Hot Water Dip Research Articles

Effect of production site, storage duration, and hot water and molybdenum dips on bioactive compounds with antioxidant properties in lemon flavedo during cold storage

Certain bioactive compounds, such as vitamin E (α-tocopherol), vitamin C (ascorbic acid), β-carotene, polyphenols (e.g. flavonoids and flavonones, viz. hesperidin and naringin) have antioxidant properties and their presence in the citrus flavedo plays a significant role in mitigating oxidative stress, which could possibly result in chilling injury during cold storage. The purpose of this investigation was, therefore, to alter the concentration of these bioactive compounds in lemon flavedo using hot water and molybdenum (Mo) treatments prior to cold storage to allow fruit to withstand such storage, and avoid the occurrence of chilling injury. Fruit from three sources (Ukulinga Farm, Sun Valley and Eston Estates) were treated for 2 min with hot water dips (HWD) (at 47 °C or 53 °C) with or without a subsequent soaking in 1 or 10 µM Na2MoO4 for 30 min. Fruit were then stored at -0.5 °C for up to 7, 14, 21 or 28 d and thereafter moved to room temperature (±21 °C and ±68% RH) for 7 d. Lemon fruit from Sun Valley Estates were chilling-susceptible and had the lowest concentration of bioactive compounds, significantly lower than chilling-resistant fruit from Ukulinga Farm. Application of HWD at 53 °C, as well as 1 µM Mo in combination with HWD at 53 °C, enhanced the flavedo concentration of bioactive compounds. Furthermore, storage duration seemed to induce an increase or decrease in flavedo bioactive compounds concentration. In general, HWD and Mo dips enhance the rind concentration of phenolics and ascorbic acid at specific storage times.

Effect of Hot-water Dipping on Inhibiting Red Discoloration of Basal Part in Chicon

