Vegetables antioxidant losses during industrial processing and refrigerated storage

Twenty-five vegetables (artichoke, asparagus, beetroot, broad bean, broccoli, Brussels sprout, carrot, cauliflower, celery, chicory, cucumber, eggplant, endive, garlic, green bean, leek, lettuce, maize, onion, pea, pepper, radish, spinach, Swiss chard and zucchini) were used to evaluate their antioxidant activity. All fresh vegetables studied were able to scavenge lipoperoxyl and hydroxyl radicals. All the vegetables also presented good total capacity antioxidant by TEAC assay except cucumber, endive, carrot and zucchini.Vegetables stored (7 days) in a home refrigerator recorded the same antioxidant activity as fresh samples, except cucumber and zucchini (lipid peroxidation) and broccoli, Brussels sprout and leek (TEAC).Canned vegetables showed a more pronounced loss of antioxidant activity than frozen vegetables compared with fresh vegetables.During the shelf life of the processed vegetables (8 months for frozen and 18 months for canned vegetables), some products showed losses (19–48%) of their lipoperoxyl radical scavenging capacity and total antioxidant activity.     

3-Chlorotyrosine formation in ready-to-eat vegetables due to hypochlorite treatment and its dietary exposure and risk assessment

Washing of iceberg lettuce with HOCl solutions in concentrations ranging from 1.41 to 141 mg/L resulted in 0.69 to 2.05 μg 3-chlorotyrosine/g vegetable. As also six commercial ready-to-eat iceberg lettuces from different producers contained 3-chlorotyrosine from 1.00 to 2.24 μg/g vegetable, a total of 122 ready-to-eat vegetable samples purchased in Belgian supermarkets were further screened for their 3-chlorotyrosine content. 3-chlorotyrosine was detected above the detection limit (0.19 μg/g sample) in 97, 24 and 14% of the lettuce mixes, vegetable mixes and frozen vegetables, respectively. In combination with consumption data of ready-to-eat vegetables by Belgian and Spanish consumers, a quantitative exposure assessment was performed, exemplifying a lower and higher ready-to-eat vegetables consuming population. Exposure to 3-chlorotyrosine from the frozen vegetables and vegetable mixes was lower compared to the lettuce mixes due to the combination of lower contamination and lower consumption. 3-chlorotyrosine exposure via lettuce mixes could be considered as a public health concern, especially in higher consuming populations represented by the Spanish population, with 17% of consumers (> 4.2 million people) and 8.5% of the total population (> 2,6 million people) exceeding the threshold of toxicological concern.     

Incidence of Listeria monocytogenes in Market Samples of Fresh and Frozen Vegetables

Samples of the outer portions of fresh beets, broccoli, cabbage, carrots, cauliflower, corn, head lettuce, leaf lettuce, mushrooms, and potatoes, as well as frozen green beans, green peas, pea pods, and spinach were examined for the presence of Listeria monocytogenes using a 7-day enrichment procedure at 30°C. Samples were streaked on modified McBrides agar, and isolates were tested for characterization reactions. Fresh carrots, lettuce, and mushrooms, and frozen spinach were also examined using a cold enrichment procedure at 4°C. Samples were taken weekly, streaked onto modified McBrides agar, and were characterized. It was determined that no L. monocytogenes was detectable in any of these samples.     

Effects of different cooking methods on the chemical and physical properties of carrots and green peas

The study was aimed to evaluate the physicochemical effects of three cooking methods i.e. sous-vide (SV), cook-vide (CV) and traditional cooking (TC) on carrots and green peas. SV and CV were performed at 60–90 °C for various time periods (SV: green peas 50–100 min, carrots 90–150 min; CV: green peas 30–70 min, carrots 20–60 min) with respect to peroxidase test. These vegetables were also cooked at atmospheric pressure for 15, 30, 45 and 60 min and the results were compared with those obtained from SV and CV. Antioxidant activity, total phenolic and vitamin C analyses reflected less harm to the green peas in CV as compared to SV and TC. However, carrots were approximately half degraded during SV than in CV and TC as shown by the antioxidant activity. Moreover, total phenolic content of carrots was highly protected when cooked in SV method. The color change values (∆ E) of green peas were slightly lower in TC when compared to CV and SV, while in carrots, they were very close to each other's in all three methods. CV-cooked green peas and carrots provided the highest general acceptance for the sensorial properties. As a conclusion, TC had more adverse effects on the quality characteristics on green peas and carrots.     

