Category Archives: Health and fitness

November 17, 2020

The cost to run a dehydrator…useful maths

This Ted Talk video came into my feed again yesterday, ‘Why math instruction is unnecessary’. which was timely as I needed a reminder that not making my kids do hours of maths drills will not ruin their lives…in fact quite the opposite…just doing the bare minimum useful maths will mean that they won’t suffer from ‘maths anxiety’ which is what makes kids avoid maths forever after school!

He explains that deductive and inductive reasoning is what our kids should be practicing.  I do have waves of doubt sometimes that my kids don’t go through thick text books of maths 🙂 But I felt pretty happy yesterday re-watching this video just after my kids had been solving a problem in their ‘Life of Fred’ book, asking them to find out how many diagonals a 200 sided polygon had.  Now I doubt they will ever need to remember or ever use this fact…but in the typical Life of Fred way it was asking this question to encourage them to logically work out a way to find the answer.  Here are the pages from their working out books:

The previous questions had asked how many diagonals a rectangle, a pentagon, and a hexagon had, which they worked out by drawing the shape and the diagonals.  2,5 and 9.  Lucas then drew a heptagon and an octagon, and identified a pattern.  He couldn’t work out how to fast track that pattern to a 200 sided shape, but he started to make a table and follow the pattern to record the number of diagonals for each shape as it increased in sides. When he got to 25 he noticed that he could safely increase his shapes in the table by 10 sides and calculate the diagonals, finally fast tracking to the conclusion that 200 x 98.5 would give him the answer he needed.

Aurora thought for a while, worked out that what she needed to find out was a value in an arithmetic series…she made a connection to a previous Fred book that had stepped the reader through a formula that students don’t normally learn till second year advanced algebra…but it was just useful for Fred at that time and fairly easy to follow…so why not?  She found the Fred book she wanted, slowly worked out the figures she needed to pop into the formula, and after a few attempts finally figured it out, 19700 diagonals 🙂

They both arrived at the same correct answer, took them both a while, but they nutted it out in their own different but logical way.

But what does this have to do with dehydrators?  Well the discussions in the house while we have had the dehydrator running all night experimenting for our long trail adventure, is whether it is economically worth it.  The treasurer of the house (Dad) having panic attacks at how much our electricity bill is going to be next time 🙂  So I asked the kids to find out how much it costs to run a dehydrator.

They found a website that gave them a formula to calculate how much it costs to use a dehydrator.

(Wattage of appliance × Hours needed) / 1000 = Kilowatt-hour (kWh) consumption

Cost = kWh x cost per kWh

They then had to find the values to put into the formula.  They had to find the wattage of our dehydrating appliance, and how much it costs us per kWh on our electric bill.  Lucas found the formula, it took them both a while to find where the cost per kWh was on our electricity bill, but they found it eventually, and Aurora neatly laid the information out, calculating how much a typical 12 hour dehydrating stint would cost.  Here are their calcs, working out that our machine would cost around 35cents to run for 12 hours.  She also did a little additional calc working out it will cost us around $21 if we were to run the machine nightly for 2 months to pre-make lots of snacks and meals.

Calculations of how much it costs to run our dehydrator

What we learned:

  • Definitely more cost effective by far than buying commercial dehydrated camp food, even if we were to run it every night for months making all our dinners for 3 months
  • We can confidently continue to experiment knowing our treasurer won’t have a heart attack 🙂
  • We can calculate anything if we can find the formula
  • If we look into buying a bigger dehydrator further down the track, to take the wattage of the appliance into consideration when comparing the ones on the market, pop it into our formula and calculate the cost to run, also taking into consideration if it is bigger then it has to be run less times 🙂
November 16, 2020

The science and safety of dehydrating food

When we hiked Wilson’s Prom (Vic) and Hinchinbrook Island (Qld), we had to be self sufficient carrying everything we needed for the 5 days on the trail.  We survived on nuts and sultanas, tuna and crackers, and noodles.  Our longer hikes in Langtang Nepal (Mandarin version of video)  and Tiger Leaping Gorge (China), we were spoiled with tea houses along the way to fill up with hearty food.

We want to do a really really long, self-sufficient trail next 🙂 On any of our expeditions, we have researched into the best, lightest and affordable equipment to ensure a safe and enjoyable hike.  It really doesn’t matter how fancy your gear is though, it’s our bodies that are moving us through the hike! We need to look after them. Which means that we are going to have to think about our nutrition…noodles and angel hair pasta with no veg for 3 months isn’t looking after that most valuable piece of equipment.

We have been watching lots of vlogs of hikers doing these long trails, and we are learning that many hikers pre make and dehydrate all their meals, box them, and mail them to towns along the route of the trail, ready for their next self-sufficient stint 🙂 It saves the $13 per meal per person you need to spend for a similar dehydrated meal in the camp shops…which would be over $3000 over 2 months JUST for DINNER alone. Plus you have preservative and additive free meals 🙂  Some just take fruit and veg dehydrated separately, and just add them to their regular noodle meals.  Some dehydrate whole dinners, whipping out their powder in a zip lock at the end of the day and rehydrating a coq au vin for dinner 🙂

We were given a used dehydrator over a year ago, and it has been sitting in the box under the stairs.  So we thought we would get it out, and start to explore the world of dehydrating foods 🙂

It takes months to experiment and master dehydrating and rehydrating full meals. So we are learning all about the science and safety of food dehydrating, starting with the easiest: fruit 🙂

Lucas in the moment slicing his favourite fruit for our first attempt in dehydrating 🙂

Over next few months we are going to experiment and learn everything we need to know about making our own dehydrated meals for a long trail 🙂 We have reserved some dehydrating books from the library 🙂  We have watched YouTube videos 🙂 We have learned up to now:

  • Food spoils because the mould and bacteria that spoil it like the moisture and in it  🙂
  • Dehydrating it will get rid of the moisture and so make it last much longer
  • Drying food is a preserving method that has been done naturally by many cultures for centuries (we saw lots of families drying their fish or chillies on the streets in China)
  • Dehydrating it also kills enzymes, which you really want to not kill…and although dehydrating machines probably aren’t as good as the sun, dehydrating longer at lower temps kills less enzymes apparently, and we can control this with our machines.
  • After our first few attempts of fruit, we found that it’s really hard to tell whether the food has dehydrated enough, and therefore if it is going to be safe to keep for months…

We are going to continue for a few months, experiment and read and learn about the science a little more, and hopefully become confident dehydrators 🙂 We may have to invest in a bigger machine though if we go ahead and try and make all our meals for a 3 month hike.

We have already discussed a future challenge once the kids have experimented with lots of foods.  They will need to make a  dehydrated meal to take on an overnight hike with us.  It will need to be nutritionally balanced, tasty, safely prepared, packaged like the ones in the camp shop, selling us with enticing images and scientific information, labelled on the back with nutrition content and reheating instructions etc.  We thought it would be a great challenge integrating science, technology, health, maths, English, marketing, design, visual arts and apparently business…as after chatting about the challenge together, they seemed pretty keen and their first question was ‘Will we get paid the $13 for it?’ 🙂

I am sure updates on our dehydrating journey will follow 🙂