Hot water dipping test was conducted for chicon to restrict red discoloration of its basal part which impairs the product value during sales. Hot water dipping treatment was given to chicon for 4 min and for 8 min at 38°C and for 2 min and 4 min at 42°C, and for 1 min and 2 min at 45°C, along with control (for one min at 20°C). The red discoloration indices of basal part of chicon during sensory evaluation on the sixth day of storage under the storage temperature at 10°C was lower at 42°C for 2 min, 42°C for 4 min and 45°C for 1 min treatments. The color change value of the basal part in chicon measured by colorimeter showed that the lowest △a* and △h were maintained in the basal part of chicon treated at 42°C for 2 min. Whereas, color changes in 42°C for 2 min and 45°C for 1 min treatments were significantly low as compared with that of control. The contents of total phenolic compounds which are the substances that cause red discoloration of basal part in chicon were lowest at 42°C for 2 min, 42°C for 4 min and 45°C for 1 min treatments. The activity of phenylalanine ammonia lyase (PAL) resposible for in the synthesis of phenolic substances was the least in 42°C for 2 min treatment. Whereas, PAL activity of the chicons treated at 42°C for 2 min and at 45°C for 1 min were significantly lower than that of control. However, red discoloration was progressed as similar level with that of control in the basal part of chicon at 45°C for 2 min. The contents of total phenolic compounds and PAL activity in this treatment were not significantly different from those in control. The polyphenol oxidase (PPO) activity which causes red discoloration of cut tissues was low in all the treatments including 42°C and 45°C treatment at which no inhibition effects of the red discoloration of basal part of chicon were observed. When the correlation coefficient between each investigated index was tested, most of them showed high correlation except the PPO activity and particularly and the red discoloration index and sensory evaluation △h values, and PAL activity and total phenolic compounds content were r = 0.927**, and r = 0.942**, respectively. Additional key words: correlation, phenolic compounds, phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), △a*, △h *Corresponding author: hominkang@kangwon.ac.kr ※ Received 8 October 2013; Revised 28 November 2013; Accepted 5 February 2014. 본 연구는 한국과학재단 기본연구지원사업(C1006679-01-03) 의 지원에 의해 수행되었음. C 2014 Korean Society for Horticultural Science 서 언 치콘은 저온처리 된 치커리(Cichorium intybus L.) 뿌리에 서 틔운 싹으로 18°C에서는 수확까지 22일이면 가능하여 농약 사용 없이 재배할 수 있어 친환경 농산물로 이용할 수 있다(Bae et al., 2005; Park, 1994). 최근 다양한 식재료에 대한 관심이 커지면서 국내 치콘 소비도 증가하고 있는데 현재 수입되고 있는 치콘은 유럽에서 생산되기 때문에 유통 Kor. J. Hort. Sci. Technol. 32(3), June 2014 354 에 장시간이 소요된다. 수확한 치콘은 뿌리쪽 절단부분이 공 기 중에 노출되면 몇 일 이내에 절단면에 붉은 반점이 생겨 상품성이 저하되는데(Vanstreels et al., 2002), 이와 같은 농 산물 절단면의 갈변 등 색변화는 절단면에 노출된 페놀물질 의 산화가 원인으로 페놀물질 합성에 관여하는 phenylalanine ammonia lyase(PAL, EC 4.3.1.5)과 페놀물질을 산화시키는 polyphenoloxidase(PPO; E.C. 1.14.18.1)에 의해 진행된다 (Saltveit, 2000). 이 중 PPO의 활성은 과일・채소류의 절단면 색변화 정도를 판단하는 주요 지표 중의 하나로 이용되고 있는데, PPO는 결구상추 등에서 절단면의 phenol 화합물을 산화시켜 갈변을 유도시킨다(Kavrayan and Aydemir, 2001; Rodriguez-Lopez et al., 2001; Takahashi et al., 1996; Van Gelder et al., 1997). 또한 PAL 활성도 결구상추의 갈변에 관여하는데, 열처리를 했을 때 PAL activity가 저하되면서 갈변이 억제되었다(Kang and Saltveit, 2003). 이러한 열처리 의 갈변 억제 효과는 상추를 대상으로 Hong et al.(2004), Loaiza-Velarde et al.(1997), 그리고 Saltveit and Qin(2008) 등이 보고한 바 있다. 치콘 절단면 적변에 관한 연구는 미비하였는데, Charles et al.(2008)는 저산소와 고이산화탄소의 MA 조건 처리에서 지 연된다고 하였다. 치콘과 같은 종인 엔디브(Cichorium intybus L.)의 신선편이의 저장 중 발생하는 적변은 CA 조건과 heat shock(46°C/120s)처리에서 지연되며, heat shock(열처리)는 PAL1의 전사를 억제하기 때문이라고 하였다(Salman et al., 2008). 그 밖에도 저장 중에 발생하는 엔디브 줄기의 적변이 acetic and propionic acid 처리로 억제된다고 한다(Castaner et al., 1999). 그러나 치콘은 친환경 농산물 형태로 생산이 가능하기 때문에 화학제 처리보다는 열처리와 같은 친환경 적 방법이 더욱 적합하다고 생각된다. 이에 본 연구는 치콘의 저장 중 품질 유지를 위해 치콘의 절단면 적변 방지를 위한 열처리 기술 개발과 열처리의 적 변 방지 원리를 알아보고자 수행하게 되었다.

Hot water dipping treatments on Tarocco orange fruit and their effects on peel essential oil

The most common and serious diseases which affect citrus fruit after harvest in Italy are induced by Penicillium digitatum Sacc. and Penicillium italicum Weh., responsible respectively for green and blue mold rots. This paper deals with the effectiveness of hot water dipping (HWD) treatments as alternative means to control postharvest decay on Tarocco orange fruit [Citrus sinensis (L.) Osbeck], and their effect on fruit quality with special regard to peel essential oils. Selected treatments were HWD at 52°C for 180s and at 56°C for 20s. These treatments were compared with an effective fungicide standard treatment (Imazalil) and an untreated control. The results showed that HWD at 56°C for 20s was more effective in inhibiting P. digitatum spore germination than HWD at 52°C for longer exposure time. In addition, HWD treatment at 56°C significantly increased the level of alcohols, esters and aliphatic (fatty) aldehydes. Therefore, the lowest values of decay incidence recorded in HWD fruit treated at 56°C may be due to the increase in oxygenated monoterpenes, esters and aldehydes. Finally, HWD treatments did not cause surface damage or color change and did not influence internal quality parameters.