Influence of postharvest gamma irradiation treatment on the content of bioactive compounds and antioxidant activity of fenugreek (Trigonella foenum–graceum L.) and spinach (Spinacia oleracea L.) leaves

Fenugreek and spinach leaves after irradiation in the dose range of 0.25–1.5 kGy were evaluated for the content of bioactive compounds and antioxidant activity using DPPH radical scavenging, ferric reducing ability power (FRAP), hydroxyl radical scavenging and ferrous ion chelating assays. Results of the study revealed that bioactive content except total ascorbic acid was significantly (p ≤ 0.05) higher in fenugreek compared to spinach. Data analysis revealed that gamma irradiation treatment significantly (p ≤ 0.05) enhanced the content of individual as well as total bioactive components of both vegetables. Positive correlation (r = 0.92) existed between gamma irradiation and total phenolics. The results of the antioxidant activity as determined by above mentioned assays revealed a significant (p ≤ 0.05) decrease in EC₅₀ values and a corresponding increase in antioxidant content and activity due to irradiation. Comparison of the increase in inhibition percentage, reducing power and chelating efficiency revealed that treatment of irradiation was significantly (p ≤ 0.05) effective in enhancing the ferric reducing power of both the vegetables (3.1–37.5% for fenugreek, 4.1–42.8% for spinach) and OH radical scavenging for spinach (1.5–22.4%) compared to fenugreek (0.78–13.1%). The present investigation suggested that postharvest radiation treatment to fenugreek and spinach has a potential to enhance their antioxidant content and activities, besides acting as a photo-sanitary treatment.Industrial relevanceThe increasing demand of convenience, wholesome and health promoting foods has resulted in search of new technologies to improve the shelf-life and at the same time preserve the nutritional quality. Prolonging postharvest storage, while enhancing the content of bioactive compounds will have a positive impact on both the industry and consumers. The present study demonstrated that postharvest radiation treatment of fenugreek and spinach can be used a novel approach to enhance their bioactive composition and antioxidant activity.     

Effect of immersion solutions on shelf-life of minimally processed lettuce

Prior to detailed quality and physiology evaluations, different immersion solutions (SIs) were analysed by means of a nontrained sensory panel. Each SI (calcium chloride, pectin, potassium sorbate, garlic extract and citric acid) was analysed at three concentrations. Based on at least 70% acceptance, the best mixed SI (P<0.05) was determined to be 2 g/L citric acid, 1 g/L calcium chloride and 250 g/L garlic extract (SI). The control treatment was washed only with 0.05 g/L active chlorine. Treated lettuce was stored at 5°C in darkness in sealed polypropylene bags, for 9 days. Some senescence indicators (weight loss, colour), certain enzymes related to colour (chlorophyllase and polyphenoloxidase), and a nutrient (ascorbic acid), were measured during storage. SI showed a positive effect on shelf-life of minimally processed lettuce, controlling enzymatic browning, chlorophyllase activity and weight loss. The microorganisms growth was not significantly controlled, but the fact that the organoleptic results of SI-treated lettuce showed about 80% acceptability during 9 days of storage, suggests that some slight modifications on SI could be the basis of a promising formula for minimally processed lettuce.     

