Pulsed Electric Fields enhances calcium infusion for improving the hardness of blanched carrots

Effect of Moderate Electric Fields on the Physical and Chemical Characteristics of Cheese Emulsions

Cheese powder is a multifunctional ingredient that is produced by spray drying a hot cheese emulsion called cheese feed. Feed stability is achieved by manipulating calcium equilibrium using emulsifying salts. However, the increased demand for 'green' products created a need for alternative production methods. Therefore, this study investigated the impact of ohmic heating (OH) on Cheddar cheese, mineral balance, and the resulting cheese feed characteristics compared with a conventional method. A full factorial design was implemented to determine the optimal OH parameters for calcium solubilization. Electric field exposure and temperature had a positive correlation with mineral solubilization, where temperature had the greatest impact. Structural differences in pre-treated cheeses (TC) were analyzed using thermorheological and microscopic techniques. Obtained feeds were analyzed for particle size, stability, and viscosity. OH-treatment caused a weaker cheese structure, indicating the potential removal of calcium phosphate complexes. Lower component retention of OH_TC was attributed to the electroporation effect of OH treatment. Microscopic images revealed structural changes, with OH_TC displaying a more porous structure. Depending on the pre-treatment method, component recovery, viscosity, particle size distribution, and colloidal stability of the obtained feeds showed differences. Our findings show the potential of OH in mineral solubilization; however, further improvements are needed for industrial application.

Effect of heat and pulsed electric field treatment on the physicochemical and nutritional properties of carrots

BACKGROUND

Carrots are widely used in home cooking and vegetable processing industries because of their high nutritional value. However, different processing methods may produce a negative impact on carrot texture and nutrition quality. Therefore, the development of better processing methods to preserve the texture and nutrition quality of carrots will be beneficial to the carrot industry.

RESULTS

The effects of heat and pulsed electric field (PEF) treatments with different heat temperatures (T) and holding time (t_h ) on comprehensive changes in thermal efficiency profiles, and physicochemical (color, hardness, cell structural damage) and nutritional (releasable β-carotene contents) properties of carrots were studied. In addition, electrical conductivity (σ) and soluble matter contents (°Brix) were determined for the heat-treated extracts. The value of total color difference (∆E) and cell structural damage index (Z) of carrots, σ and °Brix of extracts all increased with increasing T and t_h under different heat experimental conditions, whereas the value of cutting force (F) presented an opposite tendency and content of releasable β-carotene decreased after t_h  > 2 min at T = 100 °C.

CONCLUSION

The results show that PEF heating is beneficial in preventing changes in physicochemical and nutritional properties of carrots compared to traditional heat treatment. PEF has potential as a heating technology in the food industry. © 2022 Society of Chemical Industry.

Understanding In Vivo Mastication Behaviour and In Vitro Starch and Protein Digestibility of Pulsed Electric Field-Treated Black Beans after Cooking

The aim of this study was to understand (i) the in vivo mastication behaviour of cooked black beans (chewing duration, texture perception, oral bolus particle size, microstructure, and salivary α-amylase) and (ii) the in vitro digestibility of starch and protein of in vivo-generated black bean oral bolus under simulated gastrointestinal condition. The beans were pre-treated using pulsed electric field (PEF) with and without calcium chloride (CaCl₂) addition prior to cooking. The surface response model based on least square was used to optimise PEF processing condition in order to achieve the same texture properties of cooked legumes except for chewiness. In vivo mastication behaviour of the participants (n = 17) was characterized for the particle size of the resulting bolus, their salivary α-amylase activity, and the total chewing duration before the bolus was deemed ready for swallowing. In vitro starch and protein digestibility of the masticated bolus generated in vivo by each participant along the gastrointestinal phase were then studied. This study found two distinct groups of chewers—fast and slow chewers who masticated all black bean beans, on average, for <25 and >29 s, respectively, to achieve a bolus ready for swallowing. Longer durations of chewing resulted in boluses with small-sized particles (majorly composed of a higher number of broken-down cotyledons (2–5 mm² particle size), fewer seed coats (5–13 mm² particle size)), and higher activity of α-amylase. Therefore, slow chewers consistently exhibited a higher in vitro digestibility of both the starch and protein of processed black beans compared to fast chewers. Despite such distinct difference in the nutritional implication for both groups of chewers, the in vivo masticated oral bolus generated by fast chewers revealed that the processing conditions involving the PEF and addition of CaCl₂ of black beans appeared to significantly (p < 0.05) enhance the in vitro digestibility of protein (by two-fold compared to untreated samples) without stimulating a considerable increase in the starch digestibility. These findings clearly demonstrated that the food structure of cooked black beans created through PEF treatment combined with masticatory action has the potential to modulate a faster hydrolysis of protein during gastrointestinal digestion, thus offering an opportunity to upgrade the quality of legume protein intake in the daily diet.

