Rheological Properties of Acidified and UV‐Irradiated Starches

This study evaluated the effect of added lactic acid and/or UV irradiation on the depolymerization and rheological properties of cassava and corn starches. Combination of lactic acid addition and UV irradiation decreased the intrinsic viscosity of corn and cassava starches. Lactic acid addition alone also decreased paste viscosity in both starches. The paste viscosity of cassava (but not corn) starch was also reduced after UV irradiation. Acidification and UV irradiation increased expansion volume during the baking of cassava (but not corn) starch dough. The baking expansion of cassava starch may be due to its high swelling capacity and solubility resulting from molecular degradation after acidification and irradiation. For corn starch, its high gelatinization temperature and internal lipids content could interfere in starch leaching and thus delay the decrease in viscosity and inhibit dough expansion.     

Inactivation of carboxypeptidase A and trypsin by UV–visible light

In the present work, the effect of UV–visible irradiation on the activity of carboxypeptidase A, and trypsin enzymes is shown. The irradiation of the above-mentioned enzymes inhibits their activity, in such a way that sufficiently high irradiation times annul their catalytic action. For carboxypeptidase A a total inactivation after 20 min of irradiation is observed, while trypsin is inactivated completely after 12 min of irradiation. Fitting the data to the Lineweaver–Burk graphs shows that, in the case of CPA enzyme, the inhibition caused by irradiation is similar to that of uncompetitive type. For trypsin, the irradiation acts similarly to a mixed inhibition-type.

Industrial relevance

UV irradiation is a technology used in food treatment, since it has been shown to be effective in the destruction of microorganisms. It can also be applied in the sterilization of enzymatic preparations used in the food industry, but it can have harmful effects, since it can go so far as to inactivate some of the enzymes. In some cases it interests to inactivate enzymes, and it is for it that this treatment type can be effective. In other cases it interests that the enzymes remain active. This way, it will be necessary to avoid that they are exposed to the light.     

Non‐freezing points below zero induce low‐temperature breakdown of kiwifruit at harvest

To induce low‐temperature breakdown (LTB) at harvest, a post‐storage disorder of kiwifruit, kiwifruit were exposed to ?2 °C (a temperature determined to be above the freezing point), for 0 (control), 6, 12, 18, 24, 30, 36 and 42 h, followed by 5 days at 20 °C. Kiwifruit were also stored at ?0.5 °C for 16 and 24 weeks plus 5 days at 20 °C. LTB incidence and severity were measured on the cut surfaces following slicing at the upper, middle and lower parts of each fruit subjected to ?2 °C, whereas in stored fruit LTB incidence was measured following slicing at the middle part. Electrolyte leakage (ELL) was also determined. Exposure of fruit to ?2 °C resulted in induction of LTB incidence and severity, which increased with the duration of exposure, particularly, on the upper fruit part. Maximum ELL during exposure at ?2 °C for 36 h or during storage at ?0.5 °C for 16 weeks was as high as 50% of that of the frozen fruit. Fruit exposed to ?2 °C or stored at ?0.5 °C had similar LTB symptoms but both differed from those observed in frozen fruit. LTB of fruit stored at ?0.5 °C for 24 weeks was 27% and corresponded to LTB induced at harvest by exposure at ?2 °C for 24 h. The results of this study confirm that LTB is inducible by low but not freezing temperatures at harvest and therefore it might be considered as the physiological basis towards the development of an LTB incidence index for harvested kiwifruit. Copyright © 2006 Society of Chemical Industry     

Combination of UV‐C Treatment and Metschnikowia pulcherrimas for Controlling Alternaria Rot in Postharvest Winter Jujube Fruit

The potential of using antagonistic yeast Metschnikowia pulcherrimas alone or in combination with ultraviolet‐C (UV‐C) treatment for controlling Alternaria rot of winter jujube, and its effects on postharvest quality of fruit was investigated. The results showed that spore germination of Alternaria alternata was significantly inhibited by each of the 3 doses (1, 5, and 10 kJ m^?2) in vitro. In vivo, UV‐C treatment (5 kJ m^?2) or antagonist yeast was capable of reducing the percentage of infected wounds and lesion diameter in artificially inoculated jujube fruits, however, in fruit treated with combination of UV‐C treatment and M. pulcherrima, the percentage of infected wounds and lesion diameter was only 16.0% and 0.60 cm, respectively. The decay incidence on winter jujube fruits treated with the combination of UV‐C treatment and M. pulcherrima was 23% after storage at 0 ± 1 °C for 45 d followed by 22 °C for 7 d. None of the treatments impaired quality parameters of jujube fruit. Thus, the combination of UV‐C radiation and M. pulcherrima could be an alternative to synthetic fungicides for controlling postharvest Alternaria rot of winter jujube.     