Effects of heat treatment on atmospheric composition and color of peeled white asparagus in modified atmosphere packaging

Freshly harvested spears of white asparagus were subjected or not to heat treatment by immersion in a hot water bath at 55 °C for 3 min, then left unpeeled or were peeled before wrapping in 16 µm stretch film and stored at 3 °C for 6 days. During storage, the atmosphere within the packages was sampled for O₂, CO₂ and C₂H₄ determination, while spear fresh weight, color and anthocyanin content at the 3 cm apical peel segments were determined before and after storage. The results showed that CO₂ concentration in packages of white asparagus spears was not greatly influenced by peeling or heat treatment. On the other hand, a higher package O₂ depletion of treated (peeled or heated) spears was observed. Peeling also resulted in an increase of ethylene peak concentration, indicating wound-induced ethylene production, which was suppressed by heat treatment. The initial color of the whole spear was retained, while the appearance of a violet coloration on the spear tip was prevented by heat treatment in both unpeeled and peeled spears.Industrial relevancePeeled white asparagus has drawn the attention of industry as a novel lightly processed product. The combination of heat treatment with modified atmosphere packaging (MAP) could be used to improve the storage life of this product. Moreover, both peeling and heat treatment cause changes in ethylene production and respiration rate of asparagus spears and this information could be useful for development of novel application to MAP design for lightly processed (peeled) white asparagus.     

Effect of chill storage and modified atmosphere packaging (MAP) on antioxidant activity,anthocyanins, carotenoids,phenolics and sensory quality of ready-to-eat shredded orange and purple carrots

Ready-to-eat shredded orange and purple carrots, packed in air (control), or in modified atmosphere packaging [MAP; (90%N₂ + 5%O₂ + 5%CO₂ and 95%O₂ + 5%CO₂)], and stored chilled for up to 13 days, were examined for their antioxidant activity and contents of anthocyanins, carotenoids and phenolics, as well as sensory quality. Total antioxidant activity, carotenoids and phenolics of purple carrots were initially 2.8-, 2.3- and 2.9-fold higher than orange carrots, respectively. Total antioxidant activity remained relatively constant in orange carrots during storage under all treatment conditions, whereas a highly significant decrease (P<0.01) in (95%O₂ + 5%CO₂)-treated purple carrots was observed. The content of anthocyanin, only found in purple carrots, was decreased slightly during the storage period, and this was particularly significant in the 95%O₂ + 5%CO₂ treatment. In both orange and purple carrots, loss of total carotenoids occurred in the 95%O₂ + 5%CO₂ treatment. Total phenolic content of purple carrots increased at a much higher rate during storage than orange carrots. The MAP treatment (90%N₂ + 5%O₂ + 5%CO₂) gave better sensory quality and extended shelf-life for purple carrots (∼2–3 days longer shelf-life than other treatments,) but, no difference was observed for orange carrots. Shredded purple carrot can be stored under 90%N₂ + 5%CO₂ + 5%O₂ treatment for up to 10 days and high nitrogen treatment may be used in maintaining the storage quality of shredded purple carrots. Thus, purple carrots may be used in place of orange carrots to take advantage of their nutraceutical components.     

The influence of preparation method on children’s liking for vegetables

This study aimed to investigate how different preparation methods influence children’s liking for vegetables. Participants were children from three age groups (4–6 years N = 46; 7–8 years N = 25; 11–12 years N = 23) and young adults (18–25 years N = 22). The participants tasted and ranked six preparation methods for carrots and French beans: mashed, steamed, boiled, stir-fried, grilled and deep-fried. In addition, the different vegetable preparations were rated on 15 attributes. All participants preferred boiled and steamed vegetables over the other preparations (p < 0.05). Boiled and stir-fried were the most familiar preparation methods for both vegetables. Vegetable liking was positively related to a uniform surface and the typical vegetable taste, and moderately related to crunchiness, whereas brown colouring and a granular texture were negatively related to vegetable liking. On the basis of these results, we conclude that children’s vegetable liking is influenced by a complex mixture of a uniform appearance, easily controllable textures and a typical, familiar vegetable taste.     