Postharvest Quality of Nectarine cv. ‘Venus’ as Affected by Hot Water Dips and Length of Storage

The effect of hot water dip (48° C) duration (6 or 12 minutes) (HWD 48° C 6' and HWD 48° C 12') and length of storage at 0° C in normal atmosphere (two or four weeks) on chemical and sensory quality of nectarine (Prunus persica var. nectarina cv. 'Venus') was studied. After two weeks of storage, HWD-treated fruits had significantly lower weight loss and SSC compared to control. There was no significant difference between HWD 48 °C 6' and HWD 48 °C 12' – treated fruit. HWD 48 °C 12' - treated fruit maintained sensory quality after two weeks of storage. After four weeks of storage, control fruit received higher scores compared to HWD – treated fruit for all traits, except for aroma which was still higher for HWD 48 °C 12' - treated fruit. Duration of hot water dip is significant factor for maintaining postharvest quality of nectarine fruit.

Reduction in Activity/Gene Expression of Anthocyanin Degradation Enzymes in Lychee Pericarp is Responsible for the Color Protection of the Fruit by Heat and Acid Treatment

Heat and acid treatments were reported to be a promising substitute for SO2 fumigation in color protection of postharvest lychee (Litchi chinensis Sonn.) fruits, but the mechanism was not clear. In the present study, hot water (70°C) dipping followed by immersion in 2% HCl (heat-acid) substantially protected the red color of the fruit during storage at 25°C and inhibited anthocyanin degradation while hot water dipping alone (heat) led to rapidly browning and about 90% loss in anthocyanin content. The pH values in the pericarp of the heat-acid treated fruit dropped to 3.2, while the values maintained around 5.0 in the heat-treated and control fruit. No significantly different pH values were detected among the arils of heat-acid, heat treated and control fruit. Heat-acid treatment dramatically reduced the activities of anthocyanin degradation enzyme (ADE), peroxidase (POD) and polyphenol oxidase in the pericarp. A marked reduction in LcPOD gene expression was also detected in heat-acid treated fruit, in contrast, induction was found in heat treated fruit. The pericarp of heat-acid treated fruit exhibited significantly lower respiration rate but faster water loss than that of the untreated or heat treated fruit. Taken together, heat treatment triggered quick browning and anthocyanin loss in lychee fruit, while heat-acid treatment protected the fruit color by a great reduction in the activities/gene expression of anthocyanin degradation enzymes and acidification of lychee pericarp.

Control of Monilinia rots on fruit naturally infected by hot water treatment in commercial trials

In recent years, safer methods for the control of fruit postharvest pathogens have been investigated and heat treatment could represent an effective and safe approach for managing postharvest decay such as Monilinia rots. In the present study, the effect of hot water treatment (HWT) (60°C for 30 and 60s) on brown rot was investigated. More specifically, the influence of HWT was determined in in vitro trials on conidial germination of Monilinia laxa, Monilinia fructicola and Monilinia fructigena and in peach and nectarine fruit, naturally infected. The effect of hot water application on fruit quality was also assessed. M. fructicola showed a greater resistance to heat than M. laxa and M. fructigena, however conidia germination of all three species was completely inhibited by a dipping in hot water for 1min at 55°C. The results of a large scale experiment under commercial conditions and several pilot trials showed a good antifungal activity of HWT in naturally infected fruit. After 6 days at 0°C and 3 days at 20°C, in both semi-commercial and commercial trials, the inhibition of decay was higher than 78% in four trials out of six. In addition, the treated fruit showed an acceptable commercial quality and no visual damage was observed as a consequence of HWT. The results demonstrated that HWT is a promising method to control Monilinia rots of peach and nectarine, and is safe and readily available for conventional and organic production under commercial conditions.

