Process Characteristics of Micro Wet Milling and Spray Drying for Production of Whole Seabuckthorn (Hippophae rhamnoides) Powder

概要

Sea buckthorn (SB) juice is the most superior juice beverage due to its strong acid flavor and healthy properties. Moreover, it is potential source of vitamin C, E, polyphenolics, flavonoids, carotenoids, and higher antioxidants. The most recurrently attracted parts from SB are fruits (berries) and seeds because they are raw material in the manufacture of food, beverage, and pharmaceuticals. During the production of SB juice, pomace which is pulp and seeds resulted from the industrial processing of the fruit has high antioxidant but is disregarded as large amount of waste. The waste of industrial food processing is a global issue. Nowadays food engineers, as well as food processing investors are looking for develop to reduce food loses and provide further sustainable processing development. Accordingly, the purpose of our research is to develop free- waste concentrated whole SB (WSB) juice powders through utilizing the novel processing concepts of micro-wet milling (MWM), and spray drying (SD).

　In my study, it is covering 5 chapters. Beginning chapter 1 reviewed the mentioned background of this research. In addition, limitation of the conventional processing and the advantage of the novel combined methods for the development of WSB juices and powders are illustrated in detail.

　In chapter 2, the aim to apply of MWM to accomplish a SB juice with pulp and seeds, which is used to make a well-homogenized juice with small particle size. The MWM system was used to mill SB berries involving pulp and seeds and obtained micro-scale particles juice without causing adverse impacts of degradation such as frictional heat. Along with the yielded minimum particle sizes (D50 of 10.4 µm) of the SB juice, a 10 mL/min of optimal MWM operational condition of the feeding rate, a 50rpm rotational speed and an adjusted gap between two milestones with 43.03kN were achieved. The MWM WSB juice has improved color, smaller particle size, higher FRAP and DPPH antioxidant properties, and overall significant phenolics than mixer milled SB (MMSB) and commercial SB (CSB) juices. The MWM SB juice with smaller particle sizes was not only successfully produced by the MWM, but also had higher levels of ascorbic acid (AA), total flavonoid content (TFC), total phenolic content (TPC), and antioxidant activity (AA) than those of CSB juice. HPLC/UV visible detector was successfully used to quantify the effect of MWM on the phenolic compounds such as specific phenolic contents of gallic acid, catechin, p-coumaric acid, Rutin and quercetin present in the MWM SB juice and show the higher amount than that of CSB juice and MM SB juice. Moreover, the amount and profile of these organic acids provide useful information about the origin of the raw material for the microbiological growth. The process techniques with HPLC analysis were conducted to identify the major organic acids present in the resulted juice as: Acetic acid < Pyruvic acid< Formic acid< Citric acid< Tartaric acid< Succinic acid< Quinic acid< D-Malic acid< L-Malic acid. The processing of MWM conveyed superior physical properties related to improved color, smaller particle size, significantly higher antioxidant properties and phytochemicals in the comparison to the mixer milled SB (MM SB) juice, and commercial SB (CSB) juice. The MWM has been used to reduce heat sensitive bioactive compound losses during berry processing and to manufacture fiber rich juice. Finally, we obtained that MWM processing technique would play a significant role in the food industry for whole SB fruit juice. There 11 specific higher amounts of low molecular weight organic acids and 5 phenolic compounds in MWM SB compared to MMSB, CSB juice in the HPLC analysis. In additional, by microbiological investigation, the initial viable count in the MWM SB juice was within the acceptable production range.

　In chapter 3, SD process was conducted using three different drying carrier agent maltodextrin DE-20, Gum arabic, and Tapioca starch with concentrations of 25, 35, and 45 g/100 g WSB juice respectively. The powder resulted from SD under the constant drying conditions was analyzed to determine the specific effects of different drying carrier on particle size, particles morphology, the total yield of microencapsulation, moisture contents, cold water rehydration, hygroscopicity, cold water solubility, bulk and tapped density, glass transition temperature (Tg), color hunter value, antioxidant properties of DPPH, FRAP and total bioactive compounds such as TPC, TCC, and TFC. Most effective carrier in terms of improving the performance of microcirculation on the powder yield was determined. Among WSB samples, maltodextrin DE-20 produced powder particles with a smaller size (5.50–11.16 μm), and higher bulk density. However, some cracks were observed in the microstructure by morphology analysis of the surface of powders containing maltodextrin DE-20. According to the experimental investigation Gum arabic carrier showed the best result in terms of efficiency of dryer microencapsulation on powder yield and number of antioxidants and phenolic compounds. According to our results, a higher concentration of drying carrier agents was related to a lower moisture content, a higher Tg, and a narrower particle distribution of powders dried by spraying. The Gum arabic WSB powders showed higher yields in microencapsulation of WSB (37.9– 56.4%) and good solubility properties after reconstitution, regarding of the composition of wall. The use of Gum arabic in the spray drying of powders showed a good solubility in microencapsulation as the recovery properties of the reconstituted powder was similar for their emulsions before the spray drying. For all the conditions studied, Gum arabic was the carrier agent that provided the best protection of the agent and antioxidant activity.

　In Chapter 4 a new optimization research is applied for production of WSB SD juice powders. The central composite design in response surface method (CCD-RMS) was employed in this study to evaluate the impact of SD conditions on the physicochemical parameters of a powder product made from WSB juice. The mixture of two different drying agents is Gum arabic and maltodextrins - DE20. The specific impact of drying inlet air temperature (120–160 °C) with use of Gum arabic level (5-30g w/w), and maltodextrin DE20 level (5–15g, w/w) in the SD process was observed. CCD-RMS was utilized to maximize the responses of the SD of WSB juice powder. The obtained results showed that inlet air temperature, Gum arabic and maltodextrin had caused an increase in the yield of the product, a decrease of the color and water content of the obtained powder and led to the preservation of its nutritional value and phytonutrient properties. Significant (p ≤ 0.05) response surface models were obtained in every case, with the linear terms of solute concentration being the factors that affected the response variables most significantly. The overall optimum spray drying conditions for obtaining WSB juice powder were: 140 °C inlet air temperature, 17.5% (w/w) Gum arabic, and 10% (w/w) maltodextrin DE20. In all cases, significant (p ≤ 0.05) RSM models were acquired, with linear drying agent’s concentration conditions.

　In chapter 5 or conclusion, firstly we develop the free-waste WSB juice by MWM technique, with greater physicochemical, bioactive and antioxidant properties. Secondly, according to SD investigation, it found superior drying carrier agents namely Gum arabic being suit for WSB juice. F Finally, we briefly wrap up that the use of a mixture of DE20 maltodextrin and Gum arabic with in optimum condition to make improvement of the for WSB juice powders properties using CCD/RSM methodology.

　This research demonstrated that SD with the optimal condition and MWM SB can produce good quality in physicochemical compounds, bioactive and antioxidant properties in juices and powders of WSB.