I work at MathWorks and I noticed this old question of yours just now. I thought I'd leave a link to our recent MATLAB Central sumbission speech2text in case it's still useful:
This enables to leverage 3rd party speech-to-text web services (so far including from Google, Microsoft and IBM) directly from MATLAB using a simple MATLAB Function. The syntax looks like the following:
>> [samples, fs] = audioread('helloaudioPD.wav');
>> soundsc(samples, fs)
>> speechObject = speechClient('Google','languageCode','en-US');
>> outInfo = speech2text(speechObject, samples, fs);
>> outInfo.TRANSCRIPT =
'hello audio product Developers'
>> outInfo.CONFIDENCE =
Please refer to the html folder in the submission for a step-by-step getting started guide.