Postharvest hot water dipping reduces decay by inducing disease resistance and maintaining firmness in muskmelon (Cucumis melo L.) fruit

Muskmelons (Cucumis melo L.) are major economic crops in the northwestern part of China, and postharvest decay of fruit is serious. In order to reduce postharvest decay and prolong the storage time, the effect of hot water dipping (HWD) on nature decay and mechanisms involved were studied when muskmelon fruit (cv. Yujinxiang) were dipped in hot water at 53°C for 3min. The results showed that postharvest HWD effectively (p<0.01) reduced the decay incidence, 18.9% lower than that in control fruit after 18 days of storage. HWD noticeably enhanced the activities of phenylalanine ammonialyase (PAL), cinnamate-4-hydroxylase (C4H), 4-Coumarate: CoA ligase (4CL), polyphenoloxidase (PPO) and peroxidase (POD), and accumulated phenolic compounds, flavonoid, lignin and hydroxyproline-rich glycoproteins (HRGPs). The treatment effectively maintained fruit firmness by suppressing the activities of endo-1,4-β-d-glucanase (EGase), β-glucosidase (β-Glu), polygalacturonase (PG) and pectinesterase (PME), and promoting the accumulation of suberin and callose. And the data showed a higher correlation between fruit firmness and decay incidence (R2=0.8933). Furthermore, HWD could clean the surface of fruits, melt the epicuticular waxes, cover and seal the stomata. These results indicated that postharvest HWD reduced decay incidence by inducing disease resistance and maintaining the firmness in muskmelon fruit. Our data suggest that HWD has the potential to reduce or/and substitute chemical fungicides to control postharvest decay of muskmelon fruits.

Combined effect of gamma irradiation and hot water dipping on the selected nutrients and shelf life of peach

Gamma irradiation in combination with hot water dipping treatment was tested for maintaining storage quality and extending the shelf life of peach fruit. The matured peaches fruits (local variety no, Tex-A-6-69) were first dipped in hot water having temperature of 0, 40 and 60 °C for 60 seconds and they were exposed to 0.5 and 1.0 kGy doses of gamma radiation and stored in paper cartons under ambient (temperature 25 ± 2 °C, RH 70 %) conditions for their physico-chemical evaluations on weekly basis. The combine effect of hot water dipping treatment and irradiation for peach was study for the first time in Pakistan. The parameters studied included % weight loss, % ash content, % moisture content, total soluble solids (TSS), titratable acidity and ascorbic acid. The sensory indices studied were size, shape, color and overall acceptability. The sensory evaluation values at 0 days for the controlled peach sample were recorded for comparison. Statistical analysis was performed to find determinates of irradiation alone and in combination with hot water dipping techniques on peaches. Studies revealed that irradiation treatment in combination with hot water treatments significantly (LSD at 5 %) maintained the storage quality of peach fruit under ambient conditions. Data obtained for weight loss, moisture, shape and overall acceptability showed significant results while non-significant values were recorded for ash, TSS and size. Overall, consumers rated the acceptability of treated peaches higher than untreated peaches. This particular type of research also helps in improving one’s country export quality of fruits.

Influence of hot water dip on fruit quality, phenolic compounds and antioxidant capacity of Satsuma mandarin during storage

The influence of hot water dips (50, 52 and 54 for 3 min) on fruit quality, phenolic compounds and antioxidant capacity of Satsuma mandarin during 60 days' storage at 10 was investigated. Hot water dips did not affect fruit quality attributes as well as ascorbic acid content, and 50 treatment significantly reduced fruit weight loss. Significant increases of flavonoids were found in all hot water treated fruit from after treatments till 15 days of storage, whereas phenolic acids were not greatly affected. Hot water dipping at 50 significantly increased total phenolics and antioxidant capacity of Satsuma mandarin immediately after treatment and maintained similar levels with control during storage, while 52 and 54 treatments showed relatively lower levels. The results suggested that hot water dipping at 50 for 3 min can be a promising way to retain functional quality of storing Satsuma mandarin.

