Preparation of the Orange Flavoured “Boba” Ball in Milk Tea and Its Shelf-Life
Total Page：16
File Type：pdf, Size：1020Kb
applied sciences Article Preparation of the Orange Flavoured “Boba” Ball in Milk Tea and Its Shelf-Life Ying Liu 1,2, Huan Cheng 2 and Dan Wu 2,* 1 Department of Food Nutrition and Detection, Hangzhou Vocational & Technical College, Hangzhou 310018, China; [email protected] 2 College of Biosystems and Food Science, Zhejiang University, Hangzhou 310058, China; [email protected] * Correspondence: [email protected]; Tel./Fax: +86-0571-8898-2156 Featured Application: The preparation technology of fruit-flavoured “boba” balls can be applied by food ingredient companies. Through the further optimization of the fruit ball core formula, healthy substances (such as flavones, active proteins, sterols, enzymes, probiotics, and vitamins) can be embed-ded in fruit balls and applied to drinks, overcoming the traditional technical bot- tleneck, en-hancing the stability and compatibility of the substances, and effectively extending the shelf life of the products. Abstract: Boba milk tea is very popular around the world. The “boba” balls in milk tea are usually made of tapioca. Reports on calcium alginate ball encapsulation in fruit-flavoured drinks have rarely been seen. The preparation method for this kind ball was studied. The “boba” balls were obtained by membrane formation on the interface through the addition of calcium chloride fluids into a sodium alginate solution. The operation conditions were studied, including drop height, flow velocity, sodium alginate and calcium chloride solution concentration. The diameter, mechanical strength, loading ratio and encapsulation rate of the “boba” balls are discussed. The optimized preparation conditions were as follows: the diameter of adding tube was 8 mm, the drop height was 25 cm, the drop flow rate was 60 mL/min, 1.0% sodium alginate, 1.0% calcium chloride. The prepared “boba” balls were stored at different temperatures. No microorganisms were detected in 90 days, and the sensory quality decreased with storage time. Shelf life was predicted using the Arrhenius Citation: Liu, Y.; Cheng, H.; Wu, D. equation; when the storage temperature was less than 10 ◦C, it could be stored for more than 1 year. Preparation of the Orange Flavoured This preparation technology of “boba” balls has potential for application by milk tea ingredient “Boba” Ball in Milk Tea and Its companies or relevant beverage manufacturing factories. Shelf-Life. Appl. Sci. 2021, 11, 200. https://doi.org/10.3390/app11010200 Keywords: boba milk tea; calcium alginate ball; preparation method; shelf life Received: 10 December 2020 Accepted: 24 December 2020 Published: 28 December 2020 1. Introduction Publisher’s Note: MDPI stays neu- Boba milk tea originated in Taiwan in the 1980s, became very popular in Asia in the tral with regard to jurisdictional claims 1990s, and has been increasingly popular around the world since 2000 [1,2]. The “boba” in published maps and institutional balls, which are also called “pearl” balls, are the central ingredient of the milk tea. It is affiliations. usually made of tapioca, or tapioca mixed with other ingredients, such as konjac powder, sweet potato, chamomile, and so on [3–5]. There have been some studies on the calory content and obesity risk of milk tea [6], but there have been few reports related to the Copyright: © 2020 by the authors. Li- improvement of milk tea technology, including that related to the “boba” balls. censee MDPI, Basel, Switzerland. This Orange is rich in nutrition. It not only contains nutrient elements needed by the article is an open access article distributed human body, it also contains plant phenols and flavonoids, containing an especially high under the terms and conditions of the content of Vc [7,8]. It is one of the most popular fruits in the world. Neves, Trombin, Creative Commons Attribution (CC BY) and Marques et al. analysed the global consumption of frozen concentrate orange juice license (https://creativecommons.org/ from 2013 to 2018. They summarized the consumer behaviour of three kinds of orange licenses/by/4.0/). juice in the main market worldwide [9]. A large number of studies have shown that eating Appl. Sci. 2021, 11, 200. https://doi.org/10.3390/app11010200 https://www.mdpi.com/journal/applsci Appl. Sci. 2021, 11, 200 2 of 10 a large amount of citrus fruits is beneficial to anti-cancer functions and prevention of cardiovascular diseases [10–13]. In this project, orange juice was wrapped in calcium alginate film to obtain fruit balls, which were used in milk tea, forming a new type of fruit ball drink. This technique was reported in cell immobilization during the last century. For example, Rickert et al. used calcium alginate gel to embed bacteria for the fermentation of organic acids [14]. By dropping Calcium ions (Ca2+) into sodium alginate solution, Ca2+ diffused to the periphery and reacted with sodium alginate to form a gel film to wrap the liquid core, and hollow micro-capsules were prepared. Some