Effects of postharvest UV‐C treatment on carotenoids and phenolic compounds of vine‐ripe tomatoes

Light red tomatoes were exposed to different doses of ultraviolet C (UV‐C) irradiation (1.0, 3.0 and 12.2 kJ m^?2). After treatment, the tomatoes were stored for 2 days at room temperature, and then analysed to determine the effect of irradiation on the main antioxidants, carotenoids and phenolic compounds and the results compared with the control samples. The lycopene content was found to have increased by 14% with respect to the control samples, while β‐carotene decreased. Cis‐isomers from lycopene also increased when the tomatoes were exposed to irradiation for more than 3 h. UV‐C irradiation also had a positive effect on total phenolic compounds; however, the same effect was not observed in the individually analysed phenolic compounds. While chlorogenic and ferulic acids increased in content, naringenin and rutin contents decreased. These results suggest that UV‐C irradiation of tomatoes could improve the beneficial effect of red tomatoes for human health by increasing the levels of certain bioactive compounds; it could also be used to obtain higher content of bioavailability components, such as cis‐isomers from lycopene.     

Metabolomics reveals consistency of the shoot system in Medicago truncatula by HPLC‐UV‐ESI‐MS/MS

Flavonoids not only play crucial roles in plant development and resistance, but also provide one of the major natural sources in human nutrition. To investigate the distribution of flavonoids in the shoot system of Medicago truncatula, a high‐performance liquid chromatography coupled with electrospray ionisation tandem mass spectrometer (HPLC‐ESI‐MS/MS) method was established and then applied to determine the quantitation of flavonoids in different parts of the plant. There were twenty‐two, fifteen and eleven different kinds of flavonoids identified from the flower, leaf and stem of M. truncatula, respectively. The identified constituents were either aglycone or glycosides of the typical flavonoid backbones, such as myricetin, quercetin, luteolin, kaempferol, tricin, apigenin and laricitrin. It was found that the shoot system of M. truncatula can be differentiated by flavonoids in terms of structures and contents. Our results provide instruction to utilise the shoot system of legume crops as fodder and herb medicine in the future.     

Effect of UV‐C Disinfection of Beer — Sensory Analyses and Consumer Ranking

Ultraviolet (UV‐C) light irradiation is gaining rapid acceptance within the food and beverage industry as a non‐thermal disinfection technique. A series of trials, using a pilot scale UV‐C treatment system, were conducted to investigate the effect of UV‐C on beer with specific attention to lightstruck flavour formation. Both commercial and micro‐brewed beers were treated with UV‐C light at 254 nm. Samples were analysed by consumer and trained panels. Sensory analyses revealed that at a low UV‐C level, lightstruck flavour was apparent and this increasingly gave way to a more intense burnt rubber off‐flavour as the UV‐C exposure was increased. A sample enrichment probe technique coupled with a gas chromatography‐mass spectrometry (SEP/GCMS) revealed the presence of lightstruck flavour in all the treated beers.     

UV‐C irradiation reduces breakdown and chilling injury of peaches during cold storage

Pre‐storage exposure of peaches (Prunus persica cv Jefferson) with UV‐C irradiation for 3, 5 or 10 min significantly reduced chilling injury after 14 and 21 days of storage at 5 °C plus 7 days of shelf‐life at 20 °C. Similar reduction in fungal decay was also found by these treatments. Skin browning and UV damage were found to be moderate to severe in peaches after the 15 or 20 min of UV‐C treatments. The 20 min of exposure accelerated deterioration. Fruit treated with UV‐C for 3, 5 or 10 min remained firmer and softened more slowly than the control and those treated with longer durations of exposure. No differences were found in weight loss or respiration rates among the treatments. However, ethylene production was stimulated by all of the UV‐C treatments compared with the control. Putrescine levels increased initially after 3 or 5 min of exposure to UV‐C. A tendency toward higher accumulation of spermidine and spermine was found in peaches after UV exposure. These higher levels of polyamines apparently are a response to the UV‐C irradiation and might be beneficial in increasing the resistance of fruit tissue to deterioration and chilling injury. Copyright © 2004 Society of Chemical Industry     