Recent Advances toward the Application of Non-Thermal Technologies in Food Processing: An Insight on the Bioaccessibility of Health-Related Constituents in Plant-Based Products

Fruits and vegetables are rich sources of bioactive compounds and micronutrients. Some of the most abundant are phenols and carotenoids, whose consumption contributes to preventing the occurrence of degenerative diseases. Recent research has shown the potential of non-thermal processing technologies, especially pulsed electric fields (PEF), ultrasounds (US), and high pressure processing (HPP), to trigger the accumulation of bioactive compounds through the induction of a plant stress response. Furthermore, these technologies together with high pressure homogenization (HPH) also cause microstructural changes in both vegetable tissues and plant-based beverages. These modifications could enhance carotenoids, phenolic compounds, vitamins and minerals extractability, and/or bioaccessibility, which is essential to exert their positive effects on health. Nevertheless, information explaining bioaccessibility changes after non-thermal technologies is limited. Therefore, further research on food processing strategies using non-thermal technologies offers prospects to develop plant-based products with enhanced bioaccessibility of their bioactive compounds and micronutrients. In this review, we attempt to provide updated information regarding the main effects of PEF, HPP, HPH, and US on health-related compounds bioaccessibility from different vegetable matrices and the causes underlying these changes. Additionally, we propose future research on the relationship between the bioaccessibility of bioactive compounds and micronutrients, matrix structure, and non-thermal processing.

Combined Effects of Calcium Addition and Thermal Processing on the Texture and In Vitro Digestibility of Starch and Protein of Black Beans (Phaseolus vulgaris)

Legumes are typically soaked overnight to reduce antinutrients and then cooked prior to consumption. However, thermal processing can cause over-softening of legumes. This study aimed to determine the effect of calcium addition (0, 100, 300, and 500 ppm in the form of calcium chloride, CaCl₂), starting from the overnight soaking step, in reducing the loss of firmness of black beans during thermal processing for up to 2 h. The impact of calcium addition on the in vitro starch and protein digestibility of cooked beans was also assessed. Two strategies of calcium addition were employed in this study: (Strategy 1/S1) beans were soaked and then cooked in the same CaCl₂ solution, or (Strategy 2/S2) cooked in a freshly prepared CaCl₂ solution after the calcium-containing soaking medium was discarded. Despite the texture degradation of black beans brought about by increasing the cooking time, texture profile analysis (TPA) revealed that their hardness, cohesiveness, springiness, chewiness, and resilience improved significantly (p < 0.05) with increasing calcium concentration. Interestingly, beans cooked for 2 h with 300 ppm CaCl₂ shared similar hardness with beans cooked for 1 h without calcium addition. Starch and protein digestibility of calcium-treated beans generally improved with prolonged cooking. However, calcium-treated beans cooked for 1 h under S2 achieved a reduced texture loss and a lower starch digestibility than those beans treated in S1. A lower starch digestion could be desired as this reflects a slow rise in blood glucose levels. Findings from this result also showed that treating black beans with high level of CaCl₂ (i.e., 500 ppm) was not necessary, otherwise this would limit protein digestibility of cooked black beans.

Effect of pulsed electric fields on carotenoid and phenolic bioaccessibility and their relationship with carrot structure

Phenolic compounds (PC) and carotenoids from carrots are bound to dietary fibre or stored in vacuoles and chromoplasts, respectively. To exert their antioxidant effects these compounds must be released during digestion, which is hindered by such barriers. Pulsed electric fields (PEF) modify cell membrane permeability, thus enhancing their bioaccessibility. The effect of PEF on the carrot carotenoid and PC content and bioaccessibility was investigated. With this purpose, PEF-treated carrots (5 pulses of 3.5 kV cm^-1) were stored for 24 h at 4 °C and microstructure was evaluated before subjecting them to in vitro digestion. PEF did not affect carotenoid content, whereas their bioaccessibility improved (11.9%). Likewise, PEF increased the content of some PC, e.g. coumaric acid (163.2%), probably caused by their better extractability. Conversely, caffeic acid derivatives decreased, which may be associated to greater contact with oxidative enzymes. Total PC bioaccessibility (20.8%) and some derivatives increased, e.g. caffeoylshikimic (68.9%), whereas some decreased (e.g. ferulic acid). Structural changes caused by PEF may improve bioaccessibility of carotenoids and PC by favouring their release and easy access to digestive enzymes. However, other antioxidants may be further degraded or entrapped during digestion. Therefore, PEF is an effective technology for obtaining carrots with enhanced carotenoids and phenolic bioaccessibility.

