Lemon balm (Melissa officinalis L.) leaves pre-drying by using low energy laser beam

A laboratory laser beam drying method for lemon balm (Melissa officinalis L.) is presented. The aim of this study was to determine the possibility of using lasers as a pre-treatment for drying the lemon balm leaves and also to determine the variation of water content during the treatment. Leaves were illuminated from one side during a period of 180 s with 100 mW and 200 mW lasers. Both sources of coherent light were in the red part of the visible spectrum with wavelengths of 650 nm. Freshly harvested lemon balm leaves with 75.64% of water content were used for the analysis. Low-energy laser beam treatment for a period of 180 s resulted in the reduction of water content of 0.307% for 100 mW laser treatment and 0.31% for the 200 mW laser treatment. Amounts of energy emitted by low energy lasers are relatively small. Therefore, lasers thermal influence is negligible so it can be concluded that laser activity on lemon balm leaves is based solely on biostimulation. The proposed method allows effective reduction of water content without causing damage to the plant material. For practical application, dryers with integrated laser diode network were proposed. Low energy coherent radiation treatment represents an inexpensive and environmentally safe method that does not pollute the environment. This method also provides close control of the process, and in spite of the greater cost of energy, the overall increase in drying efficiency and throughput can bring about significant economic savings.</p

Application of laser and ultrasound as a pre-treatment for drying the leaf of lemon balm

Matičnjak (Melissa officinalis L.) je ljekovita i medonosna vrsta, a često se uzgaja i kao ukrasna biljka. Njeni listovi su bogat izvor različitih bioaktivnih spojeva snažnog antioksidacijskog djelovanja. Neinvazivne tehnike kao što su ultrazvuk i laser mogu se učinkovito primijeniti kao predtretmani sušenju. Cilj ovog rada bio je utvrditi mogućnost primjene lasera i ultrazvuka kao predtretmana sušenju lista matičnjaka te utvrditi utjecaj navedenih tretmana na prinos bioaktivnih spojeva u osušenom materijalu. Analizirani su svježi listovi matičnjaka, osušeni listovi konvekcijom bez predtretmana (kontrola) te listovi predtretirani laserom (izlazne snage 100 i 200 mW) i ultrazvukom (35 kHz, 140 W). U pripremljenim uzorcima svježih i osušenih listova provedene su analize osnovnog kemijskog sastava, vitamina C, sadržaja ukupnih klorofila i karotenoida, sadržaja ukupnih fenola (flavonoida i neflavonoida) i antioksidacijskog kapaciteta. Kod kontrolnog uzorka i uzoraka predtretiranih laserom nema značajnijih razlika u brzini otpuštanja vode, dok je značajnije skraćenje vremena sušenja zabilježeno kod uzoraka predtretiranih ultrazvukom. Uspoređujući rezultate uzorka kontrole (bez predtretmana) s rezultatima uzoraka predtretiranih laserom ili ultrazvukom zamijećeno je da je uzorak kontrole imao najmanji sadržaj vitamina C, ukupnih fenola, karotenoida i ukupnih klorofila što dokazuje da su predtretmani utjecali na očuvanje tih bioaktivnih spojeva. Što se tiče antioksidacijskog kapaciteta, najveću vrijednost imao je uzorak predtretiran ultrazvukom na sobnoj temperaturi, a najmanju uzorak predtretiran laserom od 200 mW.Lemon balm (Melissa officinalis L.) is a medicinal and honey species and it is often grown as an ornamental plant. Its leaves are a rich source of various bioactive compounds that have strong antioxidant activity. Non-invasive techniques such as ultrasound and laser can be applied as pre-treatment of drying. The aim of this study was to determine the possibility of using lasers and ultrasound as a pre-treatment for drying the leaf of lemon balm, and to determine the influence of these treatments on the yield of bioactive compounds in the dried material. Fresh leaves of lemon balm, convection-dried leaves without pretreatment (control), laser pretreated leaves (output power 100 and 200 mW) and ultrasound pretreated leaves were used for analyzes. The prepared fresh and dried leaf samples were analyzed for basic chemical constituents, vitamin C, total chlorophyll and carotenoid content, total phenols (flavonoids and nonflavonoids) content and the antioxidant capacity. There was no significant difference in the rate of water release for the control and pretreated laser samples, while a significant reduction in drying time was observed for the pretreated ultrasound samples. Comparing the results of the control sample (without pretreatment) with the results of the samples pretreated with laser or ultrasound, it was observed that the control sample had the lowest content of vitamin C, total phenols, carotenoids and total chlorophylls, which proves that the pretreatments affected on conservation of these bioactive compounds. Regarding on the antioxidant capacity, the highest value had the sample pretreated by ultrasound at room temperature and the lowest sample pretreated with a 200 mW laser

