Acidification,crushing and thermal treatments can influence the profile and stability of folate poly-γ-glutamates in broccoli (Brassica oleracea L. var. italica)

The influence of different treatments, i.e., crushing, high temperature short time (90 °C/4 min) (HTST) and low temperature long time (60 °C/40 min) (LTLT) blanching, acidification (pH 4.3), and sequences of these treatments on the folate poly-γ-glutamate profile and stability were investigated. In this study, broccoli was used as a case study. Regarding the folate poly-γ-glutamate profile, endogenous folate poly-γ-glutamates in broccoli florets were found predominantly as hepta- and hexa-γ-glutamates. Crushing raw broccoli, acidification and LTLT blanching enhanced folate deconjugation resulting in monoglutamate, di- and tri-γ-glutamates. Compared to other treatments, HTST blanching preformed prior to crushing resulted in the highest concentration of long chain poly-γ-glutamates. Regarding folate poly-γ-glutamates stability, acidification combined with LTLT blanching decreased folate stability whereas HTST blanching combined with different sequences of blanching and crushing did not affect folate poly-γ-glutamates stability. It was concluded that crushing (prior to heating), acidification and blanching could be strategically applied to increase the folate monoglutamate content of broccoli.     

Effect of endogenous ascorbic acid oxidase activity and stability on vitamin C in carrots (Daucus carota subsp. sativus) during thermal treatment

The purpose of this research was to study the effect of endogenous ascorbic acid oxidase (AAO) on vitamin C in carrots (Daucus carota subsp. sativus), namely Nantes, Egmont Gold and baby carrots during thermal treatment. Enzyme-substrate reaction kinetics of AAO were described using Michaelis–Menten equation. The estimated K_m and V_max values of AAO ranged from 50.34 to 63.54 μM and 23.70 to 26.82 μmol/min, respectively. Nantes carrots had the lowest AAO activity. On the other hand, Egmont Gold had the highest V_max. AAO activity in all carrot cultivars was stable up to 50 °C and inactivated above 50 °C. Irreversible thermal inactivation of AAO followed first order kinetics (55–70 °C) and the estimated activation energy of the three carrot cultivars situated between 114.33 and 191.45 kJ/mol. Regarding vitamin C stability, thermal treatment at 60–70 °C has resulted in total conversion of l-AA to DHAA due to residual AAO activity; a complete AAO inactivation was found in 80 °C-treated carrots with high vitamin C retention predominantly in l-AA form, up to 90%. On average, the carrots had a total vitamin C content amounting from 368.24 to 379.87 μg/g dry matter and the Nantes carrots had the highest vitamin C content. The effectiveness of rapid inactivation of endogenous AAO via heating (>80 °C, 10 min) prior to matrix disruption gave protection to l-AA towards enzymatic oxidation, thus resulted in a higher vitamin C content and stability in carrots.     

Effect of Infrared Blanching on Enzyme Activity and Retention of β‐Carotene and Vitamin C in Dried Mango

The objectives of this work were to evaluate infrared (IR) dry blanching in comparison with conventional water blanching prior to hot air drying of mango to inactivate polyphenol oxidase (PPO) and ascorbic acid oxidase (AAO) enzymes, and to study its effect on color change and retention of vitamin C and β‐carotene. Mango cylinders were blanched under similar temperature–time conditions either by IR heating or by immersion in a water bath during 2 min at 90 °C (high‐temperature‐short‐time—HTST) or for 10 min at 65 °C (low‐temperature‐long‐time—LTLT). After blanching mango was hot air dried at 70 °C. PPO was completely inactivated during the blanching treatments, but AAO had a moderate remaining activity after LTLT treatment (～30%) and a low remaining activity after HTST treatment (9% to 15%). A higher retention of vitamin C was observed in mango subjected to IR dry blanching, 88.3 ± 1.0% (HTST) and 69.2 ± 2.9% (LTLT), compared with water blanching, 61.4 ± 5.3% (HTST) and 50.7 ± 9.6% (LTLT). All‐trans‐β‐carotene retention was significantly higher in water blanched dried mango, 93.2 ± 5.2% (LTLT) and 91.4 ± 5.1% (HTST), compared with IR dry blanched, 73.6 ± 3.6% (LTLT) and 76.9 ± 2.9% (HTST). Increased levels of 13‐cis‐β‐carotene isomer were detected only in IR dry blanched mango, and the corresponding dried mango also had a slightly darker color. IR blanching of mango prior to drying can improve the retention of vitamin C, but not the retention of carotenoids, which showed to be more dependent on the temperature than the blanching process. A reduction of drying time was observed in LTLT IR‐blanching mango.     

