Ingrid Aguiló-Aguayo

Volatile compounds and changes in flavour-related enzymes during cold storage of high-intensity pulsed electric field- and heat-processed tomato juices.

BACKGROUND The effects of high-intensity pulsed electric field (HIPEF) processing (35 kV cm(-1) for 1500 micros, using 4 micros bipolar pulses at 100 Hz) on the production of volatile compounds and flavour-related enzymes in tomato juice were investigated and compared with those of thermal processing (90 degrees C for 30 or 60 s). RESULTS Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 degrees C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 degrees C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 degrees C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. CONCLUSION HIPEF-treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat-treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments.

High-intensity pulsed electric fields processing parameters affecting polyphenoloxidase activity of strawberry juice.

High-intensity pulsed electric fields (HIPEF) were applied to strawberry juice to study the feasibility of inactivating polyphenoloxidase (PPO). Response surface methodology was used to evaluate the effect of HIPEF processing, in which total treatment time (1000 to 2000 μs), pulse frequency (50 to 250 Hz), pulse width (1.0 to 7.0 μs), and polarity (monopolar or bipolar) were the controlled variables at a constant electric field of 35 kV/cm. The proposed 2nd-order response functions were accurate enough to fit experimental results. Strawberry juice PPO was strongly reduced within the range of assayed conditions. HIPEF treatments were more effective in bipolar than in monopolar mode in inactivating PPO. Treatments of longer duration resulted in reductions of the enzyme activity. Moreover, it was feasible to minimize residual PPO activity (down to 2.5%) by selecting bipolar treatments at frequencies higher than 229 Hz and pulse widths between 3.23 and 4.23 μs for a constant total treatment time of 2000 μs.

Influence of Modified Atmosphere Packaging on Volatile Compounds and Physicochemical and Antioxidant Attributes of Fresh-Cut Pineapple (Ananas comosus)

The effects of modified atmosphere packaging on volatile compound content and physicochemical and antioxidant attributes of Gold cultivar fresh-cut pineapples were assessed throughout storage at 5 degrees C. Fresh-cut pineapple pieces were packed under LO (low oxygen, 12% O(2), 1% CO(2)), AIR (20.9% O(2)) and HO (high oxygen, 38% O(2)) headspace atmospheres. Methyl butanoate, methyl 2-methylbutanoate, and methyl hexanoate were the most abundant volatiles regardless of the packaging atmosphere and days of storage; whereas most odor active volatiles were methyl and ethyl 2-methylbutanoate, 2,5-dimethyl-4-methoxy-3(2H)-furanone and ethyl hexanoate. Physicochemical attributes of pineapple did not significantly vary, whereas vitamin C content and total antioxidant capacity were lower for fresh-cut pineapple in HO (488 +/- 38 mg/100 mg(fw) and 54.4 +/- 5.7%, respectively) than for LO and AIR packages. Storage life of fresh-cut pineapple was limited to 14 days by volatile compounds losses and fermentation processes.

Effects of High-Intensity Pulsed Electric Fields on Lipoxygenase and Hydroperoxide Lyase Activities in Tomato Juice

The influence of high-intensity pulsed electric field (HIPEF) parameters, namely, pulse frequency, pulse width, and polarity on tomato juice lipoxygenase (LOX) and hydroperoxide lyase (HPL) activities was studied using a response surface methodology. Samples were subjected to square-shaped pulses of 35 kV/cm for 1000 micros, with pulse width ranging from 1 to 7 micros at frequencies from 50 to 250 Hz, either in monopolar or bipolar mode. Tomato LOX was more resistant to HIPEF than HPL within the range of assayed conditions. An increase in frequency or pulse width resulted in a decrease of both residual LOX (RA(LOX)) and HPL (RA(HPL)) activities. The lowest RA(LOX) (81%) was observed when tomato juice was treated at 250 Hz for 7 mus in bipolar mode. Moreover, the same conditions led to the highest HPL activity reduction (RA(HPL) = 10%). A validation of the predictive models determined that 2nd-order expressions were accurate enough to fit the experimental results.

Pulsed Electric Fields to Obtain Safe and Healthy Shelf-Stable Liquid Foods

Pulsed electric fields (PEF) technology provides the potential of ensuring safety and maintaining the physico-chemical quality of liquid food products without substantially impacting the content and composition of thermolabile compounds. This is especially relevant in the case of plant-based foods, because some of the features that are currently most appreciated by consumers, such as aroma or bioactive potential, are related to this heat-sensible fraction. Specifically, fruit juices and vegetable-based beverages exhibit a remarkable content in phytochemicals with health-promoting benefits, some of them with a significant antioxidant potential. Although the effectiveness of PEF treatments has been extensively studied during the past couple of decades, their impact on the bioactive composition of foods is still being researched. Through the presentation, some of the key factors that rule the inactivation/destruction of health-related constituents in foods will be introduced and discussed. Recently published research results will be reviewed and compared with those obtained for other thermal and non-thermal processing technologies, with a special stress on the effect of PEF-processing variables on the bioactive composition of foods throughout their whole shelf-life. Furthermore, different examples will be presented to illustrate not only the potential but also the limitations of PEF technology when aiming at preserving the health-promoting features of plant-based foods.