Application of laser and ultrasound as a pre-treatment for drying the leaf of lemon balm

Matičnjak (Melissa officinalis L.) je ljekovita i medonosna vrsta, a često se uzgaja i kao ukrasna biljka. Njeni listovi su bogat izvor različitih bioaktivnih spojeva snažnog antioksidacijskog djelovanja. Neinvazivne tehnike kao što su ultrazvuk i laser mogu se učinkovito primijeniti kao predtretmani sušenju. Cilj ovog rada bio je utvrditi mogućnost primjene lasera i ultrazvuka kao predtretmana sušenju lista matičnjaka te utvrditi utjecaj navedenih tretmana na prinos bioaktivnih spojeva u osušenom materijalu. Analizirani su svježi listovi matičnjaka, osušeni listovi konvekcijom bez predtretmana (kontrola) te listovi predtretirani laserom (izlazne snage 100 i 200 mW) i ultrazvukom (35 kHz, 140 W). U pripremljenim uzorcima svježih i osušenih listova provedene su analize osnovnog kemijskog sastava, vitamina C, sadržaja ukupnih klorofila i karotenoida, sadržaja ukupnih fenola (flavonoida i neflavonoida) i antioksidacijskog kapaciteta. Kod kontrolnog uzorka i uzoraka predtretiranih laserom nema značajnijih razlika u brzini otpuštanja vode, dok je značajnije skraćenje vremena sušenja zabilježeno kod uzoraka predtretiranih ultrazvukom. Uspoređujući rezultate uzorka kontrole (bez predtretmana) s rezultatima uzoraka predtretiranih laserom ili ultrazvukom zamijećeno je da je uzorak kontrole imao najmanji sadržaj vitamina C, ukupnih fenola, karotenoida i ukupnih klorofila što dokazuje da su predtretmani utjecali na očuvanje tih bioaktivnih spojeva. Što se tiče antioksidacijskog kapaciteta, najveću vrijednost imao je uzorak predtretiran ultrazvukom na sobnoj temperaturi, a najmanju uzorak predtretiran laserom od 200 mW.Lemon balm (Melissa officinalis L.) is a medicinal and honey species and it is often grown as an ornamental plant. Its leaves are a rich source of various bioactive compounds that have strong antioxidant activity. Non-invasive techniques such as ultrasound and laser can be applied as pre-treatment of drying. The aim of this study was to determine the possibility of using lasers and ultrasound as a pre-treatment for drying the leaf of lemon balm, and to determine the influence of these treatments on the yield of bioactive compounds in the dried material. Fresh leaves of lemon balm, convection-dried leaves without pretreatment (control), laser pretreated leaves (output power 100 and 200 mW) and ultrasound pretreated leaves were used for analyzes. The prepared fresh and dried leaf samples were analyzed for basic chemical constituents, vitamin C, total chlorophyll and carotenoid content, total phenols (flavonoids and nonflavonoids) content and the antioxidant capacity. There was no significant difference in the rate of water release for the control and pretreated laser samples, while a significant reduction in drying time was observed for the pretreated ultrasound samples. Comparing the results of the control sample (without pretreatment) with the results of the samples pretreated with laser or ultrasound, it was observed that the control sample had the lowest content of vitamin C, total phenols, carotenoids and total chlorophylls, which proves that the pretreatments affected on conservation of these bioactive compounds. Regarding on the antioxidant capacity, the highest value had the sample pretreated by ultrasound at room temperature and the lowest sample pretreated with a 200 mW laser