Ohmic cooking of whole beef muscle — Evaluation of the impact of a novel rapid ohmic cooking method on product quality

Cylindrical cores of beef semitendinosus (500 g) were cooked in a combined ohmic/convection heating system to low (72 °C, LTLT) and high (95 °C, HTST) target end-point temperatures. A control was also cooked to an end-point temperature of 72 °C at the coldest point. Microbial challenge studies on a model meat matrix confirmed product safety. Hunter L-values showed that ohmically heated meat had significantly (p < 0.05) lighter surface-colours (63.05 (LTLT) and 62.26 (HTST)) relative to the control (56.85). No significant texture differences (p ≥ 0.05) were suggested by Warner–Bratzler peak load values (34.09, 36.37 vs. 35.19 N). Cook loss was significantly (p < 0.05) lower for LTLT samples (29.3%) compared to the other meats (36.3 and 33.8%). Sensory studies largely confirmed these observations. Cook values were lower for LTLT (3.05) while HTST and the control were more comparable (6.09 and 7.71, respectively). These results demonstrate considerable potential for this application of ohmic heating for whole meats.     

Effect of thermal blanching and of high pressure treatments on sweet green and red bell pepper fruits (Capsicum annuum L.)

The effect of pressure treatments of 100 and 200 MPa (10 and 20 min) and of thermal blanching at 70 °C, 80 °C and 98 °C (1 and 2.5 min), on sweet green and red bell peppers was compared. Pressure treated peppers showed a lower reduction on soluble protein and ascorbic acid contents. Red peppers presented even an increased content of ascorbic acid (15–20%), compared to the untreated peppers. Peroxidase and pectin methylesterase (whose activity was only quantifiable in green peppers) showed a higher stability to pressure treatments, particularly the latter enzyme, while polyphenol oxidase was inactivated to the same final level by the thermal blanching and pressure treatments. Pressure treatments resulted in comparable (in green pepper) to higher (in red pepper) microbial loads compared to blanching. Pressure treated green and red peppers presented similar to better firmness before and after tunnel freezing at −30 °C, compared to thermally blanched peppers, particularly those blanched at 98 °C. The results indicated that pressure treatments of 100 and 200 MPa can be used to produce frozen peppers with similar to better nutritional (soluble protein and ascorbic acid) and texture (firmness) characteristics, comparable activity of polyphenol oxidase and higher activity of pectin methylesterase, while pressure treated peppers show a higher level of peroxidase activity. It would be interesting to use higher pressures in future studies, as an attempt to cause a higher reduction on microbial load and on enzymatic activity.     

Ohmic cooking of whole turkey meat – Effect of rapid ohmic heating on selected product parameters

Intact turkey meat was cooked using low temperature long time (LTLT) and high temperature short time (HTST) protocols in a combined ohmic/convection system and compared to conventional (CONV) steam cooking. Both ohmic protocols gave a significantly lighter (p < 0.05) and a more uniform colour vs. CONV, while no significant differences (p ? 0.05) were found in texture profile analysis attributes between LTLT and CONV though HTST showed significantly higher attributes (p < 0.05). Cook loss was significantly (p < 0.05) different between treatments (25.2%, 27.9% and 31.3% for LTLT, CONV and HTST). Sensory studies largely confirmed these observations. Cook values (p < 0.05) were lowest for LTLT (4.0) followed by HTST (5.4) and control (8.5). Lipid oxidation and sulphur-flavour-compound development (measured over 7 days) were higher for conventional than ohmic treatments. Overall, these results demonstrate considerable industrial potential for ohmic heating, yielding high quality products with an 8–15-fold reduction in cooking time.     