Hot water and molybdenum dips: The case of antioxidant assays in lemon flavedo during cold storage

Antioxidants are part of the plant’s defense system, protecting tissue against oxidative stress. In citrus fruit, oxidative stress can occur during extended cold storage ultimately result in chilling injury. Citrus fruit contain certain rind antioxidants which occur in different forms (lipophilic and hydrophilic). Previous studies demonstrated a synergistic relationship between hot water dips (HWD) and molybdenum dips (Mo) in mitigating chilling injury in citrus fruit. Therefore, the aim of this study was to investigate the potential of HWD and Mo to alleviate chilling injury by enhancing antioxidant capacity in lemon flavedo of fruit stored at -0.5°C. Fruit from different sources, commonly displaying chilling injury and other seemingly resistant to the development of chilling symptoms, were preconditioned for 2 min with HWD (47 or 53°C) and thereafter soaked in 1 or 10 µM Na2MoO4 solution for 30 min. Fruit were subsequently stored at -0.5°C for 7 or 28 days, moved to ambient temperature for a week and then evaluated for chilling injury symptoms. Chilling susceptible lemon fruit showed low Trolox equivalent total antioxidant capacity (TEAC), phenolics, and flavonoids concentration and high lipid peroxidation. Hot water dips 53°C, as well as 1 and 10 µM Mo plus HWD 53°C treatments mitigated chilling injury by enhancing total antioxidant capacity, and total phenolics and flavonoids concentrations in the flavedo. However, the ability of these treatments to alter lipophilic and hydrophilic antioxidants was fruit source dependent. Key words: Lemon (Citrus limon), chilling injury, antioxidant assays, hot water dips, molybdenum, cold storage.

Analysis of organic acids in electron beam irradiated chestnuts (Castanea sativa Mill.): Effects of radiation dose and storage time

Since 2010, methyl bromide, a widely used fumigant was banned from the European Union under the Montreal Protocol guidelines, due to its deleterious effects on health and risk to the environment. Since then, many alternatives for chestnut conservation have been studied (hot water dip treatment being the most common), among them, electron beam irradiation has been proposed as being a safe, clean and cheap alternative. Herein, the effects of this radiation at different doses up to 6kGy and over storage up to 60days in the amounts and profile of nutritionally important organic acids were evaluated. Chestnuts contained important organic acids with quinic and citric acids as main compounds. Storage time, which is traditionally well accepted by consumers, caused a slight decrease on quinic (13-9mg/g), ascorbic (1.2-0.8mg/g), malic (5-4mg/g), fumaric (0.4-0.3mg/g) and total organic (33-26mg/g) acids content. Otherwise, irradiation dose did not cause appreciable changes, either individually or in total (28-27mg/g) organic acid contents. Electron beam irradiation might constitute a valuable alternative for chestnut conservation.

An integrated approach with Trichoderma harzianum DGA01 and hot water treatment on control of crown rot disease and retention of overall quality in banana

A biological control of crown rot disease of banana fruit was analysed using an integrated approach combining hot water treatment and Trichoderma harzianum strain DGA01. Treated fruits were stored at 22–25 °C and 90–95% relative humidity for 2 weeks. The bioefficacy of fungal antagonist in vitro towards crown rot-causing pathogens, namely Lasiodiplodia theobromae, Thielaviopsis paradoxa, Colletotrichum musae and Fusarium verticillioides, was enhanced by 11.41% following hot water treatment (50 °C, 20 min). DGA01 germinated on the fruit 48 h after inoculation and parasitised the pathogen. Postharvest application showed that hot water treatment and conidial suspension of DGA01 (106 ml−1) applied singly performed significantly better than the untreated control in reducing the incidence of crown rot, but were not as effective as the fungicide. The combination of hot water treatment and DGA01 gave 93% control of fruit decay which was comparable with fungicide treatment of 95%. The quality of fruit was markedly improved in hot water treatment + DGA01 as compared to those dipped in fungicide solution. The inconsistencies of single treatments, by DGA01 or hot water dips, in controlling crown rot such as variation in severity of disease among treatments and within a treatment, were lessened by dipping the fruit in DGA01 conidial suspension following hot water treatment.