Effect of two ethnic processing technologies on reduction and composition of total and non-glucosidic cyanogens in cassava

The effectiveness of two different processing methods on reduction of total and non-glucosidic cyanogens in cassava was studied in two ethnic groups in Nkhota Kota, Malawi. Cassava cyanogen content was periodically monitored during processing. Total cyanogen reductions of 97.9 ± 0.5% and 82.4 ± 1.0% were obtained upon soaking peeled and unpeeled roots, respectively. The residual cyanogen content (2.6 ± 0.7 mg HCN eq./kg) in flour produced from peeled roots was lower than the FAO/WHO limit (10 mg HCN eq./kg). The flour from the unpeeled method contained twenty times more residual cyanogen levels (53.8 ± 1.8 mg HCN eq./kg dry matter). The peels exhibited four times higher cyanohydrin than the pulp. Inclusion of the peel during processing therefore leads to high retention of cyanogens in the pulp. Clearly, soaking of peeled roots is a more effective method and thus should be promoted among ethnic communities that soak unpeeled roots.     

Vegetable preparation practices for 5–6 years old Australian children as reported by their parents; relationships with liking and consumption

Vegetables are the food category least accepted by children, which is a key reason for their low intake. Common sense suggests that vegetable preparation, liking and consumption is idiosyncratic to each vegetable, e.g. carrots may be eaten raw, but raw broccoli may be unacceptable, however scientific evidence is largely lacking. This study measured children’s experiences, liking and consumption of vegetables in relation to preparation practices at home. Questionnaire data were collected for a comprehensive range of preparation methods (raw, boiling, steaming, frying, roasting, and seven ways of preparing it with other dishes (e.g. soup)) across five common vegetables, i.e. carrot, potato, broccoli, cauliflower, and green beans. Measures included experience with preparation methods (yes/no), liking (9 point hedonic scale) and consumption frequency (5 point scale). Data were reported by parents for their child (N = 82, 5–6 years, low and high vegetable intake), and child/parent pairs were recruited from the Sydney metropolitan area. Parents reported that children consumed an average of 6.8 (SD 3.4) different preparation methods for vegetables at home, including many mixed dishes. The number and type of preparations the child consumed depended on the vegetable type (p < .0001). Preparation method was associated with liking of carrot and potato (both p < .0001), and with consumption frequency of all vegetables (all p < .05). The most and least liked preparations were vegetable specific. Parents reported that vegetables in mixed dishes were generally well accepted by their children, and flavourings were added on average by 54%. The results also showed that a higher vegetable consumption was related to a higher liking, and exposure to more preparation methods. This study demonstrates the potential for further experimental research into preparation practices to increase vegetable acceptance and intake in children. A vegetable by vegetable approach is recommended, with potential cross-vegetable opportunities for flavour–flavour learning and flavour masking strategies including the use of mixed dishes.     

Chemical,instrumental and sensory characteristics of cooked pork ham

Instrumental, chemical and sensory parameters of cooked pork ham were evaluated. Principal component analysis was carried out on the basis of the instrumental variables related to colour and texture. The four PCs account for almost 94% of the total variance in the data set. The PCA only separated 3 hams with a¹ > 10. Hardness was correlated with non-collagen muscle protein (P ⩽ 0.01), gumminess (P ⩽ 0.01) and ash (P ⩽ 0.05). Sensory evaluated tenderness showed positive significant correlation with L¹ (P ⩽ 0.01). The most important colour parameter seems to be a¹, which was negatively correlated with sensory evaluated parameter colour (P ⩽ 0.01). The PCA performed on all parameters (sensory, chemical and textural) discriminated two groups of hams differing in non-collagen muscle protein content and hardness.     