Effects of tissue pre-degassing followed by ultrasound-assisted freezing on freezing efficiency and quality attributes of radishes

The rapid freezing technique for porous foods using tissue pre-degassing followed by ultrasound-assisted freezing (UF) was developed, and its effects on quality attributes of radishes including tissue air volume, hardness, total calcium contents, bonded calcium contents, retention rates of bonded calcium and microstructures were investigated. To evaluate the freezing efficiency, parameters including total freezing time, phase transition time, and the increases of freezing rate and phase transition rate were determined. Besides, multivariate statistical analyses including principal component analysis (PCA) and hierarchical cluster analysis (HCA) were performed to visualize and further analyze the quality differences of radishes under different treatments. Results suggested that decreasing tissue air volumes can significantly shorten the phase transition time of UF. Samples treated by pre-degassing for 5 min at -0.09 MPa followed by UF (D_-0.09MPa^5min-UF) showed the freezing rate and phase transition rate increased by 28.8% and 29.8%, respectively, as compared with the same pre-degassed samples frozen by immersion freezing (D_-0.09MPa^5min-IF). Retention rates of bonded calcium positively correlated with the sample hardness, announcing the importance of bonded calcium maintenance during radish freezing. Both PCA and HCA indicated that D_-0.09MPa^5min-UF endowed radishes with quality attributes more similar to the fresh ones, which was further verified by microstructure analysis, showing remarkably alleviated plasma membrane puncture, cell separation and deformation in D_-0.09MPa^5min-UF samples. The current study proved that the technique of tissue pre-degassing followed by UF could effectively improve the freezing efficiency and quality attributes of frozen radishes, and thus have great potentials in rapid freezing of porous foods.

Impact of Processing Factors on Quality of Frozen Vegetables and Fruits

In this paper I review the production of frozen vegetables and fruits from a chain perspective. I argue that the final quality of the frozen product still can be improved via (a) optimization of the complete existing production chain towards quality, and/or (b) introduction of some promising novel processing technology. For this optimization, knowledge is required how all processing steps impact the final quality. Hence, first I review physicochemical and biochemical processes underlying the final quality, such as water holding capacity, ice crystal growth and mechanical damage. Subsequently, I review how each individual processing step impacts the final quality via these fundamental physicochemical and biochemical processes. In this review of processing steps, I also review the potential of novel processing technologies. The results of our literature review are summarized via a causal network, linking processing steps, fundamental physicochemical and biochemical processes, and their correlation with final product quality. I conclude that there is room for optimization of the current production chains via matching processing times with time scales of the fundamental physicochemical and biochemical processes. Regarding novel processing technology, it is concluded in general that they are difficult to implement in the context of existing production chains. I do see the potential for novel processing technology combined with process intensification, incorporating the blanching pretreatment—but which involves quite a change of the production chain.

Textural Effects on Perceived Satiation and Ad Libitum Intake of Potato Chips in Males and Females

Food texture plays a critical role in influencing an individual’s perceived satiation and ad libitum intake. It remains unclear, however, whether such textural changes can also affect snack consumption. This study aimed to address this question by testing for changes in perceived satiation and ad libitum intake of two types of potato chips with varying hardness. In addition, the observed effect was compared across gender groups. With a crossover design, 74 participants (31 females and 43 males) performed a food consumption task for two types of chips produced from potatoes that were either untreated or treated with pulsed electric fields (PEF) technology. Sensory analyses indicated that these two types of chips had comparable hedonic value, despite a clear textural difference. Across sexes, the results revealed a significant difference in perceived satiation for the two types of chips (p = 0.009), but not in intake. By contrast, analyses of males alone revealed that male participants rated PEF-treated chips to be more satiating than the control chips and correspondingly consumed less (p < 0.05). Overall, findings from the study suggest that modifications of food texture can be a helpful tool in reducing energy intake from snack consumption. The contrasting results from different gender groups highlight the importance of considering gender effects in studies of eating behaviour.

The application of unconventional technologies as pulsed electric field, ultrasound and microwave-vacuum drying in the production of dried cranberry snacks

A lot of effort is put to decrease the energy consumption of drying. This effect might be achieved by shift of a drying technology e.g. from a hot-air to a microwave-vacuum method. Moreover, an unconventional pre-treatment such as ultrasound or pulsed electric field may modify a cellular tissue, what influences drying kinetics of plant tissue. The aim of the study was to analyse the quality of microwave-vacuum dried, osmodehydrated (OD) cranberries processed by the means of blanching and ultrasound (US) or blanching followed by pulsed electric field and sonication (PEF + US) in comparison to traditionally treated material. Physical, chemical and sensorial properties of cranberry fruits were assessed. What is more, the impact of aforementioned unconventional treatments on the kinetics of microwave-vacuum dried cranberries was studied. Microwave-vacuum drying process was very short (25-38 min) in comparison to convective drying, which lasted several hours (13.2 h). Most of the samples subjected to US and PEF + US treatments before OD and drying were characterized by similar or a higher amount of bioactive compounds such as polyphenols, anthocyanins and flavonoids, and better colour and taste, as compared to cut osmodehydrated cranberry fruits subjected to convective drying (reference samples).