Effects of ultraviolet irradiation, pulsed electric field, hot water dip and ethanol vapours treatment on keeping and sensory quality of mung bean (Vigna radiata L. Wilczek) sprouts

The objective of this research work was to evaluate the effects of UV- irradiation, pulsed electric field (PEF), hot water dip (HWD) and ethanol vapours on the quality and storage life of mung bean sprouts (Vigna radiata L. Wilczek). The sprouts were subjected to various treatments viz., UV-Irradiation (10 kJm(-2) in laminar flow chamber for 1h), PEF (10,000V for 10s), HWD (50°C for 2min) and ethanol vapours (1h); and then stored in thermocol cups wrapped with perforated cling films at room (25 ± 1°C) and low (7 ± 1°C) temperature conditions. The sprouts were analyzed regularly at 24h interval for sprout length, sprout weight, total soluble solids (TSS), titratable acidity, non-enzymatic browning, total plate count and overall acceptability. Sprout length and weight increased during storage. There was no significant effect of various treatments on sprout length and weight, except in ethanol treatment, where suppression was observed. HWD showed higher TSS and acidity than that of control. The least browning was observed in ethanol treatment. The total plate count was not significantly affected by various treatments. Overall acceptability under various treatments decreased during storage period both at room and low temperature. Hot water and ethanol vapour treated sprouts showed higher acceptability than other treatments. However, the acceptability scores for sprouts remained within the acceptable range (≥6) up to 72h at room temperature and 120h at low temperature conditions.

Control of a wide range of storage rots in naturally infected apples by hot-water dipping and rinsing

Hot-water rinsing (3 or 4min) and dipping (15, 20 or 25s) at a range of incubation temperatures was applied to apples (cv. ‘Ingrid Marie’ and ‘Pinova’) naturally infected with a range of North West European storage-rot fungi. Significant reductions in the incidence of fruit rot were achieved by incubation periods of 3min at 50–54°C (dipping) and 20 or 25s at 55°C (rinsing), followed by up to 100d cold-storage at 2°C and 14d at 18°C. Pathogens controlled in this way were Neofabraea alba, N. perennans, Monilinia fructigena, Colletotrichum acutatum, Phacidiopycnis washingtonensis and Cladosporium spp. Neonectria galligena was reliably controlled by dipping but not rinsing. No effects of either heat treatment on Gibberella avenacea and Botrytis cinerea were apparent. Following rinsing at 65°C for 20s, the incidence of P. washingtonensis, Penicillium expansum, Mucor spp. and Phoma exigua was higher than in untreated control fruit or in apples rinsed at lower temperatures, and was associated with heat damage. The relative contributions of heat effects on inoculum viability and activation of defence responses of apple fruit are discussed. Hot-water rinsing has several advantages over hot-water dipping related to the efficient processing of fruit either directly after harvest or after long-term storage.

The effect of delay between heat treatment and cold storage on alleviation of chilling injury in banana fruit

To understand the mechanisms leading to the enhanced chilling resistance of banana by hot-water dipping (HWD, 52 °C for 3 min), we investigated the effect of a 0.5-24 h delay between HWD and cold storage on chilling resistance and the change related to the metabolism of reactive oxygen species (ROS). The HWD-treated fruit with a delay of less than 6 h exhibited markedly less chilling injury than the non-heated control fruit, while a delay more than 6 h resulted in significant loss in chilling resistance. Increased hydrogen peroxide content and rate of superoxide radical production were detected in the fruit at 0.5-1.5 h after HWD treatment, and the levels declined with a longer delay, which may be correlated with the enhanced gene expression levels of the gene coding for a ROS-generating related enzyme, NADPH oxidase (MaNOX). Enhanced activities and gene expression of an ascorbate peroxidase (MaAPX) were recorded in the fruit at 1.5-6 h after the treatment, and after 6 h the ascorbate peroxidase levels decayed to the levels as the control fruit. The higher APX gene expression was maintained in the treated fruit with a 3 h delay during the subsequent cold storage at 7 °C, correlating with the enhanced chilling resistance. The HWD-treated fruit left at ambient temperature up to 6 h prior to cold storage maintained the effect of heat treatment and transiently increased ROS content, and the ascorbate peroxidase activity that occurred 0.5-6 h after the treatment may be correlated with the elevated chilling resistance induced by HWD treatment.