Effect of UV‐C radiation on quality of minimally processed spinach leaves

BACKGROUND: The fresh‐cut vegetable industry commonly uses sodium hypochlorite (NaOCl) for disinfection. However, certain problems with NaOCl usage have led to the investigation of alternative sanitisation treatments. In this respect, UV‐C radiation could be of interest. RESULTS: The effect of four pre‐packaging UV‐C radiation doses (0, 4.54, 7.94 and 11.35 kJ m^?2) and two storage temperatures (5 and 8 °C) on the quality of minimally processed spinach (Spinacia oleracea L.) leaves was studied over a period of 13 days. UV‐C radiation decreased mesophilic and psychrophilic counts just after its application compared with conventional sanitisation washing (150 mg L^?1 NaOCl). However, UV‐C had no residual effect on microbial growth from 6 to 13 days at 5 and 8 °C. During shelf‐life a slight loss of lightness was found, probably related to superficial tissue damage induced particularly in higher‐UV‐C treated leaves. Total antioxidant activity and polyphenol content decreased gradually throughout storage, being more evident in higher‐UV‐C treated leaves stored at 8 °C. The general trend was to maintain the initial chlorophyll content during shelf‐life. CONCLUSION: Low to moderate UV‐C radiation can be an effective alternative to chlorine for sanitising minimally processed spinach leaves and preserving their quality. Copyright © 2008 Society of Chemical Industry     

Antioxidant activity of sage extracts in rapeseed oil irradiated with UV‐rays

The antioxidant activities of sage acetone oleoresin and its methanol‐water fractions were tested in rapeseed oil at 0.1% concentrations and 80°C temperature after irradiation with UV‐rays (exposition 0.5 h). It was determined that even little doses of UV irradiation induce oxidation process in rapeseed oil samples both with additives and without them. The antioxidant activity of a synthetic antioxidant BHT was much lower than that of the sage fractions at 80°C and forced air oven conditions. This finding proves the advantage of sage extracts in comparison with BHT at high temperatures. It was also found that methanol‐water fraction separated from acetone oleoresin had the highest antioxidant activity in terms of the formation of primary and secondary oxidation products. Oil sample with this additive had the highest protection factor (PF = 4.53) when the oil was not irradiated with UV rays. The data obtained showed that all sage extracts had very strong antioxidant activity (PF > 3).     

Characterisation of single malt Scotch Whisky using low powered ultrasound and UV‐Visible spectroscopy

Scotch Whisky is a significant segment of the UK food and beverage industry in terms of both economic value and employment. The value of Scotch Whisky is determined by age and quality although there are expressions which are more valuable due to their history. Quality control and identification of Scotch Whisky is carried out by sensory experts and costly offsite analytical processes such as HPLC, GCMS and NMR. This study characterises Scotch Whisky using two affordable, simple analytical methods: UV‐Visible spectroscopy and low powered ultrasonic characterisation. Low powered acoustic techniques offer the benefits of being online, non‐destructive and economical while UV‐Visible spectroscopy offers a rapid and cheap method to determine sample composition. Alternatively aged ‘whiskies’, which utilise active maturation techniques such as highpowered ultrasound or electromagnetic radiation, produce matured spirits in a shorter time with some characteristics similar to traditionally matured Scotch Whisky, potentially disrupting the industry. Here, twenty five commercially available Scotch Whisky samples from distilleries across Scotland are characterised using UV‐Visible spectroscopy and low powered ultrasonic characterisation. An alternatively aged ‘whisky’ is analysed and compared with traditionally matured Scotch Whiskies. The techniques presented here successfully tracked both Scotch Whisky age and cask type and observed a difference between the traditionally and alternatively aged samples. Spectrophotometry was additionally used to determine the antioxidant availability of the Scotch Whisky samples via a DPPH assay and was found to positively trend with the duration of maturation. © 2020 The Institute of Brewing & Distilling     

Microbial Safety and Shelf Life of UV‐C Treated Freshly Squeezed White Grape Juice

The effects of UV‐C irradiation on the inactivation of Escherichia coli K‐12 (ATCC 25253), a surrogate of E. coli O157:H7, and on the shelf life of freshly squeezed turbid white grape juice (FSWGJ) were investigated. FSWGJ samples were processed at 0.90 mL/s for 32 min by circulating 8 times in an annular flow UV system. The UV exposure time was 244 s per cycle. The population of E. coli K‐12 was reduced by 5.34 log cycles after exposure to a total UV dosage of 9.92 J/cm² (1.24 J/cm² per cycle) at 0.90 mL/s flow rate. The microbial shelf life of UV‐C treated FSWGJ was extended up to 14 d at 4 °C. UV exposure was not found to alter pH, total soluble solid, and titratable acidity of juice. There was a significant effect (P < 0.05) on turbidity, absorbance coefficient, color, and ascorbic acid content. Furthermore, all physicochemical properties were altered during refrigerated storage. The microbial shelf life of FSWGJ was doubled after UV‐C treatment, whereas the quality of juice was adversely affected similarly observed in the control samples.     