Effect of microwave pretreatment on the kinetics of ascorbic acid degradation and peroxidase inactivation in different parts of green asparagus (Asparagus officinalis L.) during water blanching

In this study, the effects of two blanching conditions on ascorbic acid (AA) and peroxidase (POD) in different segments of asparagus (bud, upper, middle, and butt) were investigated. The blanching treatments were: blanching in water at 70, 80 and 90 °C (WB); microwave heating (900 W, 30 s) followed by water blanching (MW + WB). AA degradation and POD inactivation in all segments of asparagus for both treatments are well described by first-order models. The degradation rate of AA and POD is gradually increased from butt to bud segment of asparagus. In addition, MW pre-treatment could increase the E_a of AA degradation and decrease the E_a of POD inactivation during water blanching of asparagus. Therefore, it is recommended that the different segments of asparagus should be subjected to different blanching times, and MW pre-treatment could be applied for alleviating AA degradation and accelerating POD inactivation during blanching, cooking and pasteurisation in water.     

Effect of preliminary processing and method of preservation on the content of selected antioxidative compounds in kale (Brassica oleracea L. var. acephala) leaves

Vitamin C and polyphenol content as well as total antioxidative activity were investigated in fresh leaves of kale; in leaves after blanching or cooking; and in frozen and canned leaves. In 100 g fresh matter, kale leaves contained 384.9 mg polyphenols and 112.1 mg vitamin C, with a Trolox equivalent antioxidant capacity (TEAC) level of 1175 μM Trolox. Of the polyphenols identified in kale leaves, ferulic acid occurred in the highest amount (240.44 mg/100 g, constituting 62% of total polyphenols). Freezing was a better method of preserving kale leaves since the loss of nutritive constituents was lower than in the case of canning. Depending on preliminary processing and storage temperature, after one-year storage frozen leaves contained 82.9–171.3 mg polyphenols and 39.3–65.4 mg vitamin C, with TEAC at the level of 501–681 μM Trolox in 100 g. In canned leaves these values were: 91.3–94.1 mg polyphenols, 16.1–19.3 mg vitamin C and 268–293 μM Trolox.     

Temperate and virulent Lactobacillus delbrueckii bacteriophages: Comparison of their thermal and chemical resistance

The aim of this work was to study the efficiency of diverse chemical and thermal treatments usually used in dairy industries to control the number of virulent and temperate Lactobacillus delbrueckii bacteriophages. Two temperate (Cb1/204 and Cb1/342) and three virulent (BYM, YAB and Ib3) phages were studied. The thermal treatments applied were: 63 °C for 30 min (low temperature – long time, LTLT), 72 °C for 15 s (high temperature – short time, HTST), 82 °C for 5 min (milk destined to yogurt elaboration) and 90 °C for 15 min (FIL-IDF). The chemical agents studied were: sodium hypochlorite, ethanol, isopropanol, peracetic acid, biocides A (quaternary ammonium chloride), B (hydrogen peroxide, peracetic acid and peroctanoic acid), C (alkaline chloride foam), D (p-toluensulfonchloroamide, sodium salt) and E (ethoxylated nonylphenol and phosphoric acid). The kinetics of inactivation were drew and T₉₉ (time necessary to eliminate the 99% of phage particles) calculated. Results obtained showed that temperate phages revealed lower resistance than the virulent ones to the treatment temperatures. Biocides A, C, E and peracetic acid showed a notable efficiency to inactivate high concentrations of temperate and virulent L. delbrueckii phages. Biocide B evidenced, in general, a good capacity to eliminate the phage particles. Particularly for this biocide virulent phage Ib3 showed the highest resistance in comparison to the rest of temperate and virulent ones. On the contrary, biocide D and isopropanol presented a very low capacity to inactivate all phages studied. The efficiency of ethanol and hypochlorite was variable depending to the phages considered. These results allow a better knowledge and give useful information to outline more effective treatments to reduce the phage infections in dairy plants.     

Effect of cooking on total vitamin C contents and antioxidant activity of sweet chestnuts (Castanea sativa Mill.)