Effect of quarantine treatments on the carbohydrate and organic acid content of mangoes (cv. Tommy Atkins)

Brazil is one of the largest mango producers and the third largest mango exporter worldwide. Irradiation treatment and its commercial feasibility have been studied in our country to make it possible to develop new markets and, consequently, to compete with the major exporters of mangoes, Mexico and India. This work was designed to compare irradiation treatment with the hot water dip treatment in mangoes cv. Tommy Atkins for export and to verify that the main attributes for acceptance, color and texture, as well as carbohydrate and organic acid contents, were maintained. In this study, the fruit was divided into groups: control, hot water dip-treated (46°C for 90min), and irradiation-treated at doses of 0.4kGy and 1.0kGy. The fruit was stored at low temperature (11°C±2) for 14 days and then at room temperature (23°C±2) until the end of the study. The results indicated that the fruit given a dose of 1.0kGy remained in a less advanced stage of ripening (stage 3) throughout the storage period, but experienced a greater loss of texture in the beginning of the experiment. It was noted that only the control group had higher levels of citric acid and succinic acid on the last day of the experiment. There were no significant differences in the total sugar content between any treatment groups. Gamma radiation can be used as a quarantine treatment and does not interfere negatively with the quality attributes of mangoes.

Influence of postharvest hot water dip treatment on quality of peach fruit (Prunus persica L.)

Effect of hot water dipping and storage time on post harvest behavior that is, pH, weight loss, acidity, total soluble solids (TSS), TSS/acid ratio and ascorbic acid content of peach was investigated. Pre-storage heat treatments provide a non-damaging physical treatment, and a relevant strategy, that fits both consumers and growers expectations. pH values decreased with the passage of time while the effect of temperature was not clear. As might be expected, weight loss increased with the increase in storage time; however, meagre increase was noted in 55°C (10.83%) and higher in 40°C groups (16.73%). Similarly, TSS increased with the time factor, though the increase in control (11.9) and 50°C was quite lower compared to other treatment. Ascorbic acid decreased with time and temperature, nevertheless the decrease beyond 45°C was considerably lower. Similar trend was noted for TSS/acid ratio. With storage time the acidity decreased, while the effect of temperature cannot be ascertained. It can be inferred from the study that the temperature range of 50 to 55°C can provide a non damaging physical condition that can fit both consumer and grower expectations. Key words: Peach, post harvest behavior, storage time, temperature.

Effect of hot water dip treatment on postharvest anthracnose of banana var. Berangan

Heat treatment becomes a feasible method for controlling of postharvest decay in many freshly harvested commodities. Anthracnose is the main disease affecting the quality of banana fruits during export and marketing. In this study inoculated Berangan banana with Colletotrichum musae was dipped in hot water at 50°C for 0, 10, 20 min with or without fungicide, respectively. The disease development was determined by measuring the anthracnose infected areas after 10 days of treatment. There was a significant difference in size of lesion on Berangan banana as affected by different dipping time (0, 10 and 20 min) of hot water alone at 50°C. Anthracnose infection rating was reduced with increase dipping time. Dipping fruit in hot water at 50°C for 20 min was more effective in suppressing disease development as compared to hot water with fungicide as control (0 min). Conidia germination of C. musae was also assessed with hot water treatment at the same time-temperature combination with or without fungicide as previous. In general, conidia germination rate increases with increasing incubation time, while increasing the hot water dipping time with or without fungicide suppressed conidia germination with varying incubation times. There was a significant difference between hot water treatment alone and with fungicide for 0 min as control. Hot water dip for 10 and 20 min at 50 oC inhibited conidia germination (100 %) of C. musae better than application of fungicide alone (55.92 %). It is suggested hot water dip treatment at 50 oC for 20 min could be used to anthracnose in Berangan banana instead of using fungicide as practically used in commercial now.