Exploring the Effects of Pulsed Electric Field Processing Parameters on Polyacetylene Extraction from Carrot Slices

The effects of various pulsed electric field (PEF) parameters on the extraction of polyacetylenes from carrot slices were investigated. Optimised conditions with regard to electric field strength (1–4 kV/cm), number of pulses (100–1500), pulse frequency (10–200 Hz) and pulse width (10–30 μs) were identified using response surface methodology (RSM) to maximise the extraction of falcarinol (FaOH), falcarindiol (FaDOH) and falcarindiol-3-acetate (FaDOAc) from carrot slices. Data obtained from RSM and experiments fitted significantly (p < 0.0001) the proposed second-order response functions with high regression coefficients (R2) ranging from 0.82 to 0.75. Maximal FaOH (188%), FaDOH (164.9%) and FaDOAc (166.8%) levels relative to untreated samples were obtained from carrot slices after applying PEF treatments at 4 kV/cm with 100 number of pulses of 10 μs at 10 Hz. The predicted values from the developed quadratic polynomial equation were in close agreement with the actual experimental values with low average mean deviations (E%) ranging from 0.68% to 3.58%.

Effects of thermal and non-thermal processing of cruciferous vegetables on glucosinolates and its derived forms

Brassica vegetables, which include broccoli, kale, cauliflower, and Brussel sprouts, are known for their high glucosinolate content. Glucosinolates and their derived forms namely isothiocyanates are of special interest in the pharmaceutical and food industries due to their antimicrobial, neuroprotective, and anticarcinogenic properties. These compounds are water soluble and heat-sensitive and have been proved to be heavily lost during thermal processing. In addition, previous studies suggested that novel non-thermal technologies such as high pressure processing, pulsed electric fields, or ultraviolet irradiation can affect the glucosinolate content of cruciferous vegetables. The objective of this paper was to review current knowledge about the effects of both thermal and non-thermal processing technologies on the content of glucosinolates and their derived forms in brassica vegetables. This paper also highlights the importance of the incorporation of brassica vegetables into our diet for their health-promoting properties beyond their anticarcinogenic activities.

Evaluation of postharvest calcium treatment and biopreservation with Lactobacillus rhamnosus GG on the quality of fresh-cut ‘Conference’ pears: Evaluation of the effect of calcium and probiotic bacteria on the quality of fresh-cut pears

BACKGROUND Biological preservation with probiotic bacteria has arisen as an alternative to control the growth of foodborne pathogens on food. The objective of this work was to evaluate the effect of postharvest calcium application and biopreservation with Lactobacillus rhamnosus GG on the quality and bioaccessibility of total phenolic content and antioxidant activity in fresh-cut pears. RESULTS The immersion of whole pears in a calcium chloride solution did not provide added value. Despite the increase in observed activity of PME and PPO enzymes in fresh-cut pears during storage, the browning index and firmness values were constant for all samples. The antioxidant properties, including antioxidant activity, total phenolic content and vitamin C content, were maintained during storage, but a significant decrease was observed after in vitro simulated digestion. Ca/LGG samples showed the lowest calcium content (1.75 ± 0.00 g kg-1 ) after 9 d of storage at 4 °C. In general, the overall visual quality scores were higher in fresh-cut pears treated with L. rhamnosus GG than in non-treated pears, with the highest values in the NoCa/LGG (7.7 ± 0.2) samples after 9 d at 4 °C. CONCLUSION Fresh-cut pears with a postharvest treatment of calcium and immersed in a solution containing antioxidant agents and probiotic bacteria could be a suitable alternative to dairy products for maintaining the overall quality of fruit for up to 9 d of storage.

Physiochemical and nutritional characteristics, bioaccessibility and sensory acceptance of baked crackers containing broccoli co-products

The effects of the inclusion of broccoli co‐products into crackers on the bioaccessibility as well as their overall physical and nutritional quality were evaluated. Crackers were formulated using a 12.5 or 15.0% flour substitution level. Broccoli‐containing crackers presented higher specific volume and spread ratio and lower weight and specific volume than control crackers (P < 0.05). Crackers containing broccoli co‐products showed an increased green hue and a higher colour intensity (P < 0.05). Incorporation of broccoli co‐products into crackers significantly increased the total phenolic content and antioxidant capacity (P < 0.05). A simulated gastrointestinal digestion suggested that the amount of phenolic and antioxidant compounds released during digestion might be higher than what could be expected from common water‐organic extracts. The incorporation of broccoli co‐products into baked crackers would not only reduce the amount of food discarded as waste but also promote health and open novel commercial opportunities to food processors.