离子垃圾捕捉剂0．jkg／t纸、助留剂0．4kg／t纸时,其用量仅为6kg／t纸,相比单独用AKD复配中性胶综合成本降低。     

Inactivation kinetics of pectin methylesterase in orange juice as a function of pH and temperature/time process conditions

Pasteurisation of orange juice (OJ) is necessary to prevent spoilage due to microorganisms and enzymes, mainly pectin methylesterase (PME). PME has a higher thermal resistance than the bacteria and yeasts existing in OJ and therefore its inactivation is used as a parameter to define the time/temperature combination of the thermal process. The enzyme has isoforms with different activities and thermal resistances. A three‐parameter model can be used to describe the kinetics of PME inactivation, where the more and less thermally resistant fractions are represented. In this study the thermal inactivation kinetics was evaluated at six pH values (3.6, 3.7, 3.8, 3.9, 4.0 and 4.1), three minimal temperatures (82.5, 85.0 and 87.5 °C) and at least six holding times for each condition. It was found that the thermolabile PME fraction (a) was influenced by pH and processing temperature. A slower reaction rate constant (k₁) was found for juices with pH values of 3.8 and 3.9 at the studied temperatures. The highest inactivation levels were obtained in juices with pH values of 3.6 and 3.7. Copyright © 2006 Society of Chemical Industry     

A Theoretical Study for Determination of Quality Equivalent Points for Volume Average Quality Evaluation in Conduction Heating Canned Foods

ABSTRACT:  In the present study, a set of quality equivalent points, that is, points where the retention of a particular quality attribute at the end of a thermal process is equal to the volume average quality retention, was determined for conduction heating products in cylindrical containers. For this, initially, the temperature distribution inside the product during the thermal process was numerically calculated, assuming uniform initial product temperature, constant heating and cooling medium temperatures, and infinite heat transfer coefficient between the cylinder walls and the heating or cooling medium. Next, remaining concentration data at the end of the process were obtained at various points within the container for a heat labile quality factor following 1st-order degradation kinetics. Thereafter, the volume average remaining concentration for the quality parameter under consideration was calculated and the quality equivalent points were identified. The influence of product, quality factor, and process characteristics on the location of the quality equivalent points, was examined. For every case investigated, the entirety of quality equivalent points was modeled by the use of a single parameter, the empirical j value. For most cases of common practice, a j value between 0.34 and 0.40 was found appropriate for volume average quality retention calculations. Thus, by collecting temperature data during processing at a quality equivalent point, product quality at the end of the process can be assessed.     

Combined CFD and Experimental Approach for Determination of the Surface Heat Transfer Coefficient During Thermal Processing of Eggs

A combined Computational Fluid Dynamics (CFD) and experimentally based approach is presented for determining the surface heat transfer coefficient acting at the shell when processing intact eggs. The methodology comprises (1) determining the contour of eggs from digital photographs, (2) generating a computational geometry, and (3) predicting the transient temperature profiles in eggs filled with a conductive heating medium. CFD profiles were compared with experimentally observed data, and the surface heat transfer coefficient was obtained through an optimization procedure. Agar gel was used as a model system, having properties very similar to those of water. The approach eliminates unknown factors such as natural convection, which is expected to occur in real eggs.     

Proteomic analysis of responses of a new probiotic bacterium Lactobacillus casei Zhang to low acid stress

Tolerance to acid is an important feature for probiotic bacteria during transition through the gastrointestinal tract. Proteomics analysis of a new probiotic bacterium, Lactobacillus casei Zhang, was performed upon 30-min exposure to low acid stress (pH 2.5 vs. pH 6.4) using two-dimensional electrophoresis. Out of 33 protein spots that showed changes of expression between the two pHs, 22 showed 1.5-fold higher expression at pH 2.5 than at pH 6.4, whereas five spots had expression decreased by 1.5-fold at pH 2.5. There were also six protein spots that were exclusively present on different pH maps. Further analysis showed that eight of the enhanced proteins, NagA, NagB, PGM, GlmM, LacC, TDP, GALM and PtsI, were involved in carbohydrate catabolism. Moreover, quantitative RT-PCR showed that the mRNA expression levels of dnaK, nagB, galm, estC, tuf and luxS were consistent with changes in protein expression. We postulate that there might be some relationship between differentially expressed proteins and acid tolerance in L. casei Zhang.     

Development of a food product profile for boiled and steamed sweetpotato in Uganda for effective breeding

This study sought to understand user preferences of raw, boiled and steamed sweetpotato, a staple food in Uganda. A sequential methodology involving state of knowledge review, gendered food mapping, processing diagnosis and consumer testing was used in Lira and Kamwenge districts. Preferred raw sweetpotato characteristics were large roots (≥ 3 cm diameter) with a sweet taste, smooth skin and hard texture, while mealiness, sweet taste and good sweetpotato smell were important attributes for boiled sweetpotato. Processors, mostly women, highlighted ease of peeling and sappiness of raw roots. There were gender differences in quality characteristic preferences and perceived importance. The released variety, NASPOT 8, had the highest overall liking in Kamwenge and was well liked in Lira. Penalty analysis of consumer data showed that sweetness and firmness were key drivers of overall liking. The results will support breeding programmes in meeting specific end-user product profiles, selection criteria and uptake of new varieties.     

Effects of perimortem stress on farmed Atlantic cod product quality: a baseline study

The potential effects of handling stress on the product quality of farmed Atlantic cod were studied in a controlled experiment (fish anesthetized with metomidate or isoeugenol, or subjected to stress by chasing for 30 min). For comparison, stress and fillet quality was also studied for commercially slaughtered farmed cod (fish sampled from waiting cage, after pumping and stunning with carbon dioxide, and after bleeding and chilling). Baseline values for stress-related parameters (blood chemistry, muscle high-energy phosphates and inosine monophospate, initial pH, muscle twitches, and rigor mortis) of rested Atlantic cod have been established. Since our stress bout showed that this species was not easily excitable, we were less convinced that we actually did study the other extreme, namely, exhausted fish. Nevertheless, the present data from the commercial slaughter of cod suggested that our stress bout was of adequate magnitude to represent potential poor handling routines. Our results consistently showed largely no differences between treatments, and that perimortem handling stress did not cause inferior flesh quality. This suggested that farmed cod can be processed with little risk of reducing product quality (quality index, fillet water content, water-holding capacity, ultimate pH, adenosine triphosphate-related degradation products and K-value, skin and fillet color, water and salt-soluble proteins, hardness, and gaping). For better maintenance of skin appearance after storage, the importance of storing the gutted cod on the belly, avoiding direct contact between skin and crushed ice, is demonstrated.