Mass Gain of Carbon Fiber Reinforced Polyimide (CFRP) by Dipping in Hot Distilled Water

Influence of isothermal dipping in hot distilled water for 200 ks on the mass gain of carbon fiber reinforced polyimide (CFRP) was investigated. Dipping in distilled water raised the mass gain. Based on the kinetics equation, both reaction index (n) and kinetic constant (k) were obtained. Since the n value is approximately 0.6 from 333 to 373 K, the reaction mode was independent on the absorption temperature. Based on the results and discussion, the water absorption was probably the directional mass transport through the fiber/polyimide cylindrical interface. On the other hand, Arrhenius linear relationship between logarithmic k (log k) and reciprocal dipping temperature (1/T) was obtained. The apparent activation energy estimated by the slope of water absorption in the CFRP was approximately equal to the activation energy of self-diffusion coefficient of water molecule. Mass gain of CFRP (CF/PI) dipped in distilled water for 100 ks at 373 K probably enhanced the molecules’ density induced by water molecules’ intrusion among polyimide polymers, resulting in enhancement of (dσ/de)max and fracture stress. On the other hand, the mass gain by dipping for 200 ks at 373 K enriched the water concentration in polyimide matrix. Thus, it was assumed to enhance the intermolecular distance of polyimide polymers and then to reduce the intermolecular force among polyimide polymers, resulting in a drop of (dσ/de)max of CFRP dipped for 200 ks. On the other hand, the dipping for 200 ks probably raised the intermolecular force between water molecules and polyimide polymers, resulting in remarkable enhancements of the fracture strain, fracture energy and impact value of the CFRP.

PHYSIOLOGICAL AND BIOCHEMICAL BEHAVIOUR OF ‘WHITE SUKKARY’ AND ‘ZEBDA’ MANGOES DURING SHELF LIFE PERIOD AFTER HOT WATER DIPPING AND CALCIUM NITRATE TREATMENTS

Thermotherapy, especially hot water dipping (HWD) is widely used in many countries for insect and decay control in mangoes. Physiological and biochemical behaviour of fruit under HWD (47±1 ◦C/20 min, 53±1 ◦C/5 min) in packaged ‘White Sukkary’; (49±1 ◦C/30 min, 53±1 ◦C/8 min) in non-packaged ‘zebda’ and Ca(NO3)2 (4 and 6% /15min) in both cultivars during shelf life period was investigated. Overall valuable effect of 53±1 ◦C/5 min or 8min HWD or 6% Ca(NO3)2 on ripening acceleration and improvement was observed. In general, carotene content in peel was associated with up-regulation of catalase (CAT) activity under 53±1 ◦C/5 min or 8 min HWD or 6% Ca(NO3)2 treated fruit. 47(49) ±1 ◦C/ 20-30 min treatment alleviated peroxidase (POX) activity in peel and juice of both cultivars. Weight loose % and vitamin C (VC) values were maintained only with 6% Ca(NO3)2 treated fruit. HWD down-regulated Ascorbic acid oxidase activity (ASAO) compared to calcium treatments and control. High calcium content in peel or bulb was significantly correlated with fruit firmness only in ‘Zebda’ fruit. Also, SSC, TA%, reducing sugars and free phenols levels were estimated. Finally, using of HWD 53±1 ◦C/5 or 8 min or Ca(NO3)2 /6% treatments to accelerate and improve quality in ‘White Sukkary’ and ‘Zebda’ fruit in spite of synthetic ripening stimulators can be recommended.