scholars have performed studies on the influence of processing conditions of calcium alginate gel (CAG). The physical properties of CAG beads change with heat treatment, including rupture strength, size, sphericity and porous structures [15,16]. In general, calcium alginate gel is a solid gel; the CAG studied in this paper has an orange-flavoured drink core. When you bite it, the juice flows out of the inner core, like jam, giving people a sweet and sour, delicious, unprecedented eating experience. It is also a calcium alginate immobilized embedding technology, which has the potential to maintain the stability of sensitive food ingredients, especially some natural health ingredients, such as flavones, active proteins, sterols, enzymes, probiotics and vitamins, etc. By applying calcium alginate ball embedding methods, important breakthroughs could result in some key food industry technologies, thus achieving ideal sensory, physical and chemical indicators, and shelf life, while also achieving functional food design. For example, Lin et al. wrapped astaxanthin in the CAG. The results showed that after storage at 25 ◦C for 21 days, the contents of astaxanthin in the CAG both remained above 90% of their original amount [17]. This provides an effective way of developing the stability of sensitive compounds. Jiang et al. fixed bifidobacteria in carboxymethyl chitin–calcium alginate gel, the bifidobacteria could be delivered to the gut without being dissolved in the gastric juice [18]. Here, “boba” balls made of calcium alginate for use in milk tea were studied. Operational conditions such as drop height, flow velocity, and sodium alginate and calcium chloride solution concentration were investigated. The diameter, mechanical strength, loading ratio and encapsulation rate of the “boba” balls are discussed. The sensory and microorganisms changes of the “boba” balls at different temperatures were studied, and their shelf life is predicted by using the Arrhenius equation. 2. Materials and Methods 2.1. Materials Orange juice (sugar: 66◦Bx, acidity: 4.16%), modified starch (hydroxypropyl distarch phosphate from potato, stable to temperature, acidity and shear force), calcium chloride anhydrous and sodium alginate were provided by Hangzhou Bodo Industry and Trade Co., LTD., Hangzhou, China. Sucrose and table salt were bought from a market; citric acid anhydrous was purchased from Shandong Zhongchuang Lemon Biochemical Co., LTD., Anqiu, Shandong, China. Sunset yellow, lemon yellow, and orange essence were purchased from Hangzhou Lvjing Flavor Co., LTD., Shandong, China, Xanthan gum and Guar bean gum were purchased from Hebei Jinfeng Chemical Co., LTD., Hengshui, Hebei, China. The companies above were located in China. All of the above materials were of food grade. 2.2. The “boba” Ball Preparation The composition of the orange-flavoured drink, which was the core of the “boba” ball, was carried out with reference to Wu et al. [19] and was improved for processing. It included sucrose (22.80%), citric acid anhydrous (0.50%), salt (0.04%), sunset yellow (0.0012%), citric yellow (0.006%), orange essence (0.07%), Xanthan (0.1%), and guar gum (0.25%). All the ingredients were put into pure boiling water (100 ◦C) to be fully dis- solved, after which the mixture was cooled to 50–60 ◦C, and concentrated orange juice (5%), modified starch (3.75%), calcium chloride anhydrous (1%) were added and blended Appl. Sci. 2021, 11, x FOR PEER REVIEW 3 of 11 included sucrose (22.80%), citric acid anhydrous (0.50%), salt (0.04%), sunset yellow (0.0012%), citric yellow (0.006%), orange essence (0.07%), Xanthan (0.1%), and guar gum (0.25%). All the ingredients were put into pure boiling water (100 °C) to be fully dissolved, after which the mixture was cooled to 50–60 °C, and concentrated orange juice (5%), mod- Appl. Sci. 2021, 11, 200 ified starch (3.75%), calcium chloride anhydrous (1%) were added and blended3 of 10 together. Homogenizer (Shanghai Zollo Instrument Co., Ltd., Shanghai, China) was used to homog- enize the orange flavoured drink at the pressure of 18–22 mpa for 30 min. together.The Homogenizer preparation (Shanghai process Zollo of the Instrument “boba” Co.,ball Ltd.,is shown Shanghai, in Figure China) was1. The used orange fruit- toflavoured homogenize drink the orangewas added flavoured to the drink sodium at the pressurealginate of solution 18–22 mpa drop for 30by min. drop using the Auto- The preparation process of the “boba” ball is shown in Figure1. The orange fruit- flavouredmatic liquid drink filler was added(Newking to the Pump sodium Co., alginate Ltd., solution Shangdong, drop by China). drop using After the 1 Auto- min of reaction, maticcalcium liquid alginate filler (Newking balls were Pump filtered Co., Ltd., out Shangdong, with a China).stainless After-steel 1 min filter of reaction, spoon, and were calciumwashed alginate with ballsdistilled were filteredwater outand with then a stainless-steel transferred filterinto spoon, 5% calcium and were chloride washed solution to withreact distilled for 15 watermin.