Application of laser and ultrasound as a pre-treatment for drying the leaf of lemon balm

Matičnjak (Melissa officinalis L.) je ljekovita i medonosna vrsta, a često se uzgaja i kao ukrasna biljka. Njeni listovi su bogat izvor različitih bioaktivnih spojeva snažnog antioksidacijskog djelovanja. Neinvazivne tehnike kao što su ultrazvuk i laser mogu se učinkovito primijeniti kao predtretmani sušenju. Cilj ovog rada bio je utvrditi mogućnost primjene lasera i ultrazvuka kao predtretmana sušenju lista matičnjaka te utvrditi utjecaj navedenih tretmana na prinos bioaktivnih spojeva u osušenom materijalu. Analizirani su svježi listovi matičnjaka, osušeni listovi konvekcijom bez predtretmana (kontrola) te listovi predtretirani laserom (izlazne snage 100 i 200 mW) i ultrazvukom (35 kHz, 140 W). U pripremljenim uzorcima svježih i osušenih listova provedene su analize osnovnog kemijskog sastava, vitamina C, sadržaja ukupnih klorofila i karotenoida, sadržaja ukupnih fenola (flavonoida i neflavonoida) i antioksidacijskog kapaciteta. Kod kontrolnog uzorka i uzoraka predtretiranih laserom nema značajnijih razlika u brzini otpuštanja vode, dok je značajnije skraćenje vremena sušenja zabilježeno kod uzoraka predtretiranih ultrazvukom. Uspoređujući rezultate uzorka kontrole (bez predtretmana) s rezultatima uzoraka predtretiranih laserom ili ultrazvukom zamijećeno je da je uzorak kontrole imao najmanji sadržaj vitamina C, ukupnih fenola, karotenoida i ukupnih klorofila što dokazuje da su predtretmani utjecali na očuvanje tih bioaktivnih spojeva. Što se tiče antioksidacijskog kapaciteta, najveću vrijednost imao je uzorak predtretiran ultrazvukom na sobnoj temperaturi, a najmanju uzorak predtretiran laserom od 200 mW.Lemon balm (Melissa officinalis L.) is a medicinal and honey species and it is often grown as an ornamental plant. Its leaves are a rich source of various bioactive compounds that have strong antioxidant activity. Non-invasive techniques such as ultrasound and laser can be applied as pre-treatment of drying. The aim of this study was to determine the possibility of using lasers and ultrasound as a pre-treatment for drying the leaf of lemon balm, and to determine the influence of these treatments on the yield of bioactive compounds in the dried material. Fresh leaves of lemon balm, convection-dried leaves without pretreatment (control), laser pretreated leaves (output power 100 and 200 mW) and ultrasound pretreated leaves were used for analyzes. The prepared fresh and dried leaf samples were analyzed for basic chemical constituents, vitamin C, total chlorophyll and carotenoid content, total phenols (flavonoids and nonflavonoids) content and the antioxidant capacity. There was no significant difference in the rate of water release for the control and pretreated laser samples, while a significant reduction in drying time was observed for the pretreated ultrasound samples. Comparing the results of the control sample (without pretreatment) with the results of the samples pretreated with laser or ultrasound, it was observed that the control sample had the lowest content of vitamin C, total phenols, carotenoids and total chlorophylls, which proves that the pretreatments affected on conservation of these bioactive compounds. Regarding on the antioxidant capacity, the highest value had the sample pretreated by ultrasound at room temperature and the lowest sample pretreated with a 200 mW laser