Survival of Escherichia coli O157:H7 in soil and on carrots and onions grown in fields treated with contaminated manure composts or irrigation water

Many foodborne outbreaks of enterohemorrhagic Escherichia coli O157:H7 infection have been associated with the consumption of contaminated vegetables. On-farm contaminations through contaminated manure or irrigation water application were considered likely sources of the pathogen for several outbreaks. Field studies were done to determine the survival of E. coli O157:H7 on two subterranean crops (carrots and onions), and in soil fertilized with contaminated manure compost or irrigated with contaminated water. Three different types of composts, PM-5 (poultry manure compost), 338 (dairy manure compost) and NVIRO-4 (alkaline stabilized dairy manure compost), and irrigation water were inoculated with an avirulent strain of E. coli O157:H7 at 10⁷ cfu g⁻¹ and 10⁵ cfu ml⁻¹, respectively. A split-plot block design plan was used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but with contaminated irrigation water applied) and five replicates for a total of 25 plots, each measuring 1.8×4.6 m², for each crop. Composts were applied to soil as a strip at a rate of 4.5 metric tons ha⁻¹ before carrots and onions were sown. Contaminated irrigation water was sprayed once on the vegetables at the rate of 2 l per plot for this treatment 3 weeks after carrots and onions were sown. E. coli O157:H7 survived in soil samples for 154–196 days, and was detected for 74 and 168 days on onions and carrots, respectively. E. coli O157:H7 survival was greatest in soil amended with poultry compost and least in soil containing alkaline-stabilized dairy manure compost. Survival profiles of E. coli O157:H7 on vegetables and soil samples, contaminated either by application of contaminated compost or irrigation water, were similar. Hence, preharvest contamination of carrots and onions with E. coli O157:H7 for several months can occur through both contaminated manure compost and irrigation water.     

Texture preferences of 12-month-old infants and the role of early experiences

The present study examined infants’ preferences for different food textures and aimed to identify factors that play an important role in shaping these preferences. In a home setting, 70 twelve-month-old infants were exposed to cooked carrots prepared in two different textures; pureed and chopped. Infants’ mean intakes in grams for the pureed and the chopped carrots were 70.9 ± 49.1 g and 24.6 ± 28 g respectively. Infants consumed significantly more pureed carrots (t(69) = 8.50, p < 0.001) and mothers’ rating of the infants’ enjoyment for this texture was significantly higher (t(69) = 3.65, p < 0.01) than for chopped carrots. However a great variability in the consumption of chopped carrots was found within the infants. Spearman’s correlation and PLSR analysis showed that familiarity with different textures, especially chopped foods, is the strongest predictor of intake and liking of chopped carrots. Furthermore, infants with higher dietary variety, more teeth and a greater willingness to try new foods were more likely to consume more of the chopped carrots. Food pickiness and fussiness had a negative influence on the intake of, and liking for, chopped carrots. The present research is a first step to explain the variation in infants’ consumption and liking of different textures. It highlights the importance of not only varying the child’s experiences with different flavours but also with different textures to foster the infants’ transition to an adult diet.     

Inactivation of bacterial pathogens on lettuce,sprouts, and spinach using hurdle technology

Effects of chemical treatment using slightly acidic electrolyzed water (SAEW), fumaric acid (FA), or calcium oxide (CaO) and physical treatment using ultrasonication (US), micro-bubbles (MB), or ultraviolet (UV) to inactivate bacterial pathogens Listeria monocytogenes, Escherichia coli O157:H7, Staphylococcus aureus, and Salmonella spp. on lettuce, spinach, and sprouts were determined. Fresh produce inoculated with bacterial pathogens (~ 9 log CFU/mL) was immersed in distilled water (DW), SAEW, FA (0.5%), or CaO (0.2%) alone or in combination at 23 ± 2 °C for 3 min followed by treatment with US, MB for 3 min, or UV for 10 min. Effects of combined treatment on shelf-life of lettuce at 4 °C and 23 ± 2 °C were also determined in this study. Results revealed that the use of a combination of CaO + SAEW + FA + US exhibited significant reduction (p < 0.05) for bacterial pathogen on fresh produce compared to individual treatment or other combinations. CaO + SAEW + FA + US treatment exhibited highest reduction of E. coli O157:H7, S. aureus, L. monocytogenes and Salmonella spp. by 4.7, 4.9, 4.84 and 5.08 log CFU/g, respectively on lettuce as compared to spinach and sprouts. Microbial count reducing capability for combined treatment methods were ranked in the following order: SAEW + FA < CaO + SAEW + FA < CaO + SAEW + FA + US. However, introduction of US to CaO + SAEW + FA treatment resulted in little detrimental effect on the overall quality of lettuce. Moreover, CaO + SAEW + FA treatment effectively enhanced the shelf-life of lettuce stored at 4 °C and 23 ± 2 °C by about 6 days and 3 days, respectively as compared to control (DW treatment), with longer lag time (23.11 h on lettuce) for naturally occurring bacteria on fresh produce. These findings suggest that significant synergistic benefit could be obtained from combined sanitizer treatment to eliminate bacterial pathogens from fresh produce.     