In this work the total vitamin C contents (ascorbic acid + dehydroascorbic acid) and antioxidant activity of raw and cooked chestnuts was evaluated. The vitamin C contents of raw chestnuts varied significantly between the different cultivars (cv) studied and it varied from 400 mg/kg dry weight (cv Lada) to 693 mg/kg dry weight (cv Martaínha). The different cultivars behave differently during the cooking process concerning the loss of vitamin C. A significant decrease in the vitamin C content of the chestnuts was observed, 25–54% for the boiling process and 2–77% for the roasting process. Boiled and roasted chestnuts can be good sources of vitamin C since it may represent 22.4%, 16.2%, 26.8% and 19.4%, respectively, of the recommended dietary intake for an adult man and woman. The cooking process significantly changed the antioxidant activity of the chestnuts. A difference was observed between the cultivars during the cooking processes, concerning the antioxidant activity. For the raw chestnuts the variation in vitamin C content of the chestnuts explains 99% of the antioxidant activity variation but for the roasted and boiled chestnuts this percentage significantly decreases to 51% and 88%, respectively. Although a high antioxidant activity is still present in the cooked chestnuts, the cause for this antioxidant activity is less dependent on the vitamin C content of the chestnuts, probably due to the conversion of ascorbic acid to dehydroascorbic acid. The increase in gallic acid during the cooking process, presumably transferred from the peels to the fruit, also contributes to the high antioxidant activity observed for the cooked chestnuts.     

High-pressure treatments induce folate polyglutamate profile changes in intact broccoli (Brassica oleraceae L. cv. Italica) tissue

In plant matrices, folates exist largely as folylpoly-γ-glutamates requiring deglutamylation to monoglutamates prior to absorption, which might impair dietary folate bioavailability. This study investigated folylpoly-γ-glutamate stability and conversions in broccoli tissue during thermal (25–90 °C, 30 min) and high-pressure treatments (0.1–600 MPa, 25–45 °C, 30 min) after vacuum packaging. Folates were analyzed based on poly-γ-glutamate side chain length by RP-HPLC. During thermal treatments, folates were stable up to 90 °C, whereas differences in folylpoly-γ-glutamate profiles towards higher conjugated folylpoly-γ-glutamates were observed at elevated temperatures (70–90 °C). High-pressure treatments resulted in significant folate losses (48–78%). Depending on the pressure–temperature combinations studied, folylpoly-γ-glutamates were converted to folylmono- and folyldi-γ-glutamates, which was shown to occur mainly during the initial stages of the high-pressure treatments, i.e. during pressure build-up and subsequent equilibration. Targeted application of high-pressure treatments can hence be applied to obtain broccoli with higher monoglutamate folate content. Implications towards folate bioavailability in relation to the observed folate degradation, however, requires further investigation.     

Unexpected sources of vitamin C

Sausages are quite common in the Norwegian diet. Presently the vitamin C content in sausages is listed as zero in the Norwegian Food Composition Table as well as in several other countries’ food composition tables. In the present study, five different kinds of sausages were analysed for relevant nutrients including vitamin C. One composite sample consisting of 15–16 subsamples was analysed for each sausage type. Vitamin C was measured by high-performance liquid chromatography (HPLC) with electrochemical detection as the sum of l-ascorbic acid and dehydro-ascorbic acid. The vitamin C content in the analysed sausages varied from 11 to 40 mg/100 g. This is explained by addition of vitamin C as an antioxidant by the manufacturer mainly to preserve colour. When recalculating vitamin C intakes from the most recent Norwegian national dietary surveys in adults, children and youths using the updated vitamin C values, total vitamin C intake increased by 3–10%. Other processed meat products such as cold cuts may also contain vitamin C as an antioxidant, and a larger impact on vitamin C intake may be seen if also these products turn out to contain considerable amounts of vitamin C. When planning analytical projects for food composition databases, care should be taken to include vitamin C for products where this vitamin may have been added for antioxidant purposes.     

Short communication: Effect of homogenization on heat inactivation of Mycobacterium avium subspecies paratuberculosis in milk

Mycobacterium avium ssp. paratuberculosis (MAP) can be present in cow milk and low numbers may survive high-temperature, short-time (HTST) pasteurization. Although HTST treatment leads to inactivation of at least 5 log₁₀ cycles, it might become necessary to enhance the efficacy of HTST by additional treatments such as homogenization if the debate about the role of MAP in Crohn’s disease of humans concludes that MAP is a zoonotic agent. This study aimed to determine whether disrupting the clumps of MAP in milk by homogenization during the heat treatment process would enhance the inactivation of MAP. We used HTST pasteurization in a continuous-flow pilot-plant pasteurizer and evaluated the effect of upstream, downstream, and in-hold homogenization on inactivation of MAP. Reduction of MAP at 72°C with a holding time of 28 s was between 3.7 and 6.9 log₁₀ cycles, with an overall mean of 5.5 log₁₀ cycles. None of the 3 homogenization modes applied showed a statistically significant additional effect on the inactivation of MAP during HTST treatment.     