Improving the quality of fresh‐cut melon through inactivation of degradative oxidase and pectinase enzymatic activities by UV‐C treatment

This work investigated the effect of exposure of fresh‐cut melon (Cucumis melo L. var. reticulatus) to ultraviolet‐C (UV‐C, 254 nm, 0.04 kJ s^?1 m^?2) radiation for different times (30, 60, 120 s) on main degradative enzymatic activities (polyphenol oxidase, peroxidase, pectin methylesterase and polygalacturonase) and quality parameters (firmness, colour) during storage at 5 °C. Enzymatic activities in samples washed with water and treated with UV‐C radiation were similar to samples washed with 100 mg L^?1 NaOCl and significantly lower than untreated samples, especially after 7 days of storage at 5 °C. Tissue softening was noticed in all samples although those treated with UV‐C light resulted 7–12% firmer than untreated ones. The lowest perceptible colour variation, expressed as ΔE*, was in samples exposed to 120 s radiation (ΔE = 8.58), while the highest value was noticed in untreated sample (ΔE = 11.06). Postcut UV‐C fruit treatment was effective in extending the shelf life of minimally processed ‘Galia’ melon.     

Effects of UV‐C on antioxidant capacity,antioxidant enzyme activity and colour of fresh‐cut red cabbage during storage

Ultraviolet C (UV‐C) irradiation is a widely used nonthermal sterilisation method used to ensure the quality and safety of fresh and fresh‐cut produce. However, research focus of UV‐C has recently shifted from safety of sterilisation damage towards improvements in quality. Red cabbage (Brassica oleracea var. capitata f. rubra) is a widely consumed fresh‐cut vegetable. In this study, the effects of UV‐C irradiation on the antioxidant capacity, antioxidant enzyme activity and colour of fresh‐cut red cabbage were evaluated. The UV‐C decreased the L*, a* and b* values, and it turned the colour darker and increasingly blue. UV‐C increased the activity of four antioxidant enzymes and also stimulated the accumulation of flavonoids, glutathione and ascorbic acids. The antioxidant activity of UV‐C treatment was higher than in the control group. These results suggest that an appropriate dose of UV‐C may improve the antioxidant properties of fresh‐cut red cabbage.     

Effects of Ultraviolet Light (UV‐C) and Heat Treatment on the Quality of Fresh‐Cut Chokanan Mango and Josephine Pineapple

The effects of ultraviolet (UV‐C) and medium heat (70 °C) treatments on the quality of fresh‐cut Chokanan mango and Josephine pineapple were investigated. Quality attributes included physicochemical properties (pH, titratable acidity, and total soluble solids), ascorbic acid content (vitamin C), antioxidant activity, as well as microbial inactivation. Consumers’ acceptance was also investigated through sensory evaluation of the attributes (appearance, texture, aroma and taste). Furthermore, shelf‐life study of samples stored at 4 ± 1 °C was conducted for 15 d. The fresh‐cut fruits were exposed to UV‐C for 0, 15, 30, and 60 min while heat treatments were carried out at 70 °C for 0, 5, 10 and 20 min. Both UV‐C and medium heat treatments resulted in no significant changes to the physicochemical attributes of both fruits. The ascorbic acid content of UV‐C treated fruits was unaffected; however, medium heat treatment resulted in deterioration of ascorbic acids in both fruits. The antioxidants were enhanced with UV‐C treatment which could prove invaluable to consumers. Heat treatments on the other hand resulted in decreased antioxidant activities. Microbial count in both fruits was significantly reduced by both treatments. The shelf life of the fresh‐cut fruits were also successfully extended to a maximum of 15 d following treatments. As for consumers’ acceptance, UV‐C treated fruits were the most accepted as compared to their heat‐treated counterparts. The results obtained through this study support the use of UV‐C treatment for better retention of quality, effective microbial inactivation and enhancement of health promoting compounds for the benefit of consumers.