Taste intensities of ten vegetables commonly consumed in the Netherlands

Bitterness has been suggested to be the main reason for the limited palatability of several vegetables. Vegetable acceptance has been associated with preparation method. However, the taste intensity of a variety of vegetables prepared by different methods has not been studied yet. The objective of this study is to assess the intensity of the five basic tastes and fattiness of ten vegetables commonly consumed in the Netherlands prepared by different methods using the modified Spectrum method. Intensities of sweetness, sourness, bitterness, umami, saltiness and fattiness were assessed for ten vegetables (cauliflower, broccoli, leek, carrot, onion, red bell pepper, French beans, tomato, cucumber and iceberg lettuce) by a panel (n = 9) trained in a modified Spectrum method. Each vegetable was assessed prepared by different methods (raw, cooked, mashed and as a cold pressed juice). Spectrum based reference solutions were available with fixed reference points at 13.3 mm (R1), 33.3 mm (R2) and 66.7 mm (R3) for each taste modality on a 100 mm line scale. For saltiness, R1 and R3 differed (16.7 mm and 56.7 mm). Mean intensities of all taste modalities and fattiness for all vegetables were mostly below R1 (13.3 mm). Significant differences (p < 0.05) within vegetables between preparation methods were found. Sweetness was the most intensive taste, followed by sourness, bitterness, fattiness, umami and saltiness. In conclusion, all ten vegetables prepared by different methods showed low mean intensities of all taste modalities and fattiness. Preparation method affected taste and fattiness intensity and the effect differed by vegetable type.     

Recipe calculation of six Iranian Egg-based Dishes (KuKu)

Nutrient content of six Iranian egg- based dishes (KuKu) was estimated by recipe calculation method. Kuku dishes were prepared by mixing vegetables and herbs such as cauliflower, eggplant, green beans, green herbs and leafy vegetables, potatoes, and zucchini with eggs and seasonings through frying both sides over low heat. Proximate composition of 100 g edible part of dishes was: 45.22 - 75.61 g Water, 1.54 - 2.10 g Ash, 4.84 - 6.98 g protein, 12.28 - 37.78 g total fat, 3.83 -17.75 g carbohydrate, 1.3 - 3.82 g dietary fiber, 0.62 - 4.64 g total sugar, and 148.18 - 391.54 Kcal energy. The dishes also contain 307.01 - 463.17 mg sodium, 1.79 - 3.67 g saturated fat, 0.22 -0.81 g trans-fat, and 99.64 - 173.77 mg cholesterol. Cooking yield factors of dishes were between 0.48 and 0.86.     