Evaluation of high pressure (HP) treatment for rapid and uniform pH reduction in carrots

Acidification (pH < 4.6) of marginally low acid foods allows them to be treated like high acid foods and, hence, has the potential to improve quality and reduce energy costs by lowering the severity of processing conditions. The objective of this study was to evaluate high pressure (HP) treatment for rapid and uniform pH reduction of low acid foods using carrot. Three organic acids (citric, malic and glucono-delta-lactone) were used in the study. Conventional acidification tests were carried out at atmospheric pressure at different temperatures (36–48 °C) and different treatment times (0–36 min). HP treatments were given at room temperature (maximum process temperature <32 °C) with different pressures (200–300 MPa) and treatment times (0–14 min). Time dependent acid infusion and the resulting pH reduction were used to evaluate the acidification kinetics. Results showed that the pH reduction rates were described by a first order kinetic model. No significant differences (p > 0.05) in acidification rates were observed between the acidifying agents either in conventional or HP acidification process. Pressure (HP acidification) and temperature (conventional acidification) significantly (p < 0.05) reduced decimal reduction time (D) for pH drop. The associated D values were 2.4–4.4 times higher in conventional (slower) as compared with HP acidification. For conventional acidification, the z values (temperature sensitivity) were 34–44.8 °C and for HP acidification, the z values (pressure sensitivity) were 206–222 MPa. HP acidification provided more rapid and uniform pH reduction as compared to conventional method.     

Inactivation of Saccharomyces cerevisiae in conference pear with high pressure carbon dioxide and effects on pear quality

This work explores the use of high pressure carbon dioxide (HPCD) for the inactivation of Saccharomyces cerevisiae in fresh-cut conference pears. This fruit was chosen as an example of a ready to eat and minimally processed food. Assays were carried out with continuous CO₂ flow at different pressures (6–30 MPa), temperatures (25–55 °C), and exposure times (10–90 min). Heat treatments at similar temperatures and times were compared to the use of HPCD, wherein it was observed that HPCD was more effective. The total inactivation (5 log₁₀ cycles) of the yeast took place at 55 °C with HPCD while it was necessary to reach 70 °C when only heat was applied. Required pressures and exposure times were relatively low (?6 MPa and on the order of minutes) because of the direct contact between the CO₂ and the pear. The pH and °Brix were not affected by the HPCD treatment; however, the pears lost their texture and became darker due to a decrease in vitamin C and enzymatic browning. Peroxidase activity was only partially reduced. The addition of an antioxidant did not help to prevent darkening. Therefore, HPCD could be a low temperature conservation method that is superior to conventional thermal treatments for the preparation of fruit preserves where a firm texture is not essential.     

The survivability of Bacillus anthracis (Sterne strain) in processed liquid eggs

In this study, we investigated the survival and inactivation kinetics of a surrogate strain of Bacillus anthracis (Sterne strain) in whole egg (WE), egg white (EW), sugared egg yolk (YSU), and salted egg yolk (YSA) at low (−20, 0, and 5 °C), moderate (15, 20, 25, 30, 35, and 40 °C), and high storage temperatures (45, 50, 55, and 60 °C). Outgrowth of the spores was measured as lag phase duration (LPD). Replication of vegetative cells was measured in terms of growth rate (GR) and maximum population density (MPD). Spore inactivation was recorded as inactivation rate and percent reduction in viable count. In general, spore viability decreased at low and high temperatures and increased at moderate temperatures. At 0 and 5 °C, a 60–100% reduction in spore viability was seen within 2–3 weeks in WE and YSU, 0–30% in YSA, and 50–100% in EW. At −20 °C, however, no drop in spore titer was observed in YSU and EW but a 20% drop in titer was seen in YSA and 50% in WE within 2–3 weeks. At high temperatures, WE, EW, and YSA produced a 20–50% drop in the spore titer within 1–4 h whereas YSU showed 100% inactivation within 0.75 h. At moderate storage temperatures, as the temperature increased from 15 to 40 °C, LPD decreased from 13.5 to 0.75 h and MPD reached 0.27–2.2 × 10⁹ CFU/ml in YSU and WE, respectively. Markedly lower growth was observed in YSA (LPD = 24–270 h, MPD = 9 × 10⁵ CFU/ml) and spores were inactivated completely within 1–6 h in EW. The survivability and inactivation data of B. anthracis in liquid egg products reported in this investigation will be helpful in developing risk assessment models on food biosecurity.     

