# Digital Nose Milk Freshness Checker
## Overview
The classic method for testing for milk freshness is to give it a quick sniff check. If it smells "bad", then it probably is. This is great, as long as your sense of smell is working. But maybe covid, congenital anosmia, a stuffy cold, or something else has reduced your sense of smell. What then?
In this guide we investigate the potential for using a gas sensor as a way to test for milk freshness. An SGP30 and a CLUE are used to make a little "freshness checker" device. We then use this in a simple experiment to see if it can detect spoiled milk.
Primary:
## Hardware
Here is a summary of the hardware needed for this project.
### Adafruit CLUE - nRF52840 Express with Bluetooth® LE
[Adafruit CLUE - nRF52840 Express with Bluetooth® LE](https://www.adafruit.com/product/4500)
Do you feel like you just don't have a CLUE? Well, we can help with that - get a CLUE here at Adafruit by picking up this sensor-packed development board. We wanted to build some projects that have a small screen and a lot of sensors. To make it compatible with existing projects, we made...
In Stock
[Buy Now](https://www.adafruit.com/product/4500)
[Related Guides to the Product](https://learn.adafruit.com/products/4500/guides)
### Adafruit SGP30 Air Quality Sensor Breakout - VOC and eCO2
[Adafruit SGP30 Air Quality Sensor Breakout - VOC and eCO2](https://www.adafruit.com/product/3709)
Breathe easy with the SGP30 Multi-Pixel Gas Sensor, a fully integrated MOX gas sensor. This is a very fine air quality sensor from the sensor experts at Sensirion, with I2C interfacing and fully calibrated output signals with a typical accuracy of 15% within...
Out of Stock
[Buy Now](https://www.adafruit.com/product/3709)
[Related Guides to the Product](https://learn.adafruit.com/products/3709/guides)
### STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long
[STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long](https://www.adafruit.com/product/4210)
This 4-wire cable is a little over 100mm / 4" long and fitted with JST-SH female 4-pin connectors on both ends. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
Out of Stock
[Buy Now](https://www.adafruit.com/product/4210)
[Related Guides to the Product](https://learn.adafruit.com/products/4210/guides)
This is the battery shown in the guide:
### Lithium Ion Polymer Battery - 3.7V 350mAh
[Lithium Ion Polymer Battery - 3.7V 350mAh](https://www.adafruit.com/product/2750)
Lithium-ion polymer (also known as 'lipo' or 'lipoly') batteries are thin, light, and powerful. The output ranges from 4.2V when completely charged to 3.7V. This battery has a capacity of 350mAh for a total of about 1.3 Wh. If you need a larger (or smaller!) battery,
Out of Stock
[Buy Now](https://www.adafruit.com/product/2750)
[Related Guides to the Product](https://learn.adafruit.com/products/2750/guides)
but you can use any other similar lithium ion battery option:
[Lithium Ion Batteries](https://www.adafruit.com/category/574)
- [Next Page](https://learn.adafruit.com/digital-nose-gas-sensor-milk-freshness-checker/background-information.md)
## Featured Products
### Adafruit CLUE - nRF52840 Express with Bluetooth® LE
[Adafruit CLUE - nRF52840 Express with Bluetooth® LE](https://www.adafruit.com/product/4500)
Do you feel like you just don't have a CLUE? Well, we can help with that - get a CLUE here at Adafruit by picking up this sensor-packed development board. We wanted to build some projects that have a small screen and a lot of sensors. To make it compatible with existing projects, we made...
In Stock
[Buy Now](https://www.adafruit.com/product/4500)
[Related Guides to the Product](https://learn.adafruit.com/products/4500/guides)
### Adafruit SGP30 Air Quality Sensor Breakout - VOC and eCO2
[Adafruit SGP30 Air Quality Sensor Breakout - VOC and eCO2](https://www.adafruit.com/product/3709)
Breathe easy with the SGP30 Multi-Pixel Gas Sensor, a fully integrated MOX gas sensor. This is a very fine air quality sensor from the sensor experts at Sensirion, with I2C interfacing and fully calibrated output signals with a typical accuracy of 15% within...
Out of Stock
[Buy Now](https://www.adafruit.com/product/3709)
[Related Guides to the Product](https://learn.adafruit.com/products/3709/guides)
## Related Guides
- [Introducing Adafruit CLUE](https://learn.adafruit.com/adafruit-clue.md)
- [CLUE Text Telephone Transmitter](https://learn.adafruit.com/clue-teletype-transmitter.md)
- [PyLeap CLUE Sensor Plotter](https://learn.adafruit.com/pyleap-clue-sensor-plotter.md)
- [CLUE BLE MIDI Glove](https://learn.adafruit.com/clue-midi-glove.md)
- [Using the Bluefruit Dashboard with Web Bluetooth in Chrome](https://learn.adafruit.com/bluefruit-dashboard-web-bluetooth-chrome.md)
- [CLUE Rock, Paper, Scissors Game using Bluetooth](https://learn.adafruit.com/rock-paper-scissors-circuitpython.md)
- [FunHouse IoT Fume Extractor and Air Quality Sensor](https://learn.adafruit.com/funhouse-fume-extractor-iot-air-quality-sensor.md)
- [CircuitPython BLE Heart Rate Zone Trainer Display](https://learn.adafruit.com/circuitpython-ble-heart-rate-monitor-gizmo.md)
- [CLUE Vertical Garden Weather Visualizer](https://learn.adafruit.com/clue-vertical-garden-weather-visualizer.md)
- [CLUE Light Paint Stick with CircuitPython](https://learn.adafruit.com/clue-light-paintstick.md)
- [Chauncey the Flower Care Bot with CLUE and Bonsai Buckaroo](https://learn.adafruit.com/chauncey-flower-watering-bot-clue.md)
- [PyBadger Event Badge](https://learn.adafruit.com/pybadger-event-badge.md)
- [Bluetooth LE Sensor Nodes to Raspberry Pi WiFi Bridge](https://learn.adafruit.com/bluetooth-le-broadcastnet-sensor-node-raspberry-pi-wifi-bridge.md)
- [Bluetooth CLUE Robot Car using CircuitPython](https://learn.adafruit.com/bluetooth-clue-robot-car-using-circuitpython.md)
- [CLUE Custom CircuitPython Badge](https://learn.adafruit.com/clue-custom-circuit-python-badge.md)