Effect of Boiling and Frying on the Total Carbohydrate,Vitamin C and Mineral Contents of Irish (Solanun tuberosum) and Sweet (Ipomea batatas) Potato Tubers

In a study aimed at ascertaining whether boiling or frying best conserves nutrients; since the two methods are commonly adapted in Nigeria, the effect of boiling and frying on total carbohydrate, vitamin C and mineral contents of Irish (Solanum tuberosum) and sweet (Ipomea batatas) potato tubers were investigated. The determination of total carbohydrate was carried out using the phenol-sulphuric acid method and the spectrophotometric method was used to determine vitamin C content at 520 nm. The minerals evaluated are iron, zinc, magnesium, sodium, calcium and copper. These were determined by the atomic absorption spectrophotometric method. There was no significant difference (p > 0.05) in the total carbohydrate content of the boiled and fried sweet and Irish potatoes compared with their raw tubers. There was significant difference (p < 0.05) in the vitamin C content of the boiled and fried potato tubers. Boiling and frying of Irish potato resulted in a loss of 37.34 mg/100 ml (63.90%) and 30.44 mg/100 ml (53.90%) vitamin C respectively. Boiled sweet potato lost 51.16 mg/100 ml (72.37%) and fried lost 43.05 mg/100 ml (60.90%) of vitamin C. The mineral compositions of the boiled and fried Irish and sweet potatoes were significantly different (p < 0.05) from their raw tubers. Boiling retained more iron and copper while frying retained more zinc, magnesium, sodium and calcium in both Irish and sweet potato tubers. Boiling retained more carbohydrate while frying retained more vitamin C and minerals.     

Effect of mild heat pre-treatment with alkaline electrolyzed water on the efficacy of acidic electrolyzed water against Escherichia coli O157:H7 and Salmonella on Lettuce

Cut lettuce dip-inoculated with Escherichia coli O157:H7 and Salmonella was treated with alkaline electrolyzed water (AlEW) at 20°C for 5 min, and subsequently washed with acidic electrolyzed water (AcEW) at 20°C for 5 min. Pre-treatment with AlEW resulted in an approximate 1.8 log₁₀ cfu/g reduction of microbial populations, which was significantly (p⩽0.05) greater than microbial reductions resulting from other pre-treatment solutions, including distilled water and AcEW. Repeated AcEW treatment did not show a significant bacterial reduction. Mildly heated (50°C) sanitizers were compared with normal (20°C) or chilled (4°C) sanitizers for their bactericidal effect. Mildly heated AcEW and chlorinated water (200 ppm free available chlorine) with a treatment period of 1 or 5 min produced equal reductions of pathogenic bacteria of 3 log₁₀ and 4 log₁₀ cfu/g, respectively. The procedure of treating with mildly heated AlEW for 5 min, and subsequent washing with chilled (4°C) AcEW for period of 1 or 5 min resulted in 3–4 log₁₀ cfu/g reductions of both the pathogenic bacterial counts on lettuce. Extending the mild heat pre-treatment time increased the bactericidal effect more than that observed from the subsequent washing time with chilled AcEW. The appearance of the mildly heated lettuce was not deteriorated after the treatment. In this study, we have illustrated the efficacious application of AlEW as a pre-wash agent, and the effective combined use of AlEW and AcEW.     

Distribution of ergosterol in different tissues of mushrooms and its effect on the conversion of ergosterol to vitamin D2 by UV irradiation

Analysis of ergosterol content in different tissues of Shiitake mushrooms showed a significant difference (p < 0.01) in its distribution. Thus, the conversion of ergosterol in whole mushrooms to vitamin D₂, by exposure to UV irradiation, was significantly affected (p < 0.01) by the orientation of the mushroom tissues to the UV. The highest ergosterol content was found in button mushrooms (7.80 ± 0.35 mg/g DM) while the lowest was in enoki mushrooms (0.68 ± 0.14 mg/g DM). The conversion of ergosterol to vitamin D₂ was about four times higher when gills were exposed to UV-A irradiation than when the outer caps were exposed to the same. The lowest conversion to vitamin D₂ (12.5 ± 0.28 μg/g DM) was observed for button mushrooms while the highest value (45.1 ± 3.07 μg/g DM) was observed for oyster mushrooms. The optimum moisture content of mushrooms for this conversion was around 78% on a wet basis and the temperature was around 35 °C.