Effect of cold storage on vitamins C and E and fatty acids in human milk

Vitamins C and E and fatty acid levels in human milk were determined when fresh, after refrigeration at 4 °C for 96 h, and after freezing at −20 °C or −80 °C for 12 months. Total vitamin C content at 4 °C (6 h), −20 °C (8 months) and −80 °C (12 months) was significantly decreased. Vitamin E levels did not change at either refrigeration temperature (under 24 h) or at freezing or ultrafreezing temperatures. Our analysis revealed that fatty acids are not affected by cold storage. In conclusion, we recommend a change in milk storage practices; specifically, it should be stored up to 3 h in a refrigerator, up to 5 months in a freezer or up to 8 months in an ultrafreezer (−80 °C). Alternatively, vitamin C supplementation may be considered. In addition, we propose vitamin C as a marker for human milk stability.     

Salicylic acid enhances biocontrol efficacy of Rhodotorula glutinis against postharvest Rhizopus rot of strawberries and the possible mechanisms involved

The potential of using Rhodotorula glutinis alone or in combination with salicylic acid (SA) for the control of postharvest Rhizopus rot of strawberries, and their effects on enzyme activities of fruits were investigated. The combination of R. glutinis (1 × 10⁸ CFU ml⁻¹) with SA (100 μg ml⁻¹) resulted in a significant reduction in the disease incidence and lesion diameter of Rhizopus rot on the strawberry fruits at 20 °C and 4 °C, and more so than with SA or yeast alone. SA at the concentration of 100–1000 μg ml⁻¹ significantly inhibited spore germination of Rhizopus stolonifer. About 100 μg ml⁻¹ of SA did not inhibit the growth of the antagonistic yeast, and could significantly increase the population growth of R. glutinis in strawberry wounds at 20 °C. SA, combined with R. glutinis, increased the activity of strawberry host defence enzymes (POD) and cell wall lytic enzymes (β-1,3-glucanase).     

Vitamin C content and sensorial properties of dehydrated carrots blanched conventionally or by ultrasound

Vitamin C content and sensorial properties have been evaluated in air-dried carrots previously subjected to different ultrasound (US) or conventional blanching pretreatments. In addition, mass spectral fingerprints obtained by the Headspace ChemSensor System have been evaluated for the first time for classification of carrots according to their processing. Conventional blanching treatments at high temperature gave rise to carrots with retention of vitamin C in the range 37.5–85%, whereas carrots blanched conventionally at 60 °C and by US-probe at temperatures up to 60 and 70 °C showed vitamin C retention values lower than 4%. Regarding sensorial analysis of rehydrated carrots, US-pretreated samples presented acceptable quality, and no statistically significant differences with respect to conventionally blanched carrots, were detected. In spite of this, differentiation of samples processed under comparable intensity conditions and/or with similar composition was possible from their mass spectral fingerprints after chemometric data analysis.     

Changes in vitamin C content and antioxidant capacity of raw and germinated cowpea (Vigna sinensis var. carilla) seeds induced by high pressure treatment

The effect of high pressure treatment on the vitamin C content and antioxidant capacity of raw and germinated cowpea seeds (Vigna sinensis var. carilla) at 300, 400 and 500 MPa for 15 min at room temperature has been investigated. A considerable amount of vitamin C was detected in germinated cowpeas, but the vitamin was not detected in raw seeds. An increase on the antioxidant capacity (TEAC) in cowpea sprouts was also observed (58–67%). High pressure treatment (HP) slightly modified vitamin C content and TEAC and, after pressurization at 500 MPa, the decrease was more pronounced, although the germinated seeds submitted to this HP treatment still provided a high amount of vitamin C (15–17 mg/100 g d.m.) and the antioxidant capacity was 26–59% higher than that of the raw cowpeas. The HP process can provide minimally processed fresh